Can shape deformations of the organ of Corti influence the travelling wave in the cochlea?
Via their motile reactions outer hair cells may produce oscillatory power or amplify the fluid waves in the cochlea. When the cells move or change their lengths, the organ of Corti (OC) will change its shape. This paper describes the consequences of such shape changes for the physics of cochlear waves. The assertions posed are based on a mathematical derivation but the major conclusions can be grasped without following the mathematics in detail. There are two basic types of OC deformations. In the first type the net cross-sectional area of the OC is periodically varying, in the second type--the central subject of this paper--is is not. It is shown that for the latter type of OC shape deformation there is no interaction with the cochlear fluids, at least for long waves. Hence, in this case the outer hair cells cannot amplify cochlear waves. The other type of OC deformation has a better coupling with the cochlear waves. However, much of the pressure developed by oscillating hair cells is spent in the 'wrong' way, namely, by squeezing fluid lengthwise through the narrow channel of the OC. Therefore, in this mode power transfer from cochlear hair cells to cochlear fluids (and from there to the basilar membrane) would be very inefficient.
de Boer
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Academic Medical Centre, Amsterdam, The Netherlands.
D000818:Animals; D001306:Auditory Pathways / Q000502:physiology*; D003051:Cochlea / Q000502:physiology*; D008959:Models, Neurological; D009925:Organ of Corti / Q000502:physiology*