Split brain research into hemispheric lateralisation Flashcards
Define hemispheric lateralisation.
Hemispheric lateralisation is the idea that the two halves of the brain are functionally different and that mental processes and behaviours are mainly controlled by one hemisphere than the other.
What is the corpus callosum?
The area of the brain which connects the right and left hemispheres and allows communication between them.
Explain the purpose of Sperrys split-brain studies.
Sperrys studies involved individuals who had undergone an operation in which the corpus collosum and other tissues were cut down the middle to separate the two hemispheres of the brain and control frequent epileptic seizures. This meant that the main communication line between the two hemispheres was removed so this allowed Sperry and his colleagues to see the extent to which the two hemispheres were specialised for certain functions.
Explain the procedure of Sperry’s split-brain studies.
Sperry’s procedure involved blindfolding one of the patients eyes and then an image or word could be projected to an individuals right visual field (so processed by the left hemisphere). At the same, an image could be projected to the left visual field (processed by the right hemisphere). In a normal brain, the corpus callosum would immediately share the information between both hemispheres giving a complete picture. However, presenting the image to one hemisphere of a split-brain individual meant the information could not be conveyed from that hemisphere to the other.
What were Sperrys findings of his split-brain studies?
When a picture of an object was shown to an individuals right visual field, they could easily describe what they could see. However, when the same object was shown to the left visual field, they could not describe what was seen and said that there was nothing there. This was because of the lack of language centres in the right hemisphere. In the normal brain, messages from the right hemisphere would be relayed to the language centres in the left hemisphere.
What were the findings of Sperrys split-brain studies in terms of facial recognition?
When asked to match a face from a series of other faces, the picture processed by the right hemisphere was consistently selected, whilst the left consistently ignored. When a composite picture made up of two different halves of a face was presented (one half to each hemisphere) the left hemisphere dominated in terms of verbal description whereas the right hemisphere dominated in terms of selecting a matching picture.
Define Hemispheric Lateralisation.
The idea that the two halves of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere than the other.
Give a strength of split-brain research into hemispheric lateralisation.
(Demonstrated lateralised brain functions).
Sperry’s pioneering work into the split brain phenomenon has produced an impressive and size and body of research findings with the main conclusion being that the left hemisphere is geared towards analytic and verbal task whereas the right hemisphere is better at performing spatial tasks and music. Research suggests that the left hemisphere is the analyser and the right hemisphere is the synthesiser which shows that the two halves of the brain have different functions.
Give a strength of split-brain research into hemispheric lateralisation.
(Methodology).
The experiments involving split brain individuals made use of highly specialised and standardised procedures. Typically participants would be asked to stare at the fixation point and an image would be projected for one-tenth of a second (the split-brain individuals would not have time to move their eye across the image and spread this to both sides of the visual). This allowed Sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving information at a time.
Give a limitation of split-brain research into hemispheric lateralisation.
(Issues with generalisation).
Split brain individuals constitute such an unusual sample of people. There were only 11 who took part in all variations of the basic procedure, all of whom had a history of epileptic seizures. It has been argued that this may have caused unique changes in the brain that may have influenced the brain findings. It is also the case that some participants had experienced more disconnection of the two hemispheres as part of their surgical procedure than others. A control group of 11 people with no history of epilepsy may have been appropriate
