blindsightIt looks like quackery, but it is a medical phenomenon. A person that is 100% blind goes through a labyrinth with obstacles. Without hearing or touching anything. The patient says that he knew intuitively where to step. Scientists explain that it is a specific form of sight, working in subconscious level.

A 56-year-old resident of Burundi, known as “TN” suffers from blindness provoked by two strokes which have completely destroyed the visual cortex in both hemispheres, although other parts of the brain remained almost intact. TN’s eyes are healthy and continue to send signals to the brain.

Scientists have long known a phenomenon of the so-called blindsight, observed in patients with similar brain disorder. In experiments with a strictly controlled environment people respond to visual stimuli although they can’t see anything.

Scientists claim that the phenomenon of blindsight has to do with a simple processing of visual information outside the visual cortex, and the signals involve certain hardly used areas of the brain.

The ability of TN has long attracted the attention of researchers. In 2004 Alan Pegna from the University Hospital of Geneva (Hôpitaux Universitaires de Genève) made an experiment which showed that TN can distinguish emotional expressions of people without perceiving them visually (so in his brain there was only a “black screen”).

This time together with Beatrice de Gelder from the Tilburg University and a number of colleagues from different countries Alan has asked TN to put aside his walking stick and try to go through a corridor. The blind man has perfectly gone through it, avoiding the wall and a variety of small objects scattered on the floor. TN was looking down. He saw nothing consciously, but with the help of some sense could recognize the obstacles.

Perhaps it is echolocation? Echoes of the steps and even of his own breath might tell him where the objects are. But that is not the answer. In fact echolocation doesn’t work well with small objects. In other words, maybe it would help TN avoid the wall, but not a book lying on the floor.

Researchers say that it is an “ancient” form of sight, similar to some other cases when we act in obedience with unconscious motive without analyzing them.

In some cases these behavioral responses may be associated with visual sensations, but not those that the visual cortex shows to our consciousness like “on the screen”.

According to Pegna, TN shows a keen interest in the study of himself and really wants to help scientists understand the phenomenon of the blindsight. Perhaps in the future this knowledge will help other blind people with similar diagnosis.

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