Memory and Cognition

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Memory and Cognition

• PSY 324
• Chapter 2 Cognition and the Brain
• Part II Localization of Function
• Dr. Ellen Campana
• Arizona State University

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The Whole Brain

• Localization of function - Different parts of the
  brain serve different functions
• Many, many ways to divide the brain
• Like an onion, many layers
• Like a fractal, the closer you look the more
  complex it seems
• Descriptions may seem contradictory and/or
  overlapping because of this

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Cerebral Cortex

• Most important for Cognition

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Cerebral Cortex

• Temporal Lobe
• Language
• Memory
• Hearing
• Perceiving forms
• Occipital Lobe
• Visual information (early processing) feature
  detectors

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Cerebral Cortex

• Parietal Lobe
• Touch
• Vision
• Attention
• Frontal Lobe
• Proportionately larger in humans than in other
  species
• Language
• Thought
• Memory
• Motor functioning

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Subcortical Structures
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Subcortical Structures

• Hippocampus
• Forming memories
• Amygdala
• Emotions, emotional memories
• Thalamus
• Processing sensory information (vision, hearing,
  touch)

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Hemispheres

• Brain separated into sides (hemispheres)
• Corpus Collosum connects them

• Structurally and functionally very similar
• Lateralization specific functions occurring in
  one hemisphere or the other

Note Sperry studied split-brain patients, who
had had their corpus collosum severed as a
treatment for epilepsy. He shared Hubel
Weisels Nobel Prize for this work.
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Lateralization

• Vision of left part of the world lateralized to
  the right side (opposite also true)
• Motor Control of left side of body lateralized to
  the right side (opposite also true)
• Touch on left side of body lateralized to the
  right side (opposite also true)

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Lateralization

• Are there right-brained and left-brained
  people?
• Analytical/Logical processing (syntax of
  language) usually on the left side (not always)
• Analogy and Broad Thinking usually on the right
  side (not always)
• Everyone has (and uses) both
• Patients who have had a hemispherectomy
• Other side usually takes over missing
  functionality
• Coglab Brain Assymetry

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Localized Function

• Parietal Lobe
• Sensory Homunculus (near the front, somatosensory
  cortex)
• Motor Homunculus (near the back, motor cortex)

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Sensory Homunculus
Each side of the brain has a copy, which
processes touch from the other side
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Localized Function

• Parietal Lobe
• Sensory Homunculus (near the front, somatosensory
  cortex)
• Motor Homunculus (near the back, motor cortex)
• Temporal Lobe
• Wernickes Area metaphor, meaning in language
• Brocas Area logical structure of language
• Fusiform Face Area (FFA) specialized for faces
  (or is it things were experts at recognizing???)

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Researching Localized Function

• Neuropsychology comparing patients with
  localized brain damage
• Single dissociation single patient has some
  things impaired, other things not impaired

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Single Dissociation Phineas Gage

• Construction accident 1848
• Harlow (doctor) wrote a lot about his condition

• Gage lived, could talk, act, and do all normal
  activities, but suffered impairment of emotional,
  social, and personal traits
• Evidence for some separation of language and
  social traits, etc.

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Researching Localized Function

• Neuropsychology comparing patients with
  localized brain damage
• Single dissociation single patient has some
  things impaired, other things not impaired
• Brocas Aphasics, Wernickes aphasics,
  Prosopagnosiacs
• Double dissociation -- two (or more) patients
  show opposite single impairments
• Brocas Wernickes Aphasics considered together

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Double Dissociation
Form The boy was pushed by the girl Meaning The apple was eaten by the girl
Brocas Aphasics Impaired OK
Wernikes Aphasics OK Impaired
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What can we conclude?

• Double dissociation
• Two functions involve different mechanisms
• Two functions involve different brain areas
• Mechanisms are independent
• Single dissociation
• Two functions involve different mechanisms
• Two functions involve different brain areas
• Mechanisms may not be independent

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Limitations of Neuropsychology

• At least for human processing, brain damage comes
  about from natural means (accident, etc.)
• Members of groups rarely have exactly the same
  damage (location or extent)
• No record of processing or brain organization
  before the damage
• Difficult to assess all possible types of
  functional impairment
• Brain may actually reorganize following damage
  (called plasticity)

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Imaging Methods

• EEG- Electrodes on outside of head continuously
  measure electrical activity
• PET- Radioactive dye injected, accumulates in
  different regions over time and can be read by a
  scanner. Essentially measures metabolism of
  neurons
• fMRI- Brief magnetic pulses used to give a
  snapshot of ratio of oxygenated to deoxygenated
  blood (metabolism)
• TMS- New measure. Magnetic field can disable
  specific portions of the brain for a short time,
  simulating damage.
• Temporal resolution Detail with respect to time
• Spatial Resolution Detail with respect to
  physiology

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Image from an fMRI scan
Image from a PET scan
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Imaging Methods
Spatial Resolution Temporal Resolution
EEG Poor Good
PET Excellent Poor
fMRI Good Good
TMS Good Good
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Subtraction Technique
Visual Stimulus (light flashing)
Visual Stimulus (light flashing)

• Used for fMRI studies
• Method similar to Donders study
• Compared two situations that included different
  cognitive processes
• Data blood glucose level
• Relative measure

Perception of the light
Perception of the light
DECISION
Response
Response
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Subtraction Technique

• Activation in control condition is subtracted
  from experimental condition to get activity due
  to stimulation in the experimental condition

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The End

• Next up Representation in the Brain