BIO: Lateralisation (Split-brain Sperry)

Question 1

The brain

Answer 1

• has 2 hemispheres (Left+Right)
• the left-right arrangement is known as lateralised
• communication between structures in different hemispheres goes through the corpus callosum
• some functions are localised in identical, mirrored regions in each hemisphere
• others only occur in 1 hemisphere

Question 2

what areas are located in the left hemisphere of the brain?

Answer 2

Broca’s and Wernicke’s area

Question 3

what areas are located on both sides of the brain?

Answer 3

motor cortex
somatosensory cortex
amygdala
hippocampus
basal ganglia

Question 4

define contralateral organisation

Answer 4

functional areas that are localised in both areas will always connect to the opposite side of the body

Question 5

Split brain patients (1950s) epilepsy

Answer 5

patients with severe epilepsy that didn’t respond to drugs were virtually untreatable in the 1950s
- surgeons experimented with all sorts of operations (e.g. HM)

Question 6

what was an alternative candidate for surgery regarding Split brain patients?

Answer 6

the corpus callosum
- the whole structure was severed. In modern surgery, only a small lesion is made

Question 7

Sperry and Gazzaniga (1967) - split-brain research (AIM)

Answer 7

Aim: investigate hemispheric lateralisation of function in split-brain patients

Question 8

Sperry and Gazzaniga (1967) - split-brain research (IV 1+2)

Answer 8

IV(1): stimulus number presented to RHS (hand/eye)
IV(2): stimulus number presented to LHS (hand/eye)

Question 9

Sperry and Gazzaniga (1976) split-brain research (DV a+b)

Answer 9

DV(a): accuracy in reporting a stimulus number via hand signal
DV(b): accuracy in reporting a stimulus number via speech

Question 10

Sperry and Gazzaniga (1967) split-brain research (findings)

Answer 10

stimulus presented to RHS can be reported verbally but not signed with the right hand

stimulus presented to LHS can be signalled with the right hand but not verbally

Question 11

Sperry and Gazzaniga (1967) split-brain research (conclusion)

Answer 11

severing the corpus callosum prevents lateralised functional areas receiving signals from the opposite side of the body.
language is lateralised to the left hemisphere

Question 12

Evaluation 1:

Answer 12

P- provided lots of understanding to which areas do what
E- left hemisphere is geared towards verbal tasks as patients couldn’t verbally say it if it was in their left hand
E- However, it is not as simple as just ‘non-verbal’ and ‘verbal’ sides of the brain
L- brain is more complex than is said in this experiment- resudctionist

Question 13

Evaluation 2:

Answer 13

P- experiments were highly controlled
E- Sperry’s procedure
E- results were also very consistent across the patients
L- Internal validity

Question 14

Evaluation 3:

Answer 14

P- small sample
E- Sperry only had a small number of split-brain patients
E- Also, can’t take into account extraneous variables
L- Not generalisable to everyone, low pop validity