Transcript The Brain - CCRI Faculty Web

The Biology of Behavior
PowerPoint®
Presentation
by Jim Foley
© 2013 Worth
Publishers
Module 4: The Brain
The Brain
What we’ll discuss:
 how we learn about the brain
 the life-sustaining inner parts of the
brain: the brainstem and limbic system
 the outer, wrinkled “bark”: the cortex
 left, right, and split brains
Questions about parts of the brain:
 Do you think that the brain is the
sum of its parts, or is the brain
actually about the way they are
connected?
 What do you think might happen
if a particular area of the brain
was stimulated?
 What do you think might happen
if a particular area of the brain
was damaged or not working
well?
Is it possible to
‘understand’ the brain?
“If the human brain were
so simple that we could
understand it, we would
be so simple that we
couldn’t.”
–Emerson M. Pugh
…but we can try.
Exploring the Older Brain, Cerebral
Cortex, and Divided Brain
How we learn about the
brain:
 Scans and more
The primitive, lifesustaining, inner parts of the
brain:
 The brainstem and limbic
system
 Cerebral Cortex Structure:
The Lobes
 Motor and sensory strips
 Association areas
 Brain Plasticity
 Functioning of the right
and left hemispheres
from cases of the divided
and intact brains
Monitoring activity in the brain
Tools to read electrical, metabolic, and magnetic
activity in the brain:
EEG:
electroencephalogram
PET: positron emission
tomography
MRI: magnetic
resonance imaging
fMRI: functional MRI
EEG:
electroencephalogram
An EEG (electroencephalogram)
is a recording of the electrical
waves sweeping across the
brain’s surface.
An EEG is useful in studying
seizures and sleep.
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PET: positron emission
tomography
The PET scan allows us to see what
part of the brain is active by
tracing where a radioactive form
of glucose goes while the brain
performs a given task.
MRI: magnetic
resonance imaging
MRI (magnetic resonance imaging)
makes images from signals produced by
brain tissue after magnets align the spin
of atoms.
The arrows below show ventricular
enlargement in a schizophrenic patient
(right).
fMRI: functional MRI
Functional MRI reveals
brain activity and
function rather than
structures.
Functional MRI
compares successive
MRI images taken a
split second apart, and
shows changes in the
level of oxygen in
bloodflow in the brain.
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The Brain:
Less Complex Brain Structures
Our tour of the brain begins with parts of the human
brain found also in simpler animals; these parts
generally deal with less complex functions:
Brainstem (Pons and Medulla)
Thalamus
Reticular Formation
Cerebellum
Limbic System
The Brainstem:
Pons and Medulla
The Base of the
Brainstem:
The Medulla
 The medulla controls the most basic functions
such as heartbeat and breathing.
 Someone with total brain damage above the
medulla could still breathe independently, but
someone with damage in this area could not.
The Thalamus
The
crossover
 The thalamus is the
“sensory switchboard” or
“router”: All sensory
messages, except smell, are
routed through the
thalamus on the way to the
cortex (outer brain).
 These messages cross over
from one side of the body
to the opposite side of the
brain.
Reticular (“net-like”) Formation
 The reticular formation is a
nerve network in the
brainstem.
 It enables alertness
(arousal); stimulating this
makes us wide awake.
 It also filters incoming
sensory information and
relays it to other brain
areas.
Cerebellum (“little brain”)
The cerebellum
helps coordinate
voluntary
movement such as
playing a sport.
The cerebellum has many other
functions, including enabling
nonverbal learning and memory.
The Limbic (“Border”) System
The limbic system coordinates:
 emotions such as fear and
aggression.
 basic drives such as hunger and
sex.
 the formation of episodic
memories.
The hippocampus (“seahorse”)
 processes conscious, episodic
memories.
 works with the amygdala to
form emotionally charged
memories.
The Amygdala (“almond”)
 consists of two lima bean- sized
neural clusters.
 helps process emotions,
especially fear and aggression.
The Amygdala:
Enabling two different responses to threat
 Electrical stimulation
of one area of a cat’s
amygdala provokes
aggressive reactions.
 If you stimulate a
different part of the
amygdala and put the
cat in a cage with a
mouse, the cat will
cower in terror.
