Split Brain Flashcards
What is the Corpus Callosum
A large C-shaped nerve fibre bundle found beneath the cerebral cortex
Connects the left and right hemispheres
What is epilepsy
A neurological condition that is characterised by lots of seizures
What is a split brain patient
Someone who has had their corpus callosum cut off to treat epilepsy
Roger Sperry et al (1968)
- 11 split brain, epileptic patients used
- Was done to control epileptic seizures as it removes the communication between the two hemispheres
- researchers could now look at if the two hemispheres have specific functions and if they perform them independently
- awarded nobel prize for his research in 1981
Roger Sperry (1968) Procedure
- an image/word projected to right visual field (left hem), patients asked to say/draw the image/word (same done to lvf)
- in split brain info could not be conveyed from one hem to the other
Roger Sperry (1968) Findings
-Describing what they Saw
when shown to rvf, split brain patients could describe what they saw
when shown to lvf, could not describe
- Recognition by Touch
when shown in lvf, split brain patients could select matching object using their left hand but couldn’t describe the object
left hand also could select the most closely associated object
-Composite Words
if two words were presented simultaneously, patient would select object with left hand (lvf) and say the other word
Left Visual Field
Right Hemisphere
Left Hand
Right Visual Field
Left Hemisphere
Right Hand
Evaluation (STRENGTH) - Demonstrated Lateralisation of Brain Functions
Sperry and Gazzinga’s main conclusions are -
Left hemisphere is more geared towards analytical and verbal tasks
Right hemisphere is more geared towards spatial and music tasks
Right hemisphere can only produce rudimentary words and phrases but contributes emotional and holistic content to language
Left hem = Analyser
Right hem = Synthesiser
Evaluation (STRENGTH) - Methodology
Sperry’s method of presenting visual information was ingenious
Image was flashed up for 0.1 seconds meaning split brain patients wouldn’t have time to move eye across image to share the information
Ensured only one hemisphere was receiving the information
Very Useful and Highly Controlled procedure
Evaluation (WEAKNESS) - Theoretical Basis
Sperry’s research prompted a theoretical and philosophical debate about the degree of communication between the two hemispheres in everyday functioning and the nature of consciousness
Roland Pucetti (1977) - two hemispheres are so functionally different that they represent a form of duality in the brain (we are all two minds)
Other researchers have argued that the two hemispheres form a highly integrated system and are both involved in most everyday tasks
Evaluation (WEAKNESS) - Issues with Generalisation
Many researchers have urged caution in widespread acceptance as split brain patients constitute an unusual sample of people
Only 11 participants
All participants had a history of epileptic seizures which has been argued as a cause of unique changes in the brain that may have influenced the findings
Some participants had experienced more disconnection of the two hemispheres than others
Control group used was 11 people with no history of epilepsy may have been inappropriate
Evaluation (WEAKNESS) - Differences in Function may be Overstated
Sperry’s work overemphasises and oversimplifies the functional distinction between left and right hem
Modern neuroscientists would contend that the actual distinction is less clear-cut and much more messy
Many behaviours typically performed by one hemisphere can effectively be performed by the other when required
