Lateralisation and split brain research

• the term brain lateralisation refers to the fact that the two halves of the human brain aren't exactly alike and each hemisphere has funcational specialisations for some functions, like language, are localised primarily in one half of the brain
• the two hemispheres are connected which allows information received by one hemisphere to be sent to the other hemisphere through connecting bundles of nerve fibres like the corpus callosum
• Roger Sperry was the first to study the capabilities of split brain patients. to test the capabilities of the separated hemispheres, they were able to send visual information to just one hemisphere at a time in order to study what is known as hemispheric lateralisation
• Sperry took advantage of the fact that information from the left visual field goes to the right hemisphere because the corpus callosum is cut in split brain patients, the information presented to one hemisphere has no way of travelling to the other hemisphere and can be processed only in the hemisphere that received it
• the split-brain patient would fixate on a dot in the centre of a screen while information was presented to either the right or left visual field. they would then be asked to make responses with either their left hand or their right hand, or verbally, without being able to see what their hands were doing
• for example, if the patient was flashed a picture of a dog to the right visual field and asked what they has seen they would answer 'dog'. however, if a picture of a cat was flashed to the left visual field the patient would say that he or she sees nohing
• the information from the left visual field is processed by the right hemisphere, which can see the picture, but as it has no language centre, doesn't receive information about seeing the picture, therefore can't say that it has seen it
• work with split-brain patients has discovered a number of differences between the two hemispheres, e.g. that the left hemisphere is responsible for speech and language and the right hemisphere specialises in visual-spatial processing and facial recognition