Brain May Have 'Blindsight'

Source: Yahoo/AP
http://news.yahoo.com/s/ap/20051031/ap_on_he_me/blindsight

Study: Brain May Have 'Blindsight'

October 31, 2005 By RANDOLPH E. SCHMID, Associated Press Writer

WASHINGTON - Even when the brain can't consciously tell what the eyes are
seeing, it may still be able to sense what's there. The finding suggests
that the brain may have "blindsight" � an alternate way of processing
visual information.

That might help scientists better understand the nature of consciousness
and suggest ways to restore some types of vision loss, according to Tony
Ro, a psychology professor at Rice University in Houston.

Not all vision researchers accept the idea of blindsight, however, and
other studies into the concept are under way.

Ro and his research team studied what could be sensed by volunteers who
were temporarily blind. Their findings are reported Monday in the online
edition of Proceedings of the
National Academy of Sciences.

In the study, temporary, reversible blindness was induced in volunteers by
using magnetic pulses that affected the visual cortex, the area in the back
of the brain that processes what the eyes are seeing.

A computer screen was in front of the volunteers. In one test, during their
momentary blindness the screen flashed with either a vertical or horizontal
line. In a second test a red or green ball was shown on the screen.

When the volunteers were asked what they had seen during the temporary
blindness, they said they saw nothing, the researchers reported.

But, the researchers said, when the patients were told to guess which way
the line was oriented, they were right 75 percent of the time. And they got
the color of the ball right 81 percent of the time. Random guessing would
be expected to result in a 50 percent correct rate.

Some of the participants said they were guessing randomly and were
surprised with their high success rates, the researchers said. Others
reported they had a "feeling" about what had been there.

Asked to rate the confidence of their guesses, the higher confidence
ratings tended to correspond with more accurate guesses.

"These findings demonstrate that while certain brain areas are necessary
for awareness, there is extensive processing of information that takes
place unconsciously," Ro said via e-mail.

He said the results, "suggesting the existence of alternate visual
processing routes that function unconsciously, may provide some hope for
people with damage to the primary visual cortex."

Dr. Edmond Fitzgibbon of the National Eye Institute said the report adds
weight to the idea of a second pathway for experiencing sight, but he added
that the idea remains controversial and many researchers don't accept it.

The new study is "intriguing," Fitzgibbon said. But he added that there can
be perception that people aren't aware of, such as subliminal suggestions
briefly flashed during a film.

"If you're not aware of it, does that really mean you didn't see it?" he asked.

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Proceedings of the National Academy of Science: http://www.pnas.org