American scientists at the Harvard School of Medicine were puzzled to learn that one of their patients, who had suffered two strokes and had lost his eyesight completely, managed to navigate an obstacle course without tripping or touching any of the objects, and without help from another person or a cane. They hypothesize that the man manages to use his “sixth sense,” which is often referred to, in the case of people who cannot see, as “blindsight.”

Blindsight is the ability that totally blind humans or animals have to use alternative neural pathways for detecting obstacles in their path, without actually seeing them. In the case of TN, the “wonder” patient, this was done absolutely instinctively, which is what got scientists so excited. Usually, in people who lost their sight due to accidents, it takes a long time to learn to rely on their other senses for their daily lives, and even then, in most cases, they don't managed to go about their businesses without help from canes, dogs, or members of the family.

"You can experience a total loss of your cortical vision but still retain some capacity to move around inside and out without damage to yourself. It shows us the importance of these evolutionary ancient visual paths. They contribute more than we think they do for us to function in the real world. These are very exciting findings but it will require further research," Dr. Beatrice de Gelder explained to the BBC in an interview. She works both at the Tilburg University in the Netherlands and Harvard School of Medicine, in the United States.

Another remarkable feat of TN's ability is the fact that he can detect facial expressions of people he is talking to, even though he cannot actually see them. Researchers hypothesize that this may have something to do with the fact that his eyes are still intact. Following the strokes, TN only suffered damage in the portion of the brain responsible for processing video input.

So he cannot actually see anything, strictly speaking, but the signals his eyes still send to the brain are processed in other parts of his mind, which makes this “blindsight” of his look very similar to a sixth sense. Not even the man himself can tell how he's doing what he's doing, but he does it nevertheless.