Exploring underlying mechanisms of level- and time-dependent behaviors of the cochlea

Wenxiao Zhou, PhD Qualifying Exam, Advised by Professor Jong-Hoon Nam

Hopeman 224

Cochlear responses are level- and time-dependent. Compressive growth of single tone responses and two-tone suppression at high sound pressure levels have been commonly observed in experiments, which reveals cochlear nonlinearity. The onset of the traveling waves and frequency glide in response to pulsatile stimuli shows distinct transient behaviors of the cochlea.

We developed a nonlinear cochlear model in the time domain, which can be used to interpret experimental data and to reveal the underlying mechanisms. The multi-scale model incorporates cochlear fluid dynamics, micromechanics of the organ of Corti and outer hair cell electromotility. We plan to show applications of this versatile model in three aspects: first, it is used to estimate intrinsic properties of mechanotransduction, such as the mechanotransduction sensitivity and adaptation, by comparing with two-tone suppression measurements; second, in vitro experimental data are extrapolated using an adapted model to show outer hair cell’s selective amplification could benefit tuning quality in vivo; third, we show that the change of dimension in the cochlear fluid space from the base to the apex indicates functional difference at the two regions.