Lateralisation + split brain research

• The left and right hemispheres are connected by the corpus Callosum.

  Different functions are dominant in each hemisphere. Some mental processes in the brain are mainly controlled by either the left or the right hemispheres.
• Split brain research

  • in very severe cases of epilepsy, the only treatment available is to sever the corpus callosum, in order to stop seizures from spreading across the brain
  • side effect is that information can no longer move between them
  • allows scientists to use the split brain surgery to study the different roles of the 2 hemispheres
• Sperry and Gazzaniga (1967)

  • first to study the capabilities of split brain research
  • information from the right visual field is processed by the left hemispheres and information from the left visual field processed by the right hemisphere
  • Ps would be asked to stare at a fixed point while an image or word was presented to either the LVF or RVF
  • in the normal brain, the corpus callosum would share between the hemispheres but in the split brain patient, the information was unable to be conveyed
• Evaluation

  • Sperry and Gazzaniga (1967)
  • highly specialised and standardised procedures and metholody
• Evaluation

  • research is limited as the sample size is relatively small and hard to generalise to the wider population
  • unlikely to happen as a procedure now
  • Ps had been on meds before which makes it hard to conclude if information would be processed the same way by people without epilepsy or split brain treatment
• Evaluation

  • lateralisation of function appears to change throughout an individual's life, with normal ageing
  • across many types of tasks and many brain areas, lateralised patterns found in younger individuals tend to switch to bilateral patterns in healthy, older adults
  • a study found that language became more lateralised to the left hemisphere with increasing age in children and adolescents but after 25, decreased with each decade of life
• Evaluation

  • one limitation is that the idea of the left hemisphere being an analyser and the left as a synthesiser may be wrong
  • this is because research has challenged the idea that people are either right or left brain dominant
  • Nielsen analysed brain scans from over 1000Ps aged 7-29 years and found no evidence of a dominant side challenging the idea that there is an artists, or a mathmeticians brain
  • however, they did find evidence for lateralisation, and people did use each hemisphere for different tasks, suggests that the notion of left and right brain people is wrong