Hemispheric lateralisation and split-brain research

Question 1

What is hemispheric lateralisation

Answer 1

The idea that the hemispheres are functionally different, each controlling certain mental processes and behaviours that the other doesn’t

Question 2

What is split-brain research

Answer 2

Studies which began in 1960s involving people with epilepsy who have experienced a surgical separation of the hemispheres

Question 3

Left hemisphere

Answer 3

Language areas in LH, is the analyser

Question 4

Right hemisphere

Answer 4

RH is the synthesiser

Question 5

Contralateral

Answer 5

In both hemispheres, eg motor areas, visual areas, LVF, auditory areas

Question 6

Sperry’s research procedure

Answer 6

11 participants, split-brain operation for epilepsy

Question 7

Sperry’s findings

Answer 7

Participant shown object in RVF (LH), able to describe object, when shown in LVF, says nothing there
Object shown in LVF, cannot name but select item with left hand
Pinup picture to LVF - participant giggles but reports nothing

Question 8

Sperry’s conclusions

Answer 8

Lateralised brain, LH verbal and RH ‘silent’ but emotional

Question 9

Laterisation in the connected brain eval

Answer 9

P - strength - research - even in connected brains - two hemispheres process information different
E - PET scans - identify which brain areas active during visual processing task
E - when participants with connected brains asked to attend global elements of image - regions of RH more active - focus on finer detail then LH
L - hemispheric lateralisation feature of the connected brain as well as split

Question 10

One brain eval

Answer 10

P - idea that Lh as analyser and Rh as synthesiser wrong
E - different functions in RH and LH - people do not have dominant side
E - brain scans - 1000 people - did not find people used certain hemispheres for certain tasks - no evidence of dominant side
L - notion of light or light brained is wrong

Question 11

Lateralisation versus plasticity

Answer 11

P - lateralisation adaptive as enables two tasks performed simultaneously
E - Rogers et al - lateralised chickens - find food while watching predators - normal chickens couldnt
E - HOWEVER - neural plasticity - adaptive - some functions can be taken over by non-specific areas
L - eg language function can switch sides

Question 12

Sperry limitation - generalisation

Answer 12

P - limitation of Sperry’s research - causal relationships hard to establish
E - Sperry’s split-brain participants compared to neurotypical control group
E - non of participants in control had epilepsy - confounding variable - results may be due to epilepsy
L - some of the unique features might be due to their epilepsy

Question 13

Sperry - research support

Answer 13

P - strength is more recent split-brain research
E - Luck et al - split-brain participants perform better than connected controls on certain tasks eg faster at identifying odd one out from similar objects
E - Kingstone et al - in the normal brain LH better cognitive strategies held back by RH
L - supports Sperry’s earlier findings that hemispheres are distinct

Question 14

Opposing research

Answer 14

Real life case-studies - Jodie Miller - hemispherectomy - fails to explain her lack of visuo-motor problems - lateralisation is not fixed, the brain can adapt to new requirements

Question 15

Sperry strength - controlled

Answer 15

Controlled setting with standardised procedures - image flashed for 1/10th of a second so patient couldn’t move eyes across to image - conclusions are genuine

Question 16

Sperry limitation - ecological validity and mundane realism

Answer 16

Artificial tasks such as composite words - lack mundane realism
Everyday life a severed corpus callosum - compensated fr by unrestricted use of two eyes - setting lacks ecological validity
Unsure the left and right hemisphere works according to lateralisation theory in real-life situations