Cerebral Asymmetry

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Cerebral Asymmetry
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Hemispheres differ in

• Neuroanatomy
• Neurochemistry
• Function

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Anatomical Asymmetry
Also Brocas area larger on left w/ greater
dendritic arborization
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Neurochemical

• NE conc. higher in R thalamus
• DA conc. receptor density higher in L GP

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Historic Interlude
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Paul Broca

• Tan
• Could comprehend follow verbal commands
• Other individs w/ same deficits damage to same
  left hemispeheric area
• Analagous area on right no language deficits

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Karl Wernicke

• Damage to left temporal area comprehension
  deficits
• Fluency intact

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Sperry Gazzaniga

• Examined effects of commissurotomy on behavior
  (Split-brain)

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Left Hemisphere - language

• Able to read write word in right visual field
  only
• Able to name object in right but not left hand

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Right Hemisphere - spatial

• Block design
• left hand - rapid accurate
• right hand - disorganized
• Draw 3D structure?
• Left - yes
• Right - no

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Lateralized Temporary Lesions

• WADA
• Paralysis contralateral
• Mute side for speech output
• 95 righties left hemisphere language

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Visual Input into Hemispheres
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Are we born w/ lateralization or does it develop
as brain matures?

• Neuroanatomical asymmetries present in utero
• Young infants (1 wk old), EEG to syllable (pa,
  ba) left more active. EEG to music, right more
  active
• Hemispherectomy
• Right spatial deficits
• Left - language deficits

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Handedness

• 90 of pop right-handed
• 10 left or ambidextrous
• 95 of right-handers left dominance for speech
• 80 of left-handers left dominance for speech