The cerebral cortex

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The cerebral cortex
cerebral cortex
Up to now, structures mainly in brain stem..

• Actual appearance

For convenience, generally divided in 4 lobes
(regions)
Frontal lobe
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• The case of Phineas Gage
• good natured, industrious, good judgment, treated
  people well, well-liked)
• (Describe acciden)t

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• Following the accident
• General intelligence, language abilities, memory
  seemed unaffected yet..
• Rude, crude and lewd- lack of regard for others
• Irresponsible
• Very poor judgment, especially in social/personal
  realm
• Part of brain most affected in Gage was region of
  prefrontal cortex (part of frontal lobe)

Especially this region
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• Antonio Damasio has studied several people with
  damage to this region of brain has concluded
• Important for making judgments in
  social-emotional realm
• Damage gtgt difficulty anticipating consequences of
  actions especially regarding welfare, feelings of
  others, or of self
• Leads them to make foolish decisions, engage in
  inappropriate behavior

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• Appear to be 2 regions important for judgment and
  decision-making

Social-personal require emotional input
Abstract or impersonal decisions
Judgment in this realm can remain largely intact
even though judgment in social-emotional realm
disturbed
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Other functions of frontal lobe
Motor cortex

• Controls muscles of body
• Each part of the body controlled by specific
  region of motor cortex (as in lower-left drawing)

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Primary motor cortex was first mapped by Dr.
Wilder Penfield (at Montreal Neurological
Institute) using technique of electrical
stimulation
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• Two basic principles
• 1) Amount of cortex devoted to each part of body
  proportional to amount of information-processing
  required
• In this case, number of muscles to be controlled

• Two basic principles
• 1) Amount of cortex devoted to each part of body
  proportional to amount of information-processing
  required
• In this case, number of muscles to be controlled

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• 2) Connections between brain and body are
• contralateral

opposite side
(Implications for stroke What if patient
paralyzed on right-hand side of body?)
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• Another function of frontal lobe One of the
  brains 2 language centers located here Brocas
  Area (discuss discovery by Broca)

Note Almost always in left hemisphere

• Damage can lead to Brocas Aphasia
• Problems with production (e.g., speaking) but
  generally few problems with comprehension
• ad lib example

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• Additional functions of frontal lobes
• Short-term memory
• Reasoning
• Regulation of emotions (e.g., inhibition of fear
  responses)

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Parietal lobe

• Major function is body sense perception
• Occurs in region somatosensory cortex

first mapped by Penfield using electrical
stimulation
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• Receives input from receptors in skin, joints,
  internal organs
• responsive to hot, cold, pressure, touch, pain,
  etc
• Same 2 principles apply as for motor cortex
• 1) Amount of cortex devoted to part of body
  depends on amount of info-processing required
• in this case, number of sense receptors
  sensitivity

• 2) Connections to body are contralateral

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• Effects of damage
• Loss of sensitivity (e.g. to pain)
• Loss of ability to feel body part

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Occipital lobe

• Arrives first in primary visual cortex
• Preliminary processing done (e.g., contours,
  boundaries, rough shape)
• But wont make much sense until further analysis
  and processing done
• in surrounding areas (visual association areas)
• Required to assess size, motion, color, identity,
  etc.

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PET scan, S performing visual task much of the
visual association cortex is active

• Destruction of primary visual cortex gtgt blindness
• Over 30 specialized regions in association cortex
• Damage can lead to various forms of visual
  agnosias (loss of recognition)
• E.g., patient who had great difficulty
  recognizing crayon, lock

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• Extreme form of agnosia Neglect Syndrome

Discuss Eating food on plate shaving
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Temporal lobe
Primary function processing of auditory
information

• Similar to situation in occipital lobe
• Information first arrives in primary auditory
  cortex
• initial processing

• Sent on for more complex processing to
  surrounding auditory association areas

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• Another important speech center (located in
  temporal lobe) Wernickes Area

• Damage leads to Wernickes aphasia
• problems with both production and comprehension
  of speech (and writing)
• speech sample here

Note from Dec 06 while reading Intro papers-
they think speech could be replaced by written
lang or signing. Need to verify then add info on
effects on written language and signing. The
issue is language processing not speech per se
(I think)
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Subcortical forebrain structures

• Entire area lying above brainstem is forebrain

• By far, largest structure is cerebrum
• We have been focusing on most important part,
  outer layer cerebral cortex

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fMRI showing highest concentration mu-opiod
receptors- Zubieta nicotine study

• But several important forebrain structures lie
  beneath cortex (lt subcortical)
• A number of them involved in emotional and
  motivational functioning (limbic system)

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Amygdala

• Small structure, plays very important role in
  emotional functioning
• Especially fear
• Amygdala responds to signs of danger, threat

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Amygdala response to fear stimulus
3 views of brain, normal S, viewing fearful face
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• Amygdala-damaged Ss have difficulty recognizing
  facial expression of fear

On a scale of 1 to 6, how frightened would you
say this person is? - Normal S 5 or 6 -
Amygdala damaged S I dont know, maybe 2?
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• Amgydala also crucial for our ability to quickly
  learn to fear dangerous situations (through
  classical conditioning

(explain fear conditioning procedure) explain
what graph is showing for normal S
Test results for S.P. (Normal response to
electric shock, but no fear reaction to what
should have become a Conditioned Stimulus (blue
square associated with shock))
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Other important subcortical structures
Hippocampus

• Often considered part of limbic system
• Although, main role in memory
• Recently discovered plays important role in
  regulating stress response
• Can be damaged by protracted stress

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Hypothalamus

• Regulation of drives (e.g., hunger, sex)
• Controls fight-flight response, and major
  components of stress response

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How is the brain mapped?

• 1) Study effects of damage to specific regions or
  structures
• E.g. Phineas Gage
• E.g., Brocas discovery of Brocas Area
• 2) Electrical stimulation of brain (ESB)
• E.g., Hesss original work
• E.g., Olds Milners discovery of pleasure
  centers
• E.g., Wilder Penfields mapping of somatosensory
  motor cortex

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• 3) Brain scanning (imaging)
• 2 types
• A) Structural scans (CT and MRI)
• Give hi resolution 3D images of body structures,
  including brain

• of some limited use to psychologists (e.g.
  studies of schizophrenics)

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far more useful

• B) Functional scans (functional imaging)
• PET scans and fMRI scans (functional magnetic
  resonance imaging)
• Indicate which regions of brain most active under
  particular circumstances
• Colors represent different levels of activity

PET scan
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• Imaging studies allow researchers to answer
  questions previously unanswerable e.g.,

fMRI scan from Singer et al (2004) expt on
empathy for pain