Hemispheric Lateralisation & Split-Brain Research

Question 1

What is meant by Hemispheric Lateralisation?

Answer 1

The idea that the 2 halves (hemispheres) of the brain are functionally different, w/ certain mental processes being mainly controlled by 1 hemisphere rather than the other. The 2 hemispheres are connected by the corpus callosum, which is a bundle of nerve fibres that allows the 2 areas to communicate.

Question 2

What is split-brain research?

Answer 2

Typically involves epileptic patients who have had their hemispheres surgically separated by cutting their corpus callosum, which is in order to reduce the severity of their epileptic seizures. This allows researchers to investigate the extent to which brain functions are lateralised.

Question 3

Describe the procedure in Sperry’s split-brain research.

Answer 3

A ps sits close to a screen & fixates on a dot. A different word is simultaneously presented to the left & right of the dot for 1/10 second so there’s no time for the ps to move their eyes to view both words. There’s a selection of objects relating to the words behind the screen. Ps are then asked to:

• Say the words they see on the screen.
• Pick up the objects w/ their left hand which represents what they see.

Question 4

What were the findings in Sperry’s split-brain research?

Answer 4

When the word ‘key’ was presented to the left visual field simultaneously w/ the word ‘ring’ to the right visual field, ps:

• Said “ring”.
• Picked up the key w/ their left hand.

Question 5

What was concluded from Sperry’s split-brain research?

Answer 5

• Both hemispheres are responding independently & are not able to integrate the info due to the severed corpus callosum.
• Ps say “ring” because the image of the word in their right visual field passes to the visual cortex of the left hemisphere of the brain. The left hemisphere contains language centres, so the person is able to vocally produce the word ‘ring’.
• Ps only pick up the key because the image of the word in their left visual field passes to the visual cortex of the right hemisphere of the brain. The hemisphere contains spatial processing abilities & the right motor cortex, which controls muscles on the left side of the body, which enables the left hand to pick up the object relating to the word ‘key’.

Question 6

What does split-brain research suggest?

Answer 6

There is hemispheric lateralisation in the brain: language is lateralised to the left hemisphere & visual-spatial processing is lateralised to the right hemisphere.