3.4 Blind Vision

Watch the video on the screen: a man slowly walks down a corridor, avoiding obstacles in his path.

Nothing unusual — except that this man, known as patient TN, is clinically blind as a result of damage to his primary visual cortex after two strokes. His eyes are healthy, but the part of the brain that normally processes vision no longer functions — and at the time of filming, he had been blind for years.

When the experimenter asks him to walk across the room, TN laughs — how could he, if he cannot see?

But encouraged to try, he attempts it… and succeeds.

He navigates the space accurately — to the astonishment of everyone, including himself.

At the end of the experiment, TN states that he saw nothing.

So how is it possible?

In TN’s brain, visual information no longer reaches the primary visual cortex — the area responsible for conscious visual experience — but it still travels to other pathways that allow unconscious spatial navigation.

TN sees the obstacles — enough to avoid them — even though he does not know that he can see.