lateralisation and split brain research

Question 1

Hemispheric lateralisation

Answer 1

Refers to the fact that some mental processes in the brain are mainly specialised to either the left or right hemisphere

EG: left hemisphere is dominant for language and speech and right for visual and motor tasks

Two hemispheres are connected via the corpus callosum

Question 2

Corpus callosum

Answer 2

Bundles of nerve fibres that allow info recieved by one hemisphere to be sent to the other hemisphere

Question 3

Split brain research proc

Answer 3

Sperry and Gazzaniga

11 SB patients- disconnection of cerebral hemisphere (corpus callosum cut) due to severe epilepsy

Quasi experiment

1) present stimuli to one visual field for 1/10 of a second
- This prevented both visual fields of the eye being exposed to the information, so only one hemisphere would process it

4 things:

Describing what you see
Matching words or faces
Words presented simultaneously
Recognising objects placed in hands

Question 4

Split brain findings

Answer 4

1. Describing what you see = If the stimulus word was exposed to the right visual field, then it would be processed by the left hemisphere and the patient would say the word.

This is because the left hemisphere contains the ‘language centres’ of the brain and so allows for speech.

However, if the same stimulus word was exposed to the left visual field, then it would be processed by the right hemisphere and the patient would write the word using their left hand.

This is because the right hemisphere contains the visuo-spatial centres of the brain, allowing for the physical act of writing. The patient would not be able to give a verbal description of the word, because the right hemisphere contains no language centres.

2. Matching words or faces = The right hemisphere appeared to dominate the ability to match a list of faces to a given stimulus. This is due to the right hemisphere containing the brain’s visuo-spatial centres, thus allowing for the visual identification and processing of the faces.
3. Recognizing objects placed into the hands = If an object was placed into the patient’s right hand, they would be unable to identify that it is there, because the information would be processed by the left hemisphere which only has language centres, and no visuo-spatial centres.

Therefore, if an object was placed into the patient’s left hand, they would be able to identify the object and choose a similar one from a hidden bag, due to the action of the visuo-spatial centres.

Question 5

AO3: Lack of control with the sample selection

Answer 5

Conf variables: epileptic patients had been taking anti-eplielpy meds for extended and diff period of tim
May have affected ability due to cerebral neuronal changes

There may have been differences in the exact procedures e.g. differing extent of the lesioning of the corpus callosum. This would have affected the degree to which the two hemispheres could relay information between themselves

Therefore, these two confounding variables had not been controlled, meaning that the lateralised functions may be examples of unreliable causal conclusions.

Question 6

AO3: lateralisation changes w age

Answer 6

Lateralised patterns found in young ppl tend to switch to bilateral patterns in healthy older adults

Research: lateralisation changes w each decade

Cant determine why but one possibility is that using the extra processing resoruces of the other hemisphere may compensate for age related declines

Question 7

AO3: Increases neural processing capacity

Answer 7

by only using one hemispehre to engage in a task, leaves the other hemisphere free to engage in another function

But little emperical evidence to show this