Hemispheric lateralisation & Split-brain research

• Hemispheric lateralisation

  The idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations. For example, the left: dominant for language

  right: visual-motor tasks
• Split-brain research

  A "split-brain" operation involves severing the connection between the right and left hemisphere, mainly the "corpus callosum". This procedure is usually done to reduce epilepsy.
• Sperry & Gazzinga(1)

  Aim) To examine the extent to which the two hemispheres are specialised for certain functions.

  Procedure) 11 people who had split-brain surgery where studied using a special set up in which an image would be shown to a participants right-visual field (processed by left hemisphere) and another image was shown to the left-visual field (processed by right hemisphere).

  A "normal" brain would share the information between both hemisphere giving a complete picture but presenting a picture to one hemisphere meant that the information cannot be conveyed to the other hemisphere.
• Sperry & Gazzinga (2)

  Findings) When a picture of an object was shown to a patients right-visual field (connected to left hemisphere), they could describe what was seen. However, when presented a picture on the left-visual field (connected to r.h) they could not describe it at all. But they could match another object out of purely sight.

  Conclusions) These observations show that certain functions are laterialised in the brain.
• Sperry & Gazinga AO3

  Strength) Brain laterilisation in chickens gives them enhanced ability to multitask.

  ->Provides evidence for the advantages of brain laterilisation.

  Limitation) Language may not be restricted to left hemisphere because patient J.W, suffered damage to left-hemisphere and developed the capacity to speak using the right hemisphere.

  ->Suggests that laterilsation is not fixed and the brain can adapt following injury.