split-brain research

Question 1

split-brain research definition

Answer 1

a series of studies which began in the 1960s (still ongoing) involving people with epilepsy who has experiences a surgical separation of the hemispheres of their brain by having the corpus callosum severed (in a process called a commissurotomy) to reduce the severity of their epilepsy. this enabled researchers to test lateral functions of the brain in isolation

Question 2

what does split-brain surgery involve

Answer 2

severing connections between the RH and LH by severing the corpus callosum which is a surgical procedure to reduce epilepsy

Question 3

why is split brain surgery effective at reducing/ preventing epileptic seizures

Answer 3

during an epileptic seizure the brain experiences excessive electrical activity which travels from one hemisphere to the other

Question 4

what does split-brain surgery show

Answer 4

how the hemispheres function when they can’t communicate with each other

Question 5

who did split-brain research

Answer 5

Sperry

Question 6

when did Sperry do split-brain research

Answer 6

1968

Question 7

what did Sperry aim to study

Answer 7

how two separated hemispheres deal with, for example speech and vision

Question 8

Sperry sample

Answer 8

11 people who had split-brain surgery

Question 9

Sperry set-up

Answer 9

11 people who had split-brain surgery were in the set up where an image could be projected into the the RVF so processed by the LH or he LVF so processed by the RH. focal point

Question 10

why did Sperry set up his research like this

Answer 10

in a normal brain the corpus callosum would immediate share information between both both hemispheres giving a complete picture of the visual world. however, by presenting the image to one hemisphere of a split-brain participant meant that the information could not be conveyed from one hemisphere to another

Question 11

what were Sperry’s findings

Answer 11

-when a picture of an object was shown to a participant’s RVF so linked to LH, the participant could describe what was seen, but they could not do this if the object was shown to the LVF so linked to RH and they said there was nothing there. this is because in the connected brain, messages from the RH and relayed to the language centres in the LH, but this is not possible in a split-brain
-when object projected to LVF they could select a matching object that was out of sight when using their left hand. the left hand was able to select an object that was most closely associated with an object associated with a object presented to the LVF such as an ashtray in response to a picture of a cigarette
-if a pinup picture was shown to the LVF there was an emotional reaction such as a giggle but the participants usually reported seeing nothing to just a flash if a light
-If two words are presented simultaneously, one on either side of the visual field such as key on the left and ring on the right, a split-brain individual would select a key with their left hand (as the left visual field is linked to right hemisphere and linked to left hand) and say the word ring

Question 12

Sperry’s findings verbal

Answer 12

-when a picture of an object was shown to a participant’s RVF so linked to LH, the participant could describe what was seen, but they could not do this if the object was shown to the LVF so linked to RH and they said there was nothing there. this is because in the connected brain, messages from the RH and relayed to the language centres in the LH, but this is not possible in a split-brain

Question 13

Sperry’s findings- matching object

Answer 13

-when object projected to LVF they could select a matching object that was out of sight when using their left hand. the left hand was able to select an object that was most closely associated with an object associated with a object presented to the LVF such as an ashtray in response to a picture of a cigarette

Question 14

Sperry’s findings emotional response

Answer 14

-if a pinup picture was shown to the LVF there was an emotional reaction such as a giggle but the participants usually reported seeing nothing to just a flash if a light

Question 15

Sperry’s conclusions

Answer 15

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

Question 16

Sperry’s findings of two simultaneously presented words

Answer 16

-If two words are presented simultaneously, one on either side of the visual field such as key on the left and ring on the right, a split-brain individual would select a key with their left hand (as the left visual field is linked to right hemisphere and linked to left hand) and say the word ring

Question 17

strength of split-brain research - research support

Answer 17

-support from more recent split-brain research
-Gazzaniga (Luck et al 1989) showed that split-brain participants actually perform better than connected controls on certain tasks. for example, the 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 (kingstone et al 1955) –> supports Sperry’s earlier findings that the left brain an right brain are distinct

Question 18

limitation of split-brain research -generalisation issues

Answer 18

-casual relationships are hard to establish
-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 that were observed between the two groups may be the result of epilepsy rather than the split brain –> means that some of the unique features if the split-brain participants’ cognitive abilities might have been due to their epilepsy

Question 19

evaluation of split-brain research - ethics

Answer 19

-split-brain operation was not performed for the purpose of the research so Sperry’s participants were not deliberately harmed. in addition, all procedures were explained to the split-brain participants and their full informed consent was obtained
-however, the trauma of the operation might mean that the participants did not later fully understand the implications of what they has agreed to. they were subject to repeated testing over a lengthy period which can be stressful over time