AQA Psychology for A Level Year 2: Rev Guide

Chapter 2: Biopsychology Split-brain research Hemispheric lateralisation. Concerns behaviours controlled by just one hemisphere. Language is an example of hemispheric lateralisation (usually controlled by the left hemisphere). Split-brain studies involved a unique group of individuals. Sperry (1968) sought to demonstrate that the two hemispheres were specialised for certain functions and could perform tasks independently of one another. Normally the hemispheres are connected by the corpus callosum and a few other structures. A commissurotomy is an operation to cut the corpus callosum and is sometimes performed to control epileptic seizures. Sperry studied a group of epileptics who had the operation. Sperry devised a unique procedure to test his split- brain patients. An image or word is projected to a patient’s RVF (processed by LH) and another image to the LVF (processed by RH). In the normal brain, the corpus callosum ‘shares’ information between both hemispheres. In the split brain, the information cannot be conveyed from the chosen hemisphere to the other. Describing what was seen. Object shown to: • RVF  patient easily describes what is seen. • LVF  patient says ‘there’s nothing there’. Can’t describe objects in LVF because RH usually lacks language centres. Messages received by RH are normally relayed via the corpus callosum to language centres in LH. Recognition by touch. Objects shown to LVF: • Could not name them but could select a matching object using left hand (connected to RH receiving information from LVF). • Left hand could also select an object that was associated with image presented to the LVF (e.g. ashtray selected in response to a picture of a cigarette). In each case, the person could not verbally identify what they had seen (because the LH is needed for this) but could ‘understand’ what the object was (using the RH) and select the corresponding object. Composite words and matching faces. Two words presented on either side of the visual field (e.g. ‘key’ presented to the left and ‘ring’ to the right). Patient: • Writes ‘key’ with left hand (goes to RH linked to LVF). • Says the word ‘ring’ (RVF linked to LH). Composite picture made up of two different halves of a face was presented (one half to each hemisphere): • LH dominated the verbal description. • RH dominated the selection of a matching picture. Split-brain research into hemispheric lateralisation AO1 Description Spec spotlight Hemispheric lateralisation: split- brain research. ring The next time you describe yourself as having a ‘splitting headache’, spare a thought for Sperry’s patients. Getting it right (or left) RVF = right visual field. LVF = left visual field. RH = right hemisphere. LH = left hemisphere. Testing a split-brain patient. 34