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SCHOLAR Study Guide SQA CfE Higher Human Biology Unit 3: Neurobiology and Communication Authored by: Eoin McIntyre Reviewed by: Sheena Haddow Previously authored by: Mike Cheung Eileen Humphrey Eoin McIntyre Jim McIntyre Heriot-Watt University Edinburgh EH14 4AS, United Kingdom. First published 2014 by Heriot-Watt University. This edition published in 2014 by Heriot-Watt University SCHOLAR. Copyright © 2014 Heriot-Watt University. Members of the SCHOLAR Forum may reproduce this publication in whole or in part for educational purposes within their establishment providing that no profit accrues at any stage, Any other use of the materials is governed by the general copyright statement that follows. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, without written permission from the publisher. Heriot-Watt University accepts no responsibility or liability whatsoever with regard to the information contained in this study guide. Distributed by Heriot-Watt University. SCHOLAR Study Guide Unit 3: SQA CfE Higher Human Biology 1. SQA CfE Higher Human Biology ISBN 978-1-909633-18-6 Printed and bound in Great Britain by Graphic and Printing Services, Heriot-Watt University, Edinburgh. Acknowledgements Thanks are due to the members of Heriot-Watt University's SCHOLAR team who planned and created these materials, and to the many colleagues who reviewed the content. We would like to acknowledge the assistance of the education authorities, colleges, teachers and students who contributed to the SCHOLAR programme and who evaluated these materials. Grateful acknowledgement is made for permission to use the following material in the SCHOLAR programme: The Scottish Qualifications Authority for permission to use Past Papers assessments. The Scottish Government for financial support. All brand names, product names, logos and related devices are used for identification purposes only and are trademarks, registered trademarks or service marks of their respective holders. i Contents 1 The structure of the nervous system 1.1 Introduction . . . . . . . . . . . . . 1.2 Divisions of the nervous system . . 1.3 Parts of the brain . . . . . . . . . . 1.4 Learning points . . . . . . . . . . . 1.5 Extended response question . . . 1.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 4 10 21 23 24 2 Perception and memory 2.1 Perception . . . . . . . . . . . 2.2 Memory . . . . . . . . . . . . 2.3 A note about techniques . . . 2.4 Learning points . . . . . . . . 2.5 Extended response question 2.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 30 40 50 51 54 54 . . . . . . . . . . . . . . . . . . 3 Neurons, neurotransmitters and neural pathways 3.1 Neurons . . . . . . . . . . . . . . . . . . . . . . 3.2 Glial cells and myelination . . . . . . . . . . . . 3.3 Neurotransmitters . . . . . . . . . . . . . . . . 3.4 Neural pathways . . . . . . . . . . . . . . . . . 3.5 Learning points . . . . . . . . . . . . . . . . . . 3.6 Extended response question . . . . . . . . . . 3.7 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 60 69 72 77 83 85 86 4 Neurotransmitters, mood and behaviour 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Dopamine and the reward pathway . . . . . . . . . . . 4.3 Endorphins . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Neurotransmitter-related disorders and their treatment 4.5 Mode of action of recreational drugs . . . . . . . . . . 4.6 Drug addiction, sensitisation and tolerance . . . . . . 4.7 Learning points . . . . . . . . . . . . . . . . . . . . . . 4.8 Extended response question . . . . . . . . . . . . . . 4.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 92 93 94 95 100 103 105 106 107 5 Infant attachment and the effect of communication 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Forms of infant attachment . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Long period of dependency . . . . . . . . . . . . . . . . . . . . . . . . . 109 110 112 117 . . . . . . . . . . . . . . . . . . . . . ii CONTENTS 5.4 5.5 5.6 5.7 5.8 5.9 The effect of communication . Non-verbal communication . Verbal communication . . . . Learning points . . . . . . . . Extended response question End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 The effect of experience and social influences 6.1 Introduction . . . . . . . . . . . . . . . . . . 6.2 The effect of practice on motor skills . . . . 6.3 Imitation . . . . . . . . . . . . . . . . . . . . 6.4 Trial and error learning . . . . . . . . . . . . 6.5 Generalisation and discrimination . . . . . . 6.6 Social facilitation and deindividuation . . . . 6.7 Influences that change beliefs . . . . . . . . 6.8 Learning points . . . . . . . . . . . . . . . . 6.9 Extended response question . . . . . . . . 6.10 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 120 123 127 128 128 . . . . . . . . . . 131 132 132 133 135 137 139 141 142 143 143 7 End of unit test 145 Glossary 149 Answers to questions and activities 1 The structure of the nervous system . . . . . . . . 2 Perception and memory . . . . . . . . . . . . . . . 3 Neurons, neurotransmitters and neural pathways . 4 Neurotransmitters, mood and behaviour . . . . . . 5 Infant attachment and the effect of communication 6 The effect of experience and social influences . . 7 End of unit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 156 162 168 174 180 184 187 © H ERIOT-WATT U NIVERSITY 1 Topic 1 The structure of the nervous system Contents 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Divisions of the nervous system . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 4 1.2.1 Central and peripheral nervous systems . . . . . . . . . . . . . . . . . . 5 1.2.2 Autonomic nervous system . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Parts of the brain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 10 1.3.1 The central core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 The limbic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 13 1.3.3 The cerebral cortex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 21 1.5 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 24 Learning Objectives By the end of this topic, you should be able to: • explain the general functions of the nervous system; • describe the different divisions of the nervous system and their specific functions; • describe the basic structure of the brain; • state the functions of the central core, the limbic system and the cerebral cortex. 2 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 1.1 Introduction Learning Objective By the end of this section, you should be able to: • state that the nervous system contains three types of neuron: sensory, motor and interneurons; • state that sensory neurons connect sense receptors with the central nervous system; • state that motor neurons connect the central nervous system to muscles or glands; • state that interneurons may connect with sensory, motor or other interneurons; • state that the nervous system analyses sensory information from both the external and internal environment; • explain that the body stores some of this information which it uses to make decisions about appropriate responses and behaviours; • state that motor responses may be made by initiating muscular contractions or glandular secretions. Animals show two basic types of symmetry: radial symmetry, where there is an upper and lower side, but no front or back, e.g. jellyfish; and bilateral symmetry, where there are not only upper and lower surfaces, but a front and back as well, e.g. worms and vertebrates. In the latter types of animal, there is usually a distinct 'head', or part of the body which meets the world first, on which most external sense organs are clustered. Sense organs are structures that contain receptors which respond to stimuli. These stimuli can be changes in the external environment, which are detected as different types of energy (e.g. light, sound, chemical, kinetic and heat), or changes in the internal environment, e.g. changes in core temperature or the carbon dioxide level in the blood. To be of any use, this information must be assessed and appropriate action taken in response. This is done by neurons, of which there are three broad classes: • sensory neurons, which connect sense receptors to the central nervous system; • motor neurons, which connect the central nervous system to the muscles and glands; • interneurons (also known as relay, association or connector neurons), which are found in the central nervous system and connect with sensory, motor, and other interneurons. When stimulated, neurons pass along their length a temporary reversal of the electrical potential on their plasma membrane. These are called impulses and travel at velocities between 1 and 100 m.s -1 . By locating many sense organs in the head and developing the processing area of the central nervous system close to them, rates of reaction to incoming stimuli can be maximised. The grouping of interneurons in the same area, to form a brain, allows more interconnections and more complex processing, such as © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM learning and memory. The extent to which learning plays an important part in animal behaviour depends very much on the type of animal involved. Insects, which live for only a short period, may never see their parents and only interact with others of their own species to mate. Consequently, they rely almost entirely on inherited, innate patterns of behaviour to identify food, escape predators, and find mates and places to lay eggs. There is no time for insects to learn these things which means that the environment will weed out the less successful life strategies by natural selection. Long-lived animals, such as Primates (including humans), are social creatures with a long dependent period, which means that there is ample opportunity for them to develop responses which are based on their own experience and on the observation of others (although it would be a mistake to think that innate responses play no role in Primate behaviour). Interestingly, the same type of behaviour may be innate in one group but learned in others, e.g. mothering behaviour: a crocodile reared in isolation will still show the careful attention to her young which is typical of the species, whereas chimpanzees (normally the most attentive of mothers) when reared in isolation are most likely to reject their offspring. In summary, the nervous system provides animals with the means to collect, analyse and respond appropriately to sensory information. These motor responses may take the form of muscular contractions (e.g. reflexes such as knee-jerks or blinks) or secretions from glands (e.g. adrenal or salivary glands). Introduction to the structure of the nervous system: Questions Q1: Sensory neurons connect sense organs to a) the central nervous system b) motor neurons c) sensory neurons .......................................... Q2: Motor neurons connect the central nervous system to a) interneurons b) muscles and glands c) sense organs .......................................... Q3: Interneurons are located in a) the central nervous system b) muscles c) sense organs .......................................... © H ERIOT-WATT U NIVERSITY 3 4 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Q4: Secretions by the adrenal gland are stimulated by a) interneurons b) motor neurons c) sensory neurons .......................................... Q5: Storage of information is carried out by a) interneurons b) motor neurons c) sensory neurons .......................................... .......................................... 1.2 Divisions of the nervous system Learning Objective By the end of this section, you should be able to: • state that the nervous system is divided into the central and peripheral nervous systems; • state that the central nervous system comprises the brain and spinal cord; • state that the peripheral nervous system is divided into the somatic and autonomic nervous systems; • state that the autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The nervous system is sub-divided according to its structures and their functions. © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 5 Divisions of the nervous system: Question Q6: Complete the labelling of the diagram using the words from the list. Word list: autonomic, central, parasympathetic, peripheral, spinal cord. .......................................... 1.2.1 Central and peripheral nervous systems Learning Objective By the end of this section, you should be able to: • state that the central nervous system consists of the spinal cord and the brain, including the retinas of the eyes and the optic nerves; • state that the peripheral nervous system comprises all sensory and motor neurons outside the central nervous system; • state that the peripheral nervous system comprises the somatic and autonomic nervous systems; • state that the somatic nervous system controls the voluntary movement of skeletal muscles; • explain that this control involves sensory neurons (e.g. connected to stretch receptors in striped/striated muscle in leg) and motor neurons; • state that the autonomic nervous system is responsible for involuntary homeostatic control of many body functions; • explain that this control involves sensory neurons (e.g. connected to stretch receptors in smooth muscle of artery walls) and motor neurons; • state that the motor neurons of the autonomic nervous system may connect to smooth muscle (e.g. in the wall of the gut), cardiac muscle (e.g. pacemaker) or glands (e.g. adrenal gland). Scientists distinguish between the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS comprises the brain, including the retinas of the eyes and optic nerves, and spinal cord, whereas the PNS consists of all the other parts, such as the sensory and motor neurons. This is a purely structural division. © H ERIOT-WATT U NIVERSITY 6 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Central and peripheral nervous systems The PNS is further divided functionally into the somatic and autonomic nervous systems. Somatic nerves control voluntary movement by controlling skeletal muscles. They include sensory neurons and motor neurons. Sensory neurons send messages to the CNS from the sensory receptors, mainly in the skin, whereas motor neurons take messages to the muscles or glands causing them to function. The autonomic system tends to control our basic activities, the ones that do not tend to require conscious thought. You do not have to command, "O heart, beat faster! I see my teacher yonder." The autonomic system controls heart rate without conscious thought. Nor do you need to decide to breathe faster when your homework is late. Heart rate, breathing, peristalsis, and other similar functions are under the control of the autonomic nervous system. Muscles under voluntary control have a striped (striated) appearance like the fibres of a steak, whereas muscles under autonomic control are un-striped and referred to as 'smooth muscle'. Cardiac muscle, which must never tire, appears like a cross between striated muscle and the smooth muscle of the alimentary canal and blood vessels. © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 7 The autonomic nervous system also controls endocrine glands which regulate growth and the activities of other tissues. These include the pituitary, thyroid, pancreas and adrenal glands. Endocrine glands 5 min Pituitary gland: sometimes called the master gland, the pituitary secretes many hormones, e.g. growth hormone and ADH. It also secretes hormones which control the activity of the other endocrine glands, e.g. thyroid stimulationg hormone (TSH) stimulates the thyroid gland. Thyroid gland: When stimulated by TSH from the pituitary, the thyroid gland secretes the hormone thyroxine which regulates an individual's metabolic rate. Parathyroid glands: these secrete parathyroid hormone, which regulates the level of calcium in the blood. Adrenal glands: the adrenal glands are situated on the upper surface of each kidney (ad = at, renal = kidney). They secrete many hormones the most well-known probably being adrenalin. This hormone is involved in the 'fight or flight' mechanism which is triggered in response to danger. Ovary: found in females, ovaries produce the hormones oestrogen and progesterone when stimulated by hormones from the pituitary gland. © H ERIOT-WATT U NIVERSITY 8 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM The interplay between these hormones controls the menstrual cycle, including the maturation and release of an ovum and the build up and break down of the lining of the uterus. Oestrogen also has a role in the development and maintenance of the female secondary sexual characteristics. Testis: found in males, testes produce hormones such as testosterone when stimulated by hormones form the pituitary gland. Testosterone is involved in the production of sperm and development and maintenance of male secondary sexual characteristics. .......................................... 1.2.2 Autonomic nervous system Learning Objective By the end of this section, you should be able to: • state that the autonomic nervous system (ANS) comprises the sympathetic and parasympathetic nervous systems; • state that the sympathetic and parasympathetic nervous systems act antagonistically; • state that the sympathetic nervous system prepares the body for action: 'fight or flight'; • state that the parasympathetic nervous system returns the body to a relaxed, standby condition: 'rest and digest'; • state that the sympathetic nervous system causes increases in heart and breathing rates, and decreases in peristalsis and intestinal secretions; • state that the parasympathetic system causes decreases in heart and breathing rates, and increases in peristalsis and intestinal secretions. The two branches of the autonomic nervous system, the sympathetic and the parasympathetic, can be thought of as alert, 'fight or flight', and standby, 'rest and digest', modes respectively. The former prepares the body for action and the latter returns the organism to an energy-conserving state. Thus, the sympathetic and parasympathetic nervous systems are described as antagonistic in action. This enables the ANS to exert homeostatic control over many of the body's functions. This is clearly observed in their effects on heart rate, breathing rate, peristalsis and intestinal secretions. © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Function Sympathetic nerves speed up - prepare for action Parasympathetic nerves calm down - conserve resources Rate and force of contraction of cardiac muscle increases. Result: more blood to muscles. Rate and force of contraction of cardiac muscle decreases. Result: less blood to muscles, normal levels restored. Breathing rate Muscles in bronchioles become relaxed. Rate of contraction of diaphragm and intercostal muscles increases. Result: increased gas exchange. Muscles in bronchioles become contracted. Rate of contraction of diaphragm and intercostal muscles decreases. Result: reduced gas exchange. Digestion Rate of contraction of smooth muscle in wall of digestive tract decreases. Rate of blood flow to digestive tract decreases. Result: reduced digestion. Rate of contraction of smooth muscle in wall of digestive tract increases. Rate of blood flow to digestive tract increases. Result: normal digestion. Heart rate Adrenal gland 9 Adrenal gland stimulated. Result: secretion of hormone adrenaline. Summary of the influences of the Sympathetic and Parasympathetic Nervous Systems Sympathetic and parasympathetic effects 5 min .......................................... © H ERIOT-WATT U NIVERSITY 10 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Autonomic nervous system: Question Q7: Enter either 'Increased' or 'Decreased' at the correct places in the table. 10 min Sympathetic Parasympathetic Heart rate Stroke volume Breathing rate Depth of breathing Contractions of smooth muscle of gut wall Intestinal secretions .......................................... 1.3 Parts of the brain Learning Objective By the end of this section, you should be able to: • state that the brain consists of three major regions: medulla, cerebellum and cerebrum; • state that the cerebrum comprises two interconnected hemispheres. The vertebrate brain is the enlarged fore-end of the spinal cord, adapted to manage the mass of sensory information coming in from the sense organs and the animal's responses to it. In humans, this adaptation is taken to an incredibly complex level, but the 'primitive' areas which run the body's machinery at a subconscious level are still present (and, of course, essential). As the accompanying activity shows, the brain is divided into three main areas: the medulla, the cerebellum and the cerebrum (which consists of two interconnected cerebral hemispheres). The human organism consists of several organ systems which function in a coordinated way to respond to stimuli in the environment. Each organ system consists of organs which, in turn, comprise groups of tissues. Tissues are assemblies of cells with common functions. Every freshly-produced cell contains a nucleus which has all the instructions to allow it to perform all cellular functions. However, to ensure that chaos does not ensue, each nucleus only activates the genes necessary for it to perform the functions of that tissue of which the cell is part. Just as the nucleus controls cellular function, the nervous system coordinates organ systems. It works in tandem with the endocrine system, so that immediate responses can be effected by nerves, whilst longer term responses and functions are managed by hormones. Sensations are also mediated by nerves. © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 11 While the major parts of the brain are interconnected, each can also be subdivided into a great many areas dependent either on their cellular structure or their function. The basic layers with which we are concerned here are the central core, the limbic system and the cerebral cortex. Parts of the brain: Question Q8: Complete the labelling of the diagram using the words provided. 5 min .......................................... 1.3.1 The central core Learning Objective By the end of this section, you should be able to: • state that the central core comprises the medulla and the cerebellum; • state that the medulla regulates breathing rate, heart rate, arousal and sleep; • state that the cerebellum controls balance, muscular co-ordination, posture and movement. The central core, consisting of the medulla and the cerebellum, is an ancient part of the brain in that it does much the same in humans as it does in other mammals. It takes care of much of the housekeeping in the body that would be dangerous to leave a human in charge of. The medulla and the cerebellum are, however, very different in both structure and function. © H ERIOT-WATT U NIVERSITY 12 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Medulla The medulla, like the spinal cord, has the grey matter in the centre and the fatty white matter on the outside. It is a key part of the autonomic nervous system and, through the sympathetic and parasympathetic neurons, it controls the heart rate set by the pacemaker, or sino-atrial node (SAN). It also regulates breathing, in response to impulses from the receptors that detect blood carbon dioxide concentrations, and blood pressure, in response to the degree of stretch detected by receptors in the artery walls. Simple reflexes such as coughing, sneezing, swallowing and vomiting are controlled by the medulla, as are alertness (arousal) and consciousness (sleep). Cerebellum The cerebellum, like the cerebrum, has the grey matter on its convoluted outer surface, while the white matter is contained internally. However, the way in which the neurons interact is totally different - deep thought is the last thing that is required of the cerebellum. Although consisting of only about one eighth of the total brain mass, it contains as many neurons as the whole of the rest of the brain. It is the cerebrum which initiates movement, but the cerebellum is responsible for its accurate timing, precision, and co-ordination. This is achieved by matching the contraction of the antagonistic muscles involved; body posture is controlled in the same way. Maintaining balance is another of the cerebellum's responsibilities; think of the range of sensory information and muscular control that is needed to perform well on a skateboard and you will begin to understand what a sophisticated computer the cerebellum must be. The central core: Question Q9: Complete the table by putting the processes into their correct column. Medulla Cerebellum Processes: arousal, balance, breathing, movement, muscular coordination, posture, sleep, heart rate. .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 1.3.2 The limbic system 13 Learning Objective By the end of this section, you should be able to: • state that the limbic system is concerned with the formation of memories, influencing emotional and motivational states; • state that the limbic system contains many parts, one of which is the hypothalamus which influences the pituitary by means of the secretion of hormones; • state that other parts of the limbic system regulate homeostasis by means of the autonomic nervous system, e.g. blood pressure by contraction/relaxation of smooth muscle in artery walls; • state that the limbic system also regulates body temperature by means of the autonomic nervous system; • state that the limbic system is also involved in the control of water balance by the secretion of ADH. The limbic system forms the inner border of the cerebrum and is not a single entity but a group of brain structures with quite diverse functions. Two in particular are mentioned below: the hippocampus and the hypothalamus. Overall, it is involved in the following areas and exerts its effect by influencing the endocrine system and the autonomic nervous system. a) Determines states of emotion and motivation. These are inter-related and actually quite difficult states of mind to define. • Emotion - is associated with mood, temperament and personality, e.g. anger, desire, envy. • Motivation - determines which behaviour will take place, how strongly it will be expressed, and for how long. b) Involved in the formation of long-term memories (in the hippocampus particularly). c) Influences the production of hormones by the pituitary gland, by itself releasing hormones from the hypothalamus which stimulate or inhibit pituitary activity. d) Homeostatic regulation of: • body core temperature around the set point of 37 ◦ C, e.g. by causing vasodilation and vasoconstriction by relaxing and contracting the smooth muscle in the walls of smaller arteries and arterioles serving the skin, plus a wide range of other mechanisms; • blood pressure, by controlling the contraction/relaxation of the smooth muscle of arterial walls in response to impulses from their stretch receptors; • water balance, through the production of antidiuretic hormone (ADH) in the hypothalamus, which is stored and released from the pituitary gland. © H ERIOT-WATT U NIVERSITY 14 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 1.3.3 The cerebral cortex Learning Objective By the end of this section, you should be able to: • state that the cerebral cortex is the centre of conscious thought; • state that the cerebral cortex receives sensory information, coordinates voluntary movement, makes decisions, recalls memories and alters behaviour in the light of experience; • explain that functions are localised in the cerebral cortex into sensory areas, motor areas, and association areas; • state that the association areas deal with thought processes, language, imagination and intelligence; • state that the left cerebral hemisphere deals with information from the right visual field and the right side of the body, and vice versa; • state that the cerebral hemispheres are connected by the corpus callosum, which allows transfer of information; • state that the brain operates as an integrated whole. The cerebral cortex is the thin outer layer of the cerebrum. Being intensely folded (convoluted), its large surface area maximises the number of interconnections possible between neurons. It is 2-4mm thick and consists of grey matter which comprises the cell bodies of neurons and unmyelinated neurons (which lack a fatty myelin sheath). The inner layers of the cerebrum consist of white matter which is largely composed of myelinated axons connecting different parts of the cerebral cortex with each other and with other parts of the nervous system. This arrangement is the same in the cerebellum, but is reversed in the medulla and the spinal cord. Broadly, the cortex can be said to comprise three parts: the sensory, motor, and association areas. These reflect the evolutionary history of the cerebrum as the part of the brain which receives incoming information from the sense organs, appraises it, and sends out signals to the appropriate organs to make a response. The modern human cerebral cortex is also the centre of conscious thought. Not only does it receive sensory information, it coordinates voluntary movement (as opposed to reflexes), makes decisions, recalls memories and uses experience to modify behaviour (learning). Sensory areas The senses of vision, hearing, and touch are served by the visual cortex, auditory cortex and somatosensory cortex. On each hemisphere, the visual cortex is located at the back, the somatosensory cortex on either side, just to the rear of the midline, and the auditory cortex immediately below it. Other senses, such as taste and smell, also have localised areas which deal with them (and may include other parts of the brain). © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Motor areas The motor areas of each hemisphere are also located down the midline, immediately in front of the somatosensory areas. Both the somatosensory and motor cortices can be subdivided according to the parts of the body to which they relate, the size of each area reflecting the sensitivity and degree of fine motor control involved. Until recently, knowledge of the functions of different parts of the brain was based on the observed results of brain damage. A wide range of modern techniques, such as electroencephalographs and brain scans, have allowed much more detailed analysis. Electroencephalographs Electroencephalographs (EEGs) show electrical activity in the brain. Electroencephalographs of brain electrical activity CAT scans It is useful to compare patterns of activity using EEGs, especially when comparing normal and abnormal brainwaves. However, these do not give good evidence of localisation of function. A different brain scan called a CAT scan (Computer Assisted Tomography), shows metabolic activity, providing better evidence for localisation of function. For example, while listening, metabolic activity in the areas of the brain involved in hearing can be traced. © H ERIOT-WATT U NIVERSITY 15 16 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM CAT scans and brain activity 10 min The areas of brain activity when a subject is performing the following activities are summarised in the following diagram: 1. hearing; 2. seeing; 3. speaking; 4. areas associated with particular activities. .......................................... Unfortunately, CAT Scans and Electroencephalographs tell us little on their own. Observation of people who have suffered brain injuries and subsequent dissection of their brain tissue after death have provided much more evidence. It seems that the brain has tissues allocated to receiving information from the senses (the somatosensory area, or simply the sensory area) and tissues sending instructions to the muscles (the motor area) localised in adjacent parts of the cortex. The brain, in fact, allocates the size of each area of sensation and control according to the importance of the functions carried out. The more sophisticated the senses received, and the finer the control of the muscles, the more brain tissue is allocated. © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Localisation of function: Motor and sensory humunculi A large part of the motor area is devoted to the hands and lips. This allows a fine degree of motor control. For example, fingers can hold an egg without crushing it or manoeuvre a coin from finger to finger. Remember that the left motor cortex controls the right side of the body and vice versa. .......................................... As shown in the activity above, there is a major organisation of tissues to enable easy linkage of sensory messages from a specific area of the body with the motor impulses required to control these organs and tissues. The homunculus is a visual way of explaining this organisation. The somatosensory area receives information from cold, heat, pain, touch and kinaesthetic receptors in the skin. Thus, an impulse coming in from a leg is sensed by neurons in the somatosensory area adjacent to the neurons of the motor area which direct the movement of that leg. Large parts of the sensory area are devoted to the lips, fingers and sex organs, making them very sensitive. This explains why we kiss with the lips and why infants explore new toys with their lips. Similarly, large parts of the motor area are devoted to the tongue and lips, allowing speech, and to the fingers, allowing fine manipulation. The great apes also have fine control of lips and tongue, but, crucially, they lack a voice box which we have evolved due to different selection pressures operating during our evolution. © H ERIOT-WATT U NIVERSITY 17 18 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Association areas At the simplest level, the association areas integrate sensory information from different sensory areas and relate it to past experience. A decision is then made and neuron impulses sent to the motor areas to give responses. However, the association areas are also where the individual person resides, as they are the location of thought processes, personality, imagination, language and intelligence. These are not easy concepts to define, and fortunately are not part of this syllabus. But just to whet the appetite, here are some suggestions: • thought: mental activity of which we are aware and undertake deliberately, that generates ideas and underlies almost all human actions; • personality: the sum of an individual's emotions, attitudes and behaviour; • imagination: helps us to make sense of the world and learn, by allowing us to form visual or sensory images without actually experiencing them at the same time; • language: a system of signs, gestures or sounds which convey particular meanings; • intelligence: mental ability, either inborn or acquired, to pay attention, remember, process language, solve problems and make decisions; this is a very controversial topic. Association areas for speaking 10 min How different parts of the association area in the brain respond to written and spoken words .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 19 Left and right hemispheres The cerebrum is divided into the left and right hemispheres. These are not independent structures; they are linked by the corpus callosum which allows the transfer of information between the hemispheres. Although the hemispheres appear to duplicate many functions, there are important differences. A treatment for severe epilepsy involves cutting all or part of the corpus callosum in order to isolate the two cerebral hemispheres. The subsequent behaviour of such split-brain patients, in whom the two hemispheres cannot communicate properly, shows that tasks are not evenly divided between the two hemispheres. Images appear to be processed by the left hemisphere in most people. Language and analytical skills are also processed here. The right hemisphere controls visuospatial tasks, such as recognising facial features and arranging objects or reading maps. These findings have been corroborated by observation of subjects with trauma to particular regions of the cerebrum. Split-brain study 10 min .......................................... Despite the apparent localisation of function in many areas of the brain, it is also the case that a great many functions involve the activity not just of different areas of the cerebral hemispheres, but also the other parts of the brain. The brain in fact operates as an integrated whole, but one which shows remarkable powers of flexibility in response to damage, e.g. as a result of a stroke. © H ERIOT-WATT U NIVERSITY 20 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Limbic system and cerebral cortex: Question Q10: Complete the table by putting words from the list below to correctly match the statements about the limbic system and the cerebral cortex. Some items may be used more than once. Process Area Controls voluntary movement Processes information for the formation of memories Transfers information between hemispheres Influences the secretions of the pituitary Recalls memories Deals with language and imagination Receives impulses from the skin Centre of conscious thought Controls the left side of the body Acts as an integrated whole Word list: association area, brain, cerebral cortex, corpus callosum, hypothalamus, limbic system, motor area, right cerebral hemisphere, somatosensory area. .