Page last updated at 17:01 GMT, Monday, 22 December 2008

Blind man navigates maze

By Helen Briggs
Health reporter, BBC News

See the man navigating the obstacle course

Scientists have discovered that a blind person can navigate through a maze of obstacles unaided using undiscovered sensory pathways alone.

The man, left blind by a stroke, was able to walk around chairs and boxes without bumping into them using hidden pathways in the brain.

The study suggests we all use subconscious brain resources and can do things we think we are unable to do.

The Harvard Medical School research is published in Current Biology.

These are very exciting findings but it will require further research

Sonal Rughani, RNIB

The patient, known only as TN, was left blind after damage to the visual (striate) cortex in both hemispheres of the brain following consecutive strokes.

His eyes are normal but his brain cannot process the information they send in, rendering him totally blind.

However, he was previously known to have what is called "blindsight" - the ability to detect things in the environment without being aware of seeing them.

For instance, he responds to the facial expressions of others.

But he walks like a blind person, using a stick to track obstacles and requiring guidance by others when walking around buildings.

A video recording shows him completing the obstacle course set up by the scientists "flawlessly", without the aid of his cane or another person.

Lead researcher Dr Beatrice de Gelder of Tilburg University, The Netherlands, and Harvard Medical School, US, said TN was "not aware of doing anything exceptional" and thought all he had done was walk straight ahead along a long corridor.

It is an important message for those with brain damage in particular, she said.

"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," she told the BBC.

"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."

The research was carried out together with colleagues in the UK, Switzerland and Italy.

Sonal Rughani, optometrist and senior advisor to the UK charity, the RNIB, said it was a striking observation, and further evidence that the brain is very flexible.

But she said relatively few numbers of people were left blind through brain injury, and most people with sight problems following a stroke could be helped by complex therapy regimes.

"These are very exciting findings but it will require further research," she added.

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