Hemispheric lateralisation and split brain research Flashcards
What is hemispheric lateralisation?
The idea that the two halves of the brain function differently and that certain mental processes and behaviours are controlled by one or the other.
strength of lateralisation of function of the brain.
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 attend to global elements of an image regions of the RH were much more active.
When required to focus on the finer details, the areas of the LH tended to dominate.
This suggests that hemispheric lateralisation is a feature of the connected brain as well as the split-brain.
Limitations of hemispheric lateralisation of the brain.
Nielsen et.al analysed brain scans from over 1000 people aged between 7 and 29 years 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 and people don’t have a stronger side of the brain.
What is a split brain operation?
It involves severing the connections between the RH and LH, mainly the corpus callosum.
It is done to reduce epilepsy.
What was Sperry’s research into split brain patients?
He studied 11 people who had a split-brain operation.
He set up a study where an image would be projected to a participants RVF (processed by the LH) and the same, or different image could be projected to their LVF (processed by the RH).
In a normal brain the corpus callosum would immediately share the information between both hemispheres giving a complete picture.
They found that when a picture was shown to their RVF the participants could describe what was seen but when it was shown to the LFV they could not see what it was but with their left hand they could selecting a matching image.
This supports the conclusion that the LH is verbal and the RH is emotional.
Strengths of split brain research.
Gazzaniga- showed that split-brain participants actually perform better then connected controls on certain tasks.
This supports Sperry’s earlier findings that the left brain and right brain are distinct.
limitation of Sperry’s split brain research.
Causal relationships are hard to establish.
The behaviour of Sperry’s participants was compared to a neurotypical control group. But none of the participants in the control group had epilepsy and this is a confounding variable.
As any differences observed between the two groups may have been the result of epilepsy rather than split brain.
