split-brain research

• split-brain research involves reviewing research using epileptic patients who have experienced surgical separation of the hemispheres of the brain
• split-brain research allows researchers to investigate the extent to which the brain function is lateralised
• The corpus callosum is the link between the 2 hemispheres
• people who suffer with epilepsy but are not helped by drug treatment, brain surgery is considered as an option because the epilepsy is generated by a focus area in the brain
• However, in a small number of people with drug-resistant epilepsy, there is more than one focus of the areas that cannot be removed; this has led surgeons to cut the corpus callosum down the middle so that the epilepsy can be contained within one hemisphere. This reduces the number of seizures
• But severing communication between the 2 hemispheres can also affect an individual’s behaviour and perception
• Sperry et al studied 11 split brain patients
• Sperry presented information to either the left or right visual field, and asked the patients to respond verbally or using one of their hands.
• Sperry found that if a picture is shown to the left visual field this information is processed by the right hemisphere. It cannot respond as it does not have a language centre.
• As the hemispheres are split no communication takes place and the left hemisphere does not receive the information and therefore cannot talk about it despite having a language centre
• The main conclusions from Sperry's research are that the left hemisphere is predominantly geared towards analytical and verbal tasks where the right is geared to spatial and music
• Sperry only presented visual information to one visual field at a time. Participants looked through a fixation point with one eye only. An image was flashed for 1 tenth of a second each time.
• Sperry's methodology is a strength as the controlled standardised procedures allowed Sperry to vary aspects of the basic procedure. It was a careful and well-controlled procedure which increased the reliability of the study
• there are some theorists such as Pucetti who suggest that the 2 hemispheres are functionally very different and represent a form of duality in the brain which is emphasised in split brain patients
• other researchers such as Lashley suggest that the 2 hemispheres don’t function in isolation but work together as a highly integrated system
• Researchers have urged caution over the generalisability of the results obtained by Sperry due to the small specific group of patients used in this research
• It has been argued that the epileptic seizures experienced by these individuals may have caused unique changes to the brain and altered the findings