Transcript Brain - Paul Trapnell

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.
Investigating the
Brain and Mind:
How did we move beyond
phrenology?
How did we get inside the
skull and under the
“bumps”?
 by finding what happens
when part of the brain is
damaged or otherwise
unable to work properly
 by looking at the
structure and activity of
the brain: CAT, MRI,
fMRI, and PET scans
Strategies for finding out
what is different about the
mind when part of the
brain isn’t working
normally:
 case studies of accidents
(e.g. Phineas Gage)
 case studies of split-brain
patients (corpus callosum
cut to stop seizures)
 lesioning brain parts in
animals to find out what
happens
 chemically numbing,
magnetically deactivating,
or electrically stimulating
parts of the brain
Neuroscience
Techniques
©2001 Prentice Hall
Intentional brain damage:
Lesions (surgical
destruction of brain
tissue)
 performed on animals
 has yielded some
insights, especially
about less complex
brain structures
 no longer necessary, as
we now can chemically
or magnetically
deactivate brain areas
to get similar
information
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Studying cases of brain damage
When a stroke or injury damages part of the brain, we
have a chance to see the impact on the mind.
Phineas
Gage
(1850s)
Phineas Gage (1850s)
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


Dynamite accident
Big changes in his
personality
Became impulsive,
aggressive
Insight into frontal
lobe
Planning
Impulse control
Emotion regulation
1861 Paul Broca






Hears of patient with
progressive loss of
speech
Comprehension OK
Dies.
Broca does autopsy
LESION found on
right frontal lobel
“Broca’s
area”
Split-Brain Patients
 “Split” = surgery in
which the
connection between
the brain
hemispheres is cut
in order to end
severe full-brain
seizures
 Study of split-brain
patients has yielded
insights discussed at
the end of the
chapter
We can stimulate parts of the brain
to see what happens
 Parts of the brain, and even neurons, can
be stimulated electrically, chemically, or
magnetically.
 This can result in behaviors such as
giggling, head turning, or simulated vivid
recall.
 Researchers can see which neurons or
neural networks fire in conjunction with
certain mental experiences, and even
specific concepts.
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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EEG
EEG
Electrical Stimulation
Wilder Penfield
Chemical Stimulation
Transcranial Magnetic
Stimulation (TMS)
“The God Helmet”
Brain Imaging
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.
Brain Imaging
PET
● Inject radioactive sugars
MRI
● Magnet  spin H atoms -> radio
pulse
f-MRI (functional MRI)
● Series of quick scans (20 ms)
● BOLD: “Blood oxygen level dependent”
signal
Larmor Frequency
(Definitely NOT on the exam. )
Enlarged Ventricles
Unaffected
Persons
Persons with
Schizophrenia
Psychopaths
Normals
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Cerebral
Arteries
Human Connectome Project
Pink
= Corpus Callosum circuits connecting hemisph.
Green = Frontal Lobe circuits going to Hippocampus
Structural Connectome by gender
on a very large population (949) youths.
RESULTS
M optimized for intrahemispheric communication.
F optimized for interhemispheric communication.
Shows up very early ages
Wide differences by adolescence and adulthood.
CONCLUSION
1. MALE brains are structured to facilitate connectivity between
perception and coordinated action
2. FEMALE brains are structured to facilitate communication between
analytical and intuitive processing modes.
More Parts of the Nervous System
Peripheral nervous system
 Somatic/Skeletal
afferent nerves
efferent nerves

(incoming)
(outgoing)
Autonomic
sympathetic
(engine)
parasympathetic (brakes)
The Peripheral Nervous System
The
Autonomic
Nervous
System:
The sympathetic
NS arouses
(fight-or-flight)
The
parasympathetic
NS calms
(rest and digest)
The Central Nervous System
 The brain is a web of neural
networks.
 The spinal cord is full of
interneurons that sometimes
have a “mind of their own.”
Interneurons in the Spine
Your spine’s
interneurons trigger
your hand to pull
away from a fire
before you can say
OUCH!
This is an example
of a reflex action.
Neural Networks
These complex webs of interconnected
neurons form with experience.
Remember:
“Neurons that fire together, wire together.”
Central Nervous System
 Spinal
Cord
relay station
reflexes
Brain
a crude grouping via evolutionary stages
1. basic bodily functions
HINDBRAIN
2. motivation and emotion
LIMBIC SYSTEM
3. reasoning and foresight
FOREBRAIN
Marmoset
Meerkat
(Vicious murderers.)
Areas of the brain and their functions
The brainstem
and cerebellum:
The limbic
(border) system:
The cortex (the
outer covering):
• coordinates
the body
• manages
emotions, and
connects
thought to
body
• integrates
information
The Brainstem:
Pons and Medulla
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
Brainstem:
The Pons
The pons helps
coordinate automatic
and unconscious
movements.
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 Thalamus (“Inner Chamber”)
 The thalamus is the
“sensory switchboard” or
“router.”
 All sensory messages,
except smell, are routed
through the thalamus on
the way to the cortex
(higher, outer brain).
 The thalamus also sends
messages from the cortex
to the medulla and
cerebellum.
Reticular (“Netlike”) Formation
 The reticular formation is a
nerve network in the
brainstem.
 It enables alertness,
(arousal) from coma to
wide awake (as
demonstrated in the cat
experiments).
 It also filters incoming
sensory information.
The Midbrain

