hemispheric lateralisation +split brain research

• hemispheric lateralisation:

  • 2 hemispheres are functionally different and certain mental processes + behaviours controlled by 1 hemisphere
  • some functions the localised areas appear in both hemispheres e.g vision, other functions not e.g language
• language lateralisation:

  • left hemisphere
  • right hemisphere can only produce basic words and phrases but contributes emotional context
• motor cortex lateralisation:

  • both hemispheres
  • right hemisphere controls left movement vice versa (contralateral wiring)
• vision:

  • contralateral and ipsilateral - each eye receives light from left and right visual field
  • LVF of both eyes connected to RH and vice versa
  • similar arrangement for auditory area
• split brain research:

  • severing connection between right and left hemisphere (corpus collosum) - reduces epilepsy
  • studies show how hemispheres functions when they can't communicate
• sperry's research:

  • 11 split brain patients
  • word or image presented to RVF (processed by left hemisphere) and vice versa
  • asked to respond to stimulus either verbally or with left/right hand
• sperry's findings:

  • when presented to RVF participants could describe what was seen, couldnt do this if presented to LVF
  • if presented to LVF, could select a matching object using their left hand
• EVALUATION: lateralisation in the normal brain

  • fink et al - PET scans to see which areas of brain are active during visual processing task in normal people
  • asked to attend to global elements - right more active, focus on specific details - left dominated
  • visual processing - hemispheric lateralisation is feature of normal and split brain
• EVALUATION: one brain (oversimplified)

  • different functions in left and right, research says people dont have dominant side which creates a different personality
  • nielsen et al - analysed 1000 scans where they used certain hemispheres for task - no dominant side (artists/maths)
  • pop psychology notion of right and left brained people is incorrect
• EVALUATION: generalisation issues

  • behaviour of sperrys sample compared to neurotypical group (no epilepsy) - CVs as observed differences may be result of epilepsy not split brain
  • sample size = very small
  • issues affect internal and external validity of findings