Spilt Brain Research Flashcards
What is the background to spilt brain research??
In cases of severe epilepsy, one drastic solution for those who had not been helped by conventional medicine is to have surgery to disconnect the two sides of the brain.
This then restricts the epileptic seizures
to only one hemisphere and reduces
the severity of the attack.
This had mixed results.
Split brain patients are those who have had the connection between the left and right hemisphere severed.
In other words, their corpus colussum (the bundle of nerve fibres called commissural fibres) has been cut.
This is called a cerebral commissurotomy.
These people have proved useful to psychologists interested in studying how the different hemispheres function.
Normally, the two hemispheres share information.
In split-brain patients, this does not happen so when the eyes visual fields are restricted (info sent very briefly only to one visual field) the differences between left and right hemisphere functioning can be seen.
Although importantly in everyday life they do not show problems as the eyes are constantly moving!
What is the process of split brain research
Split brain research uses a split visual field.
Pts are sat in front of a screen and asked to gaze at a fixed point in the centre of the screen.
Visual stimuli are projected onto the screen either to the right or left visual field at a very high speed so the Pt has no chance to move their head and is only able to process the image in the visual field where it was placed.
- is a quasi exp
What was the findings of sperrys research??
What was done: Words projected to LVF (to right hemisphere).
Testing: Verbal responses to language.
Finding: Words not registered. Pt’s would say they saw nothing.
Conclusion: Left hemisphere responsible for language (so words need to be presented to RVF in order to be registered).
What was done: Words (e.g., fork) projected to LVF (to right hemisphere).
Testing: Physical responses to language.
Finding: Left hand (controlled by RH) was placed behind a screen with objects. Pt’s could feel around and select the correct object DESPITE being unable to verbally report it.
Conclusion: Right hemisphere does have some language ability for understanding words if not for speech.
What was done: A different face presented to each hemisphere at the same time. Pt’s given a set of faces and asked to select those they had seen.
Testing: Matching abilities in response to pictures.
Finding: Pt’s chose the one presented to the RH, indicating its role in identifying faces and shapes.
Conclusion: Right hemisphere is responsible for visuospatial tasks.
What are the strengths of spilt brain research??
- reliability
- application
What are the weaknesses of spilt brain research
- generalisability
- validity
How is reliability a strength
A strength of split brain research is that they use highly specialised and standardised procedures.
Sperry presented visual information to one hemispheric field at a time, asking participants to stare at a given point, the ‘fixation point’. The image projected would be flashed up for a one-tenth of a second, meaning the split-brain patient would not have time to move their eye across
the image and so spread the information across both sides.
This allowed Sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving the information at a time. Thus, he developed a very useful and well-controlled procedure.
How is application a strength
A strength of split brain research is that it has useful practical applications enabling a greater understanding of the differing functions of the hemispheres and adding to the unity of the consciousness debate.
For instance, we now know that language is largely processed in the left hemisphere…
This allows our scientific understanding of the brain to move forward from split brain research.
How is generalisability a weakness
The split brain research lacks generalisibility as there was a limited number of participants (only 10-15 have been subjected to systematic study).
In addition, the participants varied considerably in age, gender and handedness as well as the age at which they developed epilepsy and the degree of drug therapy they had experienced before their operation. All factors that will affect behaviour.
This implies split brain research…
How is validity a weakness
The split brain patients were often compared to neurotypical controls, but these people often had no history of epilepsy (i.e. not matched pairs) and therefore this could be a potential confounding variable as a history of epilepsy would affect general behaviour.
This means it is harder to establish ___________ and ___________ and there could be other explanations for split brain findings , such as…
