Split Brains and Consciousness

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Split Brains and Consciousness
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Picturing the Hemispheres

• MRI scan of brain, image from a virtual slice
  across the top of the head
• Convolutions and the longitudinal fissure
  separating hemispheres are visible

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Left Hemisphere
Longitudinal fissure
Right Hemisphere
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Brain Organization

• Hemispheric Lateralization
• cross-over control
• right brain gt left side
• left brain gt right side
• cross-over visual field
• right brain gt left visual field
• left brain gt right visual field
• lateralization of function
• language areas on left, in most people

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History of Split Brain

• Roger Sperry (1913-1994)
• winner of Nobel Prize in Medicine, 1981
• studied nerve regeneration in amphibians
• studied effects of split brain in mammals
• used split brain to treat epilepsy

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Split Brains

• Hemispheric Co-ordination
• Corpus Callosum
• Movement
• Eye movement
• Head/body movement
• Disconnecting the Hemispheres
• Treatment for Epilepsy
• Commissurotomy

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Brain Lateralization

• Visual lateralization
• visual field, not eyes, are lateralized
• Temporal hemi-retina is ipsilateral
• Nasal hemi-retina is contralateral
• Displays and Fixation Points

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Testing Split Brain Patients

• Normal responses under normal conditions
• Unusual responses under laboratory controlled
  conditions
• no naming for displays flashed on the left
• correct manual search for displays flashed on the
  left

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Understanding in the Split Brain

• Language production, right-side motor control is
  in left hemisphere
• Left-side motor control is in right hemisphere