Physics of the Auditory System
Dolores Bozovic a
a Department of Physics and Astronomy and California NanoSystems Institute, University of California Los Angeles
Proceedings of Neural Interfaces and Artificial Senses (NIAS)
Online, Spain, 2021 September 22nd - 23rd
Organizers: Tiago Costa and Georgios Spyropoulos
Invited Speaker, Dolores Bozovic, presentation 005
Publication date: 13th September 2021

The auditory system contains a remarkable biological sensor that exhibits nanometer-scale sensitivity of mechanical detection. The first step in auditory processing is performed by hair cells, which act as transducers that convert minute mechanical vibrations into electrical signals that can be sent to the brain. The hair cells operate in a viscous environment, but can nevertheless sustain oscillations, amplify incoming signals, and even exhibit spontaneous motility. Theoretical models have proposed that a hair cell constitutes a nonlinear system, and allow us to describe and predict how they respond to incoming sound. Our experiments explore the physical mechanisms behind the detection of very weak signals, and describe them using models based on dynamical systems theory. We demonstrate the presence of chaos in the innate motility of active bundles, and show both theoretically and experimentally that it enhances the sensitivity of detection. We propose that these cells utilize weakly chaotic dynamics to combine sensitive response with high temporal resolution. Secondly, we explore the neural mechanisms that control the responsiveness of the cell. Specifically, we show that the sensitivity of the mechanical response in vitro is reduced by efferent activity, indicating that these neurons modulate the biological control parameters that fine-tune the dynamic state of the hair cell.

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