Mammalian Auditory Hair Cell Bundle Stiffness Affects Frequency Tuning by Increasing Coupling along the Length of the Cochlea

Publication date: 5 June 2018
Source:Cell Reports, Volume 23, Issue 10
Author(s): James B. Dewey, Anping Xia, Ulrich Müller, Inna A. Belyantseva, Brian E. Applegate, John S. Oghalai
The stereociliary bundles of cochlear hair cells convert mechanical vibrations into the electrical signals required for auditory sensation. While the stiffness of the bundles strongly influences mechanotransduction, its influence on the vibratory response of the cochlear partition is unclear. To assess this, we measured cochlear vibrations in mutant mice with reduced bundle stiffness or with a tectorial membrane (TM) that is detached from the sensory epithelium. We found that reducing bundle stiffness decreased the high-frequency extent and sharpened the tuning of vibratory responses obtained postmortem. Detaching the TM further reduced the high-frequency extent of the vibrations but also lowered the partition's resonant frequency. Together, these results demonstrate that the bundle's stiffness and attachment to the TM contribute to passive longitudinal coupling in the cochlea. We conclude that the stereociliary bundles and TM interact to facilitate passive-wave propagation to more apical locations, possibly enhancing active-wave amplification in vivo.

Graphical abstract

Teaser

The mechanical properties of the cochlear partition determine its vibratory response to sound. Dewey et al. demonstrate that the outer hair cell stereociliary bundles' stiffness and attachment to the tectorial membrane influence the partition's passive vibratory response. The stereociliary bundles facilitate the propagation of cochlear waves to more apical regions.


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