Split brain research Flashcards
Split brain research
A split-brain operation involves severing the connections between the LH and RH, mainly the corpus callosum. This is a surgical procedure to reduce epilepsy, as during an epileptic seizure excessive electrical activity travels from one hemisphere to another. Split brain research studies how the hemispheres function when they can’t communicate with each other.
Sperry’s research - procedure
eleven people who had a split brain operation were studied. An image was projected into a participants RVF (processed by the LH) and the same, or different image could be projected to the LVF (processed by the RH). In the normal brain, the corpus callosum would share the information between both hemispheres giving a complete picture of the visual field. However, presenting the image to one hemisphere of a split-brained participant meant the information can’t be conveyed from that hemisphere to the other.
Sperry’s research - findings
when a picture of an object was shown to a participants RVF (linked to LH), the participant could describe what was seen. But they could not do this is the image was shown to LVF. This is because, in a normal brain, messages from the RH are relayed to language centres in the LH, but this isn’t possible in the split-brain. Participants, however, could select a matching object out of sight using their left hand (linked to RH). The left hand was also able to select an object that was most closely associated with an object presented to the LVF.
Sperry’s research - conclusion
these observations show how certain functions are lateralised in the brain and support the view that the LH is verbal and the RH is silent but emotional.
Evaluation of split-brain research (brief)
strength - support from Gazzaniga
weakness - generalisation issues
strength of split-brain research
one strength is that there is support from more recent split-brain research. Gazzaniga (1989) showed that split-brain participants actually perform better than connected controls on certain tasks. For example, they were faster at identifying the odd one out in an array of similar objects than normal controls. In the normal brain, the LH’s better cognitive strategies are ‘watered down’ by the inferior RH. This supports Sperry’s earlier findings that the ‘left brain’ and ‘right brain’ are distinct.
weakness of split-brain research
one weakness of Sperry’s research is that there are generalisation issues and casual relationships are hard to establish. The behaviour of Sperry’s split-brain participants was compared to a neurotypical control group. An issue though is that none of the participants in the control group had epilepsy. This is a major confounding variable. Any differences observed between the two groups may be the result of the epilepsy rather than the split brain. This means that some of the unique features of the split-brain participants’ cognitive abilities might have been due to their epilepsy.
