[accessibleimage] study blindsight

Hi,
Perhaps of subject, but thought this article would be of interest.
Regards,
Lisa

Mystery of "Blindsight" Lets Some Blind People "See," Study Shows

http://news.nationalgeographic.com/news/2005/11/1101_051101_blindsight.html
An innovative research technique is providing insight into why some blind
people are able to sense and describe objects they cannot see. 
The phenomenon of "blindsight" occurs in some people who suffer injuries
to the primary visual cortex, the region of the brain considered essential
for sight. 
Blindsight allows people to use visual information they get through their
eyes even though they have no consciousness of the visual experience, said
Christopher Mole, a postdoctoral fellow in philosophy at Washington
University in St. Louis, Missouri. 
"But that of course is quite hard to show in the lab," he said. 
A team of psychologists at Rice University in Houston, Texas, may have
found a way to directly study blindsight in the lab. 
They are using electromagnetic stimulation on the brains of people who can
see to render them partially and temporarily blind. 
"The way it works is an electric current inducts into the brain via a
magnetic pulse, and that causes a disruption of underlying neurons in the
brain," said Tony Ro, a member of the Rice team. 
"What this technique allows us to do essentially is in a safe and
noninvasive way shut down a portion of the brain temporarily," he added. 
Ro and colleagues report their technique and findings in the current issue
of the journal Proceedings of the National Academy of Sciences. 
Mole said the Rice team reports "compelling proof" for blindsight. 
Unconscious Pathway 
Blindsight is most prevalent among people who suffer damage to the primary
visual cortex, such as in some stroke victims, Mole explained
However this is never "clean" or specific damage?other parts of the brain
are also impaired. Studies with these patients are therefore difficult, he
said. 
To study blindsight directly, researchers often purposefully and
permanently disrupt the primary visual cortex in monkeys and other
mammals, a method that would be unethical to use on humans, Mole said. 
"What [Ro's team] has done is cleverly manage to interfere with the brain
in a totally temporary way ? It doesn't have any long-term lasting effects
at all," he said. 
The technique devised by the Rice researchers induced blindness for a
fraction of a second in people who ordinarily have good vision. 
During the state of temporary blindness, an object was flashed on a screen
in front of the test subjects' eyes. 
In one experiment the object was either a vertical or horizontal bar, and
the subjects were asked to guess the bar's orientation. In the second
experiment the researchers flashed a colored disc, and subjects were asked
to guess the color. 
In both experiments the blinded volunteers correctly guessed the
characteristics of the objects at much higher levels than chance alone. 
This fits the definition of blindsight and raises the question of how it
is possible. 
"What we believe is happening is people are able to discriminate
orientation and color?as our experiments showed?by processing routes into
the brain that aren't consciously accessible," Ro said. 
"We believe there are pathways that go from the eyes into the brain that
bypass the normal routes tied to conscious processing of information." 
Ro added that the study supports the theory that these pathways go to a
visual center in the brain that is more sophisticated than the visual
centers common to all mammals. This suggests the pathways may be unique to
higher-order species. 
The test results also show that volunteers were more accurate when they
were more confident in their guesses. 
"It's unclear what that reflects, but what we think it reflects is that
this unconscious processing system can contribute to feelings of
certainty," Ro said. 
In follow-up experiments the team will test why people feel varying levels
of confidence in their guesses. Perhaps the unconscious processing routes
are stronger in some people than others, Ro said. 




Lisa Yayla
Huseby Kompetansesenter 
Oslo Norway
lisa.yayla@xxxxxxxxxx

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