Split brain research into hemispheric lateralisation Flashcards
What is hemispheric lateralisation?
o Idea that the two halves of the brain are functionally different and that certain mental processes are mainly controlled by one hemisphere rather than the other
Who did split-brain research?
Sperry
What was Sperry’s procedure?
o Sperry devised a general procedure in which an image or word could be projected to a patient’s right visual field (processed by the left hemisphere) and the same, or different, image could be projected onto the left visual field (processed by the right hemisphere)
What participants did Sperry use and why was this important?
o Individuals who had their corpus callosum cut
o This meant that information could not be conveyed from one hemisphere to another
What the key findings for participants describing what they see?
o When a picture was shown to the right visual field the patient could easily describe what was seen
o If same object was shows to the left visual field patient couldn’t describe what they had seen and typically reported that nothing was there
o This was because of the lack of language centres were in the right hemisphere
What the key findings for participants recognising by touch?
o Patients couldn’t attach verbal labels to objects projected in the left visual field but they were able to select a matching object from a grab-bag of different objects using their left hand (linked to right hemisphere)
o Patient couldn’t say what they had seen but could ‘understand’ what the object was using the right hemisphere and select the corresponding object
What were the key findings for composite words?
o If two words were presented simultaneously on either side of the visual field the patient would write with their left hand the word shown to left visual field and say the word shown to right visual field
o Superiority of the right hemisphere in terms of drawing tasks
What were the key findings for matching faces?
o Right hemisphere also appeared dominant in terms of recognising faces
o When asked to match a face from a series of other faces, the picture processes by the right hemisphere was consistently selected
Evaluation points for split-brain research?
+ Demonstrate lateralised brain functions
+ Strengths of the methodology
+ Theoretical basis
– Issues with generalisation
How did Sperry’s research demonstrate lateralised brain function?
o Main conclusion of his research appears to be that the left hemisphere is more geared towards analytic and verbal tasks and the right is more adept at performing spatial tasks and music
o left is the analyser and right is the synthesiser
How did Sperry’s methodology have strengths?
o Highly specialised and standardised procedures
o Method of presenting visual information to one hemispheric field at a time was good
o Image flashed for one-tenth of a second
o Very controlled, high internal validity
How does Sperry’s research have a theoretical basis?
o Research prompted theoretical debate about the degree of communication between the two hemispheres in everyday functioning and the nature of consciousness
How are the issues of generalisation with Sperry’s research?
o Participants were such an unusual sample of people that results may not be generalisable
o History of epileptic seizures may have caused unique changes in the brain that influenced findings
