Nov 012005

The Human Eye has a summary of a study published this week in the online edition of Proceedings of the National Academy of Sciences that provides additional evidence of the phenomenon known as blindsight, residual visual sensitivity experienced in the brain even when one is blind or otherwise unable to see. While the results of the study seem to conclusively support the existence of the phenomenon, they also exacerbate the fact that there is still relatively little known about the mechanisms of human consciousness, or in this case, unconsciousness.

Performed by scientists at Rice University, the experiment itself was very straightforward. Volunteer subjects were seated in front of a computer screen. A momentary pulse of magnetic energy was applied to their visual cortices causing a moment of temporary blindness. During this fraction of a second without sight, a simple image was flashed on the screen. None of the subjects were able to identify what they had seen, but were able to correctly identify details of the image with an accuracy level significantly above the 50% level of guessing. For example, those subjects that were shown a dot were able to guess the color of that dot a statistically significant number of times.

The conclusion the researchers have drawn is that there appears to be additional pathways in the brain outside of the visual cortex through which visual information flows and is able to be processed. This research supports the results of previous studies involving blind and brain damaged subjects.

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