The Hypothalamus:
 lies below (“hypo”) the
thalamus.
 regulates body temperature and
ensures adequate food and
water intake (homeostasis), and
is involved in sex drive.
 directs the endocrine system via
messages to the pituitary gland.
Thalamus
The Hypothalamus as a Reward Center
Riddle: Why did the rat
cross the grid?
Why did the rat want to
get to the other side?
Pushing the pedal that
stimulated the electrode
placed in the
hypothalamus was much
more rewarding than food
pellets.
Review of Brain Structures
Higher Brain, Split Brain
Topics for your cortex to process:
 Cerebral Cortex
Structure: The
Lobes
 The motor and
sensory strips and
association areas
 Brain Plasticity
 Functioning of he
right and left
hemispheres from
cases of the
divided and intact
brains
The Cerebral Cortex:
 The outer grey “bark” structure that is wrinkled in order
to create more surface area for 20+ billion neurons.
 Organized into 4 lobes in each of two hemispheres.
300 billion synaptic
connections
The brain has
left and right
hemispheres
The Lobes of the Cerebral Cortex:
Preview
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; they
receive visual information from
the opposite visual field
Temporal Lobes
include the auditory processing
areas
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Functions of the Brain:
The Motor and Sensory Strips
Output: Motor
cortex (Left
hemisphere
section
controls the
body’s right
side)
Input: Sensory
cortex (Left
hemisphere
section receives
input from the
body’s right side)
 Axons
receiving motor
signals FROM
the cortex
Axons
sending
sensory
information
TO the cortex
Sensory Functions of the Cortex
 The sensory strip deals
with information from
touch stimuli.
 The occipital lobe deals
with visual information.
 Auditory information is
sent to the temporal
lobe.
The Visual Cortex
This fMRI scan
shows
increased
activity in the
visual cortex
when a person
looks at a
photograph.
Association function of the cortex
More complex animals have more cortical space
devoted to integrating/associating information
Case study: Phineas Gage
In a work accident, a metal rod
shot up through Phineas Gage’s
skull, destroying his eye and part
of his frontal lobes.
After healing, he was rude, odd,
irritable, and unpredictable.
Possible explanation for the
change in personality:
Damage to his frontal lobes hurt
his ability to inhibit emotions and
impulses.
Whole-brain Association Activity
Whole-brain association
activity involves complex
activities which require
communication among
association areas across the
brain such as:
 memory
 language
 attention
 meditation and spirituality
 consciousness
Plasticity: The Brain is Adaptable
If the brain is damaged,
especially in the general
association areas of the cortex:
 the brain does not repair
damaged neurons, BUT it can
restore some functions
 it can form new connections,
reorganize, reassign brain
areas to new functions.
 Some neurogenesis,
production of new brain cells,
helps rebuild
This 6-year-old had a
hemispherectomy to end lifethreatening seizures; her
remaining hemisphere
compensated for the damage.
SplitTo end severe
whole-brain
seizures, some
people have had
surgery to cut the
corpus callosum,
a band of axons
connecting the
hemispheres.
Brain Studies
Researchers have studied the
impact of this surgery on
patients’ functioning.
Separating the Hemispheres:
Factors to Keep in Mind
 Each hemisphere controls the opposite side of
the body AND is aware of the visual field on
that opposite side.
 Without the corpus callosum, the halves of
the body and the halves of the visual field do
not work together.
 Only the left half of the brain has enough
verbal ability to express its thoughts out loud.
Split visual field
Each hemisphere
perceives the half of the
view in front of you that
goes with the half of the
body that is controlled
by that hemisphere.
Divided Awareness in the Split Brain
Try to explain the following result:
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The divided brain in action
 Talent: people
are able to
follow two
instructions and
draw two
different shapes
simultaneously
 Drawback:
people can be
frustrated that
the right and left
sides do
different things
Our Two
Hemispheres
Lateralization (“going to one side”)
The two hemispheres serve some different functions.
How do we know about these differences?
 Brain damage studies revealed many functions of
the left hemisphere.
 Brain scans and split brain studies show more about
the functions of the two hemispheres, and how they
coordinate with each other.
The intact but lateralized brain
Right-Left Hemisphere Differences
Left Hemisphere
 Thoughts
and logic
 Language:
words and
definitions
 Pieces and
details
Right Hemisphere
 Feelings
and
intuition
 Language:
tone,
inflection,
context
 Wholes,
including
the self