hemispheric lateralisation Flashcards
hemispheric lateralisation
-idea that certain functions in the brain are dominated by one hemisphere or the other
split brain research
Sperrys research was conducted in 1968 and they were a series of studies that involve the unique group of individuals all of which and under a surgical procedure known as a commissurotomy is a procedure in which corpus callosum and other tissues that connect the two hemispheres are severed in order to control severe epileptic seizures. Allows two hemispheres to communicate.
-that then allowed Sperry and his colleagues to see the extent to which two hemispheres were actually specialised for certain functions and whether the hemispheres performed the tasks independently of one another.
-The general procedure in which an image or a word could be projected to a patient right visual field which would be processed by the left hemisphere and then the same or different image could be projected to the left visual field which would be processed by the right hemisphere, a normal brain ,Colpus callosum would actually share the information between both hemispheres, giving complete picture of outside world, in split brain patient that information couldn’t be conveyed from one hemisphere to another.
split brain research results
• Describing what you see-word was flashed in right visual field patient would be able to say what they saw-left hemisphere has language centres in.-If image was in left visual field, connected to right hemisphere, patients wouldn’t report seeing anything or say what they saw- doesn’t have any language centres.
• Recognition by touch-If word/image was flashed in right visual field, could say what they saw, but left visual field they couldn’t but with left hand they could pick blindly an item out of the bag which matched what they saw on the screen.
• Composite Words-like key ring-one word would be flashed in one visual field and another in the other VF- patients could say word ring- and draw a key with their left hand could then say the word when they saw what they drew.
• Recognising Faces-show picture of face to right or left hemisphere, then given a choice of two words, face or fruit. If picture was shown in left VF, participants would point to word face, opposite they would point to word fruit-shows right hemisphere is important for facial recognition-left hemisphere is more analytical, breaks things down.
strength-pioneering work that demonstrates lateralised brain function
Sperry’s pioneering work into the split brain phenomenon on has produced an impressive and sizeable body of research findings.
The main conclusion of these appears to be that the left hemisphere is more geared towards analytical and verbal tasks whereas the right is more adept at performing spatial tasks music and other creative things.
The right hemisphere can only produce rudimentary words and phrases will contribute emotional and holistic content to language. Furthermore research suggests that the left hemisphere is the analyser while the right hemisphere is this synthesiser.
Such findings our key contributions to our understanding of brain processes and have furthered our knowledge considerably.
limitation-issues of generalisation
A limitation of Sperry’s research into split brain patients is that it has been argued the findings are not generalisable.
This is largely down to the sample of patients that were used. Split-brain patients are such an unusual sample of people and they are rarely encountered in sufficient numbers to be useful for research.
There were only 11 people who took part in all variations of the basic procedure, all of whom had a history of epileptic seizures. It has also been argued that this may have influenced the findings.
Furthermore, it is also the case that some participants had experienced more disconnection of the two hemispheres than others. Finally, the control group Sperry used made up of 11 people who did not have epilepsy, may have been inappropriate. It may have been more valid if the control group had been made up of epileptics who had not had a commissurotomy, as a much more valid group would be epileptic people who had not had the operation. The epilepsy or the drugs used to treat the epilepsy may have affected the patients’ brains irrespective of the split-brain procedure and could be responsible for the results.
Issues such as those outlined above seriously impede the validity of the research, as it reduces the generalisability, but also the internal validity, as variables were not being controlled appropriately.
strength
P-Sperry’s work is highly scientific and standardised.
E- All participants were given a ‘fixation point’ to stare at during the task and also the image only flashed up for a tenth of a second.
E- All of this meant that Sperry could be sure that the image was only being received by one hemisphere, rather than the information being shared by both hemispheres.
L- This is a strength because it demonstrates strong internal validity meaning its objective and repeatable
