In an April study, neuroscientists led by Sasha Devore at the Massachusetts Institute of Technology tested the widely held hypothesis that specialized cells in the brain actively suppress neuronal response to echoes. Using electrodes in a cat’s midbrain, researchers measured cells’ responses to a sound and its reverberations. They found that the cells that sense a sound’s direction of origin responded more strongly to the first 50 milliseconds of sound waves than they did to the later waves—their activity simply tapered off after the onset of the sound. The tapering response, a much simpler mechanism than the earlier theory of suppression, allows the brain to easily tune in to original sounds and pinpoint who or what is making noise.
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