Split Brain Studies Flashcards
What is split brain surgery also known as?
Commisurotomy
Define: split brain surgery
Involves surgically cutting the corpus callosum (and sometimes other nerves connecting the two hemispheres), thereby disconnecting one hemisphere from the other
Why was split brain surgery done?
To prevent erratic electrical activity spreading between hemispheres in epileptic fits in epilepsy patients; greatly reduced the number of seizures.
Who conducted the split brain RESEARCH? (not surgery)
Roger Sperry (won Nobel Prize) with student Michael Gazzaniga.
How was the test refined before it was done on humans?
Done on monkeys and cats.
Describe the setup of experiment
Control group of patients with no hemispheric disconnection and experimental group of 11 split brain patients.
Participants sat in front of screen with dot in the middle to create fixed visual fields.
Tachistoscope (projector) flashed objects or words on each side (to only one visual field) and they were asked: “What do you see?”
Describe the results of the experiment (no need to explain why)
If stimulus was presented to the right visual field, they could BOTH recognise (process information about) and name the object; if presented to only the left visual field, they could only recognise but not name the object, but could pick up object with left hand
Why could stimulus be both recognised and named in the right visual field?
Stimulus from RVF is processed by the left hemisphere, which has Broca’s and Wernicke’s areas. Therefore the name of the object can be articulated.
Why could stimulus only be recognised and not named in the left visual field, but picked up with the left hand?
Not named as info from LVF is processed by the right hemisphere, which does not have Wernicke’s or Broca’s areas. Can be picked up as the stimulus is recognised by the right hemi which controls the left hand.
How do split brain patients adjust to this phenomenon in real life?
Eye movements may adjust to bring information into the right visual field.
Potentially, not all nerve fibres were cut so some sensory and motor info can still be transferred.
Not all functions are specialised
IMplicit transfer occurs
Limitations of Sperry and Gazzaniga’s research?
All parts had severe epilepsy
They were on long term medication
Surgery itself may have had side effects
Most parts were male and right handed
Implications on consciousness?
Left hemisphere makes executive decisions about whether an object is present or not
Left hemisphere is important in language, articulating names of objects
Corpus callosum enables interaction between hemis, enabling cognitive processes eg. language.
Define:implicit transfer
: hemispheres communicate by observing and responding to the b&mp’s that the other produces.
