Toward three-dimensional analysis of cochlear structure.

Recent results from a three-dimensional model of the cochlea are summarized. The features include physically realistic values of basilar membrane stiffness, mass, and fluid viscosity. The simple 'feed-forward' principle for the active process yields results in qualitative agreement with recent measurements in the cochlea. The limitation is a simplified representation of the organ of Corti, with two degrees of freedom representing the motion of the pectinate and arcuate zones of the basilar membrane. However, the inner sulcus fluid flow is included. The new feature presented in this paper is an approach to treat all the structural detail of the organ of Corti, with the sole input to the calculation in a form easily understood by anyone familiar with the cochlea. Specific results are shown for the Pakistani water buffalo, since a fairly complete anatomical description of this cochlea is available. The static stiffness from the calculation, based on only the anatomy and known values for the protein elastic moduli, are in remarkable agreement with recent measurements in the gerbil cochlea. Only preliminary results for the dynamic response with inviscid fluid are reported. Of interest, however, are the propagation modes related to significant fluid displacement and pressure in the different compartments of the organ of Corti.