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 1.4 Learning points Summary Introduction • The nervous system contains three types of neuron, namely sensory, motor and interneurons. • Sensory neurons connect sense receptors with the central nervous system. • Motor neurons connect the central nervous system to muscles or glands. • Interneurons may connect with sensory, motor or other interneurons. • The nervous system analyses sensory information from both the external and internal environment. • The body stores some of this information and makes decisions about appropriate responses and behaviours. • Motor responses may be made by initiating muscular contractions or glandular secretions. Divisions of the nervous system • The nervous system is divided into the central and peripheral nervous systems. • The central nervous system comprises the brain and spinal cord. • The peripheral nervous system is divided into the somatic and autonomic nervous systems. • The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. Central and peripheral nervous systems • The central nervous system consists of the spinal cord and the brain, including the retinas of the eyes and the optic nerve. • The peripheral nervous system comprises all sensory and motor neurons outside of the central nervous system. • The peripheral nervous system comprises the somatic and autonomic nervous systems. • The somatic nervous system controls the voluntary movement of skeletal muscles. • This control involves sensory neurons (e.g. connected to stretch receptors in striped/striated muscle in leg) and motor neurons. • The autonomic nervous system is responsible for involuntary homeostatic control of many body functions. © H ERIOT-WATT U NIVERSITY 21 22 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Summary Continued • This control also involves sensory neurons (e.g. connected to stretch receptors in smooth muscle of artery walls) and motor neurons. • The motor neurons of the autonomic nervous system may connect to smooth muscle (e.g. in the wall of the gut), cardiac muscle (e.g. pacemaker) or glands (e.g. adrenal gland). Autonomic nervous system • The autonomic nervous system parasympathetic nervous systems. • The sympathetic antagonistically. and comprises parasympathetic the sympathetic nervous systems and act • The sympathetic nervous system prepares the body for action: 'fight or flight'. • The parasympathetic nervous system returns the body to a relaxed, standby condition: 'rest and digest'. • The sympathetic nervous system causes increases in heart and breathing rates, and decreases in peristalsis and intestinal secretions. • The parasympathetic nervous system causes decreases in heart and breathing rates, and increases in peristalsis and intestinal secretions. Parts of the brain • The brain consists of three major regions: cerebrum. medulla, cerebellum and • The cerebrum comprises two interconnected hemispheres. The central core • The central core comprises the medulla and the cerebellum. • The medulla regulates breathing rate, heart rate, arousal and sleep. • The cerebellum controls balance, muscular co-ordination, posture and movement. The limbic system • The limbic system is concerned with the formation of memories, influencing emotional and motivational states. • The limbic system contains many parts, one of which is the hypothalamus which influences the pituitary through the secretion of hormones. • Other parts of the limbic system regulate homeostasis by means of the autonomic nervous system, e.g. blood pressure by contraction/relaxation of smooth muscle in artery walls. © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 23 Summary Continued • The limbic system also regulates body temperature by means of the autonomic nervous system. • The limbic system is also involved in the control of water balance by the secretion of ADH. The cerebral cortex • The cerebral cortex is the centre of conscious thought. • The cerebral cortex receives sensory information, coordinates voluntary movement, makes decisions, recalls memories and alters behaviour in the light of experience. • Functions are localised in the cerebral cortex into sensory areas, motor areas, and association areas. • The association areas deal with thought processes, language, imagination and intelligence. • The left cerebral hemisphere deals with information from the right visual field and the right side of the body, and vice versa. • The cerebral hemispheres are connected by the corpus callosum, which allows transfer of information. • The brain operates as an integrated whole. 1.5 Extended response question The activity which follows presents an extended response question similar to the style that you will encounter in the examination. You should have a good understanding of the nervous system before attempting the question. You should give your completed answer to your teacher or tutor for marking, or try to mark it yourself using the suggested marking scheme. Extended response question: Nervous system Give an account of the nervous system under the headings: 15 min A) divisions of the nervous system; (5 marks) B) homeostatic control. (5 marks) .......................................... © H ERIOT-WATT U NIVERSITY 24 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM 1.6 End of topic test End of Topic 1 test Q11: Complete the sentences by matching the parts on the left with the parts on the right. (10 marks) Types of neuron: autonomic nervous system. Connect sense receptors to CNS: somatic and autonomic. Connect CNS to muscles and glands: brain and spinal cord. Connect to other neurons of all types: central and peripheral. Analysis of information: sensory, motor, interneuron. Muscular contractions and glandular secretions: sensory neurons. Divisions of the nervous system: motor neurons. Central nervous system comprises: central nervous system. Divisions of the peripheral nervous system: interneurons. motor responses. Sympathetic and parasympathetic: .......................................... Q12: Complete the sentences by matching the parts on the left with the parts on the right. (8 marks) Controls the voluntary movement of skeletal muscles: connect to smooth and cardiac muscle. Skeletal muscle control by sensory and motor neurons is: sensory and motor neurons. Responsible for involuntary homeostatic control: sympathetic nervous system. Involuntary homeostatic control involves: parasympathetic nervous system. Motor neurons of the autonomic nervous system: autonomic nervous system. Action of the sympathetic and parasympathetic nervous system: voluntary. Increases heart rate, decreases intestinal secretions: somatic nervous system. Decreases breathing rate, increases peristalsis: antagonistic. .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM The diagram shows the main parts of the brain in vertical section. Q13: Identify the part labelled X. (1 mark) .......................................... Q14: Identify the part labelled Z. (1 mark) .......................................... Q15: To which part of the nervous system does the brain belong? (1 mark) .......................................... Q16: The part labelled Y is the corpus callosum. What is its function? (1 mark) .......................................... Q17: Identify the medulla in the diagram. (1 mark) .......................................... Q18: State two functions regulated by the medulla. (2 marks) .......................................... Q19: Name the part of the brain responsible for balance. (1 mark) .......................................... © H ERIOT-WATT U NIVERSITY 25 26 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM The diagram shows the divisions of the nervous system. Q20: Identify the part labelled A in the diagram. (1 mark) .......................................... Q21: Identify the part labelled B in the diagram. (1 mark) .......................................... Q22: Identify the part labelled C in the diagram. (1 mark) .......................................... Q23: Identify the part labelled D in the diagram. (1 mark) .......................................... Q24: Identify the part labelled E in the diagram. (1 mark) .......................................... Q25: Homeostatic control is regulated by which structures within the autonomic nervous system? (1 mark) .......................................... Q26: To which structures are impulses sent during the process of homeostatic control? (2 marks) .......................................... Q27: State the effect of the parasympathetic nervous system on heart rate. (1 mark) .......................................... Q28: State the effect of the parasympathetic nervous system on peristalsis. (1 mark) .......................................... Q29: In which part of the brain is the hypothalamus located? (1 mark) .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM Q30: How does the hypothalamus regulate the function of the pituitary? (1 mark) .......................................... Q31: State two homeostatic mechanisms regulated by the hypothalamus. (2 marks) .......................................... Q32: Which part of the cerebrum is the centre of conscious thought? (1 mark) .......................................... Q33: Apart from the association areas, what are the two localised functional areas of the cerebrum? (1 mark) .......................................... Q34: State three mental functions that are dealt with by the association areas. (3 marks) .......................................... .......................................... © H ERIOT-WATT U NIVERSITY 27 28 TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM © H ERIOT-WATT U NIVERSITY 29 Topic 2 Perception and memory Contents 2.1 Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Segregation of objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 31 2.1.2 Perception of distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.3 Recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 38 2.2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.2.1 Sensory Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Short-Term Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 43 2.2.3 Long-Term Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Location of memory in the brain . . . . . . . . . . . . . . . . . . . . . . 46 48 2.3 A note about techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 51 2.5 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 54 Learning Objectives By the end of this topic, you should be able to: • define perception as the process by which sensory information is organised, identified and interpreted by the brain so that we can make sense of it; • describe how we segregate and recognise objects; • describe the different methods by which distance is perceived; • define memory as the storage, retention and retrieval of information; • describe the nature of sensory, short-term and long-term memory, and their relationship; • describe the location of memory in the brain. 30 TOPIC 2. PERCEPTION AND MEMORY 2.1 Perception Learning Objective By the end of this section, you should be able to: • state that perception is the process by which the brain analyses and makes sense of incoming sensory information; • describe how perception allows us to segregate objects from one another and from their background; • describe how perception allows us to judge the distance of objects; • describe how perception allows us to recognise objects. We are aware of our surrounding environment as a result of the physical stimulation of our sense organs. Thus, light is detected by the rods and cones of the retina, sound waves by the organs of Corti in the cochlea of the ears, kinetic energy by mechanoreceptors in the skin, and chemicals by chemoreceptors in the nose and mouth. These energy signals must be converted into nerve impulses before they can be processed by the nervous system, a process known as transduction. In each eye we have some 7 million cones and 75-150 million rods connected to the brain by a million nerve fibres in the optic nerve. If you look out of the window, you take in the scene with all of its features, including perhaps trees, buildings, cars, people, grass and birds, but that is not what your retina detects. Its photoreceptors fire off an impulse in response to the light which they receive. It is the neurons in the retina, optic nerve and the visual cortex of the cerebrum which create the image we 'see'. Not only do they create a seamless picture for us from the individual nerve impulses (which are, of course, no different to any other impulses), but they organise and interpret this 'data' so that we do not see mere patches of brown, green, black and white, but objects such as trees, roads, sheep and clouds. This interpretation process depends on memory and an analysis of context; fluffy white objects against a green background are likely to be sheep, but against a blue background they are more likely to be clouds. Sometimes, this process can be tripped up; if you have ever been given a cup of tea when you were expecting coffee, especially when engrossed in some other activity, you may have experienced that moment of confusion when you can almost hear the cogs turning in your brain. Your system first identifies the liquid as very strange coffee, and then takes a noticeable time before it correctly recognises it as tea. It is necessary then to appreciate that what we consciously perceive is the product of considerable mental processing, and not what is recorded by our sense organs. Although the syllabus content is limited to the perception process related to vision, it applies to all the senses. To you, the bass playing on a particular musical track may be fantastic, but to your neighbour it may just be a loud noise because they do not have the experience to separate the sound of the different instruments. Have you added too much cumin to the curry? Unless they know their spices, nobody will notice. The word 'object' can therefore be used in a general way to refer to the sound of a specific instrument or a particular flavour. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 2.1.1 Segregation of objects 31 Learning Objective By the end of this section, you should be able to: • explain that the brain organises sensory information into figures (objects) and grounds (background) during perception; • explain that, in order to make sense of our environment, the brain organises sensory stimuli into coherent patterns during perception. Figure and ground All but the simplest of animals use the information from their sense organs to avoid predators and to find the essentials of life, such as food, mates, shelter, and water. To do this, they must distinguish the properties of these objects from amongst the mass of incoming stimuli so there must be a reference memory against which the information can be matched. Mammals gain much of this information by means of learning, especially from the parents. Other types of animal, e.g. most fish and insects, never meet their parents and so most of this information must be inherited genetically rather than passed on by social contact or learned by trial and error. In terms of the sense of sight, this process involves trying to identify known shapes within what we are seeing. This involves identifying the shape against its surrounding background which involves segregating the figure from the ground. The best known example of this is Edgar Rubin's vase. Rubin's figure-ground vase © H ERIOT-WATT U NIVERSITY 32 TOPIC 2. PERCEPTION AND MEMORY If we concentrate on the white area of the diagram so that the boundary from white to black represents the edge of the object, then we see a white vase against a black background. However, if the edge is visualised the other way, from black to white, then we see two faces in silhouette looking at each other in front of a white background. This is known 'edge-assignment' and is critical to shape perception. The intention of disruptive camouflage is to make this process more difficult. Examples of camouflage include: • the British Multi-terrain Pattern on army combat clothing, in which some of the colours match the surroundings and so break up the edge of the image of the wearer; • the colour patterns of animals such as the Bengal tiger, which has the same effect against a background of tall grasses during the day and the shadows of a forest at night. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY Coherent patterns In the process of interpreting sensory information, the brain seeks to organise it into coherent patterns or objects. According to one group of psychologists (Gestalt), this is achieved by six categories of principles, namely Proximity, Similarity, Closure, Good Continuation, Common Fate, and Good Form. As a knowledge of these principles is not required by the syllabus, only two are given as examples. It should be noted that these principles may not apply if other factors are involved. Proximity principle Perception tends to group objects that are close together into a single larger set, and conversely, objects that are far apart into separate sets. In line (a), the items are evenly spaced and interpreted as a single unit. In line (b), the uneven spacing causes the items to be grouped as three units. In line (c), four groups are induced by the uneven spacing. Closure principle Although the actual shape of the panda is not complete, the brain organises it into a single shape by filling in the gaps by closure. Segregation of objects: Questions Q1: What is the purpose of disruptive camouflage patterns? .......................................... Q2: How do the principles of Proximity and Closure contribute to perception? .......................................... © H ERIOT-WATT U NIVERSITY 33 34 TOPIC 2. PERCEPTION AND MEMORY 2.1.2 Perception of distance Learning Objective By the end of this section, you should be able to: • state that distance is judged in the field using visual cues such as relative size, superimposition and relative height; • state that binocular disparity is used to judge distance at close range; • explain that binocular disparity results from the visual field of the left and right eyes being different, which means seeing objects from a slightly different angle where it overlaps; • state that perceptual constancy means that as objects get closer and the viewing angle changes, they are still perceived to be the same object. The accurate estimation of distance does not matter to the same extent to all animals. Prey species, for example hare or roe deer, have no problem gauging the distance to their plant food as it does not run away. Their principal concern is to have as large a field of view as possible in order to detect any movement in their surroundings which might indicate the presence of a predator. Accordingly, their eyes are located on the side of the head to maximise their visual field. To a predatory animal, for example a peregrine falcon swooping at 100mph towards a fleeing pigeon, or a lion leaping at the back of a galloping zebra, it is a matter of life or death to both the predator and the prey that the former judges the relative position of the latter accurately. As predators ourselves, we do not close at potentially lethal speed with our prey, but the accurate judgment of the distance our arrows or spears had to travel to strike their target, or the distance to a herd of deer or a hungry-looking bear, certainly would have been of critical importance in the past. The eyes of predators are therefore located on the front of the face. If, on a wilderness safari, you notice a large animal contemplating you with a firm, two-eyed stare, it may be thinking about inviting you to dinner... In our modern human lives in the West, only recreational hunters and those involved in conservation have to estimate range accurately to ensure a humane kill. Yet we all have to judge distances, both short and long, in myriad different contexts in every day life, e.g. to climb stairs, cross roads, thread needles or dodge snowballs. We use a considerable battery of mechanisms to do this, a few of which are capable of giving an accurate measurement, and most of which tell us about the relative position of objects. The syllabus refers to two of these, namely visual cues and binocular disparity. We also consider perceptual constancy which involves the brain breaking its own rules about distance judging. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 2.1.2.1 Visual Clues We use a wide variety of visual clues to judge distance. Here, we consider three of them. Relative size Objects that possess similar dimensions can appear to have different sizes depending on their distance from our eyes. This is known as relative size. In the illustration of a road disappearing towards the horizon, which demonstrates linear perspective, the smaller telephone poles are interpreted as being further away. In the photograph of Glen Affric, the pines trees in the foreground, middle ground and in the distance are all of the same height. Linear perspective Glen Affric © H ERIOT-WATT U NIVERSITY 35 36 TOPIC 2. PERCEPTION AND MEMORY Superimposition When objects overlap, those which are partially obscured are perceived to be further away. This is know as superimposition although it is also called interposition. Relative height in field In landscape painting and photography, the horizon is often portrayed somewhere between 1 /3 and 2 /3 of the way up the image. Objects closest to the horizon appear the furthest away and those nearest to the top and bottom appear as the closest (relative height in field). In the photos of County Mayo and Glen Muick, the vegetation at the bottom of the image appears closest, as do the clouds at the top. County Mayo and Glen Muick This makes sense in that, if we look down, the ground on which we are standing is the closest to us, and if we look straight up, the clouds that we see are (usually) the ones which are closest to us. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY Perception of distance: Question Q3: Explain how visual clues give the impression of depth in the following image. Jamaica Inn, Bodmin Moor, Cornwall .......................................... 2.1.2.2 Binocular disparity 'Binocular disparity' means that your two eyes do not have the same view of anything at which you look. The distance between the pupils of our eyes is typically 60-65mm. Therefore, each eye views the world from a slightly different position, the effect of which is most marked with objects close to us. If you hold your right hand up vertically in front of your face with your thumb touching your nose and shut each eye in turn, you will appreciate this to maximum effect. Your left eye sees your palm and your right eye sees the back of your hand. If you then move your hand slowly away from your face, closing your eyes alternately and comparing each view with what you see with both eyes open, very quickly you will discover that with both eyes open you 'see' only one image, although the view from each eye is noticeably different. Your visual cortex is merging the two-dimensional images from each eye into a single, coherent three-dimensional picture. However, this only applies around the point of focus of the eyes. If you hold your index fingers in front of your face about 30cm apart and focus on one of your fingers, the other will appear twice. © H ERIOT-WATT U NIVERSITY 37 38 TOPIC 2. PERCEPTION AND MEMORY Although with both eyes open we have a total visual field of about 200 ◦ , the portion of this which is common to both eyes is only about 120 ◦ . As a result of the varying density of distribution of rods and cones across the retina, over most of this area our vision is not nearly as precise as it is in the centre, in the area on which we are focussed. Consequently, our judgement of distance is also most accurate for objects on which we are focussing. Binocular disparity is important for judging distance at ranges of up to about 10m; beyond that, the views from each of the eyes are not sufficiently different. 2.1.2.3 Perceptual constancy We tend to perceive familiar objects as having a standard shape, size, colour and even location, despite wide variations in the conditions under which we are observing them. Thus, you would recognise that the little yellow dog on the other side of the field as a Labrador and your perception would not change as the dog runs over towards you. In fact, as it runs, it changes shape; as it passes under a tree, it changes colour (because of the green light filtering through the leaves); and as it gets closer, it forms a much larger image. Even if you were looking down on the scene from an upstairs window, with a very different viewing angle, you would not be confused. The value of perceptual constancy is that it allows us to recognise familiar objects under a wide variety of conditions. This effect is reduced if exposure to the object has been limited (e.g. you have never seen a Labrador before) or if the associated clues to its identity are reduced (e.g. its colour has changed as a result of 'bog-snorkelling'). 2.1.3 Recognition Learning Objective By the end of this section, you should be able to: • state that shape is more important than detail in the recognition of objects; • explain that we match observed shapes to shape descriptions stored in memory during perception; • explain that inference is used to match incomplete information against memorised shape descriptions during perception; • explain that the perception of a stimulus or object is influenced by a perceptual set of past experience, context and expectation. Every time we see a familiar object, be it a person, tree, beach, or street, the image created on the retina is different, and yet we discern from that image that the object is not only similar to one that we have seen before, but actually that it is the same one. This process is complex, involving several different areas of the brain, yet it also takes place in any animal that is capable of recognition, e.g. an adult butterfly can identify the correct food plant for its caterpillar larvae from all of the species growing in a hedgerow. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY The role of shape in recognition Processing of the visual image takes place in a series of increasingly complex steps which are located in different areas of the cerebrum. At the simplest level, lines, colour and orientation are distinguished. Boundaries and contours are filled in next, allowing figure-ground segregation. Finally, all of the information is combined into the final object. During this process, no new information is formed, but the existing data is reorganised to emphasise the most detailed information about the object. Overall, it is shape rather than particular detail which is most important in recognition. Stored memories The highest level of processing in perception involves identifying an object by matching it with a stored memory of that object. Once identified, the object can be assigned various attributes, such as potential uses, whether we like it or not, or whether it constitutes a threat to us. These properties have been linked with this object as a result of our past experience of it. The role of inference The information provided by our sense organs is often incomplete, but our brain must still try to make sense of it. This it does by making assumptions, e.g. about where boundaries are, which leads to drawing conclusions, e.g. about what the rest of a partially concealed object will be. The influence of perceptual set Given the extent to which assumptions and inferences are involved in perception, we should not be surprised that the way in which we perceive objects is likely to quite subjective, and dependent on our previous experience, the context in which we encounter the stimulus, and what our expectations are. An obvious example would be the reaction of opposing sets of supporters to a controversial refereeing decision in a football match. Depending on past encounters with the other team, the reputations of the referee and the players, the state of the game, and the position on the pitch, supporters of each side are quite capable of genuinely perceiving the incident in very different ways. © H ERIOT-WATT U NIVERSITY 39 40 TOPIC 2. PERCEPTION AND MEMORY 2.2 Memory Learning Objective By the end of this section, you should be able to: • state that memory is the process of storage, retention and retrieval of information; • state that the information stored in memory includes past experiences, knowledge and thoughts; • explain that all information entering the brain passes first through Sensory Memory and then enters Short-Term Memory; • explain that information in Short-Term Memory is either passed into Long-Term Memory or is discarded. In the preceding section about recognition, reference was made to descriptions of objects being stored in memory. To be able to confirm that we have seen,smelt or heard something before, we must have been able to convert our initial perception into a form that can be stored and later retrieved so that we can compare it with our new percept. By the same token, any animal which can change its behaviour in the light of experience, i.e. learn, must also be able to carry out this information storage, retention and retrieval process. The information which we can store takes all forms; not only are images, smells, tastes, textures, and sounds stored, but also our feelings about events and the details of complex information such as equations or poems. Even our thoughts are remembered, although these do not pass through the sense organs. There are different stages in the process of memory. All incoming sensory information is put into Sensory Memory before some of it is passed almost immediately to Short-Term Memory (STM). As the name implies, information only remains in Short-Term Memory for a brief period and is then either discarded or passed into Long-Term Memory (LTM). © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 2.2.1 Sensory Memory 41 Learning Objective By the end of this section, you should be able to: • state that Sensory Memory retains all input from the sense organs; • state that information is retained in Sensory Memory for a few seconds. Each of our sense organs continuously feeds impulses into the region of the cerebrum which relates to that particular sense. Each form of sensory information is processed separately: • auditory - echoic memory - processed in the temporal lobe; • visual - iconic memory - processed in the occipital lobe; • tactile - haptic memory - processed in the postcentral gyrus of the parietal lobe. The classic demonstration of visual Sensory Memory (iconic memory) is the drawing of shapes with a sparkler on a dark night. As the light moves, we briefly 'see' the shape of its track through the air. The information in Sensory Memory is raw data, uninterpreted, and mostly of no relevance to us. Of this vast quantity of information, only a few items pass into ShortTerm Memory; the rest is discarded after 1 /5 to 1 /2 second. Which information is so transferred is determined by subconscious filtering through the mental process known as attention. This causes selective concentration on one aspect of the environment to the exclusion of all others. This is why you shouldn't speak into a mobile phone while driving, or worse, send a text message! Transfer into Short-Term Memory takes place in the hippocampus, where the information from the various sensory areas of the cerebrum is assimilated into a single experience. The position of the hippocampus © H ERIOT-WATT U NIVERSITY 42 TOPIC 2. PERCEPTION AND MEMORY Location of Sensory Memory: Question Q4: Complete the diagram to show the location of the different types of Sensory Memory. .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 2.2.2 Short-Term Memory 43 Learning Objective By the end of this section, you should be able to: • state that the memory span of Short-Term Memory (STM) is the number of items that can be stored; • state that the average memory span for digits is 7 (usual range 5-9); • state that information may be retained in STM by rehearsal; • state that information is lost from STM by displacement or decay; • explain the serial position effect: items at the start of a list are recalled because they have been rehearsed and passed to LTM; items at the end of a list are recalled because they are still in STM; items in the middle of the list are not recalled as they have been displaced from STM by later items and have not been transferred to LTM; • state that the memory span of STM can be increased by chunking; • explain that chunking is the grouping of separate items of information so that they pass into the memory as a single unit; • state that Working Memory is an extension of STM; • state that Working Memory is used to perform cognitive tasks (e.g. reasoning, comprehension). We often think of Short-Term Memory as information newly-received from the senses, but it may include information recently retrieved from Long-Term Memory or recent mental processing. We can call this extended form of Short-Term Memory 'Working Memory'. Short-Term Memory has a limited facility to store information which is known as the memory span. It makes sense that it is not cluttered with too much information. "The Curious Incident of the Dog in the Night-time" by Mark Haddon is an insightful fictional account of how an autistic boy has difficulty with an excess of information. Current processing of information, or Short-Term Memory, has a capacity of seven items, plus or minus two, for most people. Practice can improve this. For example, 'chunking' items to convert several pieces of information into one can increase this capacity greatly. If you were given fifteen random letters to memorise, you could chunk them in groups of three to make five nonsense words to remember. Phone numbers are often recalled in chunks, the area code as one chunk and the rest put into little groups depending on associations. Short-Term Memory lasts only 15-30 seconds unless rehearsal or repetition is involved. Rehearsal often involves repeating information, such as a telephone number, until it is dialled, although speed-dialling and mobile phone contact lists have reduced the practice of recalling numbers. Distractions greatly reduce this facility. This repetition is referred to as acoustic coding and repetition may be aloud or 'in-your-head'. © H ERIOT-WATT U NIVERSITY 44 TOPIC 2. PERCEPTION AND MEMORY Given that memories only last for a few seconds normally, and that only around seven items are remembered at any one time, Short-Term Memory decays, or is displaced, rapidly. Serial Position Effect Storage of memory is greatly enhanced by rehearsal. You may become fed up with your parents repeatedly recalling the good old days, but this is simply a way to keep memories alive. One way to demonstrate memory storage is to investigate the serial position effect. Serial position effect 1 15 min Collect at least twenty varied items. Present them briefly, one at a time, in a predetermined sequence, to a friend. Hide them when they are not being shown. Ask your friend to recall the items, using any descriptions, in any order. Where did she do best? With the earlier items (the primacy effect) or the last (the recency effect)? .......................................... Even if assuming that someone was paying attention, twenty items are too many to recall from Short-Term Memory. The subject initially tries to store the information in Long-Term Memory by rehearsal, using mnemonics, or some other trick, such as associating the items with a previously learned list. Most people can only encode seven items in the Short-Term Memory and do not have enough time to rehearse or repeat all of the items. Thus, the first few items might have been stored in the Long-Term Memory and the last few remain in the Short-Term Memory, but storage and, consequently, retrieval of the items mid-list will be haphazard. Serial position effect 2 Look at the tables of data and then answer the questions which follow. 10 min Twenty items were shown briefly to a fourth year student. The table below shows which items were recalled. For example, the student recalled item 5, but not item 6. Item Number Recalled? Item Number Recalled? 