Split-brain research Flashcards
What is split brain research used to study?
Brain lateralisation
commissurotomized patients
when patients who suffer from epilepsy have an operation that involves lesioning the nerve fibres of the corpus collusum to stop seizures. communication between the right and left hemispheres has been cut
Sperry and Gazzaniga (1967)
First researchers to study split brain patients, sending visual information to one hemisphere at a time to study hemispheric lateralisation.
Hemispheric lateralisation
What types of information is processed specifically by each hemisphere and what are the specialities of each hemisphere
What was the aim of Sperry and Gazzanigaâs (1967) research?
To examine the extent to which the two hemispheres are specialised for certain functions
What was the method of Sperry and Gazzanigaâs (1967) research?
Using the divided field procedure where an image is projected to the patients left or right visual field (processed by opposite hemispheres). When information is presented to one hemisphere the information isnât transferred to the other hemisphere in a split brain patient as the corpus callosum is cut
What type of different experiments did Sperry and Gazzaniga (1967) conduct?
1) What you see tasks
2) Tactile test
3) Drawing task
What did the âdescribe what you seeâ task by Sperry and Gazzaniga entail?
A picture was presented to either the left or right visual field and the participant had to simply describe what they saw
What did the âtactile testâ by Sperry and Gazzaniga entail?
An object was placed in the patients left or right hand and they had to either describe what they felt or select a similar object from a series of alternate objects
What did the âdrawing taskâ by Sperry and Gazzaniga entail?
Participants were presented with a picture in either their left or right visual field and they had to draw what they saw
What did Sperry and Gazzaniga find in the âdescribe what you seeâ task?
A picture presented to the right visual field allowed the patient to describe verbally what they saw, demonstrating the superiority of the left hemisphere when it comes to language production. When presented to the left visual field they couldnât describe what was shown and reported nothing was there.
What did Sperry and Gazzaniga find in the âtactile testâ?
Objects placed in the right hand meant the patients could describe verbally what they felt or identify the test object presented in the right hand through picking a similar object from a selection. When objects were placed in the left hand the patient could not describe what they felt and could only guess but they could identify a test object by selecting a similar object
What did Sperry and Gazzaniga find in the âdrawing taskâ?
When the picture was presented to the RVF and the right hand would try to draw it, it wasnât as clear as the left hand. When the picture was presented to the LVF, the left hand would draw better pictures consistently despite right handed participants. shows right hemisphere superiority in visual motor tasks
What was the conclusion of Sperry and Gazzanigaâs research?
It highlights a number of key differences between the two hemispheres, the left hemisphere is dominant in terms of speech and language and the right is dominant in visual motor tasks
What type of patients did Turk et al. (2002) study?
Split brain patients, specifically a 48 year old man, JW who had a commissurotomy for epilepsy 23 years earlier
What was Turk et al (2002) interested in?
face processing after split brain surgery, whether the patients own face was processed in a different way to the familiar face of someone else
What were the stimuli for Turk et al (2002)?
Face stimulus made of two separate faces morphed together. One was JWâs and the other was a researcher who was worked with him for years and was familiar (0% JW, 50% and 100%) and used divided field procedure
How was the trials by Turk et al carried out?
JW asked to press a button if the image was himself or a familiar person
What did the results of Turk et al show?
right hemisphere showed a bias towards identifying the morphed faces as the familiar other and the left showed a bias towards identifying morphed faces
What did they conclude from the Turk et al research?
The right hemisphere is better at face processing and the left is better at self recognition
Self recognition requires personal memories and beliefs and a self concept and the left hemisphere has a role in the networks involved in self recognition
What are the strengths of split brain research?
- can prove there is hemispheric lateralisation (L is speech and language, R is visual spatial processing and holistic processing) through Turk and Sperry and Gazzaniga
- Research support
What are the weaknesses of split brain research?
- Has not shown the brain is organised into different areas
- Issues with split brain research
- Split brain rarely carried out these days so lacks temporal validity
What are the issues with split brain research?
- Few patients that have had extensive studies (10-15) so small sample size
- Sample studies are extremely varied
- Operations werenât always comparable because some pathways remained in some cases
This threats generalisability
