Biopsychology: Split-brain research and Hemispheric Lateralisation Flashcards
what’s hemispheric lateralisation?
the idea that the 2 hemispheres are fucntionally different and that certain mental processes are controlled by 1 hemisphere rather than the other. for example, Broca’s area is controlled in the left hemisphere.
what was Sperry’s split-brain research?
he studied a epileptic group who had all undergone a commissurotomy - where the corpus callosum that connects the 2 hemispheres are cut down the middle to seperate them. this allowed Sperry to see the extent that the 2 hemispheres were specialised for certain functions and whether they can perform independently.
what was the procedure of Sperry’s research?
he showed his participants an image/word that was projected to their right visual field and another image on the left visual field. a normal brain would share the information between both hemispheres and giving a complete picture of the visual world. however to a patient with a split brain, the information can’t be transferred between hemispheres
what are the key findings for the describing what you see?
when the object was shown to the right visual field, the patient could easily describe what they could see, if shown to the left visual field, the patient couldn’t describe it. the language centres are in the left hemisphere so their inability to describe was due to lack of language centres in the right hemisphere.
what were the key findings for recognition by touch?
they were able to select a matching object from a grab-bag using their left hand. the objects couldn’t be seen. the left hand grabbed the object that was most closely associated with the object presented to the left visual field. the patient weren’t able to identify what they’ve seen but couldn’t understand the object.
what were the key findings for composite words?
if 2 words were presented simultaneously, one on either side of the visual field, the patient would selected to the left word with their left hand and say the right word.
what were the key findings for matching facves?
the right hemisphere is dominant for recognising faces. when the patients used their left visual field to match faces they did significantly better than with their right visual field and left hemisphere. the left hemsiphere was better at describing the faces.
what’s demonstrated lateralised brain functions? (A03)
Sperry’s work has produced an impressive and sizeable body of research findings, the main conclusion is that the left hemsiphere is geared towards more analytic and verbal tasks while the right is better in spatial tasks and music. research suggests the left hemisphere is the analyser while the right is the synthesiser.
what are the strengths of the methodology? (A03)
the experiment on the split-brain patients use highly specialised and standardised procedures. his method of presenting visual informatioon to the hemispheric field was considered ingenious. typically participants were told to stare at a given point and the image would flash for a 1/10 second, meaning they wouldn’t have time to move their eyes so information spreads across both visual fields. this allowed Sperry to vary aspects to ensure only 1 hemisphere was receiving information at a time. he developed a useful procedure.
what’s theoretical basis of Sperry’s research? (A03)
his work prompted a theoretical and philsophical debate about the degree of communication between the hemispheres in everyday functioning. Pucetti suggested the 2 hemisphere are so functionally different that they represent a form of duality in the brain - we are all 2 minds. in contrast, other researchers argue that the hemispheres are a highly integrated system involved in everyday tasks.