1 2 3 4 5 √ √ √ √ √ 11 12 13 14 15 6 8 9 10 √ 16 √ Items shown to the student: 7 √ 17 18 19 20 √ √ √ √ = item recalled © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 45 Q5: Using your understanding of the serial position effect, explain the results. .......................................... Q6: What is unusual about the Short-Term Memory of the subject? .......................................... Q7: Sometimes an item is recalled regardless of its position. Why might his occur? .......................................... Working Memory The concepts of 'Short-Term Memory' and 'Working Memory' have been the subject of much research since the development of a classical model of memory in the 1960s. A simple interpretation is that while information is passed into Short-Term Memory for storage (for a short period), the manipulation or organisation of this information is carried out in Working Memory by means of the processes of reasoning and comprehension. Short-Term Memory: Questions Q8: Complete the sentences by matching the parts on the left with the parts on the right. Memory span of STM is: STM. Items remain in STM for: cognitive tasks. Items are maintained in STM by: displacement and decay. Items are lost from STM by: 15-30 seconds. STM memory span can be increased by: 7 (5-9) items. Working Memory is an extension of: rehearsal. chunking. Working Memory is used to perform: .......................................... Q9: When shown a list of twenty items, people can recall a few items from the start of the list and a few from the end, but not those in the middle. i Explain why the early numbers are recalled. ii Explain why the later numbers are recalled. iii Explain why the middle numbers are not recalled. .......................................... © H ERIOT-WATT U NIVERSITY 46 TOPIC 2. PERCEPTION AND MEMORY 2.2.3 Long-Term Memory Learning Objective By the end of this topic, you should be able to: • state that encoding is the process by which information is converted into a form which can be passed from STM to LTM; • state that LTM can store unlimited information indefinitely; • state that information can be transferred from STM to LTM by rehearsal, organisation or elaboration of meaning; • state that rehearsal involves repetition of the information to be memorised; • state that organisation involves grouping the information with other similar items; • state that elaboration involves linking the information with emotions, images and other memories; • state that repetition produces shallow encoding of information; • state that organisation of information into groups with similar properties produces relational encoding of information; • state that elaboration by linking with previous memories produces elaborative encoding of information; • state that relational and elaborative encoding are more permanent than shallow encoding; • state that retrieval is the recall from LTM to the Working Memory of STM; • state that retrieval is aided by the use of contextual clues which relate to the conditions under which the memory was formed. The process of converting information in the form of impulses that enters Sensory Memory into a form which can be stored is known as encoding. Transfer from Sensory Memory to Short-Term Memory is controlled by the mental process of attention over which we have no conscious influence. Transfer from STM to LTM Transfer from STM to LTM can be achieved by three methods: 1. rehearsal (shallow encoding), which is repeating the information many times when applied to a list of random words, this repetition is a very inefficient method of transferring such information to LTM; however, as anyone who plays an instrument or any sport will know, frequent repetition is essential to the perfection of motor skills, whether it be playing arpeggios in the scale of A minor or escaping from bunkers; © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 47 2. organisation (relational encoding) - by grouping an item of information with other items of similar type is a form of deep encoding which links the new item with others already in memory; the creation of mind maps or key-word diagrams of information to be memorised for exams is a prime example of organisation, in which individual items are located within a logical framework; 3. elaboration (elaborative encoding) - by linking information to existing memories, or to other information such as emotions, scents, tastes or textures, memories can be created by another form of deep encoding; thus, if a person's name can be linked to their interesting choice of shoes/hairstyle/perfume, or the place where you met, it is much more likely to be transferred into LTM. Retrieval For us to become conscious of items stored in memory, they must be recalled from LTM to STM. This process is greatly aided by information which is linked to the conditions, or context, under which the information was encoded. The reverse of this is also true. You might only have ever seen the person who drives the school bus in that situation so when you meet her in the supermarket you find it difficult to place her because some of the key contextual clues are missing, e.g. the uniform and the bus. In the same way, the taste of an ice-cream might remind you of a childhood day by the beach. Long-Term Memory: Question Q10: Complete the sentences by matching the parts on the left with the parts on the right. Process by which information is converted to a form which can stored in memory: organisation. Transfer from STM to LTM by repetition: retrieval. Transfer from STM to LTM by grouping with similar items: rehearsal. Transfer from STM to LTM by linking with existing memories: contextual. Encoding produced by repetition: elaboration. Encoding produced by linking with emotions: encoding. Recall from LTM to STM: elaborative. Clues which aid recall: shallow. .......................................... © H ERIOT-WATT U NIVERSITY 10 min 48 TOPIC 2. PERCEPTION AND MEMORY 2.2.4 Location of memory in the brain Learning Objective By the end of this topic, you should be able to: • state that LTM can be sub-divided according to the type of information stored; • state that episodic memory stores events and experiences; • state that semantic memory stores facts and concepts; • state that procedural memory stores skills: both motor and cognitive; • state that emotional memory stores emotional responses to past events; • state that spatial memory stores information about the location of physical objects in space; • state that the different types of memory are located in different parts of the cerebrum; • state that episodic and semantic memory are located in the region of the cerebral cortex where the sensory information was first encoded; • state that procedural memories are linked to long-term changes in the motor cortex; • state that emotional memories involve links between the cortex and the limbic system; • state that spatial memory is located in the hippocampus of the limbic system. Location of memory The information which is stored in Long-Term Memory is located in different parts of the cerebrum depending on the type of information. The types of memory, the information stored and the location are summarised in the following table. Type of memory Information stored Location in cerebrum Episodic Events and experiences Area of cerebral cortex where sensory information is first encoded Semantic Facts and concepts Area of cerebral cortex where sensory information is first encoded Procedural Motor and cognitive skills Motor cortex Emotional Emotional responses Amygdala of the cortex and the limbic system Spatial Location of a physical object in space Hippocampus of the limbic system © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 49 Types of memory The main types of memory are: • episodic - the memory of events in our lives, including places, times, dates, how we felt about it, and other people involved; • semantic - the memory of the meaning of words, facts and concepts, but does not concern specific events or experiences; • declarative - episodic and semantic memory together make up one of the two main types of memory, namely declarative memory. They involve memories, such as facts and dates, that can be consciously recalled; • procedural - the memory of how to carry out tasks, both mental and physical. This covers a broad range of complex sets of procedures from putting on your socks to solving equations and reading. Key points are that these skills can be carried out without conscious thought, so do not involve the STM, and that the memories are acquired as a result of frequent repetition. There are two other forms of memory: • spatial (or topographic) - the memory of the organisation of our environment and how we are positioned within it - we store a cognitive map of our world, which allows us to navigate; this consists of the general layout of places and key locations within them; • emotional - the memory of intense emotional responses, which are usually linked with specific events, but may be stored separately - agood example is the feeling of fear; we all know what it feels like to be afraid, but it is very helpful to our survival that we should also remember situations which have made us afraid. Location of memory in the brain: Questions Q11: Complete the table with the types of memory from the list. Type of memory Information stored Events and experiences Facts and concepts Motor and cognitive skills Emotional responses Location of physical objects in space Types of memory: episodic, emotional, procedural, semantic, spatial. © H ERIOT-WATT U NIVERSITY 50 TOPIC 2. PERCEPTION AND MEMORY .......................................... Q12: Complete the sentences by matching the parts on the left with the parts on the right. Events and experiences; Facts and concepts: located in the motor cortex. Motor and cognitive skills: located in the hippocampus of the limbic system. Emotional responses: area of cerebral cortex where sensory information first encoded. Location of physical objects in located in the amygdala of the cortex and the space: limbic system. .......................................... 2.3 A note about techniques Early research on human brain function was based on observing the effect of accidental damage to particular parts of the brain and the accompanying changes in behaviour and mental abilities. In the mid-20 th century, this was amplified by the study of laboratory animals (particularly rats and monkeys) in which the brain had been deliberately damaged. Later, this rather coarse approach was superceded by the surgical implantation of micro-electrodes into the brain which allowed stimulation of very specific areas and the observation of the associated behavioural effects. In the later part of the 20 th century, the development of two techniques in particular revolutionised our understanding of human brain activity: • magnetic resonance imaging (MRI) - uses powerful electro-magnets to align some atomic nuclei in the body (especially those of hydrogen atoms in water), and then radio frequency fields to alter the direction of this alignment. The effect is to induce rotating magnetic fields which can be detected by a scanner. In the study of brain activity, Functional MRI (fMRI) is used to give an indication of changing blood flow to different parts of the brain, and hence relative levels of neural activity. As it uses magnetic fields and radio signals to detect activity, and not radioactive emissions, MRI carries much less risk than PET; • positron emission tomography (PET) - this is a form of nuclear imaging which detects radiation emitted from biologically active molecules which have been labelled with isotopes which typically have a half-life of 15mins or less (so after an hour, only 6% is left). In the study of brain function, the most frequently used molecule is a form of glucose labelled with fluorine-18. Scanners detect the emitted radiation and high levels of emission indicate a high level of respiration, and so an area of the brain which is very active. Because of the risks associated with exposure to ionising radiation, PET is mainly restricted to the detection of cancers. To maximise the acquisition of information, PET scans are now usually combined with MRI scans. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 2.4 Learning points Summary Perception • Perception is the process by which the brain analyses and makes sense of incoming sensory information. • Perception allows us to segregate objects from one another and from their background. • Perception allows us to judge the distance of objects. • Perception allows us to recognise objects. Segregation • The brain organises sensory information into figures (objects) and grounds (background) during perception. • In order to make sense of our environment, the brain organises sensory stimuli into coherent patterns during perception. Perception of distance • Distance is judged in the field, using visual clues such as relative size, superimposition, and relative height. • Binocular disparity is used to judge distance at close range. • Binocular disparity results from the visual field of the left and right eyes being different and, where it overlaps, seeing objects from a slightly different angle. • Perceptual constancy means that as objects get closer and the viewing angle changes, they are still perceived to be the same object. Recognition • Shape is more important than detail in the recognition of objects. • We match observed shapes to shape descriptions stored in memory during perception. • Inference is used to match incomplete information against memorised shape descriptions during perception. • The perception of a stimulus or object is influenced by a perceptual set of past experience, context and expectation. Memory • Memory is the process of storage, retention and retrieval of information. • The information stored in memory includes past experiences, knowledge and thoughts. © H ERIOT-WATT U NIVERSITY 51 52 TOPIC 2. PERCEPTION AND MEMORY Summary Continued • All information entering the brain passes first through Sensory Memory and then enters Short-Term Memory. • Information in Short-Term Memory is either passed into Long-Term Memory or is discarded. Sensory Memory • Sensory Memory retains all input from the sense organs. • Information is retained in Sensory Memory for a few seconds. Short-Term Memory • The memory span of Short-Term Memory (STM) is the number of items that can be stored. • The average memory span for digits is 7 (usual range 5-9). • Information may be retained in STM by rehearsal. • Information is lost from STM by displacement or decay. • The serial position effect is explained as follows: – items at the start of a list are recalled because they have been rehearsed and passed to LTM; – items at the end of a list are recalled because they are still in STM; – items in the middle of the list are not recalled as they have been displaced from STM by later items and have not been transferred to LTM. • Memory span of STM can be increased by chunking. • Chunking is the grouping of separate items of information so they pass into memory as a single unit. • Working Memory is an extension of STM. • Working Memory is used to perform cognitive tasks (e.g. comprehension). reasoning, Long-Term memory • Encoding is the process by which information is converted into a form which can be passed from STM to LTM. • LTM can store unlimited information indefinitely. • Information can be transferred from STM to LTM by rehearsal, organisation or elaboration of meaning. • Rehearsal involves repetition of the information to be memorised. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY Summary Continued • Organisation involves grouping the information with other similar items. • Elaboration involves linking the information with emotions, images and other memories. • Repetition produces shallow encoding of information. • Organisation of information into groups with similar properties produces relational encoding of information. • Elaboration by linking with previous memories produces elaborative encoding of information. • Relational and elaborative encoding are more permanent than shallow encoding. • Retrieval is the recall from LTM to the Working Memory of STM. • Retrieval is aided by the use of contextual cues which relate to the conditions under which the memory was formed. Location of memory • LTM can be sub-divided according to the type of information stored. • Episodic memory stores events and experiences. • Semantic memory stores facts and concepts. • Procedural memory stores skills, both motor and cognitive. • Emotional memory stores emotional responses to past events. • Spatial memory stores information about the location of physical objects in space. • The different types of memory are located in different parts of the cerebrum. • Episodic and semantic memory are located in the region of the cerebral cortex where the sensory information was first encoded. • Procedural memories are linked to long-term changes in the motor cortex. • Emotional memories involve links between the cortex and the limbic system. • Spatial memory is located in the hippocampus of the limbic system. © H ERIOT-WATT U NIVERSITY 53 54 TOPIC 2. PERCEPTION AND MEMORY 2.5 Extended response question The activity which follows presents an extended response question similar to the style that you will encounter in the examination. You should have a good understanding of Short-Term Memory before attempting the question. You should give your completed answer to your teacher or tutor for marking, or try to mark it yourself using the suggested marking scheme. Extended response question: Short-Term Memory Give an account of Short-Term Memory under the headings: 15 min A) increasing memory span; (3 marks) B) serial position effect; (5 marks) C) transfer from STM to LTM. (2 marks) .......................................... 2.6 End of topic test End of Topic 2 test Q13: Complete the paragraphs by selecting the correct words from the list, some of which may be used more than once. (14 marks) In the field, distance is judged by visual height. and Relative is used in such as relative refers to the apparent of similar objects, , and height refers to in the image. At close range, binocular viewpoint. , , of objects is also used. This uses the fact that each eye has a We perceive familiar objects in the same way despite changing circumstances, such as , because of perceptual . viewing Word list: angle, constancy, clues, different, dimensions, disparity, overlap, position, relative, size, superimposition. © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY 55 .......................................... Q14: Complete the sentences by matching the parts on the left with the parts on the right. (8 marks) Conversion of information into a form that can be passed into LTM: contextual. Repetition of information: retrieval. Grouping of items of information which are similar: shallow. Linking information with emotions and images: organisation and elaboration. Type of encoding produced by repetition: rehearsal. Forms more permanent memories than shallow encoding: encoding. Recall from LTM to Working Memory: elaboration. Cues which relate to the conditions under which a memory was formed: .......................................... organisation. Q15: Complete the sentences by matching the parts on the left with the parts on the right. (10 marks) Memory of events and experiences: procedural. Memory of facts and concepts: emotional. Memory of motor and cognitive skills: cerebrum. Memory of how we felt about past events: sensory regions of cortex. Memory of the location of objects: cortex and limbic system. Part of the brain where all memory is located: spatial. Memories of events and facts are stored: hippocampus. Skills memories linked to long-term changes: episodic. Our feelings about past events involve links between them: motor cortex. Part of the limbic system: semantic. .......................................... © H ERIOT-WATT U NIVERSITY 56 TOPIC 2. PERCEPTION AND MEMORY Enter a word to complete each of the definitions. Q16: The analysis and interpretation of sensory information is called (1 mark) .......................................... Q17: The brain organises sensory information into objects called (1 mark) .......................................... Q18: The background to these objects is called the (1 mark) .......................................... Q19: The type of patterns of sensory information organised by the brain is (1 mark) .......................................... Q20: The organisation of sensory information into object and background is called (1 mark) .......................................... Select the correct words to match the statements. Q21: Most important in the recognition of objects: (1 mark) a) colour b) shape c) size .......................................... Q22: Matching descriptions stored in memory: (1 mark) a) expectation b) perception c) recognition .......................................... Q23: Matching incomplete information against descriptions in memory: (1 mark) a) expectation b) experience c) inference .......................................... Q24: Not part of a perceptual set: (1 mark) a) context b) expectation c) inference .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 2. PERCEPTION AND MEMORY Q25: What is meant by the term 'memory'? (1 mark) .......................................... Q26: Through which aspect of memory does all information entering the brain first pass? (1 mark) .......................................... Q27: Which type of memory holds information for a few seconds but retains all visual or auditory input? (1 mark) .......................................... Q28: The number of items held in Working Memory is called the (1 mark) .......................................... Q29: Information is retained in Short-Term Memory by the process of (1 mark) .......................................... Q30: The process by which the storage of new memories causes the loss of other memories is called (1 mark) .......................................... Q31: Without repetition, information is lost from memory by the process of (1 mark) .......................................... Q32: Short-Term Memory can be improved using the technique of (1 mark) .......................................... Q33: Cognitive tasks involving information in Short-Term Memory are performed by the (1 mark) .......................................... Q34: Complete the sentences by matching the parts on the left with the parts on the right. .......................................... .......................................... © H ERIOT-WATT U NIVERSITY 57 58 TOPIC 2. PERCEPTION AND MEMORY © H ERIOT-WATT U NIVERSITY 59 Topic 3 Neurons, neurotransmitters and neural pathways Contents 3.1 Neurons . . . . . . . . . . . . . . . . . . . . 3.1.1 Introduction . . . . . . . . . . . . . . 3.1.2 Structure of neurons . . . . . . . . . 3.1.3 Function of the cell body . . . . . . . 3.1.4 Function of dendrites . . . . . . . . 3.1.5 Function of axons . . . . . . . . . . 3.2 Glial cells and myelination . . . . . . . . . . 3.2.1 Glial cells . . . . . . . . . . . . . . . 3.2.2 Myelination . . . . . . . . . . . . . . 3.3 Neurotransmitters . . . . . . . . . . . . . . 3.3.1 Chemical transmission at synapses 3.3.2 Neurotransmitters . . . . . . . . . . 3.3.3 Neurotransmitter threshold . . . . . 3.3.4 Removal of neurotransmitters . . . . 3.3.5 Excitatory and inhibitory transmitters 3.4 Neural pathways . . . . . . . . . . . . . . . 3.4.1 A converging pathway . . . . . . . . 3.4.2 A diverging pathway . . . . . . . . . 3.4.3 A reverberating pathway . . . . . . . 3.4.4 Plasticity of response . . . . . . . . 3.5 Learning points . . . . . . . . . . . . . . . . 3.6 Extended response question . . . . . . . . 3.7 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 60 61 65 66 67 69 69 70 72 73 74 74 74 76 77 79 79 79 80 83 85 86 Learning Objectives By the end of this topic, you should be able to: • describe the structure and function of the cells of the nervous system; • explain the way in which information is passed on in the nervous system; • describe the ways in which neurons are linked together in pathways and explain the effect of such groupings. 60 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.1 Neurons Nerve tissue comprises neurons, which transmit nerve impulses, and glial cells, which provide support for neurons. This first section considers neurons. 3.1.1 Introduction Any multi-cellular organism requires some method of passing information between cells to enable coordinated activity to take place. Cells mainly communicate with one another by means of chemicals, which travel between them in a liquid medium. When this involves the secretion of the messenger chemical into a blood stream, this is known as the endocrine system and the chemicals are hormones. If carried in a double circulation system, such as that of a mammal or a bird, this will deliver the chemical to all parts of the body in a matter of seconds. In a higher plant, such as an oak tree, things take a little longer. Although efficient, endocrine communication is not suited to dealing with a sudden emergency. All cells have a very small electrical potential difference across the cell membrane. Neurons create a temporary reversal of this potential difference to send a signal along the cell (which can be very elongated) at between 1 and 100 m.s -1 . The junction between neurons is called a synapse, at the centre of which is a gap called the synaptic cleft. By reducing the distance between adjacent neurons to 20-40nm, the diffusion of the chemical carrying the message between cells also takes place very quickly. Neurons thus provide the fast transfer of information around the body that enables complex animals to behave in the amazingly diverse and sophisticated ways that we observe. © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.1.2 Structure of neurons 61 Learning Objective By the end of this section, you should be able to: • describe that the nervous system consists of a range of different cells called neurons; • explain that neurons are grouped together to form the brain and spinal cord of the central nervous system (CNS), and the nerves of the peripheral nervous system; • state that neurons receive and transmit impulses (a form of electrical signal); • state that there are three main types of neuron: motor neurons and interneurons; sensory neurons, • state that sensory neurons carry impulses into the CNS from sense organs; • state that motor neurons carry impulses out from the CNS to effectors such as muscles and glands; • state that interneurons are found in the CNS where they connect with other neurons; • describe a neuron as consisting of a cell body with protruding fibres in the form of one axon and many dendrites. Neurons are the specialised cells which carry nervous impulses around the body, allowing the senses to communicate with the brain and the brain to coordinate responses. The human nervous system (NS) comprises some 10 12 of these cells which are typically only a few micrometres in diameter. There are many different types of neuron, of which we study three here: • sensory neurons, which carry impulses into the Central Nervous System (CNS) from sense organs; • motor neurons, which carry impulses out from the CNS to effectors such as muscles and glands; • interneurons (also called relay or association neurons), which exist in many forms and are found in the CNS where they connect with other neurons. These neurons are grouped together to form the brain and spinal cord of the CNS, and the nerves of the Peripheral Nervous System. Each neuron consists of a cell body, much like the typical animal cell in structure, with an axon extending from the cytoplasm. These can be up to a metre long in humans although they are often much shorter; in the CNS they are very short. The axon is wrapped in a sheath of lipoprotein called myelin. Impulses begin in the dendrites, which are projections from the axon in sensory neurons, and from the cell body of motor neurons. The impulses then travel towards the cell body and on to the axon terminals at the end of the axon. © H ERIOT-WATT U NIVERSITY 62 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS The cell bodies of sensory neurons are located within the vertebrae, which surround and protect the spinal cord. In motor neurons the cell body lies within the central grey matter of the spinal cord, surrounded by the outer white matter, which is composed of axons with their fatty myelin sheaths. The grey matter of the brain similarly consists mainly of cell bodies and dendrites, whilst the white matter consists of axons. The diagram shows how these cells are organised in a simple reflex. A simple reflex Neurons themselves are specialised according to function. To achieve this, they require slight adaptations in structure. Look at the different structures of sensory, motor and inter-neurons. Sensory neurons are adapted to take messages from sensory receptors in the skin and the specialised sense organs (the nose, tongue and ears) to the brain. Sensory neuron Note that the cell body sits part way along the axon and that there are no dendrites on the cell body. © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Motor neurons have many dendrites protruding from the cell body, which is end-on to the axon. Motor neuron If a motor neuron that links the spinal cord with the foot was enlarged until the cell body was the size of a tennis ball, its dendrites would fill your living room and the axon would be 1.6km long, yet only 13mm in diameter. Axons vary between 0.2 and 300μm (1 micrometre ≡ 1μm ≡ 1 x 10-6 m) in length. A human axon is typically 50μm in diameter, excluding the myelin sheath. In a large mammal, a single motor neuron that links the spinal cord with a digit might be 2 metres long, though the synapses between one neuron and its neighbour are around 200 x 10 -9 metres in size. Interneurons typically have a large number of dendrites and a very short axon, although they have a wide variety of different structures based on this basic pattern. Interneuron Note that the axon is very short and lacks myelination. © H ERIOT-WATT U NIVERSITY 63 64 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Structure of neurons: Question Q1: Complete the diagram using the labels provided. 15 min .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.1.3 Function of the cell body 65 Learning Objective By the end of this section, you should be able to: • explain that the cell body contains the nucleus with its DNA which controls the activity of the cell. A neuron is a specialised cell, but it starts life as a normal animal cell. A generalised animal/plant cell is shown below. Make sure you can label and describe all the parts of an animal cell, espeically the nucleus, cytoplasm, ribosomes and mitochondria. A generalised cell Neurons, like muscle cells, develop long extensions to help them fulfil their functions. A single neuron may be a metre long in a human. © H ERIOT-WATT U NIVERSITY 66 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Cell bodies The cell body contains a nucleus and cytoplasm like a normal cell. It has many ribosomes that make the proteins which act as neurotransmitters at the gaps, or synapses, between one neuron and the next. These tiny gaps act like switches and may allow or prevent signals passing from one neuron to the next. The messengers which 'jump' between the gaps and pass the signals are called neurotransmitters. There are also many mitochondria that provide the energy for active transport, which helps maintain electrical potential and reabsorb neurotransmitters. The nucleus controls the activity of the cell and carries the DNA coding for the formation of all proteins in the cell, including those required in the axon terminals which may be up to a metre distant from the cell body. There is, therefore, a rapid transport system of microtubules to convey the proteins vital to the functioning the axon terminals. 3.1.4 Function of dendrites Learning Objective By the end of this section, you should be able to: • state that dendrites are stimulated by sense organs or other neurons to carry impulses towards the cell body. The diagram below shows the general structure of a neuron. The dendrites are projections from the cell body or, in some sensory neurons, from the forward extension of the axon (sometimes called the dendron). Their function is to form synapses with the axon terminals of other neurons or with cells in sense organs, and to convey impulses towards the cell body. General neuron structure showing dendrites © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.1.5 Function of axons 67 Learning Objective By the end of this section, you should be able to: • state that the axon ends in many divisions called axon terminals; • state that the axon carries impulses in one direction from the dendrites to the axon terminals; • explain that myelin surrounds the axons, greatly increasing the speed of conduction of impulses along the nerve fibres as impulses jump from node to node in the myelin sheath. Each neuron has only a single axon, which ultimately divides to form several axon terminals. The axon carries the impulse away from the cell body towards the axon terminals, which form synapses with the dendrites of the next neurons on the neural pathway or with effectors such as glands and muscles (neuromuscular junctions). General neuron structure showing the axon with its myelin sheath Axons are bundled together to form the nerves that we commonly speak of. © H ERIOT-WATT U NIVERSITY 68 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Nerve bundle with many axons Electrical impulses transmit signals along these axons. Neurotransmitters take the information from the dendrite of one cell across the synapse, or gap, to the dendrite of the next axon. The axons must not leak out signals otherwise confusion would arise as signals jump from the axon terminal of one neuron to the dendrite of the next neuron. Additionally, if the signals leaked out, they would become weaker and weaker as they travelled along the axons; this occurs in people who suffer from illnesses such as MS. Consequently, they are insulated by layers of myelin sheath, which wraps around the axon like a Swiss roll. Neurons: Question Q2: Complete the sentences by matching the parts on the left with the parts on the right. Neurons: cell body, axon and dendrites. Neurons receive and transmit: dendrites. Neurons comprise: neuromuscular. DNA in the cell body codes for: type of nerve cell. Carry impulses towards the cell body: synaptic cleft. Axon terminals and dendrites form: impulses. The gap between an axon terminal and a dendrite: all cell proteins. Junction between an axon and a synapses. muscle fibre: .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.2 69 Glial cells and myelination Learning Objective By the end of this section, you should be able to: • state that glial cells support and maintain neurons by: – producing the myelin sheath; – acting homeostatically to maintain a constant environment around the neuron; – removing debris by phagocytosis. • state that myelination begins in the foetus and continues into adolescence; • explain that incomplete myelination causes an infant's response to stimuli to be slower and less co-ordinated than that of older children or adults; • explain that certain diseases cause a loss of co-ordination by destroying the myelin sheath, e.g. multiple sclerosis. This section considers glial cells, the other important type of cell in nerve tissues. 3.2.1 Glial cells Although they are not neurons, glial cells (also known as neuroglia) are an essential part of the nervous system. Just as white blood cells are a diverse group of cells, neuroglia are also a class of cells, each form of which carries out a different function. One type is found in the central nervous system. If damage occurs to the neurons, they multiply and remove debris by phagocytosis. Others constantly sample and homeostatically regulate the chemical environment of the neurons, removing excess ions and recycling neurotransmitters so that the neuron functions in very constant conditions. They are also a key element in the blood-brain barrier, which ensures that only small molecules, such as O2 , CO2 , and hormones can pass freely between the blood and the cerebrospinal fluid which bathes the brain. All other molecules, e.g. glucose, must be actively transported if they are to enter the brain. Other types of glial cells, including Schwann cells, are responsible for myelination. These cells closely surround and give physical support to the axon. Although the term 'nerve cell' is often used when referring to neurons, glial cells are also important nerve cells and so an effort should be made to always use the correct term for the neuron. © H ERIOT-WATT U NIVERSITY 70 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Glial cells: Question Q3: 15 min Complete the paragraph about glial cells by using words from the list below. The nervous system contains more than neurons. About 15% of the cells in the cells which support and maintain the neurons in several ways. cerebrum are Some of them monitor the conditions surrounding the neurons and maintain a constant . Others help repair damage by removing cell debris by environment by . Another cell of this type, called the Schwann cell, wraps lipoprotein membrane around sheath, the effect of which is to greatly the axons forming the , conduction of impulses. Starting well before birth, this process, known as . This explains why an infant's responses to stimuli are less continues until than an adult's. Word list: accelerate, adolescence, coordinated, glial, homeostasis, myelination, myelin, phagocytosis. .......................................... 3.2.2 Myelination The myelin is pinched into sausage-shaped pieces at short intervals. The constrictions are called nodes (nodes of Ranvier). These have a very important function because they speed up nervous transmission by a factor of 50. Rather than electrical impulses travelling along axons at 2 metres per second, they move along much faster, jumping from node to node. The myelin sheath stops sodium and potassium ions from crossing the membrane so the impulse 'rushes' along to the tiny gap in the myelin where ion exchange can occur. A myelinated fibre of diameter 18μm and with nodes at 1.5mm apart will conduct at 100m/s. The larger the diameter, the faster the impulse travels. Neurons fire on an 'all-or-nothing' basis. If an impulse arriving causes enough of an effect at the next neuron, it will 'fire'. If the impulse is weak, the next neuron in the circuit will not fire. However, if a very strong signal arrives, it will not make the signal passing to the next neuron any larger. The signals from several neurons which have their synapses together at any adjacent neuron may have summative or, on the other hand, competitive 'inhibitory' effects. It is repeated firing due to successive signals which causes a stronger effect, such as a tighter flexing of a muscle. When the impulse leaks out due to lack of complete myelination, as in MS, repeated firing cannot occur and full contraction becomes impossible, leading to a weak grip for example. It is interesting to note that it was this 'all-or-nothing' status of the nervous system, discovered by biologists a century ago, which led to the development of the binary revolution called computing. Slides and micrographs of neurons 15 min To examine slides and micrographs of neurons, use a computer to perform a Google image search for "micrograph neurone". .