Biopsychology - split brain research Flashcards
What is hemispheric lateralisation?
The idea that the who halves of the brain are functionally different and are mainly controlled by 1 hemisphere than the other e.g. language - left
What is split-brain research?
A series of studies beginning in the 1960s involving epileptic patients who have experienced surgical separation of the corpus callosum allowing brain lateralisation to be studies
Who conduced split-brain research?
Sperry & Gazzaniga
What was tested before human were tested?
monkeys
How did Sperry test the brain lateralisation of monkeys?
He split the corpus callosum & the optic chiasm
What was the findings of Sperry’s split-brain research involving monkeys?
TBC
What was Sperry & Gazzaniga’s procedure for research surrounding humans with split-brains?
The general procedure was an image or word that was projected into a patients right visual field and the same or different stimulus into the left visual field. Because the right visual field is controlled by the left hemisphere, they were able to describe the stimulus. However, the patients could not describe the stimulus in the left visual field, proving the left hemisphere controls speech and language
What was some of the other findings of Sperry’s split brain research?
DRAWING-> A picture is shown to the left or right visual field and the patient is asked to draw it. The drawings were consistently better when drawn by the left hand (controlled by the right hemisphere). This was despite the patients actually being right handed.
FACIAL RECOGNITION -> When asked to match a face from series of other faces, pictures presented in the left visual field (right brain) were consistently selected whilst those presented in the right visual field (left brain) were ignored. When a composite picture made up of two halves was presented (one half to each hemisphere) the left half (right visual field) dominated verbal descriptions whereas the right half (left visual field) dominated in face recognition and selecting a matching (non composite) picture.
If two words were presented simultaneously, one on either side of the visual field (for example key to left visual field and ring to the right visual field). They would say ring and they would be able to pick up the key with their left hand.
What are some strengths of Sperry & Gazzaniga’s research?
It demonstrated lateralised brain functions -> opened more research opportunities for this type of research
Methodological strengths -> the procedures were highly specialised & standardised & ingenious for the time
Theoretical basis -> the research opened up a theoretical & philosophical debate on how the brain works
What are some criticisms of Sperry & Gazzaniga’s research?
Issues with generalisation -> there were 11 patients who all had treatments for epilepsy. This could have altered their brains. As well as this, some patients could have had more disconnection of the corpus callosum than others & the control was made of 11 people with no eplepsy which is inappropriate -> differed in 2 ways than experimental group
Differences in function may be overstated -> the brain has plasticity (changes in the brain due to environmental or other changes that cause other parts of the brain to do a different job) -> rat study: had damaged brains and the other hemisphere was able to do the others tasks
Language may not be restricted to L hemisphere -> Turk et al: patients who had damage to L hemisphere but developed capacity to speak with R -> suggests lateralisation isn’t fixed and can adapt due to changes.
