Prediction of the Effect of Adaptation and Active HB Mechanics on Prestin-Based Amplification Using a Macroscopic Model of the Cochlea

Abstract

The identity of the mammalian cochlear amplifier is a highly debated issue in auditory mechanics. Two different active processes could underlie cochlear amplification: somatic motility and hair bundle (HB) motility. We use a mathematical model of the cochlea to investigate the role of somatic motility and active HB dynamics. The HB is modeled by a nonlinear six-state channel with a calcium binding event responsible for fast adaptation of the transduction and active HB force generation. The dynamics of the HB are linearized for small harmonic perturbation around the operating point and implemented in a macroscopic model of the cochlea that includes feedback from outer hair cell somatic motility. The simulations of the response of the cochlea to low intensity acoustic stimulation show that somatic motility and not HB motility can modulate the BM motion. However the effect of fast adaptation on the transduction channel is a reduction of the sensitivity of the channel to HB deflection that could serve to control the energy delivered by somatic motility and thereby the gain of the BM to low intensity acoustic stimulation. Funded by NIH grant NIH-NIDCD R01-04084.