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Myelination Myelination begins during the fourth month of pregnancy and continues into adolescence. As a result, a newly born infant has an immature nervous system. This explains the initial lack of coordination of responses. The 'bones' of the skull are incompletely closed, leaving a gap called the fontanelle to allow the brain to continue to grow for several months after birth. The skeleton is initially made of cartilage. The flexibility of cartilage, and the mobile nature of the separate 'bones' of the skull, allow easy passage down the birth canal. Crucially, continued growth of the nervous system, particularly of the brain, is accommodated. The fontanelle closes between the ages of 18 months and two years. (Recent research has shown that further re-organisation of the brain seems to occur in the late teens, especially in boys. This explains why we feel so clumsy for a wee while, then!) Infancy Myelination of axons proceeds rapidly during the months after birth. This process is essential. The axons wrap themselves around lipoprotein derived from cell membranes. Lack of myelin can have severe consequences. In Muscular Sclerosis (MS), there is patchy loss of myelin and this leads to delayed or blocked conduction of nervous impulses. There are some unmyelinated peripheral neurons that are only encased in cytoplasm and these are less insulated from leakage of electrical conduction. In addition to carrying impulses less securely, they are 50 times slower at carrying impulses because of this lack of insulation. Although impulses do not travel as fast as electricity, or light and sound waves, they can still achieve speeds of up to 100 metres per second. The speed of transmission increases with temperature, giving so-called 'warm-blooded' animals a great advantage over their cold-blooded competitors. Nerve Transmission Myelination leads to small nodes forming along an axon. Each node is around 1μm in diameter and approximately 1mm from its neighbour. Electrical impulses are carried along axons because the membrane becomes depolarised and repolarised by active exchange of ions. Depolarisation can 'jump' from one node to the next in myelinated neurons, whereas it can only flow smoothly and slowly along unmyelinated neurons. As new nervous tissue grows, the number of synapses formed between adjacent neurons multiplies exponentially. It is this massive increase in number of synapses and the ability to repeatedly fire neurotransmitters across them by means of rehearsal or repetition that leads to the impressive memory feats and communication skills of humans. Myelination: Question Q4: A myelinated fibre, 18μm in diameter, carries an impulse at 100m/s. Assuming that an impulse goes a quarter as fast through a fibre (axon) half as wide, how many seconds does it take for an impulse to travel 2m through an axon of diameter 9μm? .......................................... © H ERIOT-WATT U NIVERSITY 71 72 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.3 Neurotransmitters Learning Objective By the end of this section, you should be able to: • state that neurotransmitters are chemicals which relay signals from neuron to neuron in the central and peripheral nervous systems; • state that neurotransmitters also transmit signals between neurons and other target cells e.g. muscle fibres, endocrine glands; • state that neurotransmitters are secreted into the gap (the synaptic cleft) between the neuron and the next cell; • state that neurotransmitters are stored in vesicles; • state that the arrival of an impulse causes the release of the neurotransmitters; • state that neurotransmitters diffuse across the synaptic cleft and bind to receptors on dendrites; • state that, if sufficient neurotransmitters attach to the receptors, a threshold is reached and an impulse is triggered; • state that signals may be excitatory or inhibitory, depending only on the receptor on the receiving dendrite and not on the type of neurotransmitter; • explain that neurotransmitters must be immediately removed to prevent continuous stimulation of the post-synaptic neurons; • state that there is a wide range of different chemicals which act as neurotransmitters, e.g. noradrenalin and acetylcholine; • state that neurotransmitters are either removed by enzyme action (e.g. acetylcholine) or by re-uptake (e.g. noradrenalin); • explain that synapses can filter out weak impulses arising from insufficient secretion of a neurotransmitter; • explain that, by summation, a series of weak stimuli can combine to reach the firing threshold in the post-synaptic neuron. Neurotransmitters comprise a wide range of chemicals (often amino acids or related compounds) which transfer the 'message' of the impulse across the gap between neurons at the synapse or from a neuron to an effector organ such as an endocrine gland or a muscle. A synapse between a motor neuron and a muscle cell is called a neuromuscular junction. © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Neuromuscular junction Synapses: chemical transmission by neurotransmitters It is easy to think of synapses simply as gaps between neurons. We cannot have each muscle and sense organ supplied by its own single neuron from the brain so gaps are inevitable. Synapses, however, are not merely junctions. They act as filters and must cope with rapid and repeated firing of neurons. How do they manage this? 3.3.1 Chemical transmission at synapses Each neuron might be connected to hundreds of other neurons. The dendrites almost touch. There are thousands of possible permutations of interconnections, each separated only by a tiny gap. Chemicals called neurotransmitters are secreted at each synapse. They cross the gap to the post-synaptic dendrite. Will they excite it enough to fire? Will they inhibit it, effectively switching it off? It all depends on where the neurotransmitter arrives. Synapse anatomy © H ERIOT-WATT U NIVERSITY 73 74 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.3.2 Neurotransmitters Chemical messengers, called neurotransmitters, travel across the synaptic cleft to communicate impulses to the next neuron. The neurotransmitters acetylcholine and noradrenaline are contained in vesicles in dendrites until they are needed. This ensures that resources are not wasted and that chemicals are not promoting unwanted reactions indiscriminately. An impulse arriving at a synaptic terminal stimulates the synaptic vesicles to secrete their contents by exocytosis into the synaptic cleft. These neurotransmitters are recognised by receptors on the post-synaptic dendrite. Neurotransmitters: Questions Q5: Give two reasons why neurotransmitters are contained in vesicles. .......................................... Q6: Why are mitochondria and ribosomes found in large numbers in the pre-synaptic dendrites? .......................................... 3.3.3 Neurotransmitter threshold Neurotransmitters work on the basis that the neuron will 'fire' if a certain threshold is reached. Each neurotransmitter binds to a specific receptor molecule on the adjacent neuron in a way similar to the lock and key mechanism of enzymes. It is the receptor which determines whether signals are stimulatory or inhibitory. A tiny quantity of neurotransmitter has no effect, but a very large quantity has no extra effect. Thus weak signals are filtered out, but strong signals do not paralyse the nervous system with excessive contractions. We should remember that each neuron may receive thousands of synapses from a network of incoming neurons. As a result, a series of weak stimuli can combine to reach the firing threshold in the post-synaptic neuron, a process known as summation. 3.3.4 Removal of neurotransmitters When acetylcholine is released at the synaptic cleft, it binds to the receptors on the dendrites of the receiving neuron. If the number of excitatory signals exceeds the number of inhibitory signals, the neuron will 'fire', carrying an impulse to the next synapse, but this only occurs if a certain threshold is reached. To avoid repeated contractions from the same stimulus, acetylcholine is immediately destroyed by an enzyme called acetylcholinesterase. This process is called degradation. This enzyme was first discovered in an unfortunate individual who had no acetylcholinesterase owing to a genetic mutation. The breakdown products are reabsorbed by active transport (see below) using energy from the adjacent mitochondria. Noradrenaline also needs to be removed, but is not degraded. It is reabsorbed back into the synaptic ending whence it came. This process is called re-uptake. © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Diffusion and active transport: Comparison This activity illustrates the difference between diffusion (a process driven solely by differences in concentration) and active transport (which uses energy from ATP to move materials across membranes, even against the concentration gradient). Diffusion across a membrane is a passive process. The net movement of molecules across a membrane will stop when the concentration of molecules is the same on both sides of the membrane, although movement continues. Diffusion across a membrane Active transport across a membrane is a process that uses energy. This means that a concentration gradient can build up across the membrane, which would not be possible with diffusion. Active transport across a membrane .......................................... © H ERIOT-WATT U NIVERSITY 75 76 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.3.5 Excitatory and inhibitory transmitters Noradrenaline and acetylcholine do not by themselves have opposite effects. They act on different receptor structures, which then mediate their effects on the organs of the body. It is the receptors in the receiving neuron which are primed to have opposite effects. Think of yourself as a neurotransmitter acting on light switches in a room. Your presence can move a switch up or down (neurotransmitter-receptor binding), but which light goes on, or off, (the effect of the transmitter) depends on how the switch is wired to the lights. Acetylcholine from a parasympathetic neuron in the heart will inhibit heart rate and volume. However, acetylcholine in the alimentary canal promotes peristalsis. Some acetylcholine receptors also respond to nicotine from cigarettes, often leading to tobacco addiction in those who smoke. They can also be blocked temporarily by anaesthetics called muscle blockers (relaxants). © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.4 77 Neural pathways Learning Objective By the end of this section, you should be able to: • state that a converging pathway is where several neurons pass messages on to a single neuron; • state that a converging pathway increases the sensitivity to both excitatory and inhibitory signals; • state that rods in the retina are an example of a converging pathway; • state that a diverging pathway is where a single neuron passes messages on to several neurons; • state that a diverging pathway influences several neurons or tissues at the same time; • state that fine motor control in the fingers is an example of a diverging pathway; • state that a reverberating pathway is where neurons later in the pathway synapse with earlier ones, sending the impulse back through the circuit; • state that the wake-sleep cycle is an example of a reverberating pathway; • state that new neural pathways can be developed to: – create new responses; – bypass areas of brain damage; – suppress reflexes; – suppress responses to sensory impulses. • state that the development of new neural pathways creates a plasticity of response. The multiplicity of neuron connections confers further advantages. In some cases, converging pathways increase the strength of a signal, whilst in others, diverging pathways allow a signal from a specific area to be distributed to a group of neurons. In reverberating pathways, positive feedback causes continuous stimulation of the neurons. © H ERIOT-WATT U NIVERSITY 78 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Neural pathways: Comparison Convergent pathway Divergent pathway Reverberating pathway .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.4.1 A converging pathway In the retina of the human eye, there are cone-shaped neurons which can only be fired by a high intensity of light. They respond to colour and only fire in bright light. Their neural pathways show little convergence. Each neuron synapses with one other neuron as it takes the message to the brain. However, rod-shaped neurons take up most of the retina. They are fired by dim light. Thus each has a weak impulse. However, many rods converge to synapse with a single neuron. Summation at the synapses causes the several weak stimuli to fire the neuron, allowing rods to give us a monochrome view in dim light. Notice in the diagram below that the incoming light has to pass through the layer of nerve tissue before reaching the photoreceptor cells. This is an example of 'not-very-intelligent' design! Retina of an eye showing rods and cones 3.4.2 A diverging pathway Fine motor control of the hand is brought about by a single impulse from a neuron in the motor area of the brain. The neuron synapses with a group of neurons which carry the signal on, eventually causing contraction in the groups of skeletal muscles that control the hand and fingers. 3.4.3 A reverberating pathway In some neural pathways, branches of some axons extend backwards towards the source of the impulse, causing the earlier neurons in the pathway to be continuously stimulated. As a result, once stimulated, the pathway continues to stimulate itself. Such pathways are found in the brain-controlling rhythmic activities, such as breathing and the sleep-wake cycle, muscular coordination and consciousness. © H ERIOT-WATT U NIVERSITY 79 80 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.4.4 Plasticity of response After an injury such as a stroke, the brain can adapt, especially if therapy is quickly available. The function of a damaged part may be taken over by another, demonstrating plasticity (adaptability) of function. This is referred to as major plasticity. Minor plasticity refers to occasions when portions of the brain can be temporarily 'shut down'. Examples of the latter include suppressing a reflex sneeze or when workers in a distillery 'ignore' the smell of the mash after a while. This plasticity of response is created by the development of new neural pathways. As a result, the brain can bypass damaged areas, create new responses, and suppress both reflexes and the response to sensory stimuli. Suppressing brain reflexes 5 min Carry out an investigation into the ability of the brain to suppress reflexes or sensory impulses. For example, gently release the air from a balloon into your eye and see if you can suppress reflex blinking. Background information is given below, in case you would like to know how a reflex works, though this is not necessary for the exam. Background information It is interesting to note that special relay neurons exist in the spinal cord to allow shortcircuiting of normal response times in occasions of danger. Relay neurons short-circuit the normal pathway to the brain. The message will continue to travel to the brain, though a response will already have occurred, avoiding danger. In your experiment, you should show that plasticity of response can allow you to over-ride the reflex response. The classic reflex response is obtained by tapping the flexed knee which will kick out involuntarily. © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Reflex action in a knee This apparently artificial reflex is in fact one which helps us regain balance, straightening our legs (and arms) after a trip or slip has caused our legs to bend at the knee. This stimulates the stretch receptors in the quadriceps and triggers the reflex. .......................................... Neural pathways: Questions Q7: Pathway where several neurons pass messages to one: a) converging b) diverging c) reverberating .......................................... Q8: Pathway where a single neuron passes messages on to several: a) converging b) diverging c) reverberating .......................................... Q9: Pathway where messages are passed back to earlier neurons: a) converging b) diverging c) reverberating .......................................... © H ERIOT-WATT U NIVERSITY 81 82 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Q10: Pathway involving rods in the retinas: a) converging b) diverging c) reverberating .......................................... Q11: Pathway giving fine motor control in the fingers: a) converging b) diverging c) reverberating .......................................... Q12: Pathway controlling the wake-sleep cycle: a) converging b) diverging c) reverberating .......................................... Q13: New neural pathways create: a) brain damage b) plasticity .......................................... Q14: New neural pathways bypass: a) brain damage b) plasticity .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.5 Learning points Summary Neurons • The nervous system comprises a range of different cells called neurons. • Neurons are grouped together to form the brain and spinal cord of the central nervous system, and the nerves of the peripheral nervous system. • Neurons receive and transmit impulses (a form of electrical signal). • There are three main types of neuron: sensory neurons, motor neurons and interneurons. • Sensory neurons carry impulses into the Central Nervous System (CNS) from sense organs. • Motor neurons carry impulses out from the CNS to effectors such as muscles and glands. • Interneurons are found in the CNS where they connect with other neurons. • A neuron consists of a cell body with protruding fibres, in the form of one axon and many dendrites. • The cell body contains the nucleus with its DNA, which controls the activity of the cell. • Dendrites are stimulated by sense organs or other neurons to carry impulses towards the cell body. • The axon ends in many divisions called axon terminals. • The axon carries impulses in one direction from the dendrites to the axon terminals. • Myelin surrounds the axons, greatly increasing the speed of conduction of impulses along the nerve fibres as impulses jump from node to node in the myelin sheath. Glial Cells and Myelination • Glial cells support and maintain neurons by: – producing the myelin sheath; – acting homeostatically to maintain a constant environment around the neuron; – removing debris by phagocytosis. • Myelination begins in the foetus and continues into adolescence. • Incomplete myelination causes an infant's response to stimuli to be slower and less co-ordinated than that of older children or adults. © H ERIOT-WATT U NIVERSITY 83 84 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Summary Continued • Certain diseases cause a loss of co-ordination by destroying the myelin sheath, e.g. multiple sclerosis. Neurotransmitters • Neurotransmitters are chemicals which relay signals from neuron to neuron in the central and peripheral nervous systems. • Neurotransmitters also transmit signals between neurons and other target cells, e.g. muscle fibres, endocrine glands. • The junction between neurons is called a synapse. • The gap between one neuron and the next is called the synaptic cleft. • The junction between neurons and muscle cells is called a neuromuscular junction. • Neurotransmitters are secreted into the gap, the synaptic cleft, between the neuron and the next cell. • Neurotransmitters are stored in vesicles. • The arrival of an impulse causes the release of the neurotransmitters. • Neurotransmitters diffuse across the synaptic cleft and bind to receptors on dendrites. • If sufficient neurotransmitters attach to the receptors, a threshold is reached and an impulse is triggered. • Signals may be excitatory or inhibitory, depending only on the receptor on the receiving dendrite and not on the type of neurotransmitter. • Neurotransmitters must be immediately removed to prevent continuous stimulation of the post-synaptic neurons. • There is a wide range of different chemicals which act as neurotransmitters, e.g. noradrenalin and acetylcholine. • Neurotransmitters are either removed by the action of an enzyme (e.g. acetylcholine) or by re-uptake (e.g. noradrenalin). • Synapses can filter out weak impulses arising from insufficient secretion of neurotransmitter. • By summation, a series of weak stimuli can combine to reach the firing threshold in the post-synaptic neuron. Neural Pathways • A converging pathway is where several neurons pass messages on to a single neuron. © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 85 Summary Continued • A converging pathway increases the sensitivity to both excitatory or inhibitory signals. • Rods in the retina are an example of a converging pathway. • A diverging pathway is where a single neuron passes messages on to several neurons. • A diverging pathway influences several neurons or tissues at the same time. • Fine motor control in the fingers is an example of diverging pathways. • A reverberating pathway is where neurons later in the pathway synapse with earlier ones, sending the impulse back through the circuit. • The wake-sleep cycle is an example of a reverberating pathway. • New neural pathways can be developed to: – create new responses; – bypass areas of brain damage; – suppress reflexes; – suppress responses to sensory impulses. • The development of new neural pathways creates a plasticity of response. 3.6 Extended response question The activity which follows presents an extended response question similar to the style that you will encounter in the examination. You should have a good understanding of sensory and motor neurons before attempting the question. You should give your completed answer to your teacher or tutor for marking, or try to mark it yourself using the suggested marking scheme. Extended response question: Sensory and motor neurons Compare and contrast sensory and motor neurons and describe events that occur at a synapse. (10 marks) .......................................... © H ERIOT-WATT U NIVERSITY 15 min 86 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS 3.7 End of topic test End of Topic 3 test Q15: Complete the sentences by matching the parts on the left with the parts on the right. (10 marks) Cells that make up the nervous system: myelin. Transmitted through the nervous system: dendrites. Neurons that carry information into the CNS: motor neurons. Neurons that connect neurons: multiple sclerosis. Neurons that connect the CNS to glands: glial. Carry impulses towards the cell body: axon terminals. Found at the end of the axon: sensory. Increases speed of conduction of impulses: interneurons. Cells which produce the myelin sheath: neurons. impulses. Results from destruction of the myelin sheath: .......................................... Q16: Complete the paragraphs by selecting words from the list. (15 marks) in the CNS and Neurotransmitters are chemicals which relay signals between . The junction between neurons is called a between neurons and and that between neurons and muscle fibres is a junction. Neurotransmitters into synaptic cleft, and across the gap and bind are secreted by of the next neuron. to receptors on the , depending only on the on the Signals may be excitatory or receiving dendrite and not on the type of neurotransmitter. Neurotransmitters must be of the post-synaptic neurons. immediately removed to prevent continuous action (e.g. acetylcholine) or by Neurotransmitters are either removed by ). re-uptake (e.g. Synapses can filter out weak impulses arising from neurotransmitter. secretion of is reached and an If sufficient neurotransmitters attach to the receptors, a a series of weak stimuli can combine to reach the impulse is triggered. By firing threshold in the post-synaptic neuron. Word list: dendrites, diffuse, enzyme, exocytosis, glands, inhibitory, insufficient, neuromuscular, neurons, noradrenalin, receptor, stimulation, summation, synapse, threshold. © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS .......................................... Q17: Complete the sentences by matching the parts on the left with the parts on the right. (9 marks) Several neurons pass messages on to a single neuron: reverberating pathway. An example of a converging pathway: fine motor control. Increased by a converging pathway: converging pathway. A single neuron passes messages on to several neurons: wake-sleep cycle. An example of a diverging pathway: new neural pathways. Neurons later in the pathway synapse with earlier ones: plasticity of response. An example of a reverberating pathway: rods in the retina. New responses are created by their development: sensitivity to signals. Result of the development of new neural pathways: diverging pathway. © H ERIOT-WATT U NIVERSITY 87 88 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS .......................................... The following diagram represents a neuron in the central nervous system. Q18: Identify the structures labelled A. (1 mark) .......................................... Q19: Identify the structure labelled B. (1 mark) .......................................... Q20: Identify the structures labelled C. (1 mark) .......................................... Q21: Where is myelin found on a neuron and what is its function? (2 marks) .......................................... Q22: Which type of neuron conducts impulses between the CNS and effector organs? (1 mark) .......................................... Q23: Interneurons conduct impulses between what? (1 mark) .......................................... Q24: Which type of neuron conducts impulses between sense organs and the CNS? (1 mark) .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS Q25: What is the gap between neurons called? (1 mark) .......................................... Q26: What joins a neuron to a muscle fibre? (1 mark) .......................................... Q27: List three functions of glial cells. (3 marks) .......................................... Q28: Name a disease that destroys the myelin sheath and describe its effect. (2 marks) .......................................... Q29: Where are neurotransmitters stored? (1 mark) .......................................... Q30: What causes the release of neurotransmitters? (1 mark) .......................................... Q31: How do neurotransmitters cross between neurons? (1 mark) .......................................... Q32: What do neurotransmitters bind to? (1 mark) .......................................... Q33: Explain the process of summation. (2 marks) .......................................... Q34: What type of pathway involves several neurons passing messages to one neuron? (1 mark) .......................................... Q35: Give an example of the above type of pathway. (1 mark) .......................................... Q36: Describe the neuron connections of a diverging pathway, an example of which is the fine motor control of the fingers. (1 mark) .......................................... Q37: What type of pathway has neurons later in the pathway that synapse with earlier ones? (1 mark) .......................................... Q38: Give an example of the above type of pathway. (1 mark) .......................................... Q39: What is created by the development of new neural pathways? (1 mark) .......................................... Q40: State two results of the development of new neural pathways. (2 marks) .......................................... .......................................... © H ERIOT-WATT U NIVERSITY 89 90 TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS © H ERIOT-WATT U NIVERSITY 91 Topic 4 Neurotransmitters, mood and behaviour Contents 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Dopamine and the reward pathway . . . . . . . . . . . . . . . . . . . . . . . . . 92 93 4.3 Endorphins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 4.4 Neurotransmitter-related disorders and their treatment . . . . . . . . . . . . . . 4.4.1 Drugs used to treat neurotransmitter-related disorders . . . . . . . . . . 95 96 4.4.2 Neurotransmitter-related disorders and their treatment . . . . . . . . . . 4.5 Mode of action of recreational drugs . . . . . . . . . . . . . . . . . . . . . . . . 96 100 4.5.1 Modes of action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Drug addiction, sensitisation and tolerance . . . . . . . . . . . . . . . . . . . . 101 103 4.7 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 106 4.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Learning Objectives By the end of this topic, you should be able to: • describe the role of dopamine in the reward pathway of the brain; • describe the role of endorphins in the body and the factors which increase their production; • explain how neurotransmitter-related disorders are treated; • explain the mode of action of recreational drugs; • explain the causes of drug addiction and tolerance. 92 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 4.1 Introduction Certain neurotransmitters are particularly associated with the control of mood and behaviour. Mood is a psychological state which is less immediately affected by events than emotion, and less permanent than personality or temperament. Behaviour is the response of an organism to internal and external stimuli. In particular, we will consider the role of the neurotransmitters dopamine and endorphins. While these are both produced and exert an effect outside, as well as inside, the brain, we will restrict our study to their actions in the brain as this is where mood and behaviour are determined. Within the brain, they act not only in the cerebrum, but also in those areas of the mid-brain located in the vicinity of the hypothalamus. Dopamine causes feelings of pleasure and euphoria, and, consequently, any activity which induces dopamine release will tend to be repeated. It is therefore associated with beneficial behaviours, such as eating when hungry. This reward pathway is also used in training and teaching. The action of dopamine, particularly in relation to the reward pathway, is central to many of the other subjects in this topic. Endorphins are a group of at least twenty related chemicals which are produced from the pituitary and the hypothalamus in response to a variety of different stimuli, both physical and mental. They act like the opiate drugs after which they are named, relieving pain and creating a feeling of well-being. This effect is achieved because the increased levels of endorphins in turn stimulate the release of dopamine. A wide range of medical conditions are linked to neurotransmitters, associated both with their under- and over-production. Treatment of these disorders can be complicated by the inability of the neurotransmitters involved to cross the blood-brain barrier. An immense variety of chemicals can affect or imitate the action of neurotransmitters, especially in the reward pathway. Where these are consumed voluntarily because of the mood they induce, they are referred to as recreational drugs. Some are administered medicinally as analgesics to control pain, e.g. morphine, an opioid derived from the Opium Poppy (Papaver somniferum). Exposure to such chemicals, especially if regularly repeated or prolonged, leads to addiction and/or to tolerance. Addiction may be in the form of a physiological or a psychological dependence; tolerance means that increasingly large doses of the chemical are needed to achieve the same effect. In order to put some flesh on the bare bones of the syllabus, the names of some of the enzymes and chemicals involved under the following sections have been included, although they are not required knowledge. These can be quite long and daunting so have been broken up to emphasise the sense of the word - please do not feel patronised by this, and certainly do not try to learn them! © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 4.2 93 Dopamine and the reward pathway Learning Objective By the end of this section, you should be able to: • state that the reward pathway involves neurons which secrete or respond to the neurotransmitter dopamine; • explain that dopamine induces the feeling of pleasure and so reinforces particular behaviours; • explain that the reward pathway is activated by beneficial behaviour, e.g. eating when hungry. A reward is something that when supplied after a piece of behaviour causes that behaviour to be increased or repeated. In training, this is called reinforcement. The neurons of the reward pathway (or system) are located in the mid-brain below the cortex, linking to the areas at the base of the cortex and in the frontal areas of the cortex. The activation of this pathway by beneficial actions such as feeding, sexual contact, or successful aggression, must have developed very early in our evolution. The neurotransmitter principally associated with the reward pathway is dopamine, a relatively simple organic molecule. Dopamine also plays many other roles in the brain, being involved in behaviour, cognition, punishment, motivation, voluntary movement, sleep, mood, attention, learning, and working memory. In the reward pathway, dopamine secretion causes feelings of pleasure and euphoria (happiness and contentment). As all types of reward seem to increase the level of dopamine secretion in the brain, a good definition of a reward would be something that increases dopamine secretion in the reward pathway. Dopamine and the reward pathway: Question Q1: Explain why linking a behaviour with activation of the reward pathway would be important in evolutionary terms. .......................................... © H ERIOT-WATT U NIVERSITY 94 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 4.3 Endorphins Learning Objective By the end of this section, you should be able to: • state that endorphins stimulate the neurons that are involved in reducing the intensity of pain; • explain that increased levels of endorphins are connected with euphoric feelings, appetite modulation and the release of sex hormones; • state that increased endorphin production is associated with severe injury, prolonged continuous exercise, stress and consumption of certain foods. Endorphins are opioid peptides, their name being a strong clue as to their action; it is an amalgam of 'endogenous' and 'morphine', and reflects the fact that their chemical structure and effect are very similar to that of morphine. They are a family of some twenty compounds, which are divided into four types depending on the number of amino acids which they contain, known as alpha- (α), beta- (β), gamma- (γ) and sigma- (σ) endorphins. Of these, the β-endorphins are the most powerful and usually act in the hypothalamus and the pituitary gland. Endorphins attach to opioid receptors on neurons, and, depending on which type and where, they act to reduce pain or to increase euphoria. When they attach to neurons connected to pain receptors (nociceptors) they act as inhibitors, making it less likely that an impulse will be transmitted. Pain is the body's method of telling you that you have done some damage to yourself (headaches and period pains aside); if that damage is severe, then the increased release of endorphins reduces the perceived pain, helping the body to continue to function. Another cause of increased endorphin production is prolonged intense physical activity; intense here meaning that the activity is at a level which makes breathing difficult. One consequence of this is that during a hard training session, it is possible to do damage which only later becomes apparent. Any-one who has played a contact sport will know how sore an injury can seem in the hours after the game ends, even though it was scarcely noticed when it occurred. As endorphin secretion falls, so the impulses in the pain circuits increase. The release of endorphins during such challenging exercise also accounts for the feeling of euphoria experienced afterwards, the 'runner's high'. This is a result of endorphins in the reward system attaching to a different set of opioid receptors, with two outcomes: 1. firstly, the production of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid) is itself inhibited so that impulses are more likely to be generated (GABA is used at the great majority of fast inhibitory synapses in nearly every part of the brain) - many sedative/tranquillising drugs act by enhancing its effects; 2. secondly, the release of dopamine is stimulated. Together these have the effect of greatly increasing the number of impulses in the reward pathway. © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 95 Increased endorphin production has also been linked to the consumption of dark chocolate and spicy food, both of which can become quite addictive. Sexual orgasm also raises endorphin levels, as does the physical closeness of a loved one. Research has also suggested that endorphins play a role in appetite modulation (the control of food consumption), the release of sex hormones, and the body's reaction to stress. Endorphins: Questions Q2: Explain how endorphins reduce the sensation of pain. .......................................... Q3: Give an example, with an explanation, of situations in which pain suppression is beneficial and detrimental. .......................................... Q4: The lack of a satisfying sexual relationship is a major factor in the breakdown of many marriages. What have endorphins got to do with this? .......................................... 