FLUID-STRUCTURE INTERACTION OF THE STEREOCILIA BUNDLE IN RELATION TO MECHANOTRANSDUCTION

Current hypotheses regarding mechanotransduction rely upon motion of t he stereocilia relative to the apical surface of the hair cell. The vi scosity of the surrounding endolymphatic fluid will, however, attenuat e stereocilia motion at higher frequencies of excitation. To investiga te stereocilia motion for physiologically reasonable deflections and f requencies of excitation, the fluid-structure interaction of the stere ocilia bundle is considered analytically. Solutions in the frequency d omain are determined for stereocilia bundle dimensions at several loca tions along the cochlear duct of the chinchilla. Results indicate that motion of the stereocilia is analogous to that of a low-pass filter. Comparison of these solutions with Greenwood's frequency-place map dem onstrates that motion of the stereocilia bundle exists without substan tial attenuation at least up to frequencies appropriate for the locati on of the corresponding hair cell along the cochlear duct. The variati on in stereocilia morphology within the mammalian cochlea thus appears to provide a collection of low-pass mechanoreceptors, arranged in ord er of increasing corner frequency across the auditory spectrum. (C) 19 97 Acoustical Society of America.