What basilar-membrane tuning says about cochlear micromechanics.

Experiments performed within the last 15 years on cochleas of live animals indicate that the cochlear sound analysis is much sharper than was expected from Békésy's experiments on postmortem preparations. The mechanism underlying the sharp analysis has not yet been ascertained experimentally. However, details of mechanical tuning curves defined by the amplitude of basilar-membrane vibration as a function of sound frequency ofr a constant amplitude of stapes displacement, together with structural and physical properties of he basilar and tectorial membranes and of the organ of Corti, strongly suggest a mechanism. The mechanism is assumed to result from a resonance of the tectorial membrane produced by interaction of the membrane's mass with its viscoelastic attachments to the organ of Corti and the spiral limbus. The resonance would produce a strong vibration of the tectorial membrane in the radial plane and enhance the shear motion between the membrane and the reticular lamina. Mechanical and computer models of the mechanism have allowed the authors to reproduce in detail the empirical basilar membrane as well as corresponding neural tuning curves and to account for associated cochlear nonlinearities.