Sperry

• Regions of the brain

  The cerebral hemispheres are divided right down the middle into s right hemisphere and a left hemisphere

  These communicate with each other through a thick band of 200-250 million nerve fibers called the corpus callosum
• Lateralization of Function


  This is which hemisphere has more focus

  Left hemisphere = right side of the body and language

  The left hemisphere has two areas (Broca's and Wernicke's) which have been associated with language

  Right hemisphere = left side of the body and creativity
• Background

  Sperry has previously carried out research into brain hemispheres by splitting the brains of monkeys and cats

  He discovered you could train one hemisphere when the corpus callosum was split without the other hemisphere being aware
• Aim 


  To investigate the effects of hemisphere disconnection and to show that each hemisphere has different functions
• Method and design 


  Quasi experiment in a lab

  Independent measures design

  Could also be considered multiple case studies
• Independent variable 


  If participants had a split brain or not
• Dependent variable 


  individuals performance on tactile and visual tasks
• Sample 


  11 participants

  all were epileptics who had previously undergone a commissurotomy to deal with seizures

  One man had his surgery 5 1/2 years before

  One woman in 30's was more than 4 years

  Other 9 participants has varying times but not long before the study took place
• Material 


  A Tachistoscope

  used in exposing visual stimuli as pictures, letters or words for a brief period
• Procedure - Visual tasks

  The tachistoscope had a focal point in the middle of the screen for participants to look at. They would also have one eye covered

  This was to ensure the stimuli was being presented to the correct visual field

  Stimuli was presented for 0.1 second this was too quick for eye movements for the other visual field to see

  Left of the focal point would be seen by the left eye and then the right hemisphere
• Procedure - Tactile task

  Participants placed their hands under the tachistoscope so they could reach for objects while their hands were covered. Each object was introduced by the experimenter to the participant
• Procedure - Tactile task 1

  Visual stimuli is presented to one hemisphere and participants were then asked to name what they has saw

  Left visual field it went unnoticed or appeared as a flash but could draw what they saw

  Right they were able to non-verbally select object with left hand or state what they saw
• Procedure - Tactile task 2


  objects were placed in the right hand could be verbally stated or written down. In the left hand participants guessed or didn't know anything was placed in their hand

  An object taken from the left hand and placed into a bag could be identified and retrieved with the same hand

  Objects which were taken from both hands and placed in separate bags would be able to be identified individually
• Results - Visual 


  Stimuli shown to the left visual field it goes to the right hemisphere which is mute so participants can't state what they saw but can draw it with left hand

  Shown to the right visual field it goes to the left hemisphere so the participant can state what they saw

  When shown a pin up girl to the left visual field the participants blushed
• Result - Tactile 


  Object was placed in the left hand they were not able to state what they were holding as the right hemisphere is mute

  Could retrieve an object with the same hand it was placed in

  Could not retrieve objects with the opposite hand due to deconnection
• Conclusions


  In split brain patients perception of each hemisphere is independent as information cannot be passed

  In split brain patients memory in each hemisphere is independent

  But in everyday lives split brain patients are not obviously impaired