Hemispheric Lateralisation

• Hemispheric Lateralisation


  the idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations, e.g. the left is dominant for language, and the right excels at visual motor tasks
• Language


  language is said to be lateralised as it is only in the left hemisphere of the brain
• How are the hemispheres connected?

  nerve fibres called the corpus callosum, which facilitate interhemispheric communication: allowing the left and right hemispheres to ‘talk to’ one another
• Split-Brain research

  • Sperry and Gazzanaga (1967)
  • aim - examine the extent to which the two hemispheres are specialised for certain functions
• Sperry Procedure:

  • image/word is projected to the patient’s left visual field (which is processed by the right hemisphere) or the right visual field (which is processed by the left hemisphere). When information is presented to one hemisphere in a split-brain patient, the information is not transferred to the other hemisphere (as the corpus callosum is cut).
• Sperry different variations

  • describe what you see - picture presented (either left or right VF) and participant had to describe what they saw
  • drawing task - picture presented (either left or right VF) and participant had to draw what they saw
  • tactile task - object placed in left or right hand, participant had to either describe what they felt or select a similar object
• Sperry findings:

  • when image was shown to RVF (LH) participant could describe/draw
  • when image was shown to LVF (RH) participant could not describe/draw
• Strength of Hemispheric Lateralisation

  • research evidence - Fink (1996) - PET scans to identify which areas of the brain were active during tasks
• Limitations of Hemispheric Lateralisation

  • LH as an analyser and RH as a synthesiser may be wrong - no evidence of a dominant side of the brain
• Strengths of split brain research

  • Research support - Gazzaniga
• Limitations of Split-Brain research

  • ethical issues? - testing over a long period of time when they were already traumatised from operations
  • causal relationships are hard to establish - control group were neurotypical, did not have epilepsy - this is a confounding variable - results from research could have been a result from epilepsy and not split brain surgery