Blind Man Sees With Subconscious Eye

Scientists are reporting the remarkable case of a blind man who can see.

The case involves a middle-aged male physician living in Switzerland, who is known only by the initials "TN." A few years ago, TN had two strokes, one on either side of his brain. The strokes severely damaged the part of the brain primarily responsible for vision, known as the occipital cortex.

Extensive testing of TN confirmed that even though his eyes were just fine, he was completely blind. He couldn't see objects held in front of him and used a cane to get around. Ask him if he could see, and TN would reply, "No, I'm blind."

But neuroscientist Beatrice de Gelder wanted to study TN further. She is affiliated with Tilburg University in the Netherlands as well as Massachusetts General Hospital in Boston. First, she and her colleagues repeated tests on TN to satisfy themselves that he was indeed blind.

Then they laid out an obstacle course in a hallway. The obstacles consisted of everyday objects.

"One was a typical paper basket; one was a stack of books," says de Gelder. "They all had different shapes and sizes."

She then told TN to walk down the hall.

"We didn't give him information about obstacles or anything. So he was not aware that there were obstacles."

So TN walked down the hall, but instead of walking straight ahead, he carefully stepped around each of the obstacles.

"He never touched any of it. We were like totally amazed," says de Gelder, who reports her finding in the journal Current Biology. You can see this test by clicking on the video link above.