Backgrounds and aims

• The brain is divided into two halves called hemispheres. The right hemisphere and left hemisphere (RH and LH) of the brain communicate with each other via a small group of connections.
• The main connection between the brain's two hemispheres is the corpus callosum.
• Smaller connections between the brain's two hemispheres - the anterior commissure - hippocampal commissure - massa intermedia
• The importance of these two hemispheres is that they work independently. They 'don't talk to each other'
• Separate hemispheres (problem) for functions that are cross wired. - eg. the right hand being controlled by the left hemisphere.
• Lateralised function - certain functions localized or "lateralized" to one side of the brain.
• Some forms of brain surgery have been shown to result in major functional deficits - eg. behaviour is changed dramatically.
• Examples of brain surgeries include frontal lobotomy or unilateral lobotomies performed to treat epilepsy.
• Lobotomy - operation where connections to specific areas of the brain are cut so that part of the brain is no longer functional.
• In a frontal lobotomy connections to the frontal lobe are severed.
• Implication from Sperry:

  Cutting the corpus callosum does not have the damaging effects that occur when functionally removing other parts of the brain.
• Functional removal:

  The part of the brain is not actually removed, but connections are severed so it is as if the part has been removed.
• Hemispheric deconnection (also called the split brain operation):

  • Involves cutting through the connections.
  • Purpose of the operation is to separate the two hemispheres from each other
  • In order to alleviate the symptoms of severe epilepsy.
• Severe epilepsy:

  • Condition where the brain experiences an electrical storm.
  • Neurons of the brain generate electrical currents to transmit their messages.
  • Sometimes, some neurons discharge electrical signals inappropriately creating a 'storm'
• One of two main aims:

  • To document the psychological effects of hemispheric deconnection in split brain patients with severe epilepsy.
  • To use these results to understand how the right and left hemispheres work in 'normal' individuals.
• Two of two main aims:

  • Sperry also wanted to demonstrate that each hemisphere has independent streams of conscious awareness
  • And their own set of memories that can't be accessed by the other hemisphere.