PAPER 2 - BIOPSYCHOLOGY - hemispheric lateralisation and split brain research

Question 1

how are the 2 hemispheres connected?

Answer 1

• connected via bundles of nerve fibres (corpus callosum)
• allows info from one hemisphere to be sent to the other

Question 2

what is split brain research?

Answer 2

refers to studies of individuals who have been subjected to surgical separation of the 2 hemispheres as a result of severing the corpus callosum

Question 3

what does divided field refer to?

Answer 3

• focus eyes straight ahead, fixing gaze on single central dot
• one stimulus is presented to right visual field (projected to left hemisphere) and vice versa
• only present stimulus for short period of time (200ms)
• ask participants to say what they saw and/or draw with their left hand

Question 4

what was the procedure in the study by Sperry?

Answer 4

• asked split brain patient with eyes focused straight ahead to report any word they saw
• word flashing up in RVF was immediately reported, but were unaware of words flashing in LVF
• word in RVF projected to left hemisphere (contains language system) so can be immediately recognised
• no language system in RVF

Question 5

what did Sperry realise from his study?

Answer 5

• to report what they see, patient had to use left hemisphere language system as it controls speech
• even if right hemisphere could read the word, it couldn’t report it as it doesnt have speech

Question 6

how did Sperry allow the left and right hemispheres communicate on split brain patients?

Answer 6

• knowing right hemisphere controls left hand, he placed their left hand behind a screen among objects
• he then flashed the word “glass” and found that the left hand would select the glass
• he had demonstrated some basic language ability in the right hemisphere so could read simple nouns
• patient didn’t know why they were holding the glass because left hemisphere didn’t know what right hemisphere had seen

Question 7

what did Sperry find about visuospatial processing/tasks?

Answer 7

• different faces were presented to each hemisphere
• split-brain patient was given a set of faces and asked to choose one they’d seen earlier
• patients chose one in right hemisphere
• shows right was better than left at identifying faces
• also showed right was better at matching shapes
• shows we have a verbal left hemisphere and visuospatial left hemisphere

Question 8

what are the limitations of split-brain research?

Answer 8

• very few patients, only between 10-15 have been subjected to extensive systematic study
• those studied are varied differ in age, gender, handedness etc.
• operations not always comparable. some parts may have been left in tact allowing for some communication between hemispheres (anterior commissure)

Question 9

what are the strengths of split brain research and hemispheric lateralisation?

Answer 9

• findings from variety of studies led to general model of hemispheric lateralisation
• techniques modified for use with intact neurotypical patients
• studies have standardised procedures, replicable (methodology)
• demonstrates importance of connectivity of the brain