4.4 Neurotransmitter-related disorders and their treatment Learning Objective By the end of this section, you should be able to: • state that neurotransmitter-related disorders arise from the under- or overproduction of neurotransmitters, or an imbalance in their production; • state that many of the drugs used to treat these disorders are similar to neurotransmitters; • explain that agonists bind to and stimulate receptors, thus mimicking the neurotransmitter; • explain that antagonists bind to specific receptors, blocking the action of a neurotransmitter; • state that other drugs inhibit the enzymes which degrade neurotransmitters or inhibit re-uptake. Given the wide variety of neurotransmitters and the equal diversity of receptors, it should be unsurprising that there are a considerable range of neurotransmitterrelated disorders, some of which are well known, e.g. Alzheimer's and Parkinson's diseases, others less so, e.g. myasthenia gravis. There can be either over- or underproduction of the neurotransmitter, or an imbalance between the production of different neurotransmitters which operate together (e.g. one being inhibitory and the other excitatory). In other cases, it may be that receptors are blocked so that neurotransmitters cannot bind to them. © H ERIOT-WATT U NIVERSITY 96 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR Consequently, many of the drugs used to treat these conditions are similar to the neurotransmitters which are present in abnormal levels. 4.4.1 Drugs used to treat neurotransmitter-related disorders Among the drugs used to treat these disorders are agonists, antagonists and inhibitors. Agonists are chemicals which mimic the action of a neurotransmitter by binding to its receptor and triggering a response in the corresponding neuron. Drugs which are agonists therefore have a similar effect on the natural agonist, the neurotransmitter. Antagonists are chemicals which bind to the receptors and prevent the neurotransmitter from so doing. Similarly to enzyme inhibitors, they may exert their effect by binding to the active site of the receptor in competition with the neurotransmitter, later separating from the active site. However, some antagonists bind permanently to the active site, preventing it ever subsequently receiving a neurotransmitter. Also, similarly to enzyme inhibitors, some antagonists bind to a part of the receptor other than the active site (an allosteric site), distorting the shape of the active site and preventing neurotransmitters from binding. Enzyme inhibitors may be used either to act on the enzymes which break down the neurotransmitters at the synapse (e.g. acetyl cholin esterase) or which inhibit the re-uptake of the neurotransmitter into the presynaptic neuron (e.g. nor adrenaline/norepinephrine, dopamine). 4.4.2 Neurotransmitter-related disorders and their treatment Although you are not required to know the details of any particular disorders or their treatment, a selection are included below to illustrate why particular drugs are used in each case. It should be remembered that these are common conditions and that we will all come across them at some point in our lives, either personally or in people close to us. It should be understood that there is much current research into these conditions, and that the hypotheses about their causes and the types of treatment available are constantly evolving. Alzheimer's Disease Alzheimer's Disease is the most common cause of dementia, i.e. the premature deterioration of mental faculties. Although most commonly found in people aged 65 or over, it may occasionally develop much earlier. The disease causes a loss of neurons releasing acetylcholine in parts of the cerebral cortex and their associated mid-brain areas, and the development of clumps of amino acids known as plaques. The onset of the condition can be delayed by taking part in intellectual activities such as bridge, chess or music, which not only help to keep the brain active, but also promote social interaction which can be beneficial. There is no cure for the disease at present, but the symptoms can be ameliorated by the use of drugs. One of these is an acetyl cholin esterase inhibitor, which slows the rate at which acetylcholine is degraded, thus maintaining its concentration in the synapses, despite the reduction in its production. © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR Parkinson's Disease Parkinson's Disease is also a degenerative disorder which is most often found in people over 50 years old. The most obvious early symptoms of the disease are shaking, slowness and difficulty of movement. Later, there develop difficulties in mental functioning. One of its causes is the failure of the mid-brain to produce sufficient quantities of dopamine as a result of cell death; towards the end of the course of the disease, nearly three-quarters of the cells in this area may be affected. The overall effect of this is to reduce the flow of impulses to the relevant areas of the cortex, thus increasing the effort required to carry out any given activity. An illustration of Parkinson's disease by William Richard Gowers, which was first published in A Manual of Diseases of the Nervous System (1886) Again, there is currently no cure for the condition, but different drugs can ameliorate the symptoms at any given stage in its development: • L-DOPA (L-3,4-di hydroxy phenylalanine) is the precursor of the inter-related neurotransmitters dopamine, noradrenaline (norepinephrine) and adrenaline (epinephrine) - unlike dopamine, it can cross the blood-brain barrier in significant quantities and so can be injected into the blood stream and reach the brain, where it is converted into dopamine; • dopamine agonists are drugs which attach to the dopamine receptors and trigger impulses in the relevant neurons; • mono amine oxidase inhibitors (MAO-B inhibitors) raise the level of dopamine by acting on the enzyme mono amine oxidase-B, which degrades dopamine in the synapse; • the introduction of adult neural stem cells also represents a possible future treatment - these cells might be able to be introduced into the brain to replace the lost dopamine-secreting neurons. © H ERIOT-WATT U NIVERSITY 97 98 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR Schizophrenia Schizophrenia is a condition which has both genetic and environmental origins. The genetic component involves the action of several genes (multifactorial inheritance), and, as such, can exert a wide range of levels of influence. The prime environmental influence is drug abuse, with cannabis being most important, although cocaine and amphetamines are also strongly implicated. Other environmental factors may play a role, e.g. growing up in an urban environment doubles the likelihood of the condition developing. The typical symptoms of schizophrenia are delusions, disordered thoughts and speech, hallucinations, poor emotional responses, limited speech, social isolation, and lack of motivation. Risperidone (trade name Risperdal) is a common a typical antipsychotic medication used in the treatment of schizophrenia Until recently, it was thought that the neurological cause of schizophrenia was overstimulation of the dopamine receptors in the reward pathway, which was discovered when dopamine antagonist drugs were found to reduce the symptoms of the conditions. Other neurotransmitters (serotonin and glutamate) are now thought to also be involved. Depression Depression in the clinical sense should not be confused with feeling depressed and generally down about the world. Clinical depression has a serious impact on nearly all aspects of life, including relationships, work, sleep, eating and general health. Typically, the symptoms are very low mood, loss of enjoyment, and a sense of worthlessness and guilt. There are several hypotheses about the neurological cause of depression. In particular, a part of the brain stem close to the medulla has been implicated. In this area, serotonin secretion is suggested as having a regulatory role in relation to the other neurotransmitters norepinephrine (noradrenaline) and dopamine so that low serotonin levels will in turn reduce their secretion. This gives the key to one approach to the treatment of depression. Norepinephrine is reabsorbed into the presynaptic axon terminal so that its concentration is raised by drugs, which inhibit its re-uptake. In contrast, dopamine is degraded by enzymes in the synapse so, as in the treatment of Parkinson's Disease, monoamine oxidase (MAO-B) inhibitors are used to increase its concentration. © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 99 Generalised anxiety disorders Generalised anxiety disorders arise from a malfunction in the amygdala regions in the lower central area of each cerebral hemisphere, which are especially concerned with the feelings of fear and anxiety. The condition is characterised by excessive and irrational long-lasting worry about everyday matters, expressing itself in a very wide range of symptoms, including fatigue, breathing difficulties and insomnia. One suggested cause is an imbalance between the neurotransmitters serotonin and norepinephrine. One treatment may be to administer drugs which act as agonists on the gamma-amino butyric acid (GABA) receptors - as GABA is the principal inhibitory neurotransmitter in the body, this has the effect of reducing the stimulation of the neurons in the amygdale. Beta-blockers may also be used as a treatment; as their name implies, they are antagonists which attach to norepinephrine receptors (beta-receptors being one of several types), thus reducing the excitatory effect of the neurotransmitter in the amygdala. Neurotransmitter-related disorders and their treatment: Question Q5: Complete the following table about neurotransmitter-related diseases. Disorder Area of brain affected Neurotransmitters involved Alzheimer's disease Parkinson's disease Schizophrenia Generalised anxiety disorder Depression .......................................... © H ERIOT-WATT U NIVERSITY Drug Treatment 100 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 4.5 Mode of action of recreational drugs Learning Objective By the end of this section, you should be able to: • explain that many recreational drugs affect neurotransmission in the reward pathway; • state that changes in neurochemistry alter mood, cognition, perception and behaviour; • state that recreational drugs may: – stimulate the release of neurotransmitters; – imitate the action of neurotransmitters (agonists); – block the binding of neurotransmitters to their receptors (antagonists); – inhibit the re-uptake of neurotransmitters; – inhibit the enzymatic degradation of neurotransmitters. Drugs which are referred to as recreational are introduced into the body either because they generate pleasurable sensations in of themselves, or because they enhance some other leisure experience. They are also taken in other circumstances, e.g. to help cope with pain or other conditions. The list of chemicals which may be consumed in this way is staggering, and ever expanding. In nearly all cases, the use or possession of these substances is illegal in all countries. Major exceptions are the mild stimulants caffeine (tea, coffee, cocoa) and nicotine (all forms of tobacco), and the depressant ethanol. The use of caffeine is universally unregulated (although proscribed by certain religions), whereas the availability of tobacco and alcohol are usually regulated to some extent. All three are addictive and higher levels of intake are needed to achieve the same effect with continued use (otherwise known as tolerance). So-called 'legal highs' are usually newly synthesised compounds related to existing illegal ones or newly discovered plant substances. The fact that the law has not caught up with them does not indicate that they are safe to consume! Caffeine Caffeine is the mostly widely used psychoactive drug in the world. It does not attract legal restrictions because its stimulant effects are relatively mild. Nevertheless, it does raise blood pressure and disrupts sleep, both of which can lead to serious complications. The classic image below of the effect of caffeine on a spider's efforts to spin a web should give us pause for thought. © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR The effect of caffeine on spider web construction (Noever, R., J. Cronise, and R. A. Relwani. 1995. Using spider-web patterns to determine toxicity. NASA Tech Briefs 19(4)) Ethanol Ethanol is the most widespread drug which is abused. In those countries where its consumption is legal, it is frequently drunk in quantities which are potentially harmful, its long-term consumption causes considerable expense to health services, and the side effects on society of its misuse in terms of violence (domestic and otherwise), crime and loss of working time are huge. It is probable that it only remains legal because its use is so widespread and deeply woven into society that the public support that would be required to make a ban successful would be lacking (as was the case in the USA during the Prohibition years of the 1920s). Tobacco While not having the social dimension of alcohol abuse, smoking tobacco causes serious damage to the smoker's health and to those around them. For this reason, the practice is being increasingly regulated in many parts of world. Unlike ethanol, the nicotine stimulant present in tobacco is not the cause of the health problems, in the sense that the strong addiction which quickly develops does not itself damage health. Rather, it is the actual smoking process which releases a wide range of chemicals which cause cancers, and pulmonary and cardiovascular disease. 4.5.1 Modes of action Most recreational drugs target the brain's reward system, directly or indirectly, and cause it to be flooded with dopamine. When some drugs are taken, they can cause dopamine secretion at levels up to ten times those caused by natural rewards, which strongly motivates people to repeat the act. In a sense, this unnatural over-stimulation of the reward circuit will teach us to abuse drugs. This quickly leads to addiction and so, by definition, all recreational drugs are addictive. As mentioned in an earlier section, while the effect of increased dopamine secretion in the reward pathway is to cause feelings of pleasure and euphoria, dopamine also plays many other roles in the brain, being involved in behaviour, cognition, punishment, motivation, voluntary movement, sleep, mood, attention, learning, and working memory. Consequently, the effects of recreational drugs run far beyond the © H ERIOT-WATT U NIVERSITY 101 102 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR immediate sensations for which they are consumed, having widespread and profound effects on the neurochemistry of the brain. The modes of action of recreational drugs are very similar to those of the drugs used to treat neurotransmitter-related disorders. Stimulating the release of neurotransmitters MDMA (ecstasy) increases the level of the neurotransmitter serotonin by stimulating its release from the synaptic vesicles of neurons, and also inhibiting its re-uptake. The increased secretion of serotonin in the reward pathway in turn stimulates increased production of dopamine and norepinephrine, with their associated euphoric effects. Nicotine binds to certain acetylcholine receptors, stimulating the production of several neurotransmitters including dopamine, which leads to the feelings of euphoria and relaxation, and to addiction. In addition, nicotine stimulates the secretion of adrenaline/epinephrine, thus causing increases in blood pressure, breathing and heart rates, and higher blood sugar levels. Agonists Cannabis attaches to receptors in the neurons of the brain which naturally bind the endocannabinoid neurotransmitters produced in the brain. These receptors are located on the presynaptic neuron. The effect of their binding to cannabis is to suppress the secretion of the inhibitory neurotransmitter GABA, thus increasing stimulation of impulses in the reward pathway. Ethanol acts as an agonist in the central nervous system by binding to the GABA receptors, depressing the flow of impulses in the postsynaptic neuron. The more GABA receptors that are stimulated, the less the chance of an impulse being generated. As GABA is the most widespread neurotransmitter which causes inhibition in the brain, this explains the effect of ethanol on so many different aspects of behaviour. Antagonists Ethanol is also an antagonist of the glutamate receptor NMDA which plays a key role in memory; this is thought to explain the memory loss associated with even quite low levels of alcohol consumption. Inhibition of re-uptake of neurotransmitters Cocaine blocks the re-uptake of serotonin, norepinephrine and dopamine by binding to the transporter molecules that effect their re-absorption into the presynaptic neuron. Consequently, the levels of these chemicals are increased in the synapses, but the actual effect depends on the cells in which the receptors are located. Inhibition of degradation of neurotransmitters As well as nicotine, tobacco smoke contains two monoamine oxidase (MAO) inhibitors. Due to the fact that MAOs are the enzymes which break down the neurotransmitters dopamine, norepinephrine and serotonin, the effect is to boost the euphoric sensation associated with tobacco smoking and cause most of its addictive properties. © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 103 Modes of action: Question Q6: Complete the following table about the mode of action of drugs. Mode of action Drug Neurotransmitter Stimulating the release of neurotransmitters Agonists Antagonists Inhibition of re-uptake of neurotransmitters Inhibition of degradation of neurotransmitters .......................................... 4.6 Drug addiction, sensitisation and tolerance Learning Objective By the end of this section, you should be able to: • state that changes in the number and sensitivity of receptors underlie addiction and tolerance; • state that sensitisation is an increase in the number and sensitivity of receptors; • state that sensitisation results from exposure to antagonist drugs; • state that sensitisation leads to addiction; • state that desensitisation is a decrease in the number and sensitivity of receptors; • state that desensitisation results from exposure to agonist drugs; • state that desensitisation leads to tolerance. Whereas the hyperstimulation of the reward pathway generates a psychological dependence on a drug (often after only a few encounters with it), long-term abuse of a drug leads to changes in the nervous system which make the addiction physiological as well. This may take two forms. © H ERIOT-WATT U NIVERSITY 104 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR • Sensitisation, in which the effect of the drug increases with repeated exposure to it, i.e. the same dose has an increased effect the more often it is taken. At the level of the neurons, the effect results from an increase in the number of receptors and an increase in their sensitivity to the drug. This is caused by drugs that act as antagonists and is associated with the severe withdrawal symptoms experienced when giving up some drugs, e.g. alcohol. • Desensitisation, in which the effect of the drug reduces with repeated exposure. In this case there is a decrease in the number and sensitivity of receptors, and the drugs involved are agonists. The result is drug tolerance, in which increasing doses of the drug are required to achieve the same effect, e.g. heroin. Drug addiction, sensitisation and tolerance: Questions Q7: What underlies drug addiction and tolerance? .......................................... Q8: What causes sensitisation? .......................................... Q9: What drugs cause sensitisation? .......................................... Q10: To what does drug sensitisation contribute? .......................................... Q11: What causes desensitisation? .......................................... Q12: What drugs cause desensitisation? .......................................... Q13: What does desensitisation cause? .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 105 .......................................... 4.7 Learning points Summary Dopamine and the reward pathway • The reward pathway involves neurons which secrete or respond to the neurotransmitter dopamine. • Dopamine induces the feeling of pleasure and so reinforces particular behaviours. • The reward pathway is activated by beneficial behaviour, e.g. eating when hungry. Endorphins • Endorphins stimulate neurons involved in reducing the intensity of pain. • Increased levels of endorphins are connected with euphoric feelings, appetite modulation and the release of sex hormones. • Increased endorphin production is associated with severe injury, prolonged continuous exercise, stress and consumption of certain foods. Neurotransmitter-related disorders and their treatment • Neurotransmitter-related disorders arise from the under- or over-production of neurotransmitters, or an imbalance in their production. • Many of the drugs used to treat these disorders are similar to neurotransmitters. • Agonists bind to neurotransmitter. and stimulate receptors, • Antagonists bind to specific receptors, neurotransmitter. thus mimicking the blocking the action of a • Other drugs inhibit the enzymes which degrade neurotransmitters or inhibit re-uptake. Mode of action of recreational drugs • Many recreational drugs affect neurotransmission in the reward pathway. • Changes in neurochemistry alter mood, cognition, perception and behaviour. • Recreational drugs may: © H ERIOT-WATT U NIVERSITY 106 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR Summary Continued – stimulate the release of neurotransmitters; – imitate the action of neurotransmitters (agonists); – block the binding of neurotransmitters to their receptors (antagonists); – inhibit the re-uptake of neurotransmitters; – inhibit the enzymatic degradation of neurotransmitters. Drug addiction, sensitisation and tolerance • Changes in the number and sensitivity of receptors underlie addiction and tolerance. • Sensitisation is an increase in the number and sensitivity of receptors. • Sensitisation results from exposure to antagonist drugs. • Sensitisation leads to addiction. • Desensitisation is a decrease in the number and sensitivity of receptors. • Desensitisation results from exposure to agonist drugs. • Desensitisation leads to tolerance. 4.8 Extended response question The activity which follows presents an extended response question similar to the style that you will encounter in the examination. You should have a good understanding of the mode of action of recreational drugs before attempting the question. You should give your completed answer to your teacher or tutor for marking, or try to mark it yourself using the suggested marking scheme. Extended response question: The mode of action of recreational drugs 15 min Give an account of the mode of action of recreational drugs (with examples), under the headings: A) effects on the brain; (4 marks) B) modes of action. (6 marks) .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR 4.9 107 End of topic test End of Topic 4 test Q14: Complete the paragraphs by selecting words from the list. (12 marks) , which induces the The reward pathway involves neurons which secrete particular behaviours. The reward pathway is feeling of pleasure and so behaviour. activated by stimulate neurons involved in reducing the intensity of pain. Increased levels . endorphin production of endorphins are connected with appetite is associated with the consumption of certain foods. used to treat neurotransmitter-related disorders are similar to Many of the bind to and stimulate receptors, thus the neurotransmitters. bind to specific receptors, so the action of a neurotransmitter. neurotransmitters, neurotransmitter. Other drugs inhibit the enzymes which or inhibit reuptake. Word list: agonists, antagonists, beneficial, blocking, degrade, dopamine, drugs, endorphins, increased, mimicking, modulation, reinforces. .......................................... Q15: Complete the sentences by matching the parts on the left with the parts on the right. (12 marks) Many recreational drugs affect neurotransmission in the perception and behaviour. Changes in neurochemistry alter mood, cognition, reward pathway. Recreational drugs may stimulate the agonist drugs. Recreational drugs may inhibit the agonists. Drugs which imitate the action of neurotransmitters are tolerance. Drugs which block the binding of neurotransmitters are release of neurotransmitters. An increase in the number and sensitivity of receptors is re-uptake of neurotransmitters. Sensitisation results from exposure to addiction. Sensitisation leads to antagonists. A decrease in the number and sensitivity of receptors is sensitisation. Desensitisation results from exposure to antagonist drugs. Desensitisation leads to desensitisation. © H ERIOT-WATT U NIVERSITY 108 TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR .......................................... Q16: Which neurotransmitters are involved in reducing the intensity of pain? (1 mark) .......................................... Q17: List three factors that increase their production. (3 marks) .......................................... Q18: Which neurotransmitter is involved in the reward pathway? (1 mark) .......................................... Q19: What feelings does activation of the reward pathway engender? (1 mark) .......................................... Q20: What is the difference between agonists and antagonists? (2 marks) .......................................... Q21: State two other ways that drugs may be used to ameliorate neurotransmitterrelated disorders. (2 marks) .......................................... Q22: What part of the brain do recreational drugs affect? (1 mark) .......................................... Q23: What do the changes in neurochemistry caused by recreational drugs alter? (3 marks) .......................................... Q24: List five ways that recreational drugs exert their effect on neurotransmitters. (5 marks) .......................................... Q25: What causes drug sensitisation?(1 mark) .......................................... Q26: What type of drug is involved in sensitisation? (1 mark) .......................................... Q27: What does drug sensitisation lead to? (1 mark) .......................................... Q28: What causes drug desensitisation? (1 mark) .......................................... Q29: What type of drug is involved in desensitisation? (1 mark) .......................................... Q30: What does drug sensitisation lead to? (1 mark) .......................................... © H ERIOT-WATT U NIVERSITY 109 Topic 5 Infant attachment and the effect of communication Contents 5.1 Introduction . . . . . . . . . . . . 5.2 Forms of infant attachment . . . 5.2.1 Infant attachment . . . . . 5.2.2 Imprinting . . . . . . . . . 5.2.3 Social compensation . . . 5.3 Long period of dependency . . . 5.3.1 Parental control methods 5.4 The effect of communication . . . 5.4.1 Information transfer . . . 5.5 Non-verbal communication . . . 5.5.1 Infant bonding . . . . . . 5.5.2 Adult . . . . . . . . . . . . 5.6 Verbal communication . . . . . . 5.6.1 Language differences . . 5.6.2 Acquiring language . . . 5.6.3 Development of language 5.6.4 Mathematical notation . . 5.7 Learning points . . . . . . . . . . 5.8 Extended response question . . 5.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 112 112 113 116 117 118 119 119 120 120 121 123 123 124 124 126 127 128 128 Learning Objectives By the end of this topic, you should be able to: • explain that behaviour is influenced by the inter-related factors of inheritance, maturation and experience; • explain the development and significance of infant attachment; • describe forms of non-verbal communication and explain its role; • explain the nature and significance of verbal communication through language. 110 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 5.1 Introduction Behaviour is the response of an organism to internal and external stimuli. The nature of this response is determined by the interaction of three factors: inheritance, maturation and experience. Inheritance Some aspects of the behaviour of all animals are determined by their genes. Those with a short life history, or, more correctly, short stages in it, simply do not have time to adapt behaviour as a result of their experience of the environment. Consequently, their responses to stimuli must be programmed in their genes. For example, the Large White butterfly, which is common in most of Scotland, has a period of just a few weeks as an adult in which to find a mate and then locate suitable plants on which to lay its eggs. Making a mistake would mean that no offspring will be produced, wasting all of the resources that have gone into getting the animal through the previous stages of its life cycle. Only genes which induce the appropriate behaviour will pass into the next generation. Other insects that live longer as adults do show the ability to learn, albeit within a very limited context. Honey bee workers, which can live from six weeks to six months as adults (depending on the time of year), learn to recognise new scents very quickly, an ability that is obviously related to their task of finding nectar and pollen from whatever flowers are available at a particular time of the year. Humans lie at the other end of this spectrum, with a very high proportion of their behaviour which is developed as a result of experience. Compared to other animals, we live a long time and spend a greater proportion of our lives as juveniles in the care of adults. This provides endless opportunities to observe and copy, and to experiment with alternative responses. Learning to communicate by means of language is a good example; children usually begin to utter intelligible words and simple sentences during their second year, and most children can conduct quite complex conversations by the age of three. This is an ability that our closest Primate relatives, the chimpanzees, do not possess. At the simplest level of human behaviour are the reflexes, e.g. knee jerk (assisting the regaining of balance) or blinking (protecting the eye). These are rapid, automatic, protective responses that are common to all humans, and many are present from birth. Some of these are only found in the first few months of life, e.g. the palmar grasp reflex, by which the baby curls its fingers tightly around any object placed against its palm. It is now thought that genetics plays a significant role in much more of our behaviour than was previously imagined, contributing to many of our decisions in life (e.g. choice of mate). Maturation As mentioned in the previous section concerning the structure of the nervous system, the presence of a myelin sheath greatly increases the rate of impulse transmission by neurons. In newborn infants, the degree of myelination is relatively low; with the passing months, more and more neurons develop the myelin sheath, and thus reactions become much faster. This accounts for the developmental stages observed as infants progress from sitting, to crawling, standing, and eventually walking. Also, the slow development of myelination in the hippocampus explains why we do not have memories from our first © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION two years of life. The profound physiological changes associated with puberty are likewise expressed in behaviour. This involves not just the obvious interest in matters sexual, but also changing tastes. Children generally like sweet things, whereas adults are more likely to prefer sharper tastes, e.g. mustard or olives. Environment If it is accepted that humans depend for the development of a large part of their behaviour on learning, i.e. changing behaviour in the light of experience, then it follows that the nature of that experience will influence the behaviour that ensues. Two examples illustrate this. 1. As mentioned above, children usually start to talk by the age of two, and by three have quite a complex grasp of their language. Of course, in different countries and cultures, children learn different languages. If identical twins are separated at birth as a result of some tragedy, and subsequently reared in different cultures, they learn different languages. Humans possess a genetically determined ability to learn language, but the actual tongue that is learned depends on the child's experience. 2. In the same way, all human cultures have developed music, and all humans have (to a varied extent, admittedly) the ability to develop musical skills. Most commonly, that is expressed through song, but could equally be by means of the ability to play musical instruments, some of which are closely associated with one culture, e.g. the didgeridoo, which is associated with the Australian Aboriginal people, the balalaika with Russia, and the bagpipes with Scotland (and Brittany, the Basque country, and several other places, including parts of England!). An Estonian bagpiper © H ERIOT-WATT U NIVERSITY 111 112 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 5.2 Forms of infant attachment Learning Objective By the end of this section, you should be able to: • explain that early infant attachment is important in laying the foundation for the future formation of stable relationships; • state that attachment becomes evident between six and nine months after birth; • explain the 'strange situation' procedure; • describe the responses to the 'strange situation' procedure as secure and insecure attachment, detachment, anger, and inconsistent responses; • state that infants who form secure attachments are more likely to investigate their immediate environment, which helps the development of their cognitive abilities. In all mammalian species, the youngster is instantly identified as such. A young wild pig has a short snout and a striped body with a curly tail, as well as being much smaller than an adult. A red deer calf has a dappled coat. Somehow, these attributes invite caring in the parent. Furthermore, they can prevent a big, ugly carnivore which hasn't eaten for four days from seeing a small relative as a tender meal! Small, furry animals look cute and evoke feelings of parenting. Thus, there is often strong bonding between humans and their pets, and between youngsters and cuddly toys. Is this more apparent in girls than in boys? If you think of a human child, you think of a head that is greatly out of proportion to the small limbs, a small nose, large eyes, and a very affectionate personality. These features have not evolved by accident. Nor have the ways in which a baby communicates. Crying, clinging and suckling all communicate dependency. A strong, mutual, emotional attachment develops between the baby and its carers. The mother, or mother-figure, in particular must be very alert to read these signals from her baby. The child cannot talk, but is still very active in communicating its needs and desires. Infant attachment develops, at first indiscriminately, but often becoming specific to one parent or another at different times during the child's development. 