The split brain

Gazzaniga, Michael S., «The Split Brain Revisited,» Scientific American, July 1998

The Corpus Callosum has been severed, a treatment for epilepsy.

  • The left brain dominates for language, speech, and problem solving
  • The right brain dominates for visual-motor tasks

split2.bmp (45058 bytes)

1.  Each hemisphere was presented a picture that related to one of four cards placed in front of the split-brain subject.  The right hemisphere saw the picture on the left (a snow scene), and the left hemisphere saw the picture on the right (a chicken foot).  Both hemispheres could see all of the cards.

2.  The left and right hemispheres easily picked the card that related to the picture it saw.   The left hand pointed to the right hemisphere’s choice, and the right hand pointed to the left hemisphere’s choice.

3.  The patient was then asked why the left hand was pointing to the shovel.  Only the left hemisphere can talk, and it did not know the answer because the decision to point to the shovel was made in the right hemisphere.

4.  Immediately the left hemisphere made up a story about what it could see — the chicken.  It said the right hemisphere chose the shovel to clean out a chicken shed.