lateralisation and split brain research

Question 1

What is hemeispheric lateralisation?

Answer 1

refers to the fact that some mental processes within the brain are located to either left or right hemisphere

Question 2

What is the function of the left hemishere?

Answer 2

Language and speech

Question 3

What is the function of the right hemisphere ?

Answer 3

visual and motor movements

Question 4

what connects the two hemispheres and what is it made of?

Answer 4

Corpus callosum

A bundle of nerve fibres

Question 5

Why is it that people get their corpus callosum severed?

Answer 5

Severing the cc prevents the severe high level of electrical activity that accompanies epileptic seizures

Question 6

What are the names of the researchers who studied split brain patients?

Answer 6

Sperry and Gazzaniga

Question 7

S/G aim

Answer 7

to test the capabilities of the separate hemispheres by sending visual information to just one side at a time as in split brain patients the corpus callosum is split preventing cross information

Question 8

S/G procedure

Answer 8

• Had a control group of non split brain to note comparisons
• Studied a small number of split brain patients using a visual task
• Ppt presented with images to the left and / or right visual fields to study hemispheric lateralisation

1) Looking at a dot → so clearly separating any use of the other eye
2) Presented information
3) Then asked to perform a physical task on the opposite side (finding/describing/drawing the object) - without seeing their hands

Question 9

Why did the participants have to fixate on a dot?

Answer 9

this is so that the patient doesn’t look out of the periphery of the other eyes

Ensures that information went to one hemisphere at one time

Question 10

S/G findings

Answer 10

• Ppt only able to name the subjects presented in the right visual field and when asked what they saw in the left they said nothing
• If shown an image of a dog to the right visual field → able to articulate it was a dog as left hemisphere language and speech. But if presented to the right field they saw nothing

Question 11

Conclusions S/G

Answer 11

So if presented an image on the left visual field not able to verbally describe it

• Information from the left visual field is processed by right hemisphere which has no language centre so cannot respond verbally → as the left ( where language processing occurs) which does not receive the information therefore can not say it has seen it

Question 12

What have we learnt from split brain research?

Answer 12

Discovered differences between the two hemispheres
* Left → speech and language production
* Right → visual-spatial processing and facial recognition
Suggests the connectivity between different regions is as important as the operation of different parts.

Question 13

Case study of where it goes wrong of split brain research?

Answer 13

Karen Bryne who had Alien Hand syndrome
* Her hand act independently from her thoughts

Indicating left and right hemispheres have own agendas but when not communicating can be out of control

Question 14

Strengths

Answer 14

• S/P identified a number of key differences between hemispheres

Functionality is unique in the hemisphere → damage to one may cause lack of speech or inability or motor

High scientific contribution

Criticised by further research
Simplistic → only right hemisphere can process motor tasks (like only localisation)
But findings of connectivity limits importance of LOF

• Knowledge of hemispheric lateralization - laid foundation for latter research

Enabled understanding of having a superior hemisphere that dominates certain tasks

Superior right hemisphere → left handed = good at maths and have weaker immune system

• Scientific credibility is high → high internal validity - generalisable to extent
  Scientific methodology
  Able to be replicated and repeated as standardised and controlled as ppt had to fixate on a dot → increases internal validity that info went to one hemisphere at a time

Increasing the external validity and generalisability to certain extent

Question 15

limitations

Answer 15

• Individual differences
  Szaflarski - language is less lateralised in older people

Need to be cautious when trying to generalise from research

• Research only with split brain patients
  The sample he had to use all had surgery and history of epilepsy

Unrepresentative of general population - brains differ in important ways

Jeopardises the external validity of sperry’s conclusions on lateralisation

• Internal validity ?- confounding variables
  Procision of surgery
  Some patients had greater degree of a split then others → reducing internal validity
  Are we clear the split brain research had same procedure not damaging cells from either hemisphere if so reduce IV
  Drug therapy
  Some patients had experienced extensive drug therapy → may influenced findings –? Compromising Int validity