5.2.1 Infant attachment Infant attachment offers time for a child to observe closely, and to learn. When the child is facing a parent, it can observe and imitate facial expressions, body language and lip movements that form words. When facing a third party, the child observes and copies reactions to these cues. Thus, a long period of dependency, part of which occurs while the brain continues to grow, allows opportunities to learn communication, social and language skills in a protective environment. Informed decisions can be made with the benefit of learning by means of experience in safe surroundings. © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION In a series of experiments, conducted between 1963 and 1968, Dr. Harry Harlow offered young rhesus monkeys a choice between two surrogate 'mothers'. In the first group, the terrycloth (essentially a cloth toy) mother provided no food while the wire mother did, in the form of an attached baby bottle containing milk. In the second group, the terrycloth mother provided food while the wire mother did not. It was found that, when frightened, the young monkeys clung to the terrycloth mother whether it provided them with food or not, and that the young monkeys chose the wire surrogate only when it provided food. Apparently the terrycloth mothers provided something that was more valuable to the young monkeys than food. She was providing contact comfort. Harlow's interpretation was that the preference for the terrycloth mother demonstrated the importance of affection and emotional nurturance in mother-child relationships. Dr. Harry Harlow's surrogate 'mothers' 5.2.2 Imprinting It was initially thought that there was one critical period during which a baby had to imprint onto an adult to securely form an 'infant attachment'. More recent work has shown that imprinting occurs at several sensitive periods. It is difficult to investigate infant behaviour for ethical reasons. Researchers use other animals instead. In fact, information about the sequence of stages in the development of walking in humans was partly gleaned from experiments on pigeons. Newly fledged birds were confined in cardboard tubes until their siblings could fly. The restrained birds could fly at the same time as their peers without having had practice at stretching their wings at all! One investigation of infant attachment which has been deemed ethical is the 'strange situation' experiment, which requires video equipment, three adults, a parent/carer and one subject, an infant child. © H ERIOT-WATT U NIVERSITY 113 114 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION The 'strange situation' is a laboratory procedure which is used to assess infant attachment that was first developed by Mary Ainsworth, a Canadian developmental psychologist, in the 1970s. The procedure consists of the following eight episodes: 1. the parent and infant are introduced to the experimental room; 2. the parent and infant are alone - the parent does not participate while the infant explores; 3. a stranger enters, converses with the parent, then approaches the infant - the parent leaves, inconspicuously; 4. the 'first separation episode': the stranger's behaviour is geared to that of the infant; 5. the 'first reunion episode': the parent greets and comforts the infant, then leaves again; 6. the 'second separation episode': the infant is alone; 7. continuation of the 'second separation episode': the stranger enters and gears behaviour to that of infant; 8. the 'second reunion episode': the parent enters, greets the infant, and picks up the infant; the stranger leaves. Episode 3 of the 'strange situation' procedure Four aspects of the child's behaviour are observed: 1. the amount of exploration (e.g. playing with new toys) that the child engages in throughout; 2. the child's reactions to the departure of its parent; 3. stranger anxiety (when the baby is alone with the stranger); 4. the child's reunion behaviour with its parent. © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION Of these, the last is given most weight in determining the category to which the infant's behaviour belongs. The 'strange situation' experiment is carried out on 12 to 18 month old children, who have reached a level of maturation when they can determine that a stranger is 'foreign'. The developers of this procedure grouped children into four categories: 1. securely-attached - children play comfortably and are friendly to strangers when their parent is present, but become distressed in her absence; 2. insecurely-attached, avoidant - children pay little attention to the parent and are not distressed in her absence; they appear quite detached; 3. insecurely-attached, resistant - children cling to the parent and are distressed in her absence; they seek reassurance, but reject contact when the parent returns and can become angry; 4. disorganised attachment - children show inconsistent and contradictory responses; they may freeze for substantial periods, show very stereotyped or contradictory behaviour, e.g. they may cry when the parent is away, but then avoid her on her return and appear to be afraid of her. Securely-attached children have parents or carers who are attentive, skilled at reading the child's needs, and promote socialisation. The parents of insecurely-attached children respond more to their own moods and wishes, ignoring their children's needs. A disorganised response tends to reflect abnormal parenting, including abuse, and children with a disorganised response are more prone to psychological disorders. Alternatively, an early secure attachment tends to have a lasting positive influence, the children being more likely investigate their environment, helping their cognitive development. In today's society, primary carers are often nursery nurses or child-minders. They must be aware of fulfilling parental wishes whilst ensuring confident progress in their charges. Imprinting: Question Q1: Arrange the stages of the 'strange situation' procedure in the correct order. • Continuation of second separation episode: Stranger enters and gears behaviour to that of infant. • First reunion episode: Parent greets and comforts infant, then leaves again. • First separation episode: Stranger's behaviour is geared to that of infant. • Parent and infant are alone. Parent does not participate while infant explores. • Parent and infant are introduced to the experimental room. • Second reunion episode: Parent enters, greets infant, and picks up infant; stranger leaves. • Second separation episode: Infant is alone. • Stranger enters, converses with parent, then approaches infant. Parent leaves inconspicuously. .......................................... © H ERIOT-WATT U NIVERSITY 115 116 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 5.2.3 Social compensation Although children can suffer delays in language learning and in other social skills if deprived of social contact and stimulation during infancy, they are extremely adept at compensating for this lack of development. Humans are extremely adaptable and can recover from setbacks. Although it is true that infant attachment has an important influence on later development, local child-rearing customs and the temperament of the child may have significant bearing on the way in which an infant responds to the 'Strange Situation' mentioned in the previous section. If a child is used to very close physical contact with a carer and has little experience of free play or visits by strangers, she will inevitably respond with concern to a new situation such as this. We cannot be sure that it is simply early socialisation that gives a child security later in life. Parents who are responsive to their children's needs in infancy are likely to further imbue confidence in later years. It is also likely that children can learn social competence by imitating their peers. However, other studies have confirmed the value of the initial 'Strange situation' investigation. In one study, two year old children were shown to have more competence in the use of tools the more securely attached they had been at an earlier age. They approached problem solving with enthusiasm and persistence whilst seeking adult help when required. Insecurely-attached children became frustrated and angry easily. They refused adult help and gave up trying fairly easily. In another study, 15-month-old children were rated for infant attachment. They were then observed at an age of 40 months and their social behaviour was assessed. Those rated as securely-attached tended to be social leaders and were eager to participate. Insecurely-attached children tended to be socially withdrawn and hesitant. © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 5.3 117 Long period of dependency Learning Objective By the end of this section, you should be able to: • state that humans have a relatively long period when they are dependent on adults; • explain that the long period of dependency provides opportunities for socialisation and learning; • state that different methods of control during a child's development can influence social competence; • explain that authoritative control (providing direction) generally results in greater social competence than authoritarian or permissive control. A long period of dependency offers opportunities and time for learning. Large brains are essential for development of the discriminatory skills required to recognise other animals and learn from observation. Humans require to be adept at communication because of their complex social structures. However, we do not stay in the womb long enough for our brains to grow completely. Thus, in a sense, human babies are born prematurely compared to some mammals, which are much more highly developed at birth, e.g. horses. We still have lots of maturing to do before we will be independent, and the long period of dependency required for growth and maturation offers many opportunities for learning. The development of increased brain power, the evolution of higher level communication skills, and the development of large eyes and a complex sensory system are all interlinked. The need for well-developed senses requires a large brain, but the large brain would have no function without the developed sensory system. Similarly, the complex communication skills that developed in tandem require a large brain, but also drive forward the evolution of such a brain. An animal that leads a predominantly solitary lifestyle, such as a male otter, has to learn the basic techniques of hunting and finding suitable habitat from its mother, but is required to develop relatively little social skill beyond that which is necessary to find a mate and defend its territory. A social animal, such as a human, must learn all the subtleties of interaction that allow the individual to effectively interact with its social group and secure its supply of life's essentials. The timescale required for development of these skills offers years of opportunities to integrate into a social structure. The more skills a child develops, the easier it is to integrate. The average Scot spends the first 25% of their life learning directly from their parents and other adults. A house mouse, in comparison, is independent of its mother after three weeks, which might be only 6% of the life-time of a mouse surviving to full maturity. © H ERIOT-WATT U NIVERSITY 118 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION Long period of dependency: Question Q2: State and explain two reasons for the long period of dependency in humans. .......................................... 5.3.1 Parental control methods The methods that parents use to control and guide the behaviour of their children can be classified under three headings: authoritarian, permissive and authoritative. The authoritarian parent demands obedience from their children. It should not be assumed that this is an uncaring approach. Rather, it stems from the parent's belief that they know what is best for the child and that it is in the child's best interests to behave as the parent requires. This style tends to also be associated with the use of punishments for failure in order to reach the required standards, a lack of involvement of the child in decision-making, and a lack of responsiveness to the child's emotional needs. The permissive parent, in complete contrast to the authoritarian one, is reluctant to impose rules and standards, preferring to let their child regulate its own behaviour. Again, this is not an uncaring approach, but one based on the philosophy that the child will develop best if it is allowed to make its own decisions about its behaviour, reaching decisions based on its own experience and wishes. Punishment is not part of this regime, but involvement in decision-making and responsiveness to the child's opinions are paramount. This style is also known as indulgent parenting. The authoritative parent uses aspects of both of the preceding styles. Standards and limits are set by the parent, but these are explained to the child, and the child's point of view is respected and taken into account in decision-making. The authoritative parent expects maturity and cooperation, offering children lots of emotional support. A fourth category can also be identified, in which the parent neither sets standards nor takes the child's views into account, providing no emotional support. This is known as neglectful parenting. Research has shown that authoritative parenting is significantly the most successful approach in terms of developing social competence. Its products (i.e. children) are likely to have a higher self-esteem and sense of well-being, to enjoy better health and show less problematic behaviour, and to gain higher academic qualifications. While this may generally be the case, it is also true that there are significant exceptions, e.g. the children of certain religious or racial groups, often seen as rather authoritarian, are disproportionately high academic achievers. © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION Parental control methods: Questions Q3: Complete the table, which shows the combinations of behaviour characteristic of different methods of parental control, using the listed terms. Demanding Undemanding Responsive Unresponsive Terms: authoritarian, authoritative, neglectful and permissive. .......................................... Q4: In what ways does authoritative parenting differ from: i ii authoritarian parenting; permissive parenting? .......................................... 5.4 The effect of communication Non-verbal communication is an important part of parent-infant bonding and in adult communication. Communication is simply an exchange of information. It occurs among all animals, and, in some cases, warning calls used by one species (e.g. monkeys) which are specific to one particular danger, such as a snake or an eagle, are recognisable as such by other species. Communication does not always require a vocabulary of words. 5.4.1 Information transfer Information can be passed both intentionally and unintentionally by verbal and nonverbal language. Non-verbal communication consists of body language which is often unconscious, including grimaces and other facial movements, and gestures, which are often under conscious control. When a baby smiles at her mother, a boy mirrors his girlfriend's posture or your eyes light up when the teacher enters the room, non-verbal communication is taking place. Friendship and intimacy are often signalled as much by non-verbal clues as by the content and context of conversation. Eye contact lasts longer, proximity is closer, and may include touching, and smiling is more frequent when we are with close allies. We must be careful as we may often read non-verbal communication according to our own moods or needs rather than those intended by the author. In addition, a skilled practitioner, not always a magician by trade, can easily mis-communicate information by redirecting an observer's gaze or by giving a false sense of security using non-verbal language. © H ERIOT-WATT U NIVERSITY 119 120 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION Information transfer: Question Q5: Put the communication methods listed into the correct categories in the table: Non-verbal Body language Verbal Non-verbal Gesture Communication methods: feeling your collar when under pressure; indicating that an archer's bow finger will be cut off if he gets caught; pointing to your nose when playing charades; shouting out; showing whites of eyes when angry; sobbing loudly; talking; throwing a fist in the air; walking with an expanded chest after a victory. .......................................... 5.5 Non-verbal communication Learning Objective By the end of this section, you should be able to: • explain how non-verbal communication contributes to the formation of relationships between individuals; • state that non-verbal communication can signal attitudes and emotions; • state that non-verbal communication acts as an aid to verbal communication. This section is divided into sub-sections about communication in infants and then in adults. 5.5.1 Infant bonding During the growth of relationships, bonding occurs when a child smiles at a parent, or when a couple mirror one another's expressions or posture. This establishes strong emotional ties. Protective feelings are promoted and these behaviours have a survival value for the participant. Positive feedback ensues and so a child cooing at her parent will elicit further caring responses. When a parent responds by smiling, vocalising (often in a high-pitched, sing-song voice which is encouraging to the child) and handling the infant, the child will respond in similar fashion. From around four months, the infant recognises and prefers familiar faces and responds more to these than to others. Facial expressions are much more important to apes, and especially to ourselves, than to other species. Whereas other animals walk side to side to size one another up, © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION humans observe facial expressions with concentration. This is particularly important in infants and in adolescents, perhaps explaining why a tiny facial spot can cause such panic in a teenager's heart! This is because we communicate so much by our facial expressions, and by lip and tongue movements. We observe speech at the same time as listening to it. 'Read my lips' sounds trite, but is rife with meaning. 5.5.2 Adult In adults, non-verbal communication remains of huge importance. Even seemingly meaningless noises convey information about emotions and attitudes. Speech sounds such as "och" and "d'oh" in variants of the English language, or "ben" and "boff" in French, inform the observant listener. These sounds and inflections of the voice are sometimes referred to as para-language. Voice inflections are particularly crucial in languages, such as Chinese, where one word can have several meanings, depending on inflection and pitch. Shifting eyebrows, nodding, lack of eye contact, tears, and even sweating offer positive or negative feedback during a conversation, providing information which should not be ignored, neither by the speaker nor by the listener. Body language and gestures, such as verbal language, are culturally rooted. As previously mentioned, cultures vary across distances and across time. Beware! A gesture deemed friendly in your culture may be extremely aggressive or insulting in another. Sometimes, as adults, we have to repress our natural communication skills. A parent will often try to convey a feeling of well-being to children even though she, herself, is concerned about something. © H ERIOT-WATT U NIVERSITY 121 122 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION Facial expressions .......................................... Body language across the world Web sites about body language across the world 20 min Access the websites listed below to compare how body language differs across the world. • http://www.everythingesl.net/inservices/body language.php: compares cultures; • http://www.ai.mit.edu/projects/sociable/facial-expression.html: a robot that makes faces; • http://italian.about.com/library/weekly/aa062001a.htm: speaking Italian with your hands. .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 5.6 Verbal communication 123 Learning Objective By the end of this section, you should be able to: • state that language uses symbols to represent information; • explain that language enables information to be organised into categories and hierarchies; • state that this organisation of information accelerates learning and intellectual development; • explain that the ability of humans to communicate verbally has resulted in the transmission of knowledge, development of culture and social evolution. Humans differ from all other species in the complexity of their spoken language and in their ability to use verbal language, i.e. words and sentences rather than just sounds, whether written or spoken. In contrast to the vagueness of some body language, verbal language transmits complex information in a clear, concise and unambiguous manner. In addition, dialogue, in the form of questions and answers, can supplement and clarify communication. Rules for combinations of symbols or words developed. These are known as syntax. These rules vary from culture to culture and evolve with usage through time. The history of associated cultures can be clearly observed in the similarities between one language and another. For example, French, Spanish, Romanian and English all seem to be derived from Latin. 5.6.1 Language differences Differences also occur between language used in school (by the establishment) and the language of the playground. Knowledge of the patois gives a quick reference point defining age, interests and position in the local hierarchy. Syntax provides a framework which allows language to be constructed from phrases encoded in memory. Nouns, verbs, adverbs, adjectives and phrases each have sense in their own right. They can then be combined in a variety of ways to give sentences which have meanings of their own. This is known as semantics. To create language, thoughts that are represented by words are built into phrases which form sentences. These are governed by rules of syntax, which an infant has to somehow internalise while simultaneously growing a nervous system! A child has an enormous capacity to acquire vocabulary and to glean the rules of syntax and grammar. By the age of six, a child typically has a vocabulary of some 15,000 words. Learning the rules of semantics takes rather longer... © H ERIOT-WATT U NIVERSITY 124 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION Consider the situation where a teacher describes your project as being "outstanding work". Ambiguity of language - which is it? 5.6.2 Acquiring language The website http://www.pnas.org/cgi/content/full/98/23/12874 gives an interesting insight into the problems faced by infants in acquiring language and the success that they have from the age of around seven months in overcoming them. As we grow older, the number of facts that require to be memorised rises exponentially. Our brains compensate by using language rules to construct hierarchies of understanding. Using complex language allows us to learn and develop intellectually. We can aid our brains by putting burdens on the mind. By creating hierarchies as you memorise your work you will assist your brain in encoding, storing and retrieving information. 5.6.3 Development of language The symbols used to construct spoken language can be converted to written symbols. At some pre-historic time, man began to record debts and harvests as a series of symbols; perhaps in order that feudal lords, who did not live close enough to oversee their vassals in a rapidly-expanding population, could keep track of their dues. Using different symbols, or hieroglyphics, in different cultures, written language developed in the same way that a variety of spoken symbols evolved to represent the same items in different geographical areas. This development would inevitably have a consequential effect on spoken language because both were required to become more precise about chattels and populations. Greek letters Chinese symbols for love α, β, γ, δ, . . . Δ, Σ, Ω © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 125 The Rosetta Stone which, with text in Ancient Egyptian, and translations into Demotic and Greek, first enabled the Egyptian hieroglyphs to be interpreted Who is 'in' and who is 'out' of your crowd? Navigate to the following website: http://www.ruf.rice.edu/~kemmer/Words/shibboleth.html Words and pronunciations let us know who is 'in' and who is 'out' of our crowd. Make a list of words that describe what is important in your local sub-culture. © H ERIOT-WATT U NIVERSITY 10 min 126 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION .......................................... 5.6.4 Mathematical notation Many centuries ago, Chinese and Greek scholars developed mathematical notation, such as algebraic symbols, as a special type of language. Language had already proved its worth as a means of codifying information. Symbols allow organisation of information into categories and hierarchies. Mathematical symbols ≡, , ⊥ , ∝, =, ∠, ≈, ∞, ± Logic symbols in electronic circuits Language developed as a form of communication between people who were present simultaneously. Crucially, we can now communicate verbally when we are apart and leave messages for later. We can also leave written messages for later. We can form images using cameras to be stored or transmitted. With the development of logarithms and calculators, codification of language went even further, allowing the development of computers, originally called 'difference engines', cell phones, mp3 players and many other gadgets that we now take for granted. Mathematical notation: Further reading Go to http://www.macs.hw.ac.uk/~greg/calculators/napier/great.html http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Babbage.html to about the contributions of John Napier and Charles Babbage to this revolution. and read .......................................... Verbal communication: Further reading 10 min You may wish to compare communication among chimpanzees with communication by humans which you can do so by investiagating the following website: http://www.janegoodall.org/chimpanzees/communication © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION .......................................... 5.7 Learning points Summary Forms of infant attachment • Early infant attachment is important in laying the foundation for the future formation of stable relationships. • Attachment becomes evident between six and nine months after birth. • Explain the 'strange situation' procedure. • Describe the responses to the 'strange situation' procedure as: secure and insecure attachment, detachment, anger, and inconsistent responses. • Infants who form secure attachments are more likely to investigate their immediate environment, which helps the development of their cognitive abilities. Long period of dependency • Humans have a relatively long period when they are dependent on adults. • The long period of dependency provides opportunities for socialisation and learning. • Different methods of control during a child's development can influence social competence. • Authoritative control (providing direction) generally results in greater social competence than authoritarian or permissive control. Non-verbal communication • Non-verbal communication contributes to the formation of relationships between individuals. • Non-verbal communication can signal attitudes and emotions. • Non-verbal communication acts as an aid to verbal communication. Verbal communication • Language uses symbols to represent information. • Language enables information to be organised into categories and hierarchies. • This organisation of information accelerates learning and intellectual development. • The ability of humans to communicate verbally has resulted in the transmission of knowledge, development of culture and social evolution. © H ERIOT-WATT U NIVERSITY 127 128 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION 5.8 Extended response question The activity which follows presents an extended response question similar to the style that you will encounter in the examination. You should have a good understanding of human communication before attempting the question. You should give your completed answer to your teacher or tutor for marking, or try to mark it yourself using the suggested marking scheme. Extended response question: Human communication Describe ways in which humans communicate under the headings: 15 min A) non-verbal communication; (4 marks) B) verbal communication. (6 marks) .......................................... 5.9 End of topic test End of Topic 5 test Q6: Complete the sentences by matching the parts on the left with the parts on the right. (8 marks) Early infant attachment is important for investigate their environment. Attachment becomes evident between different methods of control. Two responses to the strange situation experiment are dependent on adults. Infants who form secure attachments are more likely to greater social competence. Humans have a relatively long period when they are six and nine months after birth. The long period of dependency provides opportunities for detachment and anger. Social competence can be influenced by future stable relationships. Authoritative control generally results in socialisation and learning. © H ERIOT-WATT U NIVERSITY TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION .......................................... Q7: Complete the paragraphs by selecting words from the list. (10 marks) Non-verbal communication contributes to the of relationships between and emotions, and acts as an to verbal individuals. It can signal communication. Language uses to represent and enables information to be and hierarchies. This organisation of information accelerates organised into and development. The ability of humans to communicate verbally , development of , and social has resulted in the transmission of evolution. Word list: aid, attitudes, categories, culture, formation, information, intellectual, knowledge, learning, symbols. .......................................... The following four questions refer to infant attachment the 'strange situation' procedure. Q8: Which people would be involved in the procedure other than an infant and a parent/carer? (2 marks) .......................................... Q9: Which observation is most significant in deciding the category to which the infant belongs? (1 mark) .......................................... Q10: Which group of infants are not distressed by the parent/carer's absence? (1 mark) a) b) c) d) Securely attached Insecurely attached, avoidant Insecurely attached, resistant Disorganised attachment .......................................... Q11: Which type of response is most likely to develop the infant's cognitive abilities? (1 mark) a) b) c) d) Securely attached Insecurely attached, avoidant Insecurely attached, resistant Disorganised attachment .......................................... Q12: When does infant attachment first become evident? (1 mark) .......................................... Q13: State two aspects of an infant's development for which the human's long period of dependency provides opportunities. (1 mark) .......................................... © H ERIOT-WATT U NIVERSITY 129 130 TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION Q14: Which type of parental control results in the greatest social competence? (1 mark) a) b) c) d) Authoritative Authoritarian Neglectful Permissive .......................................... Q15: What are the characteristics of neglectful parenting? (2 marks) .......................................... Q16: What can be signalled by non-verbal communication? (1 mark) .......................................... Q17: How does language represent information? (1 mark) .......................................... Q18: Into what does language enable information to be organised? (1 mark) .......................................... Q19: List two advantages of this organisation of information. (1 mark) .......................................... Q20: State two key characteristics of humans that are facilitated by language. (2 marks) .......................................... .......................................... © H ERIOT-WATT U NIVERSITY 131 Topic 6 The effect of experience and social influences Contents 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 The effect of practice on motor skills . . . . . . . . . . . . . . . . . . . . . . . . 132 132 6.3 Imitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 6.3.1 Monkey see, monkey do! . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Trial and error learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 135 6.5 Generalisation and discrimination . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 Social facilitation and deindividuation . . . . . . . . . . . . . . . . . . . . . . . . 137 139 6.7 Influences that change beliefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 142 6.9 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 143 Learning Objectives By the end of this topic, you should be able to: • define the term 'learning'; • explain why practice improves motor skills; • describe the role of imitation in learning; • explain how learning can be improved by means of reinforcement, shaping, extinction, and trial and error; • describe the processes of generalisation and discrimination. 132 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 6.1 Introduction Like nearly all Primates, humans are social animals, i.e. they live in groups rather than on their own. These groups consist of closely related individuals belonging to several generations. The social changes brought about by industrial and agricultural development have disrupted these groups, but it is only a few generations ago that they were the units around which our society was structured, e.g. the clans of the Highlands and the Borders. In such a social structure, the children live throughout their dependent years in close proximity to adults at home and at work, and this provides abundant opportunities to observe and copy behaviour, and to experiment within the sheltered confines of the group. Furthermore, it allows the adults to supervise the young, applauding good behaviour and discouraging bad. By the time a person has reached the status of adult, they will have been thoroughly versed in the ways of their tribe and their local environment, and in the skills necessary to survive in both. Principal among these skills is the ability to learn, i.e. to change behaviour in the light of experience. 6.2 The effect of practice on motor skills Learning Objective By the end of this section, you should be able to: • state that learning is a change in behaviour brought about by experience; • explain that motor skills are improved by repeated practice; • state that practice of a motor skill establishes a motor pathway in the brain. Learning can be defined simply as a change in behaviour as a result of experience. In other words, if you start climbing a set of stairs on a different side to normal as a result of standing on a squeaky floor-board, you have learned. Changing behaviour underlies all teaching and learning. Motor skills are sequences of movements that are necessary to perform a particular task. An apparently simple action, such as picking up a pencil, belies the complexity of the neural activity which enables it to be carried out smoothly and without conscious thought. There is the sensory input that is required to recognise the pencil amongst its surroundings, and to judge its position relative to the hand. Then there is the activity of the motor cortex of the brain to initiate the necessary muscular contractions to move the arms and fingers, and the action of the cerebellum to co-ordinate the contractions and relaxations of these muscles to give the fine motor control involved in precisely closing the fingers around the pencil. Easy, but definitely not simple! Learning motor skills from a book is very ineffective. Even with diagrams and pictures, it is still very hard to make the right movements. On the other hand, observing someone else perform the task and then copying them works very well. Although we usually don't get things right straight away, repeated demonstration quickly corrects mistakes. This establishes the movements that must be produced, but to be able to reproduce © H ERIOT-WATT U NIVERSITY TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 133 them reliably requires the establishment of a motor pathway linking all the parts of the nervous system, which must work together to make the movement possible. That can only be done by repetition. This is why professional golfers spend hundreds of hours working on a new swing, or professional tennis players practice serve after serve for hours on end. They are 'grooving in' the movements so that they automatically perform them correctly in a match situation. Indeed, if things go wrong and they have to start thinking about it, their game can fall apart. These principles apply to mere mortals as well. If you want to play guitar better, or cast a fishing fly more accurately, there is only one route to success - practice, practice, practice... It is said that to learn a folk tune, you have to play it faultlessly eighty times, and that to become competent on an instrument takes 10,000 hours of practice. Fortunately, correctly managed, the learning process itself can be enjoyable, and the sense of achievement as progress is made is a reward in itself. The effect of practice on motor skills: Questions Q1: What is meant by the term 'learning'? .......................................... Q2: What must be established to learn a motor skill? .......................................... Q3: What is meant by practising a motor skill? .......................................... 6.3 Imitation Learning Objective By the end of this section, you should be able to: • explain that a great deal of human behaviour is learned by observing and imitating the behaviour of others. As mentioned in the previous section, imitation is a very effective method of learning certain types of skill. The apparent simplicity of the activity once more masks the considerable underlying complexity of the actions that take place in the nervous system. Once the other person's actions are observed (seen or heard), somehow the brain co-ordinates the activity of the appropriate muscles to produce the same activity. The underlying neurological processes seem to be very complex and, as yet, little understood, although certain cells in the motor cortex may be involved which are known as mirror neurons. These fire impulses when an activity is the same as that observed in another person. © H ERIOT-WATT U NIVERSITY 134 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES However it may come about, imitation is the mechanism by which a great deal of basic human behaviour is learned, whether it be how to use a knife and fork, or how to behave towards our children. The importance of parents as role models for their children is obvious and well-known. Much of this, such as gender stereotyping, is wholly unconscious learning, and only becomes apparent in our actions and responses to particular situations. 