Hemispheric lateralisation + split brain research Flashcards
what is hemispheric lateralisation?
Hemispheric lateralisation- the idea that the two halves of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other.
what is split brain research?
a series of studies which began in 1960 involving people with epilepsy who had experienced a surgical separation of the hemispheres of their brain to reduce the severity of their epilepsy. Enabled researchers to test lateral functions of the brain in isolation.
explain how the brain in contralateral?
- The brain is contralateral, this means that each hemisphere controls the opposite side of the body.
- Vision is both contralateral and ipsilateral. The left vison field of both eyes is connected to the right side and the right vision field of both sides is connected to the left side.
- The language centre, however, is only on the left side of the brain.
- The hemispheres are connected by the corpus callosum, cutting the connection (which is used in the treatment of epilepsy) would stop the communication between the hemispheres and show how they are specialised.
outline Sperry’s split brain research
• Split brain research studies how hemispheres function when they can’t communicate with each other
• Procedure - Sperry conducted a quasi experiment with 11 participants who had undergone corpus colostomy.
Using equipment that would project information to each visual field, Sperry controlled the information each hemisphere had access to.
Participants would be required to either say what they had seen, draw the object or select from objects that were hidden from view with their hands.
what were Sperry’s findings?
→ Sperry found that information presented to the left hemisphere could be spoken, but not spoken if delivered to the right hemisphere.
→ The right hemisphere could draw or select a object using the left hand.
→ This suggests that both hemispheres are capable of acting independently, also supporting theory that the language centres are located on the left side of the brain.
Gazzaniga et al also found that the right side of the brain was more able to recognise faces. This suggests that the right hemisphere could be specialised for facial recognition.
what is a strength of hemispheric lateralisation?
- One strength is research showing that even in connected brains the two hemispheres process information differently.
- Fink et al used PET scans to identify which brain areas were active during a visual processing task.
- When participants with connected brains were asked to global elements of a active image regions of the RH were much more active.
- When required to focus on the finer detail in the image the LH was more active.
- Suggests that hemispheric lateralisation is a feature not only present in a split brain.
what is a limitation of hemispheric lateralisation?
• One limitation is the idea of the LH as analyser and RH as synthesiser may be wrong.
• Research suggests that people do not have a dominant side of their brain which creates a different personality.
• Nielsen et al analysed brain scans from over 1000 people aged 7 to 29 and did find that people used certain hemispheres for certain tasks but there was no evidence of a dominant side.
This suggests that the notion of right or left brained people is wrong.
what is support for split brain research?
- Gazzaniga showed that split-brain participants actually perform better than connected controls on certain tasks.
- Faster at identifying the odd one out in a array of similar objects than normal controls. In the normal brain the LH’s better cognitive strategies are ‘watered down’ by the inferior RH.
- Supports Sperry’s earlier findings that the ‘left brain’ and ‘right brain’ are distinct.
what is a limitation of Sperry’s split brain research?
- The behaviour of Sperry’s slit-brain research was compared to a neurotypical control group. None of the participants in the control group had epilepsy.
- This is a major cofounding variable, any differences that may have been observed could be due to the epilepsy rather than the split brain.
- It was also a small sample, the participants had varying amounts of connections cut and the patients had all undergone drug therapy.
- Study also lacks mundane realism, the procedure is unlike how these individuals would process information in their lives.
However the study had fundamental impact on the understanding of the brain. Suggesting that the brain is a combination or separate intelligent processes working together.
