Split-Brain Research into Hemisphere Lateralisation Flashcards
1
Q
hemispheric lateralisation - left hemisphere
A
- the ability to produce and understand language for most people is controlled by their left hemisphere
- supported the idea of hemispheric lateralisation
2
Q
hemispheric lateralisation explanation
A
- the idea that the 2 hemispheres are functionally different, with some mental processes and behaviours being controlled mainly by one hemisphere of the two
3
Q
hemispheric lateralisation - right hemisphere
A
- right hemisphere is dominant for spatial tasks and facial recognition
4
Q
contralateral brain
A
- left hemisphere controls the right-hand side of the body, and the right hemisphere controls the left-hand side
5
Q
Sperry (1968) - aims
A
- studied unique group of people who underwent commissurotomy, which is a surgical procedure in which the corpus callosum is cut, separating the hemispheres
Corpus callosum - nerve bundle which connects the left and right hemispheres
- corpus callosum is cut to control frequent and severe epileptic seizures
- Sperry was able to investigate the extent to which the dhesmipheres are specialised to certain functions, and whether tasks are performed independently
6
Q
Sperry (1968) - procedure
A
participants - 11 males and females which had had their hemispheres disconnected to combat severe epilepsy
- standardised procedure was used, in which he projected a word or image into the patient’s right visual field, controlled by the left-hemisphere
- another or the same image would be projected into the left visual field, processed. by the right hemisphere
- if present, the corpus callosum would share info between the hemispheres, allowing an image or word in either visual field to be understood
- but a split brain patient doesn’t have the ability to convey info from one hemisphere to another
7
Q
Sperry (1968) - the 4 tasks
A
- describe what you see
- recognition by touch
- two word shown at the same time
- matching up faces
8
Q
Sperry (1968) findings - task one
A
first task - describe what they saw
- when pictures were seen in the right visual field of the patent they could easily describe what they saw, but if an image was shown in the left visual field, patients weren’t able to describe them
- they would generally say that there was nothing there
- language for most people is processed in the left hemisphere, so the left visual field, processed in the right hemisphere, has no language centres, meaning the patient couldn’t describe what they saw
- if the hemispheres were joined by the corpus callosum, info would be passed from the right hemisphere to the left hemisphere
9
Q
Sperry (1968) findings - task two
A
second task - recognition by touch
- patients were unable to describe objects in the left visual fields, but could select a matching object from a bag of other items using their left hand, linked their right hemisphere
- using their right hemisphere, they could understand what the object was, since this hemisphere is better at spatial awareness
10
Q
Sperry (1968) findings - task three
A
third task - two words presented at the same time
- one word presented in each hemisphere, and in response the patient would select the object correlating to the word in their left visual field, controlled by right hemisphere
- the patient could however say the word in their right visual field, controlled by the left hemisphere
- patients were also able to draw the object which the word correlated to in their left visual field since the right hemisphere has better drawing skills
11
Q
Sperry (1968) findings - task four
A
task four - match faces
- when patients were asked to match a face from a series of other faces, the picture in the left visual field was consistently selected, whereas the picture in the right visual field was consistently ignored
- this is an example of right hemisphere dominance
- when a composite picture was shown, made up of two different face halves, with one in each hemisphere, the left dominated the realm of verbal description, but the right was better at selecting a matching picture
12
Q
(+) EVAL - demonstrated lateralised brain functions
A
- the work of both Sperry and Gazzaniga has pioneered the study of split-brain phenomenon, producing a large body of research findings
- main conclusions made are that the left hemisphere is geared towards verbal and analytical tasks, and the right is more weighted towards spatial tasks and music
- right contributes to holistic, emotional content to language, but is only able to produce rudimentary, basic words and phrases
- all of these findings are key in contributing to our understanding of brain processes
13
Q
(+) EVAL - strengths of methodology
A
- these studies use highly specialised and standardised procedures
- Sperry’s method specifically was ingenious and allowed him to vary aspects of the basic procedure and keep a high level of control
- developed very useful, well controlled procedure with great methodological strength
14
Q
(+) EVAL - theoretical basis
A
- as a result of Sperry’s work a philosophical and theoretical debate was started
- this was to do with the degree to which communication takes place between hemispheres in everyday functioning and nature of consciousness
- Pucetti (1977) suggested that the hemispheres are so different in function that they represent duality within the brain, which is the concept that we all have two minds
- other researchers, in contrast, have argued that both hemispheres are part of a very integrated syste, with both being involved in everyday tasks
15
Q
(-) EVAL - issues with generalisation
A
- Sperry’s study used a very small and unique sample, which may limit the generalisability of the findings
- all patients had a history of epilepsy, which may have caused unique damage that could have influenced their performance on tasks compared to any other patient with the lack of a corpus callosum
- there is also a lack of an appropriate control group, since none of them had any history of epilepsy
- the validity of this study is challenged by the lack of generalisability
