Watching the brain switch ...( Everybody has experienced a sense of l...),Health

Everybody has experienced a sense of "losing oneself" in an activity--whether a movie, sport, sex, or meditation. Now, researchers have caught the brain in the act of losing "self" as it shuts down introspection during a demanding sensory task. The researchers--led by Rafael Malach and Ilan Goldberg of the Weizmann Institute of Science reporting in the April 20, 2006, issue of Neuron--say their findings show that self-related function actually shuts down during such intense sensory tasks. Thus, an "observer" function in the brain does not appear to play an active part of in the production of our vivid sensory experiences. These findings go against common models of sensory experience that assume that there is some kind of "homunculus", or observer function in the brain that "looks at" sensory brain areas. Thus the finding, they said, has significance for understanding the basic nature of consciousness and perception.

The experimental challenge that the researchers faced was to design one task that could be used to activate specifically either sensory processing or introspection brain areas. Their solution was to ask subjects to look at the same pictures or listen to the same musical phrases, but to perform two different kinds of processing on them. To explore sensory processing, the researchers asked the subjects to use buttons to classify the images as animal/non-animal, or the musical passages as trumpet/non-trumpet. And to study introspection, the researchers asked the subjects to indicate whether emotionally they felt strongly or neutrally about the image or musical passage.

During the tests, the researchers scanned the volunteers' brains using functional magnetic resonance imaging. In this widely used technique, harmless magnetic fields and radio waves are used to scan blood flow in brain regions, which indicates activity.

The researchers found that regions of the brain activated during sensory processing or self-reflective introspection
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Contact: Heidi Hardman
hhardman@cell.com
617-397-2879
Cell Press
19-Apr-2006

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