Scientists prove blind people can 'see' with sixth sense

[abdulhakeem]

Tue 1 Nov 2005
RHIANNON EDWARD

THE uncanny ability of blind people to "sense" unseen objects has been demonstrated for the first time in sighted volunteers whose vision was blanked out by scientists.

The findings suggest "blindsight", which has been observed in blind people whose eyes function normally but who have suffered damage to the brain's visual centre, is a real and not imagined phenomenon.

In tests, the blind have been able to distinguish basic shapes of objects they cannot see, as well as their orientation and direction of motion. On other occasions a blind person has reported experiencing a "feeling" that an object is present, while not being able to see it.

A number of theories have been proposed to explain "blindsight". Generally, it is suggested that other parts of the brain besides the primary visual cortex respond to nerve messages from the eyes at an unconscious level.

Scientists from the University of Houston in Texas, temporarily blinded a group of 12 volunteers by using an

electromagnetic field to shut down the primary visual cortex. Images were then flashed in front of them on a screen.

In one experiment, volunteers were shown either a horizontal or vertical bar. In another, a red or green dot appeared.

Most of the time, the volunteers were unaware of the images with which they were presented. But they guessed either the orientation of the bar or the colour of the dot correctly more often than would have been expected by the law of averages.

The researchers wrote in the journal Proceedings of the National Academy of Sciences: "Despite unawareness of these 'targets', performance on forced-choice discrimination tasks for orientation and colour were both significantly above chance."

They said the findings suggested that a visual pathway bypassing the primary visual cortex must be responsible for "blindsight".

http://news.scotsman.com/uk.cfm?id=2176562005

[abdulhakeem]

Out Of Sight, Out Of Mind? Not Necessarily

Source:
Rice University (http://fcx(this.href);/)

2005-11-01

Visual information can be processed unconsciously when the area of the brain that records what the eye sees is temporarily shut down, according to research at Rice University in Houston.

The research, published the week of Oct. 31 in the Proceedings of the National Academy of Sciences' (PNAS) online Early Edition, suggests the brain has more than one pathway along which visual information can be sent.

For the study, the researchers induced temporary, reversible blindness lasting only a fraction of a second in nine volunteers with normal vision. Transcranial magnetic stimulation (TMS), a harmless noninvasive technique using brief magnetic pulses, was applied to the volunteers' visual cortex -- the area at the back of the brain that processes what the eye sees - to interrupt the normal visual pathway. The volunteers looked at a computer screen, and during their momentary blindness, either a horizontal or a vertical line or a red or a green dot flashed on the screen.

Researchers then asked the study participants whether they had seen a horizontal or a vertical line; because their primary visual pathway had been shut down, the participants reported that they saw nothing. However, when forced to guess which line had appeared on their computer screen, the participants gave the correct answer 75 percent of the time. When the participants had to guess whether a red or a green dot had flashed on the screen, they gave the correct answer with 81 percent accuracy.

"This high degree of accuracy for both the directional orientation and color tasks was significantly above chance," said Tony Ro, associate professor of psychology and principal investigator for the study. "Even though the human primary visual cortex activity was temporarily shut down, it's clear that detailed visual information was still being processed unconsciously."

Because only a certain region of the thalamus - the area of the brain where all sensory information is relayed -- can process color, the study provides evidence that there must be a pathway that goes through this region of the thalamus to the higher visual centers of the brain, Ro said.

"In addition to providing direct evidence that unconscious processing takes place within the brain - a controversial claim that was advanced by the likes of Sigmund Freud and William James - our results suggest that multiple pathways relay visual input into the central nervous system for different types of processing," Ro said. "And our study also begins to shed light on the brain structures that are necessary for consciousness, with the primary visual cortex playing an essential role for visual awareness."

The phenomenon of "blindsight" has been reported in patients with brain damage who report not seeing something but correctly identify the shape and location when forced to guess. Ro noted that his study demonstrates that TMS can be used successfully to induce blindsight in people with normal vision.

Ro's co-authors on the PNAS paper were graduate student Jennifer Boyer and Stephanie Harrison, a summer intern.

Editor's Note: The original news release can be found here (http://fcx(this.href);/).

http://www.sciencedaily.com/releases/2005/11/051101075951.htm

[abdulhakeem]

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

John Roach
for National Geographic News (http://news.nationalgeographic.com/)

November 1, 2005



http://news.nationalgeographic.com/news/2005/11/images/051101_blindsight.jpg Researchers at Rice University in Houston, Texas, are using electromagnetic stimulation on the brains of people who can see to render them partially and temporarily blind.

Scientists can then measure the subjects' ability to sense objects they cannot see, a phenomenon that has been difficult to study in the lab.

Photograph courtesy PNAS

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.

http://news.nationalgeographic.com/news/2005/11/1101_051101_blindsight.html