Brain maps perceptions, n...( trinsic signal optical imaging to study...),Health

trinsic signal optical imaging to study the reaction to the same illusion in the brains of squirrel monkeys. Intrinsic signal optical imaging uses a specially designed video camera to detect changes in light reflectance viewed through a "window on the brain." These cortical reflectance changes are related to changes in blood flow that occur when neurons respond to specific sensory stimuli.

When the monkeys were touched on one digit alone, the researchers observed a response in Area 3b of the somatosensory cortex, the area previously determined to process information from that digit. When an adjacent digit was stimulated on its own, a response was seen in the cortical map for that digit. However, when the monkey was touched simultaneously on both digits, a single cortical location between the maps of the two individual digits responded, explaining the perceived location of the illusion. In addition, the perceived intensity of this illusion is caused by the integration of activity across all three locations (two actual, one illusory).

"The merger of signals from adjacent fingers demonstrated in this elegant study may serve an important function in hand use," Esther Gardner, professor of physiology and neuroscience at NYU School of Medicine, said. "It allows the fingers to be controlled as a single functional group centered opposite the thumb when grasping large objects, rather than as distinct individuals." In addition to establishing that the cortical map reflects perception rather than physical location, the researchers found the brain processes touch perceptions at an unexpectedly early stage.

"The cortical area we studied, 3b, is an early entry level in the cortex for information from the skin," said Friedman. "We did not expect to see perception being reflected that early. This gives us a much better understanding of how much work the brain is doing, even at this early level of processing."

"How we perceive the world is an endu
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Contact: Melanie Catania
melanie.catania@vanderbilt.edu
615-322-6397
Vanderbilt University
31-Oct-2003

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