Split brain research

Cards (10)

  • Corpus callosum is a thick bundle of nerve fibres (white matter) connecting the left and right hemispheres.
  • In patients suffering from epileptic seizures, the brain experiences excessive electrical activity which travels from one hemisphere to the other. To reduce this, patients have their corpus callosum cut, splitting their brain into two halves.
  • Split-brain research studies allow us to identify how the hemispheres function when they can't communicate with one another.
  • Sperry and Gazzaniga (1968) investigation into lateralisation:
    • Participants - 11
    • Procedure - An image / word is projected into the left visual field and right visual fields (both controlled by the opposite sides of the brain).
  • Sperry and Gazzaniga (1968) - Descriptions:
    • Describe what you see - When picture was presented to the RVF, they could describe. When presented to the LVF they could not. This shows the superiority of the left hemisphere when it comes to language production.
  • Sperry and Gazzaniga (1968) - Tactile tests:
    • Tactile test - Feeling object in right hand, patients could verbally describe what they felt or identify the object by choosing a similar object from a set of other objects. On the left hand side, they could not describe the object but only guess. BUT the left hand could identify the object in the right hand by choosing a similar object from a set of objects.
  • Sperry and Gazzaniga (1968) - Drawing:
    • Drawing tasks - Picture in the RVF and drawn by the right hand was not as clear as drawing with the left hand. This shows superiority of the right hemisphere when it comes to visual motor tasks.
  • Sperry and Gazzaniga (1968) - Conclusions:
    • Left hemisphere is dominant in speech and language,
    • Right hemisphere is dominant in visual-motor tasks.
  • Strengths of split brain research:
    • Standardised procedures - Sperry's method of presenting visual information to one field at a time. Participants were asked to stare at a fixation point with one eye blindfolded. Image would be flashed for 1/10th of a second so patient would not be able to move their eye across to the image. This allowed for basic aspects of the procedure to be varied and ensured only one hemisphere was receiving information at a time.
  • Limitations of split brain research:
    • Generalisability - Sample is usually an 'unusual sample'. Only 11 who took part in all variations of the procedure had a history of epileptic seizures. It has been argued that this might have caused unique changes in the brain, which may have influenced the findings.