hemispheric lateralisation and split brain research

• what is hemispheric lateralisation?

  idea that two halves of brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere
• what is split brain research?

  series of studies involving people with epilepsy who experienced a surgical separation of the hemispheres of their brain to reduce severity of epilepsy. enabled to test lateral functions of brain in isolation.
• what was sperrys research?

  11 participants who had a split brain operation studied.

  found when words shown to the RIGHT visual field could SAY word back. But not point to image just seen. When words shown to LEFT visual field could POINT to the image but not say word. When objects felt with RIGHT hand they could SAY the name.  When objects felt with the LEFT hand they couldn’t say name. When objects felt by RIGHT hand, could only be found again using RIGHT hand. When objects were by LEFT hand, could only be found again using LEFT hand because two hemispheres can’t communicate
• strength of lateralisation?

  p- research showing that even in connected brain, 2 hemispheres process info differently

  e- fink et al used PET scans to identify which brain areas active during visual processing task. when participants with connected brains asked to attend to global elements of an image, regions of RH more active.

  l- so hemispheric lateralisation is a feature of the connected brain as well as the split brain.
• limitation of hemispheric lateralisation?

  p- idea that LH as analyser and RH as synthesiser may be wrong.

  e- may be different functions in RH and LH but research suggests no dominant side of brain which creates different personality.

  e- nielson et al analysed brain scans from over 1000 people and found that people used certain hemispheres for certain tasks but no evidence of a dominant side.

  l- so the notion of right or left brained people is wrong.
• strength of split brain research?

  p- support from more recent split brain research

  e- gazzaniga showed that split brain participants perform better than connected controls on certain tasks. were faster at identifying odd one out in array of similar objects. in normal brain LH's better cognitive tsratgees watered down by inferior RH.

  l- supports sperrys earlier findings that left brain and right brain are distinct
• limitation of split brain research?

  p- causal relationships hard to establish.

  e- behaviour of sherry's participants compared to neurotypical control group. issue is that none of participants in control group had epilepsy so major confounding variable. any differences observed r result of epilepsy rather than split brain.

  l- so some unique features of split brain participants cognitive abilities due to their epilepsy