The Roots Of Consciousness: We’re of 2 Minds
from NPR’s All Things Considered
After surgery to treat her epilepsy severed the connection between the two halves of her brain, Karen’s left hand took on a mind of its own, acting against her will to undress or even to slap her. Amazing, to be sure. But what may be even more amazing is that most people who have split-brain surgery don’t notice anything different at all.
But there’s more to the story than that. In the 1960s, a young neuroscientist named Michael Gazzaniga began a series of experiments with split-brain patients that would change our understanding of the human brain forever. Working in the lab of Roger Sperry, who later won a Nobel Prize for his work, Gazzaniga discovered that the two halves of the brain experience the world quite differently.
When Gazzaniga and his colleagues flashed a picture in front of a patient’s right eye, the information was processed in the left side of the brain and the split-brain patient could easily describe the scene verbally. But when a picture was flashed in front of the left eye, which connects to the right side of the brain, the patient would report seeing nothing. If allowed to respond nonverbally, however, the right brain could adeptly point at or draw what was seen by the left eye. So the right brain knew what it was seeing; it just couldn’t talk about it. These experiments showed for the first time that each brain hemisphere has specialized tasks.