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HEMISPHERIC LATERALISATION
Hemispheric Lateralisation → refers to the idea that certain functions are mainly controlled by one hemisphere of the brain
EXAMPLES:
Broca’s area (responsible for producing language), and Wernicke’s area (responsible for understanding language) are both lateralised to the left hemisphere
~RESEARCH INTO HEMISPHERIC LATERALISATION~
Sperry (1968) studied a group of patients who had all undergone a surgical procedure known as a commissurotomy
In this procedure, the corpus callousness that connects the two hemispheres is cut in order to reduce the severity of epileptic seizures
These patients are known as ‘split brain’ patients
In his research procedures, Sperry took advantage of the fact that language is lateralised to the left hemisphere, and that information from the left visual field (LVF) is processed in the right hemisphere and vice versa
→ Normally, visual information that is received by one hemisphere is immediately transmitted across the corpus callosum to the other hemisphere
→ This means that both hemispheres are aware of the visual information
→ However, in a split-brain patient, the corpus callosum has been cut, meaning that visual information cannot be transmitted across hemispheres, meaning it’s confined to the hemisphere it was received by (e.g. visual info received by right hemisphere is confined to the right hemisphere)
PROCEDURE 1:
Sperry asked participants to fixate on a dot in the centre of a screen
A word or image was presented to the LVF or RVF for a brief period
When a word or image was presented to the RVF, the split-brain patients could describe what they had seen, however when it was presented to the LVF, they were unable to describe what they had seen
This is because there are no language centres in the right hemisphere
PROCEDURE 2:
Sperry asked participants to fixate on a dot in the centre of a screen
A word or image was then presented to the LVF or RVF
When the word or image was presented to the LVF, patients were able to select a matching object from a set of objects using their left hand
They were also able to draw the object using their left hand, however they were still unable to describe what they had seen
