Tuesday, November 08, 2005

"Mystery of 'Blindsight' Lets Some Blind People 'See,' Study Shows"

An innovative research technique is providing insight into why some blind people are able to sense and describe objects they cannot see.

The phenomenon of "blindsight" occurs in some people who suffer injuries to the primary visual cortex, the region of the brain considered essential for sight.

Blindsight allows people to use visual information they get through their eyes even though they have no consciousness of the visual experience, said Christopher Mole, a postdoctoral fellow in philosophy at Washington University in St. Louis, Missouri....

Unconscious Pathway

Blindsight is most prevalent among people who suffer damage to the primary visual cortex, such as in some stroke victims, Mole explained....

"We believe there are pathways that go from the eyes into the brain that bypass the normal routes tied to conscious processing of information."

Ro added that the study supports the theory that these pathways go to a visual center in the brain that is more sophisticated than the visual centers common to all mammals. This suggests the pathways may be unique to higher-order species.

The test results also show that volunteers were more accurate when they were more confident in their guesses.

"It's unclear what that reflects, but what we think it reflects is that this unconscious processing system can contribute to feelings of certainty," Ro said.

In follow-up experiments the team will test why people feel varying levels of confidence in their guesses. Perhaps the unconscious processing routes are stronger in some people than others, Ro said.

More @ National Geographic


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