Cochlear frequency sharpening-a new synthesis.

Recent evidence indicates a substantial difference in sharpness of tuning between basilar membrane mechanics and primary neuron responses in mammals. This paper describes a new qualitative model for a sharpening mechanism. It is suggested that the inner hair cells are sensitive to d.c. potential changes in scala media that are induced by sound stimuli, and that these d.c. potentials can suppress neuron activity in a frequency-dependent way. The model explains sharpening of both sides of neural tuning curves, the shape of the low-frequency part of the tuning curves and is also compatible with other phenomena such as two-tone inhibition and the effects of electrical polarization of the basilar membrane.