AO1

• What is hemispheric lateralisation?

  The idea that the 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, as in the example of language (which is both localised and lateralised)
• What is split brain research?

  A series of studies which began in the 1960s involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain. This allowed researchers to investigate the extent to which brain function is lateralised
• Who conducted split brian research?

  Roger Sperry
• What is corpus callosotomy?

  Surgical procedure in which the corpus callosum and other tissues which connect the two hemispheres were cut down in the middle in order to separate the two hemispheres
• What did separating the two hemispheres do?

  Control frequent and severe epileptic seizures
• When could the patient easily describe a picture of an object?

  When it was shown to the right visual field
• If the object was shown to the left visual field, the patient could not describe what was seen, and typically reported that there was nothing there
• The patient’s inability to describe the objects in the left visual field (processed by the right hemisphere) was because of a lack of language centres in the right hemisphere
• In the normal brain, messages from the right hemisphere would be relayed to the language centres in the left hemisphere
• Composite words: If two words were presented simultaneously, one on either side of the visual field (for example, a 'key' on the left and 'ring' on the right as in the picture), the patient would write with their left hand the word 'key' ( right hemisphere linked to left visual field also controls the left hand) and say the word 'ring'.
• When asked to match a face from a series of other faces, the picture processed by the right hemisphere (left visual field) was consistently selected, whilst the picture presented to the left hemisphere was consistently ignored. When a composite picture made up of two different halves of a face was presented - one half to each hemisphere - the left hemisphere dominated in terms of verbal description whereas the right hemisphere dominated in terms of selecting a matching picture.
• Which hemisphere is better at recognising faces ?

  Right hemisphere