Split Brain Research

A01:

Hemispheric Lateralisation:

The idea that two halves (hemispheres) of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other.

Each hemisphere has functional specialisations, i.e. neural mechanisms for some functions (such as language) are localised primarily in one half of the brain. For example, research has found that the left hemisphere is dominant for language and speech, whereas the right is more on visual-motor tasks. In 1861, Paul Broca identified that damage to the left brain hemisphere lead to language deficits, yet damage to the same area of the right hemisphere did not have the same consequences. This suggests that different hemispheres of the brain govern different functions.

Split-Brain Studies:

Sperry’s (1968) studies involved 11 epileptic patients all of whom has undergone the same surgical procedure, called commissurotomy, where the corpus callosum and other tissues which connect the two hemispheres were cut down the middle in order to separate the two hemispheres and control frequent severe epileptic seizures. This meant that the main communication line between the two hemispheres was removed. This allowed Sperry to see the extent of the ability of the hemispheres were specialised for certain functions and whether the hemispheres performed tasks independently.

Key Findings:

Describe what you see: When a picture of an object was shown to a patient’s right visual field, they could easily describe what was seen. However, if the same object was shown to the left visual field, they could not describe what was seen.

Recognition by touch: When an object is presented to the left visual field, for example a cigarette, the patient was unable to name it (as the left side is controlled by the right hemisphere for visual tasks.) The patients could not name it; however they could select the same object or an object of association, e.g. an ash tray from a grab bag, showing the right hemisphere to be linked to visual tasks and motor tasks, and not speech.

Composite words: When two words are simultaneously presented. One on either side of the visual field e.g. ‘Key’ on the left and ‘ring’ on the right, in form of pictures. The…