Role of Passive Mechanical Properties of Outer Hair Cells in Determination of Cochlear Mechanics

Abstract

The feasibility of a resonant mechanical system in the cochlea, consisting of outer hair cells (OHCs) and the tectorial membrane (TM), playing a significant role in frequency selectivity has been investigated. As proposed initially by Zwislocki (J. Acoust. Soc. Am. 67, 1679–1688, 1980), such a resonant OHC-TM system, with stiffness provided by the sensory hairs of the three rows of OHC and mass by the overlying TM, would be mechanically coupled to the basilar membrane (BM) via the sensory hairs and would vibrate in a plane parallel to the reticular lamina. Since the TM mass is estimated to be 1/5 – 1/4 of the mass of the organ of Corti, OHC-TM vibrations would have a significant effect upon BM frequency selectivity if OHC-TM resonant frequency along the length of the cochlea were close to the BM frequency at the same location.Determination of the length and stiffness of OHC sensory hairs in the isolated guinea pig organ of Corti (Strelioff and Flock, Hearing Res., 15, 19–28, 1984) has made possible quantitative computations of OHC-TM resonant frequencies for the simple case where the effects of the TM attachement to the limbus are neglected. Computed OHC-TM resonant frequencies, assuming no variation in TM mass along the length of the cochlea, range from 1.2 kHz at the apex to 22 kHz at the base. These computed frequencies, based upon data from in vitro preparations, are sufficiently close to BM frequencies to demonstrate the feasibility of Zwislocki’s proposal. As more data on the mass and elasticity of the TM and the characteristics of its attachment to the limbus become available, it will be possible to more accurately evaluate the role of OHC-TM micromechanics in BM frequency selectivity.KeywordsHair CellOuter Hair CellBasilar MembraneHair BundleSensory HairThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.