Split-brain Research Flashcards
What is hemispheric lateralisation
Fact that some mental processes in the brain are mainly specialised to either left/right hemi
What are left hemi functions and which visual field and hand does it control
Language
-info from right visual field and sends info to right hand
What is the role of the right hemisphere and which visual field and hand does it control
Focuses on Visuo-spatial tasks
-info from left visual field and controls left hand
What is the corpus callosum
Bundle of nerve fibres which joins the two halves of the brain, allows communication between left and right side
What is a commissurotomy and why is it done
Division of the two hemis by surgery, occasionally done to improve epilepsy
What type of experiment is Sperry’s Split brain experiment and who were the ppts
Quasi experiment, 11ppts who were epileptics who could not be treated with drugs and had already had their corpus callosum split
Procedure of sperry’s split brain experiment
-ppts gazes at fixation point on upright screen
-slides projected either side of fixation point(one visual field or the other) at a rate of one picture per 1/10 sec (to isolate visual fields)
-presenting the image to one hemi meant info could not be passed from one hemi to the other
Findings about describing what you see
When picture of object shown to rvf could easily describe what was seen
-when same object shown to lvf could not describe what was seen- due to lack of language centres in right hemi, would normally relay messages from left to right hemi
Findings about recognition of objects by touch
Although ppts could not attach verbal labels to objects projected in lvf, we’re able to select matching object from grab bag of dif objects placed behind screen using left hand(linked to right hemi)
-also able to select object most closely associated with an object presented to lvf (eg ashtray selected in response to picture of cigarette)
-in each case not able to verbally identify what had seen but could ‘understand’ what object was using right hemi and select corresponding object
Findings about composite words
Two words presented simultaneously with one on either side of visual field (eg key on left and ring on right) and would select key with left hand (lvf goes to right hemi, linked to left hand) and say word ring
-right hemi superior in terms of drawing tasks
Findings for matching faces
Right hemi dominant in recognising faces, when asked to match a face from series of other faces, picture processed by right hemi(lvf) consistently selected whilst picture presented to left hemi (rvf) consistently ignored
-when composite picture made up of two dif halves of face, left hemi dominated in terms of verbal description while right hemi dominated in terms of selecting matching picture
Expand on strength that the research demonstrated lateralised brain functions
-pioneering work has produced sizeable body of research findings
-suggests LH more geared towards analytical and verbal tasks while RH more adept at performing spatial tasks and music, RH can only produce rudimentary words and phrases but contributes emotional and holistic content to language
-key contribution to our understanding of brain processes
Expand on strength that standardised procedure
-fast presentation of words meant only exposed to one visual field, not have time to move their eye across the image so spread the info across both sides of the visual field
-more sure it was only one visual field exposed to the word which caused differences in descriptions of it
Expand on limitation that issue with generalisation
-only 11 ppts who all had epilepsy which may have caused unique changes in the brain that may have influenced findings, some ppts had experienced more disconnection of the two hemis as part of their surgical procedure than others
-control group made up of ppts with no history of epilepsy may have been inappropriate
-low population validity, may tell us little about lateralisation in those without epilepsy
Expand on limitation that may not lateralisation may not apply to all
-research found language becomes more lateralised to left hemi with increasing age up to 25 but after this lateralisation decreases with each decade in life
-suggests lateralisation changes with normal ageing, tend to switch to bilateral functions in healthy older adults (may be because using extra processing resources of other hemi to compensate for age related decline in function)
-lateralised brain only feature of young adults and not valid for everyone
