split-brain research Flashcards
1
Q
what does a ‘split-brain’ operation involve and what is it used for?
A
- involves severing the connections between the RH and LH, mainly the corpus callosum
- this is a surgical procedure used to reduce epilepsy
- during an epileptic seizure, the brain experiences excessive electrical activity which travels from one hemisphere to the other
- to reduce these fits, the connects are cut, ‘splitting’ the brain in 2 halves
2
Q
what does split-brain research study?
A
how the hemispheres function when they can’t communicate with each other
3
Q
what did sperry’s (1968) research involve?
A
he devised a system to study how two separated hemispheres deal with eg. speech and vision
4
Q
sperry’s research: procedure
A
- 11 people who had a split-brain operation were studied using a special set up where an image could be projected to a pt’s RVF (processed by LH)
- the same, or different, image could be projected to the LVF (processed by the RH)
- in the ‘normal’ brain, the corpus callosum would immediately share the information between both hemispheres giving a complete picture of the visual world
- however, presenting the image to one hemisphere of a SB participant meant that the info cannot be conveyed from that hemisphere to the other
5
Q
sperry’s research: findings
A
- when picture of an object was shown to RVF (linked to LH), they could describe what was seen
- could not do this if the object was shown to LVF (RH), said there was ‘nothing there’
- pts could not give verbal labels to objects projected to LVF but could select a matching object out of sight using their left hand (linked to RH)
- left hand was able to select an object that was most closely associated with an object presented to the LVF (eg. ashtray selected in response to picture of cigarette)
- if a pinup picture was shown to LVF, there was an emotional response (eg. giggle) but pts usually reported seeing nothing or just a flash of light
6
Q
explain sperry’s research findings
A
- in the connected brain, messages from the RH are relayed to the language centres in LH
- this is not possible in the split-brain
7
Q
sperry’s research: conclusions
A
- certain functions are lateralised
- LH is verbal
- RH is ‘silent’ but emotional
8
Q
evaluation: research support
A
- micael gazzaniga (luck et al. 1989) showed that SBP perfom better than connected controls on certain tasks
- eg. faster at identifying odd one out in an array of similar objects than controls
- in normal brain, LH’s better cognitive strategies are watered down by inferior RH (kingstone et al. 1995)
- this support’s sperry’s earlier findings that the ‘left brain’ and ‘right brain’ are distinct
9
Q
evaluation: generalisation issues
A
- limitation of sperry’s research is that causal relationships are hard to establish
- behaviour of sperry’s SBP was compared to a neurotypical control group ie. no controls had epilepsy
- major confounding variable as any differences observed between the 2 groups may the result of the epilepsy rather than SB
- therefore, some of the unique features of SBP’s cognitive abilities may be due to their epilepsy instead
10
Q
evaluation: ethics
A
- SB operation was not performed for the purpose of the research so in that sense, sperry’s pts were not deliberately harmed
- all procedures were also explained to the SBP and their full informed consent was obtained
- however, the trauma of the operation might mean that the pts did not later fully understand the implcations of what they had agreed to
- they were subject to repeated testing over a lengthy period (sometimes years), which may have been stressful over time
11
Q
evaluation: kim peek, a natural split-brain
A
- was born with a total absence of a corpus callosum
- unlike sperry’s participants, peek’s SB was due to natural causes
- had prodigous powers
- he could recall word-for-word 12,000 books
- could read 2 pages in around 10 seconds, employing his SB to simultaneously read one page with his RVF and one page with his LVF
