Split Brain Research Flashcards
What can cutting the connections between hemispheres tell us?
Can tell us about hemispheric lateralisation.
It can be useful in understanding the role of each hemisphere and the extent to which functions are lateralised.
We can investigate which activities and behaviours are dominated or controlled by one hemisphere or the other.
Split brain research began to take place in the 1960’s (is still ongoing) on epileptic patients who had experienced surgical separation of the hemispheres.
Name something lateralised to the left hemisphere, and something lateralised to the right hemisphere.
E.g. speech production lateralised to the left.
E.g. voluntary movement of the left, is lateralised to the right.
What is a commissurotomy?
The severing of the corpus callosum.
What is a hemispherectomy?
A very rare neurosurgical procedure in which a cerebral hemisphere (half of the brain) is removed, disconnected, or disabled.
Why would the corpus callosum need to be severed? Why is this?
Reduce the symptoms of epilepsy.
In epilepsy, one hemisphere of the brain is usually responsible.
What happens when an epileptic episode occurs? Why does the severing of the corpus callosum work?
An electrical storm in one hemisphere of the brain, which then travels across the corpus callosum, causing the entire brain to be affected and then a blackout occurs.
By severing the corpus callosum this travelling of the electrical storm cannot occur and thus blackout and epileptic seizures cease/are reduced in severity.
What were the aims of Sperry’s study in 1968?
To investigate the extent to which the two hemispheres were specialised for certain functions, and whether the hemispheres performed tasks independently of one another.
What was the procedure of Sperry’s study in 1968? How many procedures were there?
Compared split brain patients to others with no hemisphere separation.
There were 2 types of procedure.
Outline the ‘visual task’ procedure of Sperry’s study in 1968?
A word or image is projected into the left or right visual field and patient will be asked about that stimuli.
Outline the ‘tactile task’ procedure of Sperry’s study in 1968?
Touch with objects.
Carried out with the PP’s hands underneath a screen so the they couldn’t see what they were doing.
They had to use ‘feel’ only.
What were the 4 categories of findings that Sperry found in his 1968 study?
Describing what they see.
Recognition by touch.
Drawings.
Composite words.
What would happen in a split-brain patient if an object is presented to the left visual field and the patient is asked to pick the object up with their right hand? (Sperry, 1968).
They would be unable to select the object because it was seen by the right hemisphere and the right hand is controlled by the left hemisphere.
What would happen in a split-brain patient if an object is placed in the left hand and the patient is asked to name it?
The patient could not describe what they felt and could only make a wild guess.
What would happen in a split-brain patient if a word is presented to the right visual field and the patient is asked to name it?
They could easily describe what was seen.
What would happen in a split-brain patient if an object is placed in the right hand and the patient is asked to find the object with the same hand?
The patient would easily relocate the object.
What would happen in a split-brain patient if an object is placed in the left hand and the patient is asked to find the object with their right hand?
The patient would not be able to locate the object, only being able to make wild guesses.
What would happen in a split-brain patient if two different objects are placed in the left hand (key) and the right hand (ring). The objects are then hidden within other objects and the patient is asked to find them?
The individual hands would find their respective object.
What would happen in a split-brain patient if they were shown an object to the right visual field and asked to draw it with the left hand and then the right hand?
They would only be able to draw it with their right hand.
What would happen in a split-brain patient if they were presented with two words ‘ball’ to the left visual field, and ‘pen’ to the right visual field. They are asked to name one and pick the other up?
The patient would name ‘pen’ and pick up ‘ball’.
Outline the findings about ‘drawings’ that Sperry found in 1968.
A picture is shown to the left or right visual field and the patient is asked to draw it.
The drawings were consistently better when drawn by the left hand (controlled by the right hemisphere).
This was despite the patients actually being right-handed.
Outline the findings about ‘composite words’ that Sperry found in 1968. (Patient shown two different words simultaneously).
Describe the word presented in their right visual field, as this was processed by their left hemisphere.
Pick up the word presented in their left visual field, as this was processed by their right hemisphere.
What do the ‘drawing’ finding from Sperry’s 1968 study suggest?
Suggests that the right hemisphere (and therefore left hand) was superior at drawing ability.
What three things did Sperry conclude from his 1968 study?
In split-brain patients the hemispheres of the brain process information separately.
Hemispheres have differing functions (e.g language tasks left) supporting lateralisation.
Participants seem to have two separate streams of consciousness with their own memories and perceptions.
What did Sperry win in 1981?
Sperry‘s award winning research won him the Nobel Prize in 1981.
