60-Second Mind

A Blind Man Sees

A recent paper in Current Biology provides one of the few human cases of blindsight, the ability for perceptively blind people to respond to visual stimuli, even though they have no awareness of seeing anything. Christie Nicholson reports.

[Below is the original script. But a few changes may have been made during the recording of this audio podcast.]

Given that we just said goodbye to another year, we are all pretty familiar with the hindsight. But have you heard of blindsight?

The phenomenon is the ability to see without having the visual brain hardware to actually see. It’s been proven that monkeys have blindsight for navigating through a space, but never in a human, until now.

A recent paper in Current Biology describes a patient who lost his ability to see after suffering strokes that wiped out his visual cortex, the brain area that processes visual input. His eyes and optic nerves remained intact, and the researchers confirmed that some information was being gathered via his still-functioning eyes.

So they gave him what many would think was the impossible test for a blind person. He had to navigate a hallway, around chairs and boxes, without his cane.

He passed the test perfectly. What this implies is that visual information can reach areas of the brain, by routes other than the visual cortex. Meaning, we don’t have to be conscious of the experience of seeing to capture, and respond to, visual stimuli.

“All the time, we are using hidden resources of our brain and doing things we think we are unable to do,” said Beatrice de Gelder, one of the authors.

Gives new meaning to the old saying:  "I see, said the blind man."

—Christie Nicholson


For more on blindsight, and this study, please see this 60-Second Science post.


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