Blind man navigates obstacle course perfectly

December 26th, 2008 - 3:07 pm ICT by IANS  

Washington, Dec 26 (IANS) Researchers have demonstrated that people can successfully navigate an obstacle course even after the loss of their vision.The findings reveal the importance of alternative routes in the brain, active in those who have suffered severe brain damage to the visual cortex as well as in all of our everyday lives.

Earlier studies had shown a similar ability in monkeys with comparable brain lesions.

The new study was possible only because of the participation of an unusual patient known as TN, who became blind after selective damage to the visual cortex in both hemispheres of his brain following consecutive strokes.

“This is absolutely the first study of this ability in humans,” said Beatrice de Gelder of Tilburg University, The Netherlands and of the Martinos Centre for Biomedical Imaging and Harvard Medical School.

“It shows us the importance of these evolutionarily ancient visual paths. They contribute more than we think they do for us to function in the real world,” she said.

TN 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, as indicated by activity in brain regions consistent with emotional expressions of fear, anger, and joy.

He is nevertheless totally blind. He walks like a blind person, using a stick to track obstacles and requiring guidance by another person when walking around buildings, according to a Harvard Medical School release. The findings were published in the December issue of Current Biology.

To test his navigational ability in the current study, the researchers constructed an obstacle course consisting of randomly arranged boxes and chairs and asked him to cross it without the help of his cane or another person.

Astonishingly, they report, he negotiated the course perfectly, never once colliding with any obstacle. Several onlookers witnessed the feat and applauded spontaneously when he reached the end of the maze.

The demonstration shows that alternative visual paths available in the brain allow people to orient themselves and rapidly detect obstacles in the environment without any conscious attention or experience of seeing them.

“It’s a part of our vision that’s for orienting and doing in the world rather than for understanding,” de Gelder said. “All the time, we are using hidden resources of our brain and doing things we think we are unable to do.”

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