Split-brain research

Question 1

Outline Sperry and Gazzaniga’s research

Answer 1

• Sperry and Gazzaniga were the first to study the capabilities of split-brain patients.
• To test the capabilities of separated hemispheres, they were able to send visual info to one hemisphere at a time in order to study what is called hemispheric lateralisation

Question 2

How did Sperry and Gazzaniga conduct their research?

Answer 2

• They took advantage of the fact that info from the left visual field goes to the right hemisphere and info from the right visual field goes to the left hemisphere .
• As the corpus callosum is cut in split brain patients, the info presented to one hemisphere has no way of travelling to the other and can be processed only in the hemisphere that received

Question 3

Describe a typical split-brain study

Answer 3

• The split-brain patient would fixate on a dot in the centre of a screen while info was presented to either the left or right visual field.
• They would then be asked to make responses with either their left hand (controlled by right hemisphere) or right hand, or verbally (both controlled by left hemisphere), without being able to see what their hands were doing

Question 4

Give an example of a typical split-brain study

Answer 4

• If the patient was a flashed a pic of a dog to the right visual field and asked what they had seen, they would answer ‘dog’.
• However if a pic of a cat was flashed to the left visual field, they would say that they saw nothing.
• The info from the left visual field is processed by the right hemisphere, but as it has no language centre, it can’t be answered verbally.
• The left hemisphere, doesn’t receive info about seeing the cat, therefore can’t say that it’s seen it

Question 5

What have we learned from split-brain research?

Answer 5

• Discovered differences between the 2 hemispheres e.g. left is responsible or speech and language.
• However research hasn’t shown that the brain is organised into discrete regions with specific sections for specific tasks. Instead, it suggests that the connectivity between regions is as important as the operation of the different parts

Question 6

Give evaluation of split-brain research (language isn’t restricted)

Answer 6

• Gazzaniga suggests that some of the early discoveries from split-brain research have been disconfirmed by more recent discoveries
• Damage to the left hemisphere was more detrimental to language function than was damage to the right.
• However, JW developed the capacity to speak out of the right hemisphere, and can now speak about info presented to the left or to the right brain (Turk et al)
• This challenges the claim that the right hemisphere can’t handle basic language and that it’s restricted to the left hemisphere

Question 7

Give evaluation of split-brain research (limitations)

Answer 7

• The split-brain procedure is now rarely carried out, and Andrewes points out that many studies are presented with 3 or just 1 participant
• Andrewes claims some conclusions have been drawn from individuals who have a confounding disorder that made the procedure necessary, or have had a less complete sectioning of the two hemispheres than was originally believed
• As a result, patients who’ve had this procedure without these confounding factors are rarely encountered in sufficient numbers to be useful for research