6.3.1 Monkey see, monkey do! Researchers have recently demonstrated that monkeys 'imitate with a purpose', copying behaviour as a form of social learning. Such mimicry had previously been established only in great apes, including humans and chimps, but now Italian researchers have recorded the phenomenon in newborn rhesus macaques. Most of us have delighted in very young relatives mimicking our facial expressions. This 'imitation period' lasts up to three months in human infants. Newborns rely on watching adults to learn facial expressions, and mimicry is thought to be crucial in the successful development of parent-infant relationships. It is thought that specific brain cells, called 'mirror neurons', fire in a human infant when it watches an adult expression and copies it. Similar mirror neurons are active during brain scans when rhesus monkeys watch another animal perform an action, and also when they copy that action. This similarity suggests a common brain pathway in humans and monkeys. A newborn macaque (less than 10 days old) imitates tongue protrusion by a human (Evolution of Neonatal Imitation. Gross L, PLoS Biology Vol. 4/9/2006, e311 doi:10.1371/journal.pbio.0040311) Pier Ferrari at the University of Parma, Italy, and colleagues, tested 21 newborn macaques by holding each in front of a researcher who made various facial expressions as illustrated above. © H ERIOT-WATT U NIVERSITY TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 135 None of the infants showed any imitation at one day old. By day three, infants started to copy the researchers' expressions, including sticking their tongues out, opening their mouths on cue, and smacking their lips. These are all expressions that are typical of normal macaque behaviour. Watch footage of macaques copying tongue poking and mouth opening in the video at the end of this topic. Although it is possible that macaques may copy other macaques for longer in the wild, imitation of researchers had ceased by the age of two weeks. It seems that the capacity for imitation evolved earlier in primate evolution than previously thought, and definitely before the rhesus monkey ancestor split from the human line of descent, about 25 million years ago. 6.4 Trial and error learning Learning Objective By the end of this section, you should be able to: • explain that behaviour patterns which have positive consequences for the individual are likely to be repeated; • state that positive outcomes reinforce a behaviour; • state that behaviours which are not rewarded by positive outcomes, or have negative outcomes, will disappear; • state that a behaviour which is extinguished is said to be extinct; • explain shaping as rewarding behaviour that successively approximates to the desired behaviour. Trial and error Even more than other mammals, humans are inquisitive creatures. They are constantly exploring, whether it be new continents or new foods, and they are always asking questions of their environment. Equally, especially in our youth, we are prone to challenge the ways in which things are done and to try alternatives. This behaviour is what has brought us from the Stone Age to the Computer Age within the span of only some 400 generations in Britain. How many of us start pressing buttons without consulting the manual when taking a new electronic gadget out of its packaging? In doing this, we are using one of the simplest of our learning techniques, called Trial and Error. We try something to see whether it works; if it has a desired outcome, that reinforces the behaviour and we are likely to repeat it. If it has no effect, or worse still, results in an undesirable outcome, then the behaviour of pressing that button will not be repeated; it will become extinct. © H ERIOT-WATT U NIVERSITY 136 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES Reinforcement The process of training and teaching seeks to reinforce positive outcomes and extinguish negative ones. Rewarding desirable behaviour is a very effective method of reinforcing it. When a puppy lies down on command, you show your pleasure by your tone of voice and the treat that you give it. This is a reward for the puppy, and it is more likely to repeat the behaviour when the command is given again. Alternatively, jumping up with muddy paws to greet people is a behaviour of a puppy that we would want to extinguish. This can either be done by ignoring it, or by showing displeasure in your tone of voice. Providing a reward is positive reinforcement, whereas something removed or avoided acts as negative reinforcement. A good example of negative reinforcement is putting up an umbrella when the rain starts. This is classed as negative in that it is the removal of the stimulus of the rain on the head which reinforces the behaviour. Another example would be donning earphones when the next-door neighbour starts playing his banjo. Negative reinforcement is frequently confused with punishment. Whereas showing disapproval often works very effectively towards extinguishing a behaviour, e.g. the word "No!" exclaimed very firmly, physical punishment usually has outcomes which are not intended. A puppy that is struck learns to fear the person who hits it rather than to keep its paws on the floor. It is also worth pointing out that the reward, or indeed the punishment, must have meaning for the subject. You are unlikely to reinforce desired behaviour in a young child by offering her dark chocolate, or depriving her of the chance to watch the news on the television. Shaping Shaping is rather more than the rewarding of behaviour that approximates to that desired. More correctly, it is the differential reinforcement of successive approximations to a desired behaviour. It was first identified by the American psychologist and behaviourist B. F. Skinner who initially worked with pigeons, even developing a pigeonguided missile for the US navy in World War II. His later analyses of teaching and learning processes were, and still are, enormously influential. Although its definition sounds very complex, shaping is, in fact, very simple and used all the time in training and teaching situations. Anyone who has had to endure the initial stages of a relative learning to play a musical instrument will be familiar with the screeches and wails of their early efforts. Yet, these same excruciating sounds will elicit high praise from the teacher, for the pupil has actually managed to make a sound with the instrument. Soon though, only more melodious efforts will lead to praise. Thus, the instructor keeps raising the bar for the pupil, demanding more achievement each time before the reward of praise is forthcoming. Think of your own efforts at learning to pronounce words in a foreign language and how they were dealt with by your teacher. © H ERIOT-WATT U NIVERSITY TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 137 Trial and error learning: Question Q4: Complete the sentences by matching the parts on the left with the parts on the right. Trial and error becomes extinguished. Extinct behaviour involves differential reinforcement of successive approximations to a desired behaviour. Reinforcement involves random responses to a stimulus. Shaping 6.5 involves making similar response to a stimulus more likely on subsequent occasions. .......................................... Generalisation and discrimination Learning Objective By the end of this section, you should be able to: • explain that generalisation is the process by which a response learned to in reaction to one stimulus is evoked by a different, but similar, stimulus; • explain that discrimination is the process by which people learn to make different responses to different, but similar, stimuli. Generalisation and discrimination are vital parts of our learning skills in that they allow us to develop fundamental responses to aspects of our environment. Generalisation How often do you hear someone declaring that they don't like fish or green vegetables, probably as a result of an encounter with a particularly poorly cooked example early in life? While these are trivial examples (although not to the anguished grandparent who sees a carefully prepared meal refused), learning to avoid snakes or stripy flying insects are not. Generalisation involves identifying some key, common feature of objects which allows us to group them together despite their being different in other respects. The classic example is the child who generalises the response to being bitten by a dog once to a fear of all dogs. In practice, the opposite situation is more dangerous: a child who is accustomed to running up to pat a friendly dog is in much more danger if she generalises this to assume that all the dogs she meets will be friendly. © H ERIOT-WATT U NIVERSITY 138 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES Discrimination The process of discrimination involves the identification of key features of an object that will allow us to distinguish it from other similar objects. Chanterelles are very tasty golden-yellow fungi which grow quite widely in Scottish woods. Unfortunately, there are some seriously poisonous species with which they can be confused. It is essential to know the precise characteristics which differentiate it from other yellow fungi found on the forest floor if a truly mouth-watering omelette is to be confidently enjoyed. Many tourists visiting the Highlands go home happy that they have spotted Golden Eagles soaring over the glens, when in fact they have seen the similar, but far more common, buzzard. As with the Chanterelle, once the real thing has been seen, it is unlikely that there will be further confusion because the key features of the organism are recognised. Again, the classic example involves dogs. A postman who has been given a little nip by a Jack Russell terrier will be very wary of this breed even though he may cheerily greet much larger dogs such as Labradors. Generalisation and discrimination: Question Q5: Complete the table by placing the activities in the correct column. Generalisation Discrimination Activities: • Catching the No. 54 bus at the bus station • Checking the tomatoes in the supermarket before putting them in the bag. • Enjoying travelling by train. • Midges spoil camping holidays in Britain. • Not liking the people from a particular city. • Only eating the sweets in the purple wrappers. • Picking the spotted puppy from the litter. • Randomly choosing any dish on the menu. .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 6.6 Social facilitation and deindividuation 139 Learning Objective By the end of this section, you should be able to: • explain that the performance of a task may be improved in the presence of others; • state that the presence of others in a competitive situation may enhance performance; • state that the presence of an audience may improve performance; • state that deindividuation is responsible for the loss of identity in a crowd; • explain that deindividuation leads to diminished restraints on behaviour; • state that deindividuation leads to behaviour which would not be shown by individuals on their own. This topic considers the positive and, sometimes, negative effects that the presence of other people can have. Social facilitation The presence of other people can have a marked effect on our performance of a task. This is known as social facilitation. Sometimes, this effect can have a positive influence, e.g. when playing a team sport, most of us will endeavour to improve our performance for the good of the team. This is called the co-actor effect: increased performance in competitive situations. When a group of cyclists were timed on their own, against the clock, they did much worse than when cycling in groups. This effect is present even in situations which would not normally be seen as competitive. For example, car drivers take 15% longer to travel the first 100 metres after drawing away from a green light if there is no other car in the next lane. A second kind of social facilitation operates when performing in front of an audience: the audience effect. When people talk about a home advantage in sporting events, it is the effect of the home crowd inspiring their team that is involved. If a team is required to play a fixture in an empty stadium, it very seldom results in an entertaining game. In the 2012 London Olympics, many of the British medal winners cited the crowds as a major contributor to their success. On the other hand, some research has shown, and you may empathise with this, that the presence of others can impair performance. This gives a clue as to how social facilitation can operate. A certain level of arousal of the nervous system will lead to improved performance. After this, further arousal will cause distress. Arousal seems to help when we feel in control of a situation. When performing a task which is well within our capabilities, social pressure improves performance, but, when the task is unfamiliar, we perform below par. In one study, expert pool players who potted 71% of their shots when practising alone made 80% of the shots with an audience of four people. As you would expect, poor players who made only 36% of their shots when unobserved, collapsed to just 25% when observed. This explains why confidence is so © H ERIOT-WATT U NIVERSITY 140 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES important when performing. If confidence is high, social facilitation makes us do well and vice versa. Deindividuation Anyone who has attended a big club football match will be aware that the behaviour of some of the crowd can be quite surprising if you are not used to it. The chanting, swearing, and gesturing towards opposition players and supporters, and of course the referee, would quickly lead to a person being arrested if it was to be repeated in the local High Street. And yet, these same people, when dispersed from the stadium, do not behave in this way - it is, in fact, quite atypical of them. Also, it is more than just believing that in a mob you are less likely to be caught and that, therefore, you can take greater risks than usual. This effect has a name: de-individuation. It is defined as the loss of personal identity in groups, leading to diminished restraints on behaviour. When we become a member of a group, we somehow submerge our own personality into a group identity. There is diminished restraint, and anti-social behaviour can occur. This same effect can influence individuals in groups outside the confines of a football stadium, where it can lead to vandalism, looting and rioting as it did in London and other English cities in the summer of 2011. A classic experiment that demonstrates this behaviour involved giving students various problems, alone or in groups. If shown a line and asked to compare it with several other lines for length, solo students performed very well. However, when invited to perform the same task along with three or four 'plants' who were primed to give obviously incorrect answers, the subjects doubted themselves to the extent that they joined in with the group behaviour and gave answers that they clearly knew were wrong. Similarly, in another classic experiment, students who had been invited to administer electric shocks to other students in a room next door would keep turning up the voltage when instructed by their supervisor, who would urge them to continue even when they raised objections. No shocks were actually administered, of course, although the subject heard the wails of an actor in mock pain, which increased with the severity of the voltage 'applied'. They were prepared to over-ride their own reservations about their actions when they were in conflict with orders from an authority figure, even though they were aware of the apparent effect of their actions. This is known as the Milgram experiment. In fact, participation in this experiment had quite disturbing effects on the students. Its origin was the defence given by soldiers on trial for committing atrocities during World War II that "they were only following orders". Social facilitation and deindividuation: Question Q6: Match the phrases on the left with the words on the right. Performance improved by the presence of others: deindividuation. Performance improved in front of a crowd: co-actor effect. Performance improved by having competition: audience effect. Loss of identity in a crowd: social facilitation. .......................................... © H ERIOT-WATT U NIVERSITY TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 6.7 141 Influences that change beliefs Learning Objective By the end of this section, you should be able to: • explain that internalisation is the changing of one's beliefs as a result of persuasion; • explain that identification is the changing of one's beliefs to those of an admired influencing source. Internalisation We have defined behaviour as our range of responses to stimuli in our environment, and to other humans who form part of that environment. During our interactions with others we frequently seek to change their views, and they try to change ours. Our usual approach is to attempt to persuade our audience to share our view by presenting them with convincing evidence. You may, or may not, be impressed by the argument that "my team has won ten games this season and yours has only won five, so we are twice as good as you", but similar versions are heard all the time. This approach to changing beliefs is called internalisation. It is used frequently by the advertising industry, e.g. "Nine out of ten cats interviewed said they preferred Purr-fect Cat Food". A more convincing use of the technique is found in the 502 pages of evidence presented by Charles Darwin in his seminal book "On the origin of species by means of natural selection". Identification Advertisers also utilise another approach to changing behaviour. They have worked out that humans are social animals and prefer to have group membership. Individuals try to have a high status in groups because this confers all sorts of benefits, such as preferential access to food and mates. One way in which to gain this status is to impress the group by being identified with famous people. Consequently, sponsors pay large sums of money to entice iconic figures to endorse their products. Advertisements often feature well-known celebrity figures from sport, film or TV, associating them with products, e.g. after-shave or shampoo. The rationale of this technique is that people will want to be linked to a star, purchasing a product to be like them. This is known as identification and is defined as the changing of one's beliefs to those of an admired influencing source. Influences that change beliefs: TV adverts The next time that you watch a commercial TV station, try to decide which technique is being used by each advertisement. Various techniques are used, sometimes at the same time, so you might like to make up a table headed with the different approaches that you have identified, and note the products that are being sold under each heading. .......................................... © H ERIOT-WATT U NIVERSITY 142 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 6.8 Learning points Summary The effect of practice on motor skills • Learning is a change in behaviour brought about by experience. • Motor skills are improved by repeated practice. • Practice of a motor skill establishes a motor pathway in the brain. Imitation • A great deal of human behaviour is learned by observing and imitating the behaviour of others. Trial and error learning • Behaviour patterns that have positive consequences for the individual are likely to be repeated. • Positive outcomes reinforce a behaviour. • Behaviours that are not rewarded by positive outcomes, or have negative outcomes, will disappear. • A behaviour that is extinguished is said to be extinct. • Shaping is rewarding behaviour that successively approximates to the desired behaviour. Generalisation and discrimination • Generalisation is the process by which a response learned in response to one stimulus is evoked by a different, but similar, stimulus. • Discrimination is the process by which people learn to make different responses to different, but similar, stimuli. Social Facilitation and deindividuation • Performance of a task may be improved in the presence of others. • The presence of others in a competitive situation may enhance performance. • The presence of an audience may improve performance. • Deindividuation is responsible for the loss of identity in a crowd. • Deindividuation leads to diminished restraints on behaviour. • Deindividuation leads to behaviour which would not be shown by individuals on their own. Influences that change beliefs • Internalisation is the changing of one's beliefs as a result of persuasion. • Identification is the changing of one's beliefs to those of an admired influencing source. © H ERIOT-WATT U NIVERSITY TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES 6.9 143 Extended response question The activity which follows presents an extended response question similar to the style that you will encounter in the examination. You should have a good understanding of group behaviour and social influence before attempting the question. You should give your completed answer to your teacher or tutor for marking, or try to mark it yourself using the suggested marking scheme. Extended response question: Group behaviour and social influence Give an account of group behaviour and social influence under the headings: 15 min A) social facilitation; (3 marks) B) deindividuation; (4 marks) C) influences that change beliefs. (4 marks) .......................................... 6.10 End of topic test End of Topic 6 test Q7: Complete the sentences by matching the parts on the left with the parts on the right. (9 marks) A change in behaviour brought about by experience: shaping. An important part of learning: imitation. Improved by repeated practice: extinct. Established by practice of a motor skill: learning. Copying behaviour: reinforcement. Makes behaviour patterns likely to be repeated: observing. Rewarding desired behaviour: motor skills. Fate of behaviour that is not rewarded: motor pathway. Rewarding behaviour as it gets closer to what is wanted: positive outcomes. © H ERIOT-WATT U NIVERSITY 144 TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES .......................................... Q8: Complete the paragraphs by selecting words from the list. (11 marks) is the process by which a response learned to one stimulus is evoked by but similar stimulus, whereas is the process by which people a stimuli. learn to make different responses to situation may enhance performance, as can the The presence of others in a may improve performance. These are examples of different presence of an . is responsible for the loss of identity in a crowd types of social on behaviour. which may lead to diminished is the changing of beliefs as a result of persuasion. changing of one's beliefs to those of an admired influencing source. is the Word list: audience, competitive, deindividuation, different, discrimination, facilitation, generalisation, identification, internalisation, restraints, similar. .......................................... Q9: Explain why certain behaviours are likely to be repeated and others become extinct. (2 marks) .......................................... Q10: Describe the process of simple reinforcement. (1 mark) .......................................... Q11: Describe the process of shaping. (1 mark) .......................................... Q12: Explain why a child being bitten by a small white dog might lead to discrimination. (1 mark) .......................................... Q13: Explain why a child being bitten by a small white dog might lead to generalisation. (1 mark) .......................................... Q14: Suggest why athletes almost invariably achieve their best performances in big competitions. (2 marks) .......................................... Q15: Advertisers of facial creams use either celebrities or actors dressed as scientists to try to sell the product. Explain their reasoning. (2 marks) .......................................... © H ERIOT-WATT U NIVERSITY 145 Topic 7 End of unit test Contents 146 TOPIC 7. END OF UNIT TEST End of Unit 3 test Q1: Complete the sentences by matching the parts on the left with the parts on the right. (12 marks) The central nervous system comprises the brain and sensory information. The sympathetic and parasympathetic nervous systems act information. The limbic system influences the pituitary through the secretion of the spinal cord. Perception is the process by which the brain analyses incoming severe injury. Information is lost from Short-Term Memory by antagonistically. Glial cells support and maintain neurons by removing debris by attachment. Increased endorphin production is associated with persuasion. Recreational drugs may inhibit the enzymatic degradation of hormones. A trait that becomes evident between six and nine months after birth is experience. Language uses symbols to represent phagocytosis. Learning is a change in behaviour brought about by neurotransmitters. Internalisation is the changing of beliefs as a result of displacement or decay. © H ERIOT-WATT U NIVERSITY TOPIC 7. END OF UNIT TEST 147 .......................................... In an experiment into the serial position effect, pupils in a class were shown how to answer by watching a teacher do a similar experiment. They were then shown twelve pictures and asked to recall them. The table below records their success at recalling each picture. Pupil 1 2 3 4 5 1st 2nd 3rd 4th √ √ √ √ √ √ √ √ √ √ √ √ 80 80 Recall 100 (%) 6th 7th 8th √ 9th √ √ √ √ 5th √ √ √ ? √ √ 20 √ √ √ 40 10th 11th 12th 40 Position of picture in list shown to pupils: 40 √ 60 √ √ √ √ √ √ √ √ √ √ √ √ 80 100 80 = picture recalled Q2: What is the percentage recall of the 5th picture? (1 mark) .......................................... Q3: Express the percentage recall of the 3rd and 9th pictures as a simple wholenumber ratio. (1 mark) .......................................... Q4: Describe the trends shown in the data. (2 marks) .......................................... Q5: Suggest two ways in which the reliability of this experiment might be improved. (1 mark) .......................................... Q6: Suggest two variables that would have to be kept constant in this experiment. (2 marks) .......................................... Q7: Predict how the results table would look if twenty pictures had been used instead of twelve. (1 mark) .......................................... Q8: With reference to the brain, state two functions regulated by the medulla. (2 marks) .......................................... © H ERIOT-WATT U NIVERSITY 148 TOPIC 7. END OF UNIT TEST Q9: What is the part of the brain that is responsible for muscular co-ordination? (1 mark) .......................................... Q10: State one secretory function of the hypothalamus. (1 mark) .......................................... Q11: State one regulatory function of the hypothalamus. (1 mark) .......................................... Q12: Name one state that the limbic system influences. (1 mark) .......................................... Q13: Name the neurotransmitter involved in the reward pathway. (1 mark) .......................................... Perception is the process by which the brain analyses and makes sense of incoming sensory information. Q14: Into what do we organise our perceptions to segregate them? (1 mark) .......................................... Q15: State two visual clues used in the perception of distance. (2 marks) .......................................... Q16: What feature is most important in the recognition of objects? (1 mark) .......................................... Q17: What does language use to represent information? (1 mark) .......................................... Q18: What term is used to describe the process by which a child who has been scratched by a cat comes to fear all cats? (1 mark) .......................................... Q19: What causes some-one to change their beliefs by internalisation? (1 mark) .......................................... .......................................... © H ERIOT-WATT U NIVERSITY GLOSSARY Glossary Addiction continued indulgence in a behaviour despite the negative consequences - may be psychological (a habit) or physiological (a dependence) Antagonistic muscles which work against each other at a joint to produce controlled movement, e.g. biceps and triceps at the elbow Autonomic nervous system (ANS) responsible for involuntary homeostatic control of many body functions Axon the long, slender projection of a neuron, that typically conducts impulses in one direction, away from the neuron's cell body and dendrites to the axon terminals Behaviour the response of an organism to internal and external stimuli Binocular disparity our two eyes have a slightly different view of the same scene because their pupils are about 65mm apart Cell body part of the neuron which contains the nucleus with its DNA and which controls the activity of the cell Central core the medulla and the cerebellum Central nervous system (CNS) the brain, spinal cord, retina and optic nerve Cerebellum part of the brain which controls balance and muscular coordination Cerebral cortex the thin outer layer of the cerebrum, comprising three parts: the sensory, motor, and association areas Chunking the grouping of separate items of information so they pass into memory as a single unit Dendrite part of the neuron which carries impulses towards the cell body Desensitisation the effect of the drug reduces with repeated exposure because there is a decrease in the number and sensitivity of receptors - the drugs involved are agonists © H ERIOT-WATT U NIVERSITY 149 150 GLOSSARY Discrimination identifying key features of an object to distinguish it from similar objects Dopamine neurotransmitter involved in the reward pathway of the brain, which is also important in a wide range of other brain functions including sleep, mode, attention, working memory, and learning Double circulation a blood circulation which passes the blood through the heart twice for every complete pass around the body Effector any organ capable of responding to a stimulus from a motor neuron, e.g. muscles, glands Elaboration linking new information with emotions, images and other memories Elaborative encoding transfer of information from STM to LTM by elaboration Encoding process by which information is converted into a form which can be passed from STM to LTM Endocannabinoid lipid signalling molecules which act like neurotransmitters in some ways, but are very different in others Endorphins opioid peptides produced by the pituitary gland and hypothalamus which act as neurotransmitters to reduce pain and increase feelings of well-being Figure object differentiated from its surroundings (ground) GABA gamma-amino-butyric acid is an inhibitory neurotransmitter found at most fast inhibitory synapses throughout the brain Generalisation the process by which a response learned in reaction to one stimulus is evoked by a different, but similar, stimulus Glial cells cells that support and maintain neurons Grey matter comprises the cell bodies of neurons and unmyelinated neurons (which lack a fatty myelin sheath) © H ERIOT-WATT U NIVERSITY GLOSSARY Ground background sensory information against which objects (figures) are discerned Hippocampus part of the limbic system, located in the lower central region of the cerebrum, which is important in moving information from short- to long-term memory and spatial navigation Hypothalamus a small portion of the brain lying in the centre at the base of the cerebrum; part of the limbic system which links the nervous system to the endocrine system through the pituitary gland; also controls body temperature, hunger, thirst, sleep and circadian cycles through the autonomic nervous system Identification changing of one's beliefs to those of an admired influencing source Imitation behaviour whereby an individual observes and replicates another's Impulse the temporary reversal of the electrical potential difference across the plasma membrane of the cell of a neuron which passes along the axon of a neuron Innate inborn Internalisation changing of one's beliefs as a result of persuasion Interneuron a neuron which connects with other neurons (including sensory, motor or other interneurons) in the CNS Limbic system located at the base of the cerebrum, this is a system consisting of many parts of the brain, including the hypothalamus, which is concerned with the formation of memories, and influences emotional and motivational states; it also regulates blood pressure, body temperature and water balance Medulla part of the brain which controls heart rate, breathing rate and blood pressure, as well as several simple reflexes Memory span the number of items that can be stored in Short-Term Memory Metabolic activity all of the chemical reactions going on within cells © H ERIOT-WATT U NIVERSITY 151 152 GLOSSARY Mood a psychological state which is less immediately affected by events than emotion, and less permanent than personality or temperament Motor neuron a neuron which connects effectors such as the muscles or glands to the central nervous system Motor skills sequences of movements that are necessary to perform a particular task Myelin a substance made largely of lipoprotein which is wrapped around the axon of sensory-motor neurons by a type of glial cell called a Schwann cell Nerve an enclosed bundle of axons in the peripheral nervous system (in the CNS these are known as tracts) Neuroglia glial cells Neuromuscular junction the connection between the axon terminal of a motor neuron and a muscle fibre Neuron a cell that transmits and processes information by means of electrical and chemical signals; such cells are often referred to as nerve cells, which is strictly incorrect because nerves contain other types of cells as well as neurons, e.g. Schwann cells Neurotransmitters a range of chemicals which convey messages between neurons, or neurons and effectors Opioid substances which attach to the opioid receptors in the central and peripheral nervous systems - endorphins are the chemicals made in the body which do this Organisation grouping new information with other similar items in memory Pacemaker also known as the sinoatrial node (SAN), a group of modified heart muscle cells which generate the electrical impulses that regulate the contractions of the heart; located in the upper part of the right atrium, the SAN naturally generates impulses between 60 - 100 times a minute Parasympathetic nervous system causes decreases in heart and breathing rates, and increases in peristalsis and intestinal secretions © H ERIOT-WATT U NIVERSITY GLOSSARY Perception the process by which the brain analyses and interprets incoming sensory information Perceptual constancy despite changing conditions of size, shape and colour, familiar objects are perceived in the same way Peripheral nervous system (PNS) all of the sensory and motor neurons outside of the central nervous system which conduct impulses to and from it Phagocytosis absorption of materials into the cell by engulfing Pituitary gland an endocrine gland about the size of a pea, which, although not part of the brain, is attached to the hypothalamus at the base of the brain; secretes nine hormones which regulate homeostasis Postsynaptic a neuron which carries receptors to bind to neurotransmitters released by the presynaptic neuron in response to the arrival of a stimulus Presynaptic a neuron at which an impulse arrives first at a synapse, and which releases neurotransmitters to signal to the postsynaptic neuron Receptor a specialised neuron which responds to stimulation by a particular stimulus Recognition identifying a perceived object as having been encountered before Reflex behaviour involving a reflex arc of sensory, inter and motor neurons, which is rapid, involuntary and often protective in nature Reflexes rapid, automatic responses to stimuli, usually involving a sensory, inter- and motor neuron reflex arc - many are protective (e.g. knee-jerk to regain balance), but others are part of routine bodily functions (e.g. swallowing) Reinforcement action which makes a behaviour more likely to be repeated Relative height the position of an object relative to the top and the bottom of an image © H ERIOT-WATT U NIVERSITY 153 154 GLOSSARY Relative size if two objects are of the same shape, the larger is perceived as closer Retina light-sensitive tissue lining of the inner surface of the eye which is considered part of the CNS, and is actually brain tissue Retrieval recall from LTM to the Working Memory of STM Reward pathway interconnected areas of the cerebral cortex and mid-brain which regulate and control behaviour by inducing pleasurable effects and, when activated, reinforce behaviours Rods cells in the retina which react to light of all colours, but are much more responsive to light than the cones which can distinguish colour - by connecting to interneurons in a convergent neural pathways, they further increase their sensitivity Segregation sorting sensory information by separating it into coherent objects and their surroundings Sensitisation the effect of a drug increases the more it is taken as a result of an increase in the number and sensitivity of neurons - the drugs involved are antagonists Sensory neuron a neuron which connects sense receptors to the central nervous system Serotonin a neurotransmitter found mainly in the gastrointestinal tract (gut), platelets and central nervous system (CNS) - in the CNS it regulates mood, appetite and sleep, as well as being involved in memory and learning Shallow encoding transfer of information from STM to LTM by rehearsal Shaping differential reinforcement of successive approximations to a desired behaviour Somatic nervous system controls the voluntary movement of skeletal muscles Stimulus (plural: stimuli) a change in the environment, internal or external, detected by an organism © H ERIOT-WATT U NIVERSITY GLOSSARY Superimposition when objects overlap, the one which is partially obscured is perceived to be further away Sympathetic nervous system causes increases in heart and breathing rates, and decreases in peristalsis and intestinal secretions Synapse the junction between the axon terminal of one neuron and the dendrite of the next in a neural pathway Synaptic cleft the gap between the axon terminal of a presynaptic neuron and the dendrite of a postsynaptic neuron at a synapse Tolerance increasing doses of a drug are required to achieve the same effect. Results from the reduction in the number and sensitivity of receptors caused by repeated exposure to agonist drugs Vesicles small lipoprotein-lined, vacuole-like structures, in the case of synaptic vesicles about 40nm in diameter Visual cortex each cerebral hemisphere has a visual cortex that is located at the back of the brain, the one on the left processing visual information from the right eye and vice versa Visual cue the aspect of an image which is used to estimate relative positions of objects or their distance from us Wake-sleep cycle the daily rhythm of waking and sleeping, determined by the internal body clock and fine-tuned to environmental cues White matter largely composed of myelinated axons © H ERIOT-WATT U NIVERSITY 155 156 ANSWERS: TOPIC 1 Answers to questions and activities 1 The structure of the nervous system Introduction to the structure of the nervous system: Questions (page 3) Q1: a) the central nervous system Q2: b) muscles and glands Q3: a) the central nervous system Q4: b) motor neurons Q5: a) interneurons Divisions of the nervous system: Question (page 5) Q6: Autonomic nervous system: Question (page 10) Q7: Sympathetic Parasympathetic Heart rate Increased Decreased Stroke volume Increased Decreased Breathing rate Increased Decreased Depth of breathing Increased Decreased Contractions of smooth muscle of gut wall Decreased Increased Intestinal secretions Decreased Increased © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 1 157 Parts of the brain: Question (page 11) Q8: The central core: Question (page 12) Q9: Medulla Cerebellum arousal balance breathing movement heart rate muscular coordination sleep posture © H ERIOT-WATT U NIVERSITY 158 ANSWERS: TOPIC 1 Limbic system and cerebral cortex: Question (page 20) Q10: Process Area Controls voluntary movement motor area Processes information for the formation of memories limbic system Transfers information between hemispheres corpus callosum Influences the secretions of the pituitary hypothalamus Recalls memories cerebral cortex Deals with language and imagination association area Receives impulses from the skin somatosensory area Centre of conscious thought cerebral cortex Controls the left side of the body right cerebral hemisphere Acts as an integrated whole brain Extended response question: Nervous system (page 23) Suggested marking scheme Each line represents a point worth one mark. The concept may be expressed in other words. Words which are bracketed are not essential. Alternative answers are separated by a solidus (/); if both such answers are given, only a single mark is allocated. In checking the answer, the number of the point being allocated a mark should be written on the answer paper. A maximum of ten marks can be gained. A) Divisions of the nervous system(maximum of 5 marks): 1. The nervous system is divided into the central nervous system and the peripheral nervous system. 