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Behavioral Neuroscience Dr Rosh Rauf Aziz MBChB MRCPsych Behavioral Neuroscience The Body’s Communication Networks The Neuron The Brain Prospects for the Future Neurotransmission The Body’s Communication Networks The Nervous System Central Nervous System(CNS) The network of nerves contained within the brain and spinal cord Peripheral Nervous System(PNS) The PNS comprises the somatic and autonomic nervous systems The Body’s Communication Networks Divisions of the Nervous System The Body’s Communication Networks The Endocrine System Endocrine system: Ductless glands that regulate growth, reproduction, metabolism, mood, and some behavior. Hormones: Chemical messengers secreted into the bloodstream. The Neuron Neurons Nerve cells that serve as the building blocks of the nervous system Sensory Neurons Neurons that send signals from the senses, skin, muscles, and internal organs to the CNS Motor Neurons Neurons that transmit commands from the CNS to the muscles, glands, and organs The Neuron The Withdrawal Reflex The Neuron The Structure of a Neuron The Neuron The Neuron in Action Action Potential An electrical impulse that surges along an axon, caused by an influx of positive ions in the neuron Threshold The level of stimulation needed to trigger an action potential Neurotransmitters Chemical messengers that transmit information by crossing the synapse from one neuron to another The Neuron How Neurons Communicate Impulse releases neurotransmitter from axon terminals. Neurotransmitter enters synaptic gap. Neurotransmitter binds to receptors on the receiving neuron. The Neuron Neurotransmitters Acetylcholine (ACh) Dopamine Endorphins Norepinephrine Serotonin Gamma amino butyric acid (GABA) The Brain Tools of Behavioral Neuroscience Clinical Case Studies Experimental Interventions Electrical Recordings Brain-Imaging Techniques The Brain Tools of Behavioral Neuroscience Electroencephalogram (EEG) •An instrument used to measure electrical activity in the brain through electrodes placed on the scalp The Brain Tools of Behavioral Neuroscience Magnetic Resonance Imaging A brain-imaging technique that uses magnetic fields and radio waves to produce, clear three-dimensional images The Brain Tools of Behavioral Neuroscience Positron Emission Tomography A visual display of brain activity, as measured by the amount of glucose being used Radioactive isotopes (small amounts) are placed in the blood. Sensors detect radioactivity. Different tasks show distinct activity patterns. Cortical Lobes © 2004 John Wiley & Sons, Inc. Huffman: PSYCHOLOGY IN The Brain Regions of the Brain The Brain Regions of the Brain Medulla Vital involuntary functions Pons Sleep and arousal Reticular formation Sleep, arousal, attention Cerebellum Motor coordination The Brainstem The Brain Regions of the Brain Thalamus Sensory relay station Amygdala Fear, anger, and aggression Hippocampus Memory formation Hypothalamus Regulates glands, autonomic NS The Limbic System The Brain Regions of the Brain The Cerebral Cortex in Animals •The outermost covering of the brain, largely responsible for higher-order mental processes The Brain Regions of the Brain Within the Lobes of the Cerebral Cortex Are: The Somatosensory Cortex Receives sensory information The Motor Cortex Sends impulses to voluntary muscles The Association Cortex Houses the brain’s higher mental processes The Somatosensory and Motor Areas The Brain Regions of the Brain Broca’s Area Language Processing Located in the left hemisphere, directs the muscle movements in speech production Wernicke’s Area Located in the left hemisphere, involved in the comprehension of language The brain operates as an integrated system. The Brain The Split Brain The Corpus Callosum A bundle of nerve fibers that connects the left and right hemispheres If surgically severed for treatment of epilepsy, hemispheres cannot communicate directly. The Brain The Split Brain Both eyes send information to both hemispheres. Images in the right half of the visual field go to the left hemisphere. Images in the left half of the visual field go to the right hemisphere. Visual Processing The Brain The Split Brain The Talking Left Hemisphere Brighter areas indicate higher activity levels. When hearing words, for example, auditory cortex and Wernicke’s area are the most active. The Brain The Split Brain A patient with a stroke in the right hemisphere was asked to copy the drawings. Typical of neglect syndromes, the left side of the model is almost completely ignored. Neglect Syndrome THE BRAIN The cerebral cortex is a higher-level brain structure…it’s responsible for higher-level cognitive processes The cerebral cortex covers the two hemispheres of the brain with wrinkled folds (sort of like a cauliflower)….these “wrinkles” increase the entire surface area of