How much can you see with non-functioning visual
cortex? A clinically blind man, with lesions on
both sides of his visual cortex, was able to
flawlessly navigate an obstacle course, a paper
to be published tomorrow in
Current Biology
reports.
The patient, called only TN in the paper, is a
former doctor, who had suffered two strokes that
damaged both sides of his striate cortex, the
brain region dedicated to processing vision. The
findings reinforce previous observations that
other routes in the brain besides the visual
cortex can process visual information, the
study's authors say.
"I don't think there's ever been a bilateral
blindsight patient that's been studied in any
depth whatsoever, that's why it's interesting,"
Robert Kentridge, from the University of
Durham, who was not involved in the study, told
The Scientist.
TN has a condition known as blindsight. He is
blind in every sense of the word: He walks with
a sensing stick and needs guidance by another
person. However, he is able to sense facial
expressions, indicated by activity in brain
regions that respond to facial expressions such
as fear or anger.
To test TN's ability for locomotion, the
researchers, led by
Beatrice de Gelder, from Tilburg University
in the Netherlands, set up a crude obstacle
course in a narrow hallway. To the researchers'
shock TN walked flawlessly through the course,
sidestepping boxes and chairs without the help
of a guide. (Click on the movie below to watch
TN navigate the obstacle course)
