hemispheric lateralisation Flashcards
what is hemispheric lateralisation?
the idea that two halves (hemispheres) of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other, as in the example of language (which is localised as well as lateralised)
what is split brain research?
a series of studies which began in the 1960s (and are still ongoing) involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain. this allowed researchers to investigate the extent to which brain function is lateralised.
what is are the neurons connecting the two hemispheres called?
the corpus callosum
where is the corpus callosum located?
in the neocortex
language is subject to…
hemispheric lateralisation. the specialised areas associated with language are found in one of the brains areas rather than both.
what was the procedures of Perry’s study?
•he used 11 patients who had an operation to split their corpus callosum to control their epilepsy, which meant the connection between the two hemispheres were split
•sperry projected a word or image to either the left or right visual field, which would then be processed by the opposite hemisphere
•information could not be conveyed from one hemisphere to another
what are the results of sperry’s study?
•when a picture of an object was shown to a patients right visual field, the patient could easily describe what was seen
•if, however, the same object was shown to the left visual field, the patient could not describe what was seen and typically reported that there was nothing there
•language centres are in the left hemisphere
•when the word was shown to the left visual field it could be drawn by the left hand using the right motor area
•recognition by touch, although patients could not attach verbal labels to objects projected in the left visual field, they were able to select a matching object from a grab-bag of different objects using their left hand
what are the evaluation points for split brain research?
strength: demonstrated lateralised brain functions
strengths of the methodology
theoretical basis
limitation: issues with generalisation
limitation: differences in function may be overstated
what are the evaluation points for split brain research?
strength: demonstrated lateralised brain functions
strengths of the methodology
theoretical basis
limitation: issues with generalisation
limitation: differences in function may be overstated
strength: demonstrated lateralised brain functions
•the main conclusion was that the left hemisphere is more geared towards analytical and verbal tasks whereas the right is more adept at performing spatial tasks and music
•research suggests that the left hemisphere is the analysed whilst the right hemisphere is the synthesiser- a key contribution to our understanding of brain processes
strengths of the methodology
•the procedures used were standardised
•the task allowed sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving information at a time
•he developed a very useful and well-controlled procedure, allowed for replicability
theoretical basis
•psychologists suggest that the hemispheres are so functionally different that we effectively have ‘two minds’
•however, other researchers have argued that the hemispheres are highly integrated and both are involved in most everyday tasks
•
limitation: issues with generalisation
•11 people who had a history of epileptic seizures and had undergone brain structural changes (had unique changes in the brain) , so the differences between the hemispheres may have been more apparent
•also some participants had experienced more disconnection of the two hemispheres as part of their surgical procedures than others
limitation: differences in function may be overstated
•researchers suggest that the differences between the left and right hemispheres have been overemphasised and oversimplified (as sometimes they are classified by ‘verbal’ and ‘non-verbal’)
•in a normal brain the two hemispheres are in constant communication when performing everyday tasks, and many of the behaviours typically associated with one hemisphere can be effectively performed by the other when the situation requires it
