Split-brain research

• The corpus callosum is a large bundle of nerve fibres that connects the two hemispheres of the brain.

  • Its primary function is to enable communication and coordination between the hemispheres, allowing them to work together to process and integrate information.
• In split-brain patients (those who have had their corpus callosum severed), this communication is disrupted, leading to unusual behaviours where the hemispheres act independently.
• Briefly evaluate research using split-brain patients to investigate hemispheric lateralisation of function (4)

  • the disconnection between the hemispheres was greater in some patients than in others
  • some patients had experienced drug therapy for much longer than others
  • the comparison groups were not considered to be valid as they were often people with no history of epileptic seizures
  • research relates to small sample sizes
• Sperry and Gazzaniga aimed to investigate the extent to which the two hemispheres have specialised functions and how they work independently in split-brain patients.
• Procedure: (visual tasks)

  • patient would fixate on a dot in the centre of the screen
  • images or words were flashed to either the left visual field (processed by the right hemisphere) or the right visual field (processed by the left hemisphere)
  • the patients would respond by selecting/drawing the item with their left or right hand or verbally.
• Procedure: (tactile tasks)

  • Objects were placed in one hand without the patient being able to see them.
  • Each hand’s sensory input is processed by the opposite hemisphere.
  • Patient would identify the item verbally or non-verbally.
• Findings: (visual tasks)

  • When words or objects were presented to the right visual field (left hemisphere), patients could describe or name them verbally.
  • When words or objects were presented to the left visual field (right hemisphere), patients could not name them verbally.
  • However, they could draw or select the object using their left hand, showing non-verbal processing abilities.
• Method: (tactile tasks)

  • Objects placed in the right hand (left hemisphere) could be identified verbally.
  • Objects placed in the left hand (right hemisphere) could not be named but could be recognized non-verbally (e.g., pointing).
• Conclusions:

  • Hemispheric Lateralisation: The study demonstrated that the left hemisphere is dominant for language and verbal tasks, while the right hemisphere excels in spatial and non-verbal tasks.
  • Independent Functioning: The severed corpus callosum prevents information transfer between the hemispheres, showing that each hemisphere can function independently in certain tasks.