Hemispheric Lateralisation

Question 1

What is Hemispheric Lateralisation?

Answer 1

The idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisation.

Question 2

Give examples of Hemispheric Lateralisation

Answer 2

The left is dominant for language

Question 3

The left hemisphere controls….

Answer 3

The right side of the body

Question 4

The right hemisphere controls….

Answer 4

The left side of the body

Question 5

What is the Wada Test?

Answer 5

A test which provides evidence for lateralisation of language

Question 6

Describe the Wada Test

Answer 6

• Anaesthetic is injected is injected into the carotid artery on one side of the head
• This anaesthetises one hemisphere
• The participant then reads aloud, when the left hemisphere is is anaesthetised , reading aloud is disrupted for more than 90% of people

Question 7

What is a Split Brain Patient?

Answer 7

A patient who’s Corpus Callosum is severed, meaning each hemisphere can not communicate with one another.

Question 8

Right Visual Field sends information to the….

Answer 8

Left Hemisphere

Question 9

Left Visual Field sends information to the….

Answer 9

Right Hemisphere

Question 10

Describe the Method of Sperry (1968)

Answer 10

• Sperry used eleven participants in this quasi experiment (IV is naturally occurring)
• The participants’ hemisphere were disconnected by cutting the corpus callosum
• Apparatus was used which could present information to one hemisphere
• The patient sat at a table with their hands under a screen or visual stimuli were projected onto a screen.
• The screen divided the left and right halves of visual fields. Visual stimuli were projected for 1/10th of a second which is too fast for eye movements (so info cannot go to the wrong hemisphere)
• Many different tests were done on the participants’ vision, emotion, olfaction, consciousness and so on.

Question 11

Describe the Results for Sperry (1968)

Answer 11

• Disconnecting the hemispheres does not affect the participants’ ordinary behaviour, intelligence or personality. However, there were some short-term memory deficits, orientation problems and mental fatigue.
• The tests show that the hemispheres have different abilities and functions (Lateralisation of function)
• One hemispheres does not know what the other had seen or felt.
• When info was presented to LVF they could not name what they had seen
• If two different images were flashed simultaneously to the RVF and LVF, patients could draw the image they had seen on left half with their left hand, but when asked what they have drawn, they identify what they have seen in the RVF

Question 12

What is the conclusion for Sperry (1968)?

Answer 12

Sperry concluded that the two hemispheres have different function and that split-brain patients’ have a “divided consciousness”

Question 13

Strengths of Sperry (1968)

Answer 13

• Highlights the differences between the hemispheres
• Provides some Insight into how the normal brains function

Question 14

Weaknesses of Sperry (1968)

Answer 14

• As it is a quasi experiment, Sperry could not manipulate which group participants were in and there were no controls.
• Corpus callosum being severed is extremely rare, hence use of small sample
• Limited generalisation as the study mainly used right-handers and split-brain patients are in the minority
• People who suffered long term epilepsy were on long-term drug treatments, so it may not be valid to compare their brains with “normal brains”