Wow. What to make of this story about a man who became blind as a result of stroke damage to both hemispheres of his brain but who retains the ability to navigate an obstacle course? Here's a portion of the news article at ScienceDaily:
"This is absolutely the first study of this ability in humans," said
Beatrice de Gelder of Tilburg University, The Netherlands and of the
Martinos Center for Biomedical Imaging and Harvard Medical School. "We
see what humans can do, even with no awareness of seeing or any
intentional avoidance of obstacles. 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."
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.
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," she
said. "All the time, we are using hidden resources of our brain and
doing things we think we are unable to do."
The original article appears in the December 23rd issue of the journal Current Biology.