Download The Brain

Module 4
The Brain
The Nervous System
The Brain
 Centerpiece of the nervous system
 weighs 1300 - 1400 g
 made up of about 100 billion neurons
 works by firing millions of synapses and
releasing billions of neurotransmitter
molecules.
 “the most complex living structure on the
universe”
The Case of Phineas Gage
the historical beginnings of the study of the biological basis of behavior
Lesions, autopsies, EEG
 Lesions: the site and extent of the brain
tissue damage are important guides to the
kind of disruption in behavior that is
observed and vice versa.
 Lesioned brains can be autopsied and studies
in detail
 Electrocephalograms (EEG): Electrodes
are attached to the subject’s scalp, and
the device records the patterns of brain
waves.
How do we study the brain?
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Autopsies
Clinical observations
Lesions
EEG
Neuroimaging
Neuroimaging
 PET (positron emission tomography) Scan
 Radioactive form of sugar is given
 Sugar goes to the region of the brain that is
active
 MRI (magnetic resonance imaging)
 uses magnetic fields and radio waves
 Generates images that distinguish among
different types of soft tissue
 Functional MRI
 Reveals blood flow, therefore brain activity
 Compares successive MRI scans while the
patient is performing a task
Mapping the Brain
The Cerebral Cortex
 Functional MRI
scan shows the
visual cortex
activated as the
subject looks at
faces
The Brain
 The core (older brain structures)
 The limbic system
 The cerebral cortex
Older/lower brain
structures
Older Brain Structures
Relays sensory
input except smell
Filters information
Controls alertness
Heartbeat
and
breathing
Cerebellum
Pons
Coordinates
movements
Brainstem
Older brain structures
 Brainstem – the crossover point
 Medulla – autonomic vital functions
 Pons – Coordination of movement
 Reticular Formation – nerve network
 Filters and relays information from spinal cord
 Controls arousal and alertness
 Thalamus – sensory switchboard for sight,
hearing, touch, and taste
 Cerebellum - the “little brain” at the rear of the
brainstem
 Enables non- verbal behavior & memory
 Decision making
 Coordinate voluntary movement and balance
The Limbic System
 Resides around the
older brain parts and
the cerebral
hemispheres
 Involved in emotion,
memory, drives
The Limbic System
 Hippocampus: processes memory
 Amygdala: influences aggression and fear
 Perception of these emotions
 Processing of emotional memories
 Hypothalamus: monitors the pituitary gland
 Influences feelings of hunger, thirst, body
temperature and sexual arousal
 Houses the pleasure or reward centers
The Cerebral Cortex:
our resource for adaptability
 Largest part of the brain
 Cerebral cortex
 Cerebral hemispheres
 Corpus callosum
 Body’s ultimate control and
information processing
system
 Adaptation of species resulted
in changes in the cerebral
cortex
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Structure of the Cerebral Cortex
 Frontal Lobes:
Thinking, planning,
movement
 Parietal Lobes: body
sensation
 Occipital Lobes: Vision
 Temporal Lobes:
Hearing, language
Functions of the Cerebral Cortex
Functions of the Cerebral Cortex
 Motor Functions
 Message send out to the body is controlled by the
motor cortex – the area at the rear of the frontal
lobes
 Sensory Functions
 Incoming messages are controlled by the
sensory cortex - area at the front of the parietal
lobes
 The rest (90% of the cortex): Association
areas
 Integrate information
 Involved in higher mental functions such as
language, remembering, thinking.
Our divided brain
 Hemispheres control and receive
information from the opposite sides of the
body
 Hemispheric Specialization 
 Left hemisphere: language, logic, and
complex motor behavior
 Right hemisphere: non-linguistic functions
including recognition of faces, places, and
sounds (music)
Localizing cognitive activities
 Are abilities asymmetrically represented in
the two hemispheres?
 Left Hemisphere (LH) hemisphere critical
for language
 the idea of hemispheric specialization by the
end of 1860s
 hemispheric specialization : : the tendency
for a given psychological function to be
served by one of the hemispheres
 evidence: LH lesions disrupt damage
language; RH damage disrupt visual-spatial
abilities
 language faculty served by the LH; musical
and visual-spatial cognition by the RH
Language areas of the brain
Split-Brain research
 removal of corpus callosum, the
connective tissue that communicates
info between the LH and the RH, from
epilectic patients
 background: lateralization of visual,
auditory, and tactile systems
 one side of the brain controls the opposite
of the body and information receiving field
 set up a task that poses a question to
one hemisphere and requires the
answer from another
Split brain: visual field study
HE ART
Left visual field
Right visual field
Interpretation of split-brain work
 the RH of a split-brain patient has some
awareness of the stimulus when a
stimulus is presented to the left visual field
 but cannot perform tasks where language
skills are required
 Hemispheric specialization/lateralization:
the RH has a limited ability to perform
language skills
The brain acts as a unifed whole
Ex: Language functions
READING
Register in
visual area
Transform
words into
auditory code
Auditory code
received and
understood
Motor area
produces the
word
Brain Plasticity
 The brain’s capacity for modification
 Not only genes but also our expriences shape
the brain
 Brain reorganizes itself following damage
(especially in children)
 Many possibilities within the neural networks
 Brain reorganizes itself through intense
learning experiences
 Blind people– use a finger to read Braille
 Video--- woman born with half a brain