the cortex. The cerebral cortex consists of 30 billion nerve cells and around 300 trillion synaptic connections! The cerebral cortex For convenience sake, each hemisphere of the brain is often subdivided into four different lobes—or four different geographic regions. The cerebral cortex provides many functions for the body—some of these functions have been “localized” (i.e., the particular part of the cortex that carries the functions out have been identified) but it is important to realize that multiple areas of the brain work together for most complex human behaviors. The Cerebral Cortex Frontal Lobes involved in speaking and muscle movements and in making plans and judgments Parietal Lobes include the sensory cortex Occipital Lobes include the visual areas, which receive visual information from the opposite visual field Temporal Lobes include the auditory areas Functions of the cerebral cortex Motor functions—the motor cortex is located at the rear of the frontal lobe. Sensory functions—the sensory cortex is located in the front of the parietal lobe (right behind the motor cortex) Note that each hemisphere of the brain controls and receives info from the OPPOSITE side of the body. So the command for moving your left arm originates from the motor cortex in your right hemisphere. Functions of the cerebral cortex Sensory functions (continued) Information from the optic nerve is sent to the visual cortex located in the occipital lobe Information from the sensory organs in our ears are sent to the auditory cortex located in the temporal lobes Functions of the cerebral cortex Associational functions— Our brain does lots of organizing and interpretation of information. This organization and interpretation is accomplished by association areas in the brain Association areas are believed to make up ¾ of the area of the brain Association areas of the brain used for planning ahead are believed to be located in the frontal lobes of the brain Association Areas Areas of the cerebral cortex that are not involved in primary motor or sensory functions Involved in higher mental functions such as learning, remembering, thinking, and speaking Functions of the cerebral cortex Motor functions Sensory functions Associational functions Language functions—Two important brain areas for language are: Wernicke’s area—located in the left temporal lobe— important for our understanding of language Broca’s area—located in the left frontal lobe— important for spoken language Prefrontal cortex • %3.5 of cat brain • %7 of dog brain • %17 of chimphanzee brain • %29 of human brain • A multimodal association cortex which receive connections from all over the brain • Executive functions, stepwise thinking, control of impulses, inhibitions • A variety of functions that permit us to integrate information from various sources, to plan and make decisions and to generate new thoughts and ideas Limbic system Limbic System • Located in the centre of the brain, on top of the brain stem, inside the temporal lobes • Integrates visceral information with perceptions from external environment by using input from multiple modalities (visual, auditory cues etc). • Relates this information with previous experience • Emotional significance or meaning of our perceptions and experiences • Important in emotion and memory • The Amygdala and the Hippocampus are the main structure Hippocampus • • • • Greek word for seahorse Curves over the amygdala Essential for storing new memories a person with bilateral hippocampus injury cannot remember anything that happened after the injury. He cannot remember you even if he met you 10 minutes ago Stress and hippocampus • Stress causes structural changes in hippocampus Amygdala • Located between the hippocampus and the hypothalamus • Essential in emotional learning and regulating emotions • Stimulation of amygdala: Fear, horror • Damage to it results in emotional disorders Evidence from animal, neuropsychological and imaging studies suggest that the Amygdala is of primary importance in the recognition of fear. The amygdala and fear - evidence from human neuropsychology Bilateral amygdala damage; -Reduces recognition of fear-inducing stimuli -Reduces recognition of fear in others -Reduces ability to express fear Prospects for the Future The Brain’s Capacity for Growth & Reorganization Plasticity A capacity to change as a result of experience Richer environments lead to heavier, thicker brains, more synapses, and better learning. The cost of plasticity is the case of the phantom limb. Psychology, 4/e by Saul Kassin ©2004 Prentice Hall Prospects for the Future The Brain’s Capacity for Growth & Reorganization Neurogenesis The production of new brain cells Neural Graft Technique of transplanting healthy tissue from the nervous system of one animal into that of another Psychology, 4/e by Saul Kassin ©2004 Prentice Hall Communication between neurons is chemical In this “lock & key” fashion, neurotransmitters unlock tiny channels at the receiving sites on nearby neurons, and electrically charged atoms enter the receiving neuron. These electrically charged atoms—through altering the electrical charge of the receiving neuron—either excite or inhibit its readiness to fire an electrical impulse down it’s axon Communication within neurons is electrical Neurons fire when their electrical charge reaches what is called the threshold of excitation. When this threshold is reached, they send an electrical charge or impulse down their axons. This electrical impulse is called (as I mentioned earlier) “an action potential.” Communication between neurons is chemical and within neurons is electrical… Through binding with receptor cells, neurotransmitters alter the likelihood of the receiving neurons reaching the threshold of excitation, thus they are either inhibitory (make the firing of the receiving neuron LESS likely) or excitatory (make the firing of the receiving neuron MORE likely). Neurotransmitters… are chemicals that are released into the synapse by neurons. These neurotransmitters are “taken back up” into the terminal buttons of neurons through the process of reuptake Neurotransmitters… The balance of neurotransmitters in the body have been implicated in a number of Psychiatric conditions , such as depression or schizophrenia (a mental disorder in which an individual loses touch with reality and e.g., may hear voices or see things that aren’t there—called hallucinations) The Synapse Terminal Dendrite • Action potential releases stored neurotransmitters • They flood across synapse and interact with complex receptors on the dendrite side Neurotransmitters • Transmit information from one neuron to another • Probably hundreds of neurotransmitters • They govern every brain function—thought, feeling, sleep, pain etc. • Some are specific to one brain area Neurotransmitters • • • • • • Glutamate GABA Serotonin Acetylcholine Dopamine And many others…. Glutamate • The main excitatory neurotransmitter in CNS • Excitation: stimulation, increasing the activity GABA • The main inhibitory neurotransmitter in CNS • Inhibition: decreasing the action • Directly involves in regulating muscle tone Serotonin • • • • Projects to wide range of CNS regions A general modulator Involved in pain, sleep and emotions. Serotonin hypothesis of depression Norepinephrine • • • • Have effects on almost every brain region Diffusely projected through CNS Diffuse modulatory effect within CNS Related to pleasure, memory, arousal, wakefulness. • Increased amounts increase alertness • Role in depression Acetylcholine (Ach) • Important in sleep and dream • Related to attention, encoding of memory and to muscle action. • In Alzheimer’s disease losses of acetlycholine projections Dopamine • Dopamine system is more specifically localized in brain • Related to voluntary movement • Important for cognition, emotion, memory • A synthetic form treats Parkinson’s Disease by fitting onto the post synaptic membrane. Psychotropic drugs (drugs used to treat psychological conditions) work through altering neurotransmitter balances in the body Psychotropic drugs Agonists mimic the neurotransmitter by binding to the receptor sites just as the neurotransmitters do and having the same effect on the receiving neuron. Agonists are used when it is believed that there is not enough neurotransmitter Antagonists BLOCK the neurotransmitter by binding to the receptor sites without affecting the receiving neuron in the same way. Because they “fill” the receptor sites. Antagonists are used when it is believed that there is TOO much of the neurotransmitter in the body. Psychotropic drugs When there is TOO LITTLE neurotransmitter in the body, drugs can block its reuptake and thus increase the amount of neurotransmitter in the synapse Prozac is an example of this sort of drug. Prozac falls in a class of drugs called SSRI’s (Selective Serotonin Reuptake Inhibitor) and by inhibiting reuptake of serotonin, they increase the levels of this neurotransmitter in the brain. The two communication systems for body are: The nervous system (which we’ve just been discussing) AND The endocrine system Neural and Hormonal Systems Endocrine System the body’s “slow” chemical communication system a set of glands that secrete hormones into the bloodstream Hormones chemical messengers, mostly those manufactured by the endocrine glands, that are produced in one tissue and affect another Neural and Hormonal Systems Adrenal Glands a pair of endocrine glands just above the kidneys secrete the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline), which help to arouse the body in times of stress Pituitary Gland under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands