Hemispheric Lateralisation & Split Brain Research

Question 1

What is the purpose of the corpus callosum?

Answer 1

Allows both hemispheres to communicate with each other.

Question 2

What is hemispheric lateralisation?

Answer 2

The specialisation of each hemisphere of the brain for physical and psychological functions (e.g. language areas on the left side).

Question 3

What are the two hemispheres of the brain connected with?

Answer 3

The corpus callosum.

Question 4

What is contralateral?

Answer 4

Where one side of a hemisphere deals with the other side of the body.

Question 5

Evidence that the left hemisphere is dominant for language (lateralisation):

Answer 5

-Wada Test: one hemisphere is put under anaesthetic. Participants then read aloud. When the left hemisphere is anaesthetised, reading is disrupted for 90% of people.
-Brain damage to Broca’s area and Wernicke’s area leads to aphasia (impaired language abilities).

Question 6

Evidence that the right hemisphere is dominant for emotion (lateralisation):

Answer 6

-Sperry (1968) showed a picture of a naked person for 0.1 seconds to a split brain patient’s left visual field (LVF). The patients reported that they saw nothing, but smiled, blushed and giggled without knowing why.

Question 7

What was the aim of Sperry (1968)?

Answer 7

To examine the extent to which the two hemispheres are specialised for different functions.

Question 8

What was the method of Sperry (1968)?

Answer 8

Images are projected to the patient’s left visual field (LVF) (processed by the right hemisphere) or the right visual field (RVF) (processed by the left hemisphere).

This is flashed for 0.1 seconds to prevent eye movements, along with information entering the ‘wrong hemisphere’.

-Describe what you can see.
-Drawing.

Question 9

What were the results of Sperry (1968)?

Answer 9

-Describe what you can see:
LVF/Right hemisphere: saw nothing.
RVF/Left hemisphere: described what they saw.
-Drawing:
Drew what they saw in the LVF.
Said what they had seen in the RVF.

Question 10

What was the conclusion of Sperry (1968)?

Answer 10

-The left hemisphere is dominant in terms of speech & language.
-The right hemisphere is dominant in terms of visual-motor tasks.

Question 11

Evaluation for Sperry (1968):

Answer 11

+Highlighted the differences between the hemispheres.
-Small sample, as patients who had their corpus callosum severed due to severe epilepsy are rare.
-The patients had suffered severe epilepsy and long term drug treatment, so it may be invalid to compare their brains with ‘normal’ brains.