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publicado em 12/05/2011 às 19h06:00
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Scientists show how adversity dulls our perceptions

Perceptions learned in an adverse environment are not as sharp as those learned in other circumstances

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Adversity, we are told, increases our senses, printing pictures and sounds with precision in our memories. But new research at the Weizmann Institute in Israel, suggests just the opposite: Perceptions learned in an adverse environment are not as sharp as those learned in other circumstances. The results, which suggest that this trend is rooted in the evolution of our species, may help explain how the syndrome of posttraumatic stress disorder and other anxiety disorders develop in some people.

To investigate learning in unfavorable situations, Dr. Ron Peace, Department of Neurobiology Institute, together with his student Jennifer Resnik, put the volunteers to learn that some tones lead to an offensive result (eg a very bad odor), while other tones are followed by pleasing results or else, for nothing. The volunteers had their perception thresholds tested later - ie, how well they were able to distinguish "bad" and "good" tones and other similar tones.

As expected from previous studies, in neutral or positive, the volunteers have become better with practice to differentiate between the tones. But surprisingly, when they were exposed to a negative stimulus, possibly disturbing, his performance worsened.

The differences in learning were really very basic differences in perception. After learning that a stimulus is associated with an extremely unpleasant experience, the individuals could not distinguish it from other similar stimuli, although they could do it before, under normal conditions. In other words, no matter how well they usually learn new things, individuals who received the "enhanced adverse" realized the two tones in the same way.

Peace said: "This probably made sense in our evolutionary past: If you've heard the sound of a lion attacking its survival may be at risk from a noise that sounds similar to you - so the same emotional reaction is uncocked. Your instincts, then they will tell you to run, rather than considering whether that sound was in fact identical to the lion's roar the next day. "

Paz believes that this trend may be stronger in people suffering from stress syndrome, post-traumatic stress. As an example he points to the terrorist attacks of September 11 in New York. Many who witnessed the attacks on the towers developed syndrome of post-traumatic stress, which, for many, can be triggered by high buildings. Intellectually, they may know that the building before them bears little resemblance to the destroyed towers, but in a more fundamental level, instinctive, they can see all the tall buildings in the same way and thus associate them with the terrible destruction.

The scientific team is now investigating this idea in ongoing research in which they expect, among other things, identify areas of the brain that are involved in defining the different levels of perception. Peace says: "We think this is a trick of the brain that evolved to help us deal with the threats, but now that is dysfunctional in many cases. In addition to revealing this fundamental aspect of our perception, we hope to shed light on the development of disorders anxiety as the syndrome of post-traumatic stress. "

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