Hemispheric Lateralisation - Split-Brain Research

• Hemispheric Lateralisation 


  Refers to the idea that the two halves of the brain have mental processes that are mainly/solely controlled by them (e.g. Brocas and Wernickes areas in the left hemisphere)
• Corpus Callosum


  The bundle of nerve fibres that connect the two hemispheres together so they can communicate. In order to speak about something the RH has seen (from the LVF), the RH must transfer info to the language centres in the LH
• Split-Brain Research


  In 1967 Roger Sperry conducted experiments on 11 split-brain patients (CC removed due to seizures) and a control group (quasi). Ps took part in many activities, one including looking at a dot in the centre of a screen using a tachistoscope (0.1 of a second image displayed). Then showed pics to only one eye. Items shown to the LVF could not be verbalised as language centre are in the LH. However, the Ps could draw what they had seen in the LVF. Also shown composite words to each VF but could not fit them together. Shows how important CC is and supports lateralisation.
• Split-Brain Research - Strength

  Can be used as key evidence to support the idea of hemispheric lateralisation. As the two hemispheres operate independently in these unique patients, it is possible to isolate specific cognitive tasks to LH or RH. Led to a greater understanding of hemispheric lateralisation (e.g. lateralisation of language centres)
• Split-Brain Research - Strength

  Sperry used carefully controlled and standardised procedures (e.g. the use of a tachistoscope meant participants didn't have time to view stimuli with other VF). The study is therefore replicable, and many similar studies have proved its reliability. The LH is the analytical and verbal hemisphere (the analyser) and the RH is the spatial and emotional hemisphere (the synthesiser).
• Split-Brain Research - Weakness

  Issue of generalisability as Sperry's sample was a small sample of very rare individuals. Therefore any conclusions made lack validity. This limits the extent of how findings can support hemispheric lateralisation
• Split-Brain Research - Weakness

  Differences in hemispheric functions may have been overstated. Lots of theories oversimplify and overstate the difference in function between the two hemispheres. Modern neuroscientists argue these distinctions are not all clear-cut and many behaviour that are typically associated with one hemisphere can be performed by the other one situations require (plasticity and functional recovery). Sperry's conclusions may be too simplistic.