biopsych - split brain research - y13

Question 1

what is hemispheric lateralisation?

Answer 1

the idea that the two halves of the brain are functionally different and that certain processes are mainly controlled by one hemisphere rather than the other.

Question 2

what is split brain research?

Answer 2

a series of ongoing studies where epileptic patients had their corpus collosum lesioned (commisurotomy) effectively separating the two hemispheres allowing researchers to study the extent of brain lateralisation.

Question 3

which three processes are not lateralised?

Answer 3

vision, motor and somatosensory.

Question 4

what is contralateral wiring?

Answer 4

the case of the motor area is cross wired. the right hemisphere controls the movement of the left side while the left hemisphere controls the right.

Question 5

is vision contralateral or ipsilateral?

Answer 5

both.
-each eye receives light from the left visual field and the right visual field.
-the left visual field of both eyes are connected to the right hemisphere and the right visual field of both eyes is connected to the left hemisphere.
-this enables the visual areas to compare the slightly different perspective from each eye and aids depth perception.
-there is a similar arrangement for auditory input to the auditory area and the disparity from the two inputs helps us locate the source of sounds.

Question 6

split brain studies by sperry (1968)

Answer 6

studied patients who had a commisurotomy to control frequent and severe epileptic seizures. therefore, the main communication line between the two hemispheres was removed allowing sperry and colleagues to determine which hemispheres were specialised for certain functions and whether tasks were performed independently.

Question 7

sperrys procedure? (1968)

Answer 7

an image or word would projected to a patients right visual field, processed by the left hemisphere, and the same or different image, would be projected to a patients left visual field, processed by the right hemisphere. In a normal brain, the corpus collosum would have shared the information with the other hemisphere, giving a complete picture of the visual world. presenting information to just one hemisphere meant it could not be shared in split-brain patients, as the corpus collosum is removed.

Question 8

sperrys findings? (1968) - visual

Answer 8

when a picture of an object was shown to a patients right visual field they could easily describe what they had seen. but they couldn’t when the same object was shown in the left visual field and often said there was nothing there. this is because the language centre is in the left hemisphere so when the image is presented in the left visual field it is processed in the right hemisphere, which has no language centre, and the corpus collosum is absent so the information is not shared to the left hemisphere.

Question 9

sperrys findings (1968) - touch

Answer 9

although patients could not attach verbal labels to objets in their left visual field, using their left hand and therefore right hemisphere, they could elect a matching object from a grab bag closely associated with the object shown.

Question 10

sperrys findings (1968) - composite words

Answer 10

if two words were presented at the same time, one on either side of the visual field, the patient would write the word ‘ key’ with their left hand (the right hemisphere has superior drawing abilities) and say the word ‘ring’ (as the right visual field is processed in the left hemisphere which has the language centres)

Question 11

sperrys findings (1968) - matching faces

Answer 11

the right hemisphere appears dominant for face recognition: when asked to match a face from a series of other faces, the picture processed by the right hemisphere (left visual field) was consistently selected, whereas the pictures presented to the left hemisphere (right visual field) were ignored. when a composite picture made up of two different halves of a face was presented with one half to each hemisphere, the left hemisphere dominated in verbal description, but the right hemisphere dominated in selecting a matching picture.

Question 12

evaluation - learned more about lateralisation

Answer 12

used pet scans to identify what brain areas were active during a visual processing tasks. when ‘normal’ participants were asked to attend to global elements of sn image, regions of the right hemisphere were much more active. when we focus on the finer detail, the specific areas of the left hemisphere tended to dominate. hemispheric lateralisation us a feature of the normal brain as well as the split-brain.

Question 13

sperry and gazzinga work into split brain research (support)

Answer 13

well supported by research, the conclusion of which is that the left hemisphere is geared toward analytic and verbal tasks, while the right hemisphere id better at spatial tasks and music. the right hemisphere produces rudimentary words and phrases, but contributes emotional and holistic language. the left hemisphere is the analyser and the right hemisphere is the synthesiser

Question 14

however, according to Nielsen et al (2013) - evidence against sperry and gazzinga

Answer 14

there may be different functions, but research suggests people do not have a dominant side of the brain which creates a different personality. Nielsen et al (2013) analysed brain scans from over 100 people aged 7-29 and did find that people used certain hemispheres for certain tasks but there was no evidence of a dominant side. this suggests that the notion of right or left brained people is wrong.

Question 15

strengths of the methodology?

Answer 15

the split brain studies used highly specialised and standardised procedures which allowed him to ensure that participants were only able to see an object in one visual field at a time, and not the other. this allowed him to vary aspects of the procedure so only one hemisphere was receiving information at any time

Question 16

the unity of consciousness debate - strength

Answer 16

sperrys work prompted much debate, both theoretical and philosophical, about how much communication occurs between the two hemispheres in every day functioning, and the nature of consciousness. Pucetti (1977) suggested the two hemispheres are so functionally different that they represent a form of duality in the brain - we are all of two-minds, not just split brain patients.

Question 17

the unity of consciousness debate - weakness

Answer 17

others have argued that the two hemispheres from a highly integrated system and are both involved in most everyday tasks. they argue that most everyday tasks involve a mixture of ‘left’ and ‘right’ skills thus, rather than ‘doing their own thing’ the two hemispheres very much work together.

Question 18

issues with generalisation?

Answer 18

the findings from the sperry studies should be viewed with caution as only 11 prticipants were used and theyd all had a history of epilepsy which may have caused unique changes in the brain, which then influenced the findings. the 11 split-brain particpants were lumped together as the experimental group, but some patientd has experienced more disconnection than others.

Question 19

counterpoint ot the issues with generalisation?

Answer 19

however, sperry may not have had any control over this - there may not be many split-brained patients available to study. the small sample also enabled sperry to gain more in depth data.

Question 20

issues with the control group?

Answer 20

the comparison group used by sperry did not have any history of epilepsy or inter-hemispheric disconnection. therefore, it may have been more suitable to use participants who are epileptic but with no inner-disconnection.

Question 21

overstatement of differences?

Answer 21

modern neuroscientists would argue that the actual distinction is less clear-cut and messier than sperrys work would suggest. they are in constant communication during everyday tasks, and each can perform the tasks of the other if needed.