tectum ("roof")
superior colliculus
inferior colliculus

substantia nigra
dopamine factory
The Forebrain
Thalamus
Midbrain
Practice Questions!
After suffering an accidental brain injury,
Kira has difficulty walking in a smooth and
coordinated manner. It is most probable
that she has suffered damage to her:
A.
B.
C.
D.
amygdala.
angular gyrus.
cerebellum.
corpus callosum.
What disease is related to degeneration
of the neuron’s myelin sheath?
A.
B.
C.
D.
Parkinson’s disease
multiple sclerosis
Alzheimer’s disease
schizophrenia
Antidepressants such as Prozac target
which neurotransmitter?
A.
B.
C.
D.
serotonin
glutamate
GABA
acetylcholine
Which technique is most useful for seeing
which regions of the brain are most active
while a person reads a poem?
A.
B.
C.
D.
EEG
fMRI
EKG
PET
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 beansized neural clusters.
 helps process emotions,
especially fear and
aggression.
The Amygdala
 Electrical
stimulation of a
cat’s amygdala
provokes aggressive
reactions.
 If you move the
electrode very
slightly and cage
the cat 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
The Cerebral Cortex
The lobes consist of:
 outer grey “bark” structure that is wrinkled in order to
create more surface area for 20+ billion neurons.
 inner white stuff—axons linking parts of the brain.
 180+ billion glial cells, which feed and protect neurons
and assist neural transmission.
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
Association Areas:
Frontal Lobes
 The frontal lobes are
active in “executive
functions” such as
judgment, planning, and
inhibition of impulses.
 The frontal lobes are also
active in the use of
working memory and the
processing of new
memories.
Phineas Gage (1823-1860)
Case study: 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 able to function
in many ways, but his personality
changed; he was rude, odd, irritable,
and unpredictable.
Possible explanation:
Damage to the frontal lobes could
result in loss of the ability to suppress
impulses and to modulate emotions.
Parietal Lobe Association Areas
This part of the brain has many functions in the
association areas behind the sensory strip:
 managing input from multiple senses
 performing spatial and mathematical reasoning
 monitoring the sensation of movement
Temporal Lobe Association Areas
Some abilities managed by association areas in this “by
the temples” lobe:
 recognizing specific faces
 managing sensory input related to sound, which helps
the understanding of spoken words
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
Specialization and Integration
Five steps in reading a word aloud:
Plasticity: The Brain is Flexible
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, reassign
existing networks, and
insert new neurons,
some grown from stem
cells
This 6-year-old had a
hemispherectomy to end lifethreatening seizures; her
remaining hemisphere
compensated for the damage.
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
Details such as “trees”
Language: words and
definitions
Linear and literal
Calculation
Pieces and details
Right Hemisphere
Feelings and intuition
Big picture such as “forest”
Language: tone, inflection,
context
Inferences and associations
Perception
Wholes, including the self
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 does
not perceive what each
EYE sees. Instead, it
perceives the half of the
view in front of you that
goes with the half of the
body that is controlled
by that hemisphere.
Split Brain Experiments
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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
A blue circle is briefly flashed in the left visual field,
and a red square is flashed in the right visual field.
Based on Roger Sperry’s work with split-brain patients,
what would split-brain patients say that they saw?
A)
B)
C)
D)
blue circle.
nothing.
blue circle around a red square.
red square.
Split Brain Video
Results of Split Brain Research
• Left side of the brain:
– seems to control language, writing, logical thought,
analysis, and mathematical abilities,
– processes information sequentially,
– can speak.
• Right side of the brain
– controls emotional expression, spatial perception,
recognition of faces, patterns, melodies, and
emotions,
– processes information globally,
– cannot speak.
Neural Plasticity
Synaptic plasticity
– Learning (e.g., long-term potentiation)
– Pruning (e.g., during development)
Neurogenesis
Structural mod. of neural circuits
– Functional modification of brain circuitry
–
for example, after a stroke or trauma
Neural Plasticity
https://www.dynamicb
rain.ca/the-nature-ofthings.html
http://www.cbc.ca/nat
ureofthings/episodes/c
hanging-your-mind