2. The central nervous system consists of the brain and spinal cord. 3. The peripheral nervous system comprises all the sensory and motor neurons which connect it to the rest of the body. 4. The peripheral nervous system is sub-divided into the somatic and the autonomic nervous systems. 5. The somatic nervous system controls the voluntary activity of the skeletal muscles (and thus all movement) via its sensory and motor neurons. 6. The autonomic nervous system is further divided into the sympathetic and the parasympathetic nervous systems, which act antagonistically. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 1 159 B) Homeostatic control (maximum of 5 marks): i The autonomic nervous system plays an important part in many involuntary homeostatic processes. . . ii . . .by conducting impulses through its sensory and motor neurons to the smooth muscle of artery walls, the cardiac muscle of the heart, and to glands. iii The sympathetic nervous system prepares the body for action, 'fight or flight'. . . iv . . .by speeding up heart and breathing rates, and slowing down peristalsis and intestinal secretions. v The parasympathetic nervous system calms the body down, 'rest and digest'. . . vi . . .by slowing down the heart and breathing rates, and increasing peristalsis and intestinal secretions. End of Topic 1 test (page 24) Q11: Types of neuron: sensory, motor, interneuron. Connect sense receptors to CNS: sensory neurons. Connect CNS to muscles and glands: motor neurons. Connect to other neurons of all types: interneurons. Analysis of information: central nervous system. Muscular contractions and glandular secretions: motor responses. Divisions of the nervous system: central and peripheral. Central nervous system comprises: brain and spinal cord. Divisions of the peripheral nervous system: somatic and autonomic. Sympathetic and parasympathetic: autonomic nervous system. © H ERIOT-WATT U NIVERSITY 160 ANSWERS: TOPIC 1 Q12: Controls the movement of skeletal muscles: somatic nervous system. Skeletal muscle control by sensory and motor neurons is: voluntary. Responsible for involuntary homeostatic control: autonomic nervous system. Involuntary homeostatic control involves: sensory and motor neurons. Motor neurons of the autonomic nervous system connect to: smooth and cardiac muscle. Action of the sympathetic and parasympathetic nervous system: antagonistic. Increases heart rate, decreases intestinal secretions: sympathetic nervous system. Decreases breathing rate, increases peristalsis: parasympathetic nervous system. Q13: Cerebrum Q14: Cerebellum Q15: Central nervous system Q16: To pass information between the cerebral hemispheres. Q17: Q18: Any two from: • arousal; • breathing; • heart rate; • sleep. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 1 Q19: Cerebellum Q20: Central Q21: Peripheral Q22: Brain Q23: Somatic Q24: Sympathetic Q25: Sensory and motor neurons. Q26: Any two from: • cardiac muscle; • glands; • smooth muscle. Q27: Decrease Q28: Increase Q29: Limbic system Q30: Hormones Q31: Any two from: • blood pressure; • body temperature; • water balance Q32: Cerebral cortex Q33: Sensory and motor Q34: Any three from: • imagination; • intelligence; • language; • personality; • thought. (any one or two correct for 1 mark, any three correct for 2 marks) © H ERIOT-WATT U NIVERSITY 161 162 ANSWERS: TOPIC 2 2 Perception and memory Segregation of objects: Questions (page 33) Q1: To prevent the shape of the object being recognised against its background as its edges are no longer clear. Q2: They enable the organisation of stimuli into coherent patterns. Perception of distance: Question (page 37) Q3: • Relative size - the human figures, parasols and the paving setts are smaller towards the front of the building. • Superimposition - the sign in the foreground partly conceals the people behind it; the parasols in the mid-ground partly conceal those closer to the building. • Relative height in the field - the sign at the foot of the photo appears much closer than the tables higher in the image. Location of Sensory Memory: Question (page 42) Q4: Serial position effect 2 (page 44) Q5: The first few items are recalled from Long-Term Memory, possibly using mnemonics. The middle few items are often not recalled at all. The last few items are still in Short-Term Memory. Q6: Seven items are usually held in the Short-Term Memory. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 2 163 Q7: If it is a particularly unusual item or a favourite item of the subject. Short-Term Memory: Questions (page 45) Q8: Memory span of STM is: 7 (5-9) items. Items remain in STM for: 15-30 seconds. Items are maintained in STM by: rehearsal. Items are lost from STM by: displacement and decay. STM memory span can be increased by: chunking. Working Memory is an extension of: STM. Working Memory is used to perform: cognitive tasks. Q9: i The early numbers have been rehearsed by repetition. ii The later numbers are still in STM. iii The middle numbers have been displaced from STM. Long-Term Memory: Question (page 47) Q10: Process by which information is converted to a form which can stored in memory: encoding. Transfer from STM to LTM by repetition: rehearsal. Transfer from STM to LTM by grouping with similar items: organisation. Transfer from STM to LTM by linking with existing memories: elaboration. Encoding produced by repetition: shallow. Encoding produced by linking with emotions: elaborative. Recall from LTM to STM: retrieval. Clues which aid recall: contextual. © H ERIOT-WATT U NIVERSITY 164 ANSWERS: TOPIC 2 Location of memory in the brain: Questions (page 49) Q11: Type of memory Information stored Episodic Events and experiences Semantic Facts and concepts Procedural Motor and cognitive skills Emotional Emotional responses Spatial Location of physical objects in space Q12: Events and experiences; Facts and concepts: area of cerebral cortex where sensory information first encoded. Motor and cognitive skills: located in the motor cortex. Emotional responses: located in the amygdala of the cortex and the limbic system. Location of physical objects in space: located in the hippocampus of the limbic system. Extended response question: Short-Term Memory (page 54) Suggested marking scheme Each line represents a point worth one mark. The concept may be expressed in other words. Words which are bracketed are not essential. Alternative answers are separated by a solidus (/); if both such answers are given, only a single mark is allocated. In checking the answer, the number of the point being allocated a mark should be written on the answer paper. A maximum of ten marks can be gained. A) Increasing memory span (maximum of 3 marks): 1. Memory span is the number of items that can be retained in STM. 2. The normal short-term memory span is 7± 2 items. 3. Information is retained in STM for 15-30s. 4. 'Chunking' of memory helps short-term memory in particular as several items are grouped as one. B) Serial position effect (maximum of 5 marks): i A large number of items is shown briefly to the subjects so that they cannot all be retained in short-term memory. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 2 ii 165 Items recalled by the subjects are recorded. iii Subjects usually recall items presented early and late in the series. iv Items at the end of the series are still retained in STM (the recency effect). v Items from the start of the series have been transferred to long-term memory (the primacy effect). vi Items from the middle of the list have been displaced from STM. . . vii . . .and have not been transferred to LTM. C) Transfer from STM to LTM (maximum of 2 marks): I Rehearsal - repetition of information. II Elaboration of meaning by linking to other memories/emotions. III Organisation - linking to other similar memories. End of Topic 2 test (page 54) Q13: In the field, distance is judged by visual cues such as relative size, superimposition, and relative height. Relative size refers to the apparent dimensions of similar objects, overlap of objects is used in superimposition, and relative height refers to position in the image. At close range, binocular disparity is also used. This uses the fact that each eye has a different viewpoint. We perceive familiar objects in the same way despite changing circumstances, such as viewing angle, because of perceptual constancy. Q14: Conversion of information into a form that can be passed into LTM: encoding. Repetition of information: rehearsal. Grouping of items of information which are similar: organisation. Linking information with emotions and images: elaboration. Type of encoding produced by repetition: shallow. Forms more permanent memories than shallow encoding: organisation and elaboration. Recall from LTM to Working Memory: retrieval. Cues which relate to the conditions under which a memory was formed: contextual. © H ERIOT-WATT U NIVERSITY 166 ANSWERS: TOPIC 2 Q15: Memory of events and experiences: episodic. Memory of facts and concepts: semantic. Memory of motor and cognitive skills: procedural. Memory of how we felt about past events: emotional. Memory of the location of objects: spatial. Part of the brain where all memory is located: cerebrum. Where memories of events and facts are stored: sensory regions of cortex. Where skill-related memories are linked to long-term changes: motor cortex. Our feelings about past events involve links between: cortex and limbic system. Part of the limbic system: hippocampus. Q16: perception Q17: figures Q18: ground Q19: coherent Q20: segregation Q21: b) shape Q22: c) recognition Q23: c) inference Q24: c) inference Q25: The process of storage, retention and retrieval of information. Q26: Sensory Q27: Sensory Q28: memory span Q29: rehearsal Q30: displacement Q31: decay © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 2 167 Q32: chunking Q33: Working Memory Q34: Average number of items held: memory span. Maintains items in STM: rehearsal. New information causes loss: displacement. Without repetition, items are lost: decay. Improves STM: chunking. Performs cognitive tasks involving information in STM: working memory. © H ERIOT-WATT U NIVERSITY 168 ANSWERS: TOPIC 3 3 Neurons, neurotransmitters and neural pathways Structure of neurons: Question (page 64) Q1: © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 3 169 Neurons: Question (page 68) Q2: Neurons: type of nerve cell. Neurons receive and transmit: impulses. Neurons comprise: cell body, axon and dendrites. DNA in the cell body codes for: all cell proteins. Carry impulses towards the cell body: dendrites. Axon terminals and dendrites form: synapses. The gap between an axon terminal and a dendrite: synaptic cleft. Junction between an axon and a muscle fibre: neuromuscular. Glial cells: Question (page 70) Q3: The nervous system contains more than neurons. About 15% of the cells in the cerebrum are glial cells which support and maintain the neurons in several ways. Some of them monitor the conditions surrounding the neurons and maintain a constant environment by homeostasis. Others help repair damage by removing cell debris by phagocytosis. Another cell of this type, called the Schwann cell, wraps lipoprotein membrane around axons forming the myelin sheath, the effect of which is to greatly accelerate the conduction of impulses. Starting well before birth, this process, known as myelination, continues until adolescence. This explains why an infant's responses to stimuli are less coordinated than an adult's. Myelination: Question (page 71) Q4: 0.08 Neurotransmitters: Questions (page 74) Q5: To ensure that they do not act on cell contents and to conserve resources. Q6: Mitochondria: supply energy for active uptake of noradrenaline after its use and to provide energy for cellular functions. Ribosomes: synthesise proteins essential to produce neurotransmitters. © H ERIOT-WATT U NIVERSITY 170 ANSWERS: TOPIC 3 Neural pathways: Questions (page 81) Q7: a) converging Q8: b) diverging Q9: c) reverberating Q10: a) converging Q11: b) diverging Q12: c) reverberating Q13: b) plasticity Q14: a) brain damage Extended response question: Sensory and motor neurons (page 85) Suggested marking scheme Each line represents a point worth one mark. The concept may be expressed in other words. Words which are bracketed are not essential. Alternative answers are separated by a solidus (/); if both such answers are given, only a single mark is allocated. In checking the answer, the number of the point being allocated a mark should be written on the answer paper. A maximum of ten marks can be gained. 1. Sensory neurons pass messages from sense organs to the central nervous system whereas motor neurons transfer messages from the CNS to muscles and glands. 2. Both neurons consist of cell body, axon and dendrites. 3. The cell body is found part way along the axon of a sensory neuron, whereas the axon grows out from one side of the cell body in the motor neuron. 4. In each case, the axon is wrapped in a myelin sheath with nodes every few millimetres. 5. At a synapse, neurotransmitters cross from the pre-synaptic neuron to the postsynaptic neuron. 6. Neurotransmitters include acetylcholine and noradrenaline. 7. The type of receptor on the post-synaptic dendrite, to which the transmitter chemical binds, determines whether the next neuron is inhibited or excited. 8. Acetylcholine is immediately degraded by an enzyme. 9. Noradrenaline is reabsorbed by active uptake. 10. Synapses filter out single weak impulses, but can sum several weak impulses. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 3 171 End of Topic 3 test (page 86) Q15: Cells that make up the nervous system: neurons. Transmitted through the nervous system: impulses. Neurons that carry information into the CNS: sensory. Neurons that connect neurons: interneurons. Neurons that connect the CNS to glands: motor neurons. Carry impulses towards the cell body: dendrites. Found at the end of the axon: axon terminals. Increases speed of conduction of impulses: myelin. Cells which produce the myelin sheath: glial. Results from destruction of the myelin sheath: multiple sclerosis. Q16: Neurotransmitters are chemicals which relay signals between neurons in the CNS and between neurons and glands. The junction between neurons is called a synapse and that between neurons and muscle fibres is a neuromuscular junction. Neurotransmitters are secreted by exocytosis into synaptic cleft, and diffuse across the gap and bind to receptors on the dendrites of the next neuron. Signals may be excitatory or inhibitory, depending only on the receptor on the receiving dendrite and not on the type of neurotransmitter. Neurotransmitters must be immediately removed to prevent continuous stimulation of the post-synaptic neurons. Neurotransmitters are either removed by enzyme action (e.g. acetylcholine) or by reuptake (e.g. noradrenalin). Synapses can filter out weak impulses arising from insufficient secretion of neurotransmitter. If sufficient neurotransmitters attach to the receptors, a threshold is reached and an impulse is triggered. By summation a series of weak stimuli can combine to reach the firing threshold in the post-synaptic neuron. © H ERIOT-WATT U NIVERSITY 172 ANSWERS: TOPIC 3 Q17: Several neurons pass messages on to a single neuron: converging pathway. An example of a converging pathway: rods in the retina. Increased by a converging pathway: sensitivity to signals. A single neuron passes messages on to several neurons: diverging pathway. An example of a diverging pathway: fine motor control. Neurons later in the pathway synapse with earlier ones: reverberating pathway. An example of a reverberating pathway: wake-sleep cycle. New responses are created by their development: new neural pathways. Result of the development of new neural pathways: plasticity of response. Q18: Dendrites Q19: Axon Q20: Axon terminals Q21: It is found surrounding the axon, and its function is to insulate the axon and speed up neuron transmission. Q22: Motor Q23: Other neurons Q24: Sensory Q25: Synaptic cleft Q26: Neuromuscular junction Q27: • Maintaining a constant environment around the neuron. • Producing myelin sheath. • Removing debris by phagocytosis. Q28: Multiple sclerosis (or other suitable) Normal neuron transmission is prevented leading to loss of co-ordination. Q29: Synaptic vesicles Q30: The arrival of a nerve impulse. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 3 Q31: Diffusion Q32: Receptors Q33: It is the process by which several weak stimuli combine. . . . . .to reach the threshold to fire/release an impulse in the post-synaptic neuron. Q34: Converging Q35: Rods in the retina (other answers are possible) Q36: A single neuron passes messages on to several neurons. Q37: Converging Q38: Wake-sleep cycle (other answers are possible) Q39: Plasticity of response Q40: Any two from: • bypass areas of brain damage; • create new responses; • suppress reflexes; • suppress responses to sensory impulses. © H ERIOT-WATT U NIVERSITY 173 174 ANSWERS: TOPIC 4 4 Neurotransmitters, mood and behaviour Dopamine and the reward pathway: Question (page 93) Q1: Organisms which do not carry out key activities will not rear many offspring or even survive. Linking an activity to the reward pathway will increase its frequency / intensity; the organism is more likely to carry out these beneficial activities. Endorphins: Questions (page 95) Q2: They inhibit the triggering of impulses in the neurons linked to pain receptors. Q3: Beneficial: after a serious accident, an injured person may still be able to help others or walk to find help. Detrimental: during a tight game, a footballer may damage a muscle but continue to play, only to later discover the extent of her injury. Q4: Both sexual orgasm and the close physical presence of a loved one increase endorphin secretion. Increased endorphin levels lead to feelings of pleasure and euphoria. Without these feelings, it is hard to sustain a partnership. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 4 175 Neurotransmitter-related disorders and their treatment: Question (page 99) Q5: Disorder Alzheimer's disease Parkinson's disease Area of brain affected Cerebral cortex and mid-brain Mid-brain Neurotransmitters involved Drug Treatment Acetylcholine Acetylcholinesterase inhibitor to raise neurotransmitter levels by slowing degradation Dopamine L-DOPA as precursor of dopamine; dopamine agonists; MAO-B inhibitors to slow dopamine degradation Schizophrenia Reward pathway Dopamine Dopamine antagonists to slow uptake Generalised anxiety disorder Amygdala in cortex Serotonin Norepinephrine GABA receptor agonists, Beta-blockers Brain-stem near medulla Serotonin Norepinephrine Dopamine Drugs inhibiting norepinephrine re-uptake; MAO-B to inhibit dopamine degradation Depression © H ERIOT-WATT U NIVERSITY 176 ANSWERS: TOPIC 4 Modes of action: Question (page 103) Q6: Drug Mode of action Neurotransmitter Stimulating the release of neurotransmitters MDMA serotonin Agonists Cannabis GABA Antagonists Ethanol glutamate Inhibition of re-uptake of neurotransmitters Cocaine serotonin, norepinephrine and dopamine Inhibition of degradation of neurotransmitters Tobacco - monoamine oxidase (MAO) inhibitors monoamine oxidase (MAO) Drug addiction, sensitisation and tolerance: Questions (page 104) Q7: Changes to the number and sensitivity of receptors. Q8: An increase in the number and sensitivity of receptors. Q9: Antagonists Q10: Addiction Q11: A decrease in the number and sensitivity of receptors. Q12: Agonists Q13: Tolerance © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 4 Extended response question: The mode of action of recreational drugs (page 106) Suggested marking scheme Each line represents a point worth one mark. The concept may be expressed in other words. Words which are bracketed are not essential. Alternative answers are separated by a solidus (/); if both such answers are given, only a single mark is allocated. In checking the answer, the number of the point being allocated a mark should be written on the answer paper. A maximum of ten marks can be gained. A) Effects on the brain (maximum of 4 marks): 1. Recreational drugs mainly affect the reward circuit of the brain. . . 2. . . .by stimulating increased secretion of dopamine. . . 3. . . .which causes feelings of euphoria and relaxation. . . 4. . . .and leads quickly to addiction. 5. The changed neurochemistry leads to changes in mood / cognition / perception / behaviour. (mention of all four examples gains this mark) B) Modes of action (maximum of 6 marks): i Stimulation of release of neurotransmitter, . . . ii . . .e.g. MDMA stimulates release of serotonin. iii Agonists , imitating the action of a neurotransmitter, . . . iv . . .e.g. cannabis binds to cannabinoid receptors and suppresses GABA secretion. v Antagonists bind to receptors and prevent neurotransmitter from doing so, . . . vi . . .e.g. ethanol binds to GABA receptors and depresses impulse generation. vii Inhibiting re-uptake of neurotransmitter, . . . viii . . .e.g. cocaine blocks the re-uptake of serotonin / norepinephrine / dopamine. ix Inhibiting neurotransmitter degradation, . . . x . . .e.g. tobacco contains two MAO inhibitors which suppress dopamine breakdown. © H ERIOT-WATT U NIVERSITY 177 178 ANSWERS: TOPIC 4 End of Topic 4 test (page 107) Q14: The reward pathway involves neurons which secrete dopamine, which induces the feeling of pleasure and so reinforces particular behaviours. The reward pathway is activated by beneficial behaviour. Endorphins stimulate neurons involved in reducing the intensity of pain. Increased levels of endorphins are connected with appetite modulation. Increased endorphin production is associated with the consumption of certain foods. Many of the drugs used to treat neurotransmitter-related disorders are similar to neurotransmitters. Agonists bind to and stimulate receptors, thus mimicking the neurotransmitter. Antagonists bind to specific receptors, so blocking the action of a neurotransmitter. Other drugs inhibit the enzymes which degrade neurotransmitters, or inhibit reuptake. Q15: Many recreational drugs affect neurotransmission in the reward pathway. Changes in neurochemistry alter mood, cognition, perception and behaviour. Recreational drugs may stimulate the release of neurotransmitters. Recreational drugs may inhibit the re-uptake of neurotransmitters. Drugs which imitate the action of neurotransmitters are agonists. Drugs which block the binding of neurotransmitters are antagonists. An increase in the number and sensitivity of receptors is sensitisation. Sensitisation results from exposure to antagonist drugs. Sensitisation leads to addiction. A decrease in the number and sensitivity of receptors is desensitisation. Desensitisation results from exposure to agonist drugs. Desensitisation leads to tolerance. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 4 Q16: Endorphins Q17: Any three from: • certain foods; • prolonged and continuous exercise; • severe injury; • stress. Q18: Dopamine Q19: Pleasure / euphoria Q20: Agonists mimic the action of the neurotransmitter. Antagonists bind to the receptor and block the action of the neurotransmitter. Q21: Inhibit enzymes that degrade neurotransmitters. Inhibit neurotransmitter re-uptake. Q22: The reward pathway/circuit. Q23: Any three from: • behaviour; • cognition; • mood; • perception. Q24: • Block their binding. • Imitate their action. • Inhibit their degradation. • Inhibit their re-uptake. • stimulate their release. Q25: An increase in the number and sensitisation of receptors. Q26: Antagonists Q27: Addiction Q28: A decrease in the number and sensitisation of receptors. Q29: Agonists Q30: Tolerance © H ERIOT-WATT U NIVERSITY 179 180 ANSWERS: TOPIC 5 5 Infant attachment and the effect of communication Imprinting: Question (page 115) Q1: 1. Parent and infant are introduced to the experimental room. 2. Parent and infant are alone. Parent does not participate while infant explores. 3. Stranger enters, converses with parent, then approaches infant. Parent leaves inconspicuously. 4. First separation episode: Stranger's behaviour is geared to that of infant. 5. First reunion episode: Parent greets and comforts infant, then leaves again. 6. Second separation episode: Infant is alone. 7. Continuation of second separation episode: Stranger enters and gears behaviour to that of infant. 8. Second reunion episode: Parent enters, greets infant, and picks up infant; stranger leaves. Long period of dependency: Question (page 118) Q2: i Reason: learning Explanation: humans require to learn more of their behaviour than any other animals, e.g. language ii Reason: socialisation Explanation: humans have to learn how to live in complex social groups and have to interact with others in a wide range of situations. Parental control methods: Questions (page 119) Q3: Demanding Undemanding Responsive Authoritative Permissive Unresponsive Authoritarian Neglectful Q4: i Authoritative parenting is responsive to the child's views, involves the child in decision making, and supports the child emotionally. ii Authoritative parenting sets rules and standards, and expects maturity and cooperation. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 5 181 Information transfer: Question (page 120) Q5: Non-verbal Body language Non-verbal Gesture Shouting out Walking with an expanded chest after a victory Indicating that an archer's bow finger will be cut off if he gets caught Talking Feeling your collar when under pressure Pointing to your nose when playing charades Sobbing loudly Showing whites of eyes when angry Throwing a fist in the air Verbal Extended response question: Human communication (page 128) Suggested marking scheme Each line represents a point worth one mark. The concept may be expressed in other words. Words which are bracketed are not essential. Alternative answers are separated by a solidus (/); if both such answers are given, only a single mark is allocated. In checking the answer, the number of the point being allocated a mark should be written on the answer paper. A maximum of ten marks can be gained. A) Non-verbal communication (maximum of 4 marks): 1. Non-verbal communication involves gestures, signs, facial movements and posture. 2. Non-verbal communication aids verbal communication. 3. Attitudes and emotions are signalled by non-verbal communication. 4. Mirroring of non-verbal communication strengthens bonds. 5. Examples of non-verbal communication include winking, folding arms and smiling. (three listed for one mark) 6. Any two examples explained in terms of meaning conveyed. B) Verbal communication (maximum of 6 marks): i Language uses symbols to represent information ii Language enables information to be organised into categories and hierarchies. iii This organisation of information accelerates learning. iv Organisation of information aids intellectual development. v The ability of humans to communicate verbally has resulted in the transmission of knowledge. (plus explanation) © H ERIOT-WATT U NIVERSITY 182 ANSWERS: TOPIC 5 vi The ability of humans to communicate verbally has resulted in the development of culture. (plus explanation) vii The ability of humans to communicate verbally has resulted in social evolution. (plus explanation) viii The ability of humans to communicate verbally has resulted in the transmission of knowledge, development of culture and social evolution. End of Topic 5 test (page 128) Q6: Early infant attachment is important for future stable relationships. Attachment becomes evident between six and nine months after birth. Two responses to the strange situation experiment are detachment and anger. Infants who form secure attachments are more likely to investigate their environment. Humans have a relatively long period when they are dependent on adults. The long period of dependency provides opportunities for socialisation and learning. Social competence can be influenced by different methods of control. Authoritative control generally results in greater social competence. Q7: Non-verbal communication contributes to the formation of relationships between individuals. It can signal attitudes and emotions, and acts as an aid to verbal communication. Language uses symbols to represent information and enables information to be organised into categories and hierarchies. This organisation of information accelerates learning and intellectual development. The ability of humans to communicate verbally has resulted in the transmission of knowledge, development of culture, and social evolution. Q8: A stranger and an observer. Q9: The infant's reunion behaviour with its parent/carer. Q10: b) Insecurely attached, avoidant Q11: a) Securely attached Q12: 6-9 months © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 5 Q13: Socialisation and learning. Q14: a) Authoritative Q15: Any two from: • child's views ignored; • no emotional support; • standards not set. Q16: Attitudes and emotions. Q17: Symbols Q18: Categories and hierarchies. Q19: It accelerates learning and intellectual development. Q20: Any two from: • development of culture; • social evolution; • transmission of knowledge. © H ERIOT-WATT U NIVERSITY 183 184 ANSWERS: TOPIC 6 6 The effect of experience and social influences The effect of practice on motor skills: Questions (page 133) Q1: A change in behaviour as a result of experience. Q2: Motor pathway Q3: Repeated use Trial and error learning: Question (page 137) Q4: Trial and error involves random responses to a stimulus. Extinct behaviour becomes extinguished. Reinforcement involves making similar response to a stimulus more likely on subsequent occasions. Shaping involves differential reinforcement of successive approximations to a desired behaviour. Generalisation and discrimination: Question (page 138) Q5: Generalisation Discrimination Not liking the people from a particular city Only eating the sweets in the purple wrappers Randomly choosing any dish on the menu Checking the tomatoes in the supermarket before putting them in the bag Enjoying travelling by train Picking the spotted puppy from the litter Midges spoil camping holidays in Britain Catching the No. 54 bus at the bus station © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 6 185 Social facilitation and deindividuation: Question (page 140) Q6: Performance improved by the presence of others: social facilitation. Performance improved in front of a crowd: audience effect. Performance improved by having competition: co-actor effect. Loss of identity in a crowd: deindividuation. Extended response question: Group behaviour and social influence (page 143) Suggested marking scheme Each line represents a point worth one mark. The concept may be expressed in other words. Words which are bracketed are not essential. Alternative answers are separated by a solidus (/); if both such answers are given, only a single mark is allocated. In checking the answer, the number of the point being allocated a mark should be written on the answer paper. A maximum of eleven marks can be gained. A) Social facilitation (maximum of 3 marks): 1. Performance of a task may be improved in the presence of others. 2. The presence of others in a competitive situation may enhance performance 3. Detailed example of the point above 4. The presence of an audience may improve performance. 5. Detailed example of the point above B) Deindividuation (maximum of 4 marks): i Deindividuation is responsible for the loss of identity in a crowd. ii Detailed example of the point above iii Deindividuation leads to diminished restraints on behaviour. iv Deindividuation leads to behaviour which would not be shown by individuals on their own. v Detailed example of the point above C) Influences that change beliefs (maximum of 4 marks): I Internalisation is the changing of one's beliefs as a result of persuasion. II Detailed example of the point above III Identification is the changing of one's beliefs to those of an admired influencing source. IV Detailed example of the point above © H ERIOT-WATT U NIVERSITY 186 ANSWERS: TOPIC 6 End of Topic 6 test (page 143) Q7: A change in behaviour brought about by experience: learning. An important part of learning: observing. Improved by repeated practice: motor skills. Established by practice of a motor skill: motor pathway. Copying behaviour: imitation. Makes behaviour patterns likely to be repeated: positive outcomes. Rewarding desired behaviour: reinforcement. Fate of behaviour that is not rewarded: becomes extinct. Rewarding behaviour as it gets closer to what is wanted: shaping. Q8: Generalisation is the process by which a response learned to one stimulus is evoked by a different but similar stimulus, whereas discrimination is the process by which people learn to make different responses to similar stimuli. The presence of others in a competitive situation may enhance performance, as can the presence of an audience may improve performance. These are examples of different types of social facilitation. Deindividuation is responsible for the loss of identity in a crowd which may lead to diminished restraints on behaviour. Internalisation is the changing of beliefs as a result of persuasion. Identification is the changing of one's beliefs to those of an admired influencing source. Q9: Behaviour with positive outcomes will be repeated; behaviour with negative outcome will become extinct. Q10: Desired behaviour is rewarded. Q11: Behaviour which successively more closely approximates to the desired behaviour is rewarded. Q12: The child becomes afraid of small and/or white dogs, but not others Q13: The child becomes afraid of all dogs. Q14: Social facilitation means that individuals perform better when competing with others and when performing in front of an audience. Q15: Celebrities: people may want to be like the celebrity and imitate them by using the cream. 'Scientists': people may be persuaded that they should use the product by the pseudoscience presented. © H ERIOT-WATT U NIVERSITY ANSWERS: TOPIC 7 187 7 End of unit test End of Unit 3 test (page 146) Q1: The central nervous system comprises the brain and the spinal cord. The sympathetic and parasympathetic nervous systems act antagonistically. The limbic system influences the pituitary through the secretion of hormones. Perception is the process by which the brain analyses incoming sensory information. Information is lost from Short-Term Memory by displacement or decay. Glial cells support and maintain neurons by removing debris by phagocytosis. Increased endorphin production is associated with severe injury. Recreational drugs may inhibit the enzymatic degradation of neurotransmitters. A trait that becomes evident between six and nine months after birth is attachment. Language uses symbols to represent information. Learning is a change in behaviour brought about by experience. Internalisation is the changing of beliefs as a result of persuasion. Q2: 20 % Q3: 4:3 Q4: Percentage recall decreases from the 1st to the 5th pictures. . . . . .then increases back up to 11th picture. Q5: • Increase the number of children used. • Repeat the experiment several times. Q6: Any two from: • age of pupils; • gender of pupils; • pictures used; © H ERIOT-WATT U NIVERSITY 188 ANSWERS: TOPIC 7 • time allowed to look at the pictures; • time delay before asking to recall the pictures after last one viewed; • time of day when test is taken. Q7: The first and last five pictures would be the same, the middle ten would be very low. Q8: Any two from: • arousal; • breathing; • heart rate; • sleep. Q9: Cerebellum Q10: Either of: • influences the pituitary; • secretes ADH. Q11: Any one from: • body temperature; • controls contraction of smooth muscle; • water balance. Q12: Either of: • emotional; • motivational. Q13: Dopamine Q14: Figure and ground. Q15: Any two from: • relative height in field; • relative size; • superimposition. Q16: Shape Q17: Symbols Q18: Generalisation Q19: Persuasion © H ERIOT-WATT U NIVERSITY