Split Brain Research Flashcards
(14 cards)
What type of surgery have split brain patients undergone?
Commissurotomy - where the corpus callosum has been split to reduce symptoms of epilepsy
What is the corpus collosum
Thick and of nerve fibres that divides the cerebral cortex lobes into left and right hemispheres
Connects both sides allowing for communication between both hemispheres
What was the effect of the commisurotomy
The patients two hemispheres functioned completely separately as independent brains
What was the aim of sperry’s study
Investigate hemispheric lateralisation in split brain patients who have surgically separated hemispheres to see whether each hemispheres is responsible for separate functioning
What is the procedure of Sperry’s research
- In an experiment 11 epileptic males were asked to complete a series of tasks a involving sitting in front of a screen with the ability to freely move their hands and gable objects which appeared behind the screen and hidden from sight
- visual stimuli tests: participants were asked to gaze on a fixation point in the middle of the screen. Then presented with words (Eg:key) either to the left or right of the fixation point for a 10th of a second
What were the findings for the visual stimuli tests
If a participant is presented with the word “key” the the right visual field they would verbally respond with key
If the Ppts were presented with this info t the left visual field they are unable to respond verbally, although could draw the image with their left hand
What was the procedure for tactile stimuli tests
Ppts were presented with objects to the left or right behind the screen
What were the findings for the tactile stimuli tests
If Ppts are placed with an object in their right hand, they are able to describe th object verbally and in writing
If the Ppts are presented with objects in their left hand, they are verbally unable to describe it but can point to the correct image from pictures
What were the conclusions from sperry’s research
Each hemisphere ias responsible for different functions supporting hemispheric lateralisation
The left hemisphere is responsible for language production and the right hemisphere can recall and identify stimuli, but cannot verbalise this, meaning it has limited language ability
Strength: supporting evidence
I: supporting evidence from split brain patients who
E: sperry found that patients with disconnected hemispheres are unable to verbalise information presented to them in the left visual field and presented to them in their left hand
Meaning that each hemisphere is responsible for different functions supporting
Left - speech production
Right - visual recognition and motor skills
Continuing point strength
I: the research is highly reliable
E: research took place under very controlled labatory conditions, using specialised equipment, standardised procedures. For example pictures were always shown for only 10th of a second to prevent eye movement allowing for the other hemispheres input
C: sperry has developed a useful and well - controlled procedure, allowing findings to be replicated
The facts that finishing shave been labelled consistent means that hemipsheric lateralisation is a reliable theory
Weakness: unrepresentative
I: the samples are often unrepresentative
E: this is because it was a small sample of only 11 male epileptics experiencing a corpus callosotomy
Control group did not exist, making it difficult to establish cause and effect between hemispheres reconnection and language production
Epileptics without the corpus cut should have acted as the control
C: this means the theory that each hemisphere has different functions may not be generalised to the wider population, given the limitations with the samples
Weakness: ecological
I: the findings lack ecological validity/mundane realism
E: very few people who have the corpus colosseum cut and cannot see with both eyes. Most split brain patients can compensate for their loss because they have the use of both eyes
Can be argued that the 2 hemispheres do not function in isolation but form an integrative system - most tasks involved a combination of left and right skills =, the hemispheres are actually always working together
C: the theory that different hemispheres have different functions may not be relevant to real life
weakness: restricted
I: language may not be restricted to just the left hemisphere of the brain
E: Turk et al studied a patienent known as JW who suffered damge to the left hemisphere but developed the capacity to speak in the right hemisphere. with time JW was able to verbalise information presented to either hemisphere of the brain
C: findings of this case ean that functions may not be fixed and that the brain can adapt following damage to certain areas
