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Technology and Health News > Monday, July-28-2008

Right or left?



The brain responds to stimuli, tactile and visual contradiction in delaying the processing of information that comes from the skin.

A fly is laying on the right elbow. Slight itching, moving vision towards the elbow, identification of the intruder and its position and, finally, blow. This reaction is not as instantaneous as you can imagine. Indeed, the brain seems to delay affixed aware of the tactile perception, as reported a study in Current Biology Group for Research in Cognitive Neuroscience (Grnc) in Barcelona.

The brain is often having to generate rapid responses integrating stimuli that produce information in contradiction: if, for example, the subject has crossed his arms and brings his right arm on the left side and left arm on the right side, his hands will be in a position that is reversed from the original location. In this case, the brain must be able to correctly integrate the information of the tactile stimulus (for example pinch) on the right hand, although the visual stimulus comes in fact from the left. To avoid mistakes the brain needs time to make a realignment of the information space of two different maps: that rof the body and one that covers everything else.

To understand how the mechanism works, researchers have assessed the response of 32 university students to a series of visual and tactile stimuli. Each student has been subjected to 600 tests. "First we asked participants to cross the arms, so that the position of hands was in conflict with the anatomical position" says Salvador Soto-Faraco, one of the authors of the study, "we have stimulated one of two hands." Few tenths of a second later, a small light (visual stimulus) I had left or right. Both the tactile stimuli that those visual products were in a totally random. In addition, the flash of light could be generated 60 or 200 milliseconds after the tactile stimulus. In order to assess whether the time elapsed between the two stimuli does influence or not the answer.



Result? Only when the visual stimulus was produced with asufficient delay (200 milliseconds) and its position corresponds with that of tactile stimulation (left with the left or right with right), the brain was able to locate the position of tactile stimulus to the skin correct. "The results clearly show," says Elena Azañón, the second author, "that the brain is able to correctly identify a point on the body only when it is not in conflict with an external stimulus, such as the view of the fly."

In practice the brain, to avoid confusion, notes the tactile perception at the subliminal level, looks up other details, and then produces a response, congruent to the stimulus. "In a nutshell, it's like when we take quick notes" concludes Salvador Soto-Faraco "but then we write the final paper without even considering the draft."

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Comments for Right or left?

Gish

Uhh... what images.
posted by Guest at Monday, July-28-2008 11:39am


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