A differentially amplified motion in the ear for near-threshold sound detection

Abstract

The ear is a remarkably sensitive pressure fluctuation detector. In guinea pigs, behavioral measurements indicate a minimum detectable sound pressure of ∼20 μPa at 16 kHz. Such faint sounds produce 0.1-nm basilar membrane displacements, a distance smaller than conformational transitions in ion channels. It seems that noise within the auditory system would swamp such tiny motions, making weak sounds imperceptible. Here we propose a new mechanism contributing to a resolution of this problem and validate it through direct measurement. We hypothesized that vibration at the apical side of hair cells is enhanced compared with that at the commonly measured basilar membrane side. Using in vivo optical coherence tomography, we demonstrated that apical-side vibrations peaked at a higher frequency, had different timing and were enhanced compared with those at the basilar membrane. These effects depend nonlinearly on the stimulus sound pressure level. The timing difference and enhancement of vibrations are important for explaining how the noise problem is circumvented.

DOI: 10.1038/nn.2827

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@inproceedings{Chen2011ADA, title={A differentially amplified motion in the ear for near-threshold sound detection}, author={Fangyi Chen and Dingjun Zha and Anders Fridberger and Jiefu Zheng and Niloy Choudhury and Steven L. Jacques and Ruikang K. Wang and Xiaorui Shi and Alfred L. Nuttall}, booktitle={Nature Neuroscience}, year={2011} }