Blindsight enables blind man to navigate obstacle course

Scientists have conducted research which demonstrates that there is such a phenomenon as "blindsight".

A team from the University of Tilburg in the Netherlands, the Martinos Center for Biomedical Imaging and Harvard Medical School, have been astonished by a man who completely lost his sight after brain damage was able to negotiate an obstacle course without his cane.

The scientists led by Professor Beatrice de Gelder say they have witnessed a powerful demonstration of the eerie phenomenon known as "blindsight".

The man was blinded by strokes on both sides of his brain which left him devoid of any activity in the brain regions that control vision and unable to see.

Though he uses a stick to detect obstacles and needs to be guided around buildings he was known for having blindsight - an unusual ability possessed by some blind people where they are able to detect things that they cannot see.

The man apparently reacts to the facial expressions of other people and scans of his brain have confirmed that it registers facial emotions such as joy, anger and fear but he has now demonstrated an even more remarkable skill - the ability to navigate without being able to see.

The scientists conducted an experiment where a series of boxes and chairs were arranged from one side of the room to the other, as an obstacle course, the man was then asked to move through the course without using his cane and to the amazement of the scientific team he managed to complete the course perfectly.

Professor de Gelder says this is the first study conducted into this ability in humans and shows even with no awareness of seeing or any intentional avoidance of obstacles, what humans are capable of doing.

Professor de Gelder says it demonstrates the importance of evolutionarily ancient visual paths which contribute more than is realised for people to function in the real world.

The researchers believe the man's blindsight can be explained by these alternative visual paths in the brain, which allow him to process information received through his eyes, which are still functional and then use this information to navigate even though he is unaware that he has the ability to see.

Professor de Gelder says this is a part of our vision used for orienting and doing in the world rather than for understanding and we are constantly using the hidden resources of our brain to do things we are unaware we are able to do.

The researchers say the study has implications for treating patients with brain damage.

The study is published in the current issue of Current Biology.