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----------------------------------------------------------------------- The brain works like an FM radio, study finds ----------------------------------------------------------------------- WASHINGTON (October 14, 1997 01:52 a.m. EDT http://www.nando.net) - The brain works much like an FM radio when it interprets touch, Israeli scientists reported Monday. They said tests on rats showed brain cells use a kind of frequency modulation -- the same method used by FM radio signals. "We found that certain circuits in the brain work on the same principle as an FM radio," Ehud Ahissar of the Weizmann Institute in Rehovot said in a statement. "We hope that our study will contribute to the deciphering of the neural code, the way in which information is encoded by the sensory organs and decoded by the brain." Radio waves carry information in two ways. Frequency modulation (FM) involves changing the frequency with which radio waves oscillate, while amplitude modulation (AM) changes the height of the waves. Radio sets interpret these small changes, which can carry the information that we hear as music or speech. Similarly, the brain contains cells that oscillate at certain frequencies. Ahissar's team said they found the brain uses these cells as a yardstick to help it interpret the timing of incoming signals. Writing in the Proceedings of the National Academy of Sciences, which is based in Washington, they gave as an example a finger rubbing a piece of corduroy. Each ridge is a set distance from the next; the thinner and closer the ridges, the more frequent the signal. Nerve endings in the finger send that signal to the brain. "The timing of the sensory signals appears to be an inherent part of the sensory code," Ahissar said. "In fact, this timing contains so much information about the external world that it would be surprising if the brain made no use of it." Testing rats, Ahissar's team found their whiskers -- an important sensory organ for rats -- twitched at a frequency of about 8 motions per second or 8 Hertz (Hz). When they touch something, additional signals are triggered that modulate that 8 Hz signal. These signals are sent to the oscillating brain cells. "The brains of primates contain similar oscillating cells, which are tuned to the characteristic frequencies generated when the fingertips rub against an external object," Ahissar said. They are now testing to see if the brain uses similar methods to decode visual input. ------------------------------------------------------------------------ Copyright 1997 Nando.net Copyright 1997 Reuters <http://www.nando.net/newsroom/ntn/health/101497/health12_10948_noframes.html>