April 5, 2011
It’s Not Over When It’s Over: Storing Sounds In The Inner Ear
Research shows that vibrations in the inner ear continue even after a sound has ended, perhaps serving as a kind of mechanical memory of recent sounds. In addition to contributing to the understanding of the complex process of sound perception, the results may shed light on other fascinating aspects of the auditory system, such as why some gaps between sounds are too brief to be perceived by the human ear. The study is published by Cell Press in the April 5th issue of Biophysical Journal.
The inner ear contains a structure called the cochlea that serves as the organ of hearing. The cochlea is a coiled, fluid filled structure that contains a "basilar" membrane and associated "hair cells". Essentially, sound-evoked vibrations of the basilar membrane are sensed by the hair cells which in turn convey auditory information to the nervous system. Some hair cells respond to basilar membrane vibrations by producing forces that increase hearing sensitivity and frequency selectivity through mechanisms that are not completely understood. "Because hair cell force production is initiated by the acoustic stimulus, it was assumed to end when the stimulus was removed," says senior study author, Dr. Alfred L. Nuttall from the Oregon Hearing Research Center. "However, there is evidence that some tones produce vibrations that continue even after the end of the stimulus."
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