Of Mice and Chickens: Revisiting the RC Time Constant Problem

TL;DR

This paper explores how outer hair cells in the ear utilize piezoelectric resonance to overcome the RC time constant limitation, enhancing frequency selectivity in mammalian hearing.

Contribution

It introduces the concept of piezoelectric resonance in outer hair cells as a solution to the RC time constant problem in auditory frequency tuning.

Findings

Piezoelectric resonance can nullify membrane capacitance.

Outer hair cells leverage mechanical resonance for frequency selectivity.

The RC problem is addressed through a novel resonance mechanism.

Abstract

Avian hair cells depend on electrical resonance for frequency selectivity. The upper bound of the frequency range is limited by the RC time constant of hair cells because the sharpness of tuning requires that the resonance frequency must be lower than the RC roll-off frequency. In contrast, tuned mechanical vibration of the inner ear is the basis of frequency selectivity of the mammalian ear. This mechanical vibration is supported by outer hair cells (OHC) with their electromotility based on piezoelectricity, which is driven by the receptor potential. Thus it is also subjected to the RC time constant problem. Association of OHCs with a system with mechanical resonance leads to piezoelectric resonance. This resonance can nullify the membrane capacitance and solves the RC time constant problem for OHCs.