Transcript Behavioral Neuroscience

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
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Neurons that send signals from the senses,
skin, muscles, and internal organs to the
CNS
 Motor Neurons
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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
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Acetylcholine (ACh)
Dopamine
Endorphins
Norepinephrine
Serotonin
Gamma amino butyric acid (GABA)
The Brain
Tools of Behavioral Neuroscience
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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
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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
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Vital involuntary
functions
 Pons
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Sleep and arousal
 Reticular formation

Sleep, arousal,
attention
 Cerebellum
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Motor coordination
The Brainstem
The Brain
Regions of the Brain
 Thalamus
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Sensory relay station
 Amygdala
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Fear, anger, and
aggression
 Hippocampus
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Memory formation
 Hypothalamus
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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
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Receives sensory information
 The Motor Cortex
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Sends impulses to voluntary muscles
 The Association Cortex
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Houses the brain’s higher mental processes
The Somatosensory and Motor Areas
The Brain
Regions of the Brain
 Broca’s Area
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Language Processing
Located in the left
hemisphere, directs the
muscle movements in
speech production
 Wernicke’s Area
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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
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involved in speaking and muscle movements and in making plans and
judgments
 Parietal Lobes
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include the sensory cortex
 Occipital Lobes
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include the visual areas, which receive visual information from the
opposite visual field
 Temporal Lobes
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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)
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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:
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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
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%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
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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
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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
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The production of new brain cells
 Neural Graft
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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
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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
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Projects to wide range of CNS regions
A general modulator
Involved in pain, sleep and emotions.
Serotonin hypothesis of depression
Norepinephrine
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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