Sperry

Question 1

Define lateralisation of function.

Answer 1

The two hemispheres have a different function, with the left specialising in language processing.

Question 2

Define contralateral control.

Answer 2

Each hemisphere of the brain controls the opposite side of the body and the opposite visual field.

Question 3

Define corpus callosum.

Answer 3

The bundle of nerve fibres that connect and allow communication between the hemispheres.

Question 4

Define commissurotomy.

Answer 4

Surgery which was carried out to cut the nerve fibres between the two brain hemispheres (usually to control epilepsy symptoms).

Question 5

What was the background to Sperry’s study?

Answer 5

A split brain operation (commissurotomy) entails cutting the commisual fibres and completely separating the two hemispheres. This has been done for some people with extreme epilepsy in the hope that the electrical discharge within the brain can be controlled to the hemisphere in which it originated rather than spreading across the whole of the brain.

Question 6

What was the aim of Sperry’s study?

Answer 6

• To investigate the function / abilities of each hemisphere of the brain.
• To investigate the effect of deconnecting the two hemispheres of the brain.

Question 7

What was the sample in Sperry’s study?

Answer 7

• 11 patients who had had a commissurotomy in order to treat their epilepsy.
• Males and females.
• 2 had been operated on several years ago whilst the other 9 had only recently undergone the surgery.

Question 8

What piece of equipment was used in Sperry’s study?

Answer 8

A tachistoscope: An instrument used for displaying visual images for a very brief period of time (1/10th of a second).

Question 9

What controls were out in place in Sperry’s study?

Answer 9

• Participants could only speak when asked a direct question.
• Participants’ hands were shielded from view.
• Images were only shown for 1/10th of a second.

Question 10

What were the two types of task participants completed in Sperry’s study?

Answer 10

• Tactile tasks
• Visual tasks

Question 11

What was the procedure for the tactile task in Sperry’s study?

Answer 11

• Participants sat down with their hands shielded from view and were asked to pick up objects with one hand from behind the screen.
• They were then asked to either name the object they had felt, point to it from an area of other objects or pick up the object again.

Question 12

What were the findings from the tactile task when objects were felt with the right hand only (unseen by participants) in Sperry’s study?

Answer 12

• The information went to the left hemisphere.
• Participants could name the object they were feeling point towards to object with their right hand.

Question 13

What were the findings from the tactile task when objects were felt with the left hand only (unseen by participants) in Sperry’s study?

Answer 13

• The information went to the right hemisphere.
• The participants had no conscious awareness of the object they had felt and couldn’t name it but could point towards it with their left hand.

Question 14

What was the procedure for the visual task in Sperry’s study?

Answer 14

• Participants sat down in front of the tachistoscope with one eye covered.
• They were asked to stare at a fixation point on a screen in front of them and images flashed up on the screen for 1/10th if a second.
• They were asked to either name the object verbally, draw the object, or point towards the object from a collection of items on their desk.

Question 15

What were the findings from the visual task when objects were flashed to the right visual field in Sperry’s study?

Answer 15

• Information went to the left hemisphere.
• Participants could name the object, draw it with their right hand and find it with their right hand from an array of different objects.

Question 16

What were the findings from the visual task when objects were flashed to the left visual field in Sperry’s study?

Answer 16

• The information went to the right hemisphere.
• Participants could draw the object with their left hand and find it with their left hand from an array of different objects.
• They could not verbally say what object they had seen.

Question 17

What were the findings from the visual task when different visual stimuli were flashed to each visual field at the same time in Sperry’s study?

[Use the example of an image of an apple to the LVF and an image of a key to the RVF.]

Answer 17

• The apple went to the right hemisphere and the key went to the left hemisphere.
• Participants were asked to draw with their left hand what they had seen.
• They could draw a picture of an apple with their left hand but would say they had seen a key.
• They could not explain why they had drawn an apple.

Question 18

What were the conclusions made from Sperry’s study?

Answer 18

• With the corpus callosum cut, one side of the brain does not know what the other side is doing (they have their own separate consciousness).
• There is lateralisation of brain function where each side of the brain has its own specialised roles:
  
  • The left hemisphere controls speech, writing, language and the right side of your body (and receives information from the RVF of both eyes).
  • The right hemisphere controls non-verbal processes and the left side of your body (and receives information from the LVF of both eyes).