Fluctuation-response theorem for the active noisy oscillator of the hair-cell bundle

TL;DR

This study investigates the active, noisy oscillations of hair-cell bundles in the ear, demonstrating a generalized fluctuation-dissipation theorem applicable to non-equilibrium biological systems.

Contribution

It shows that a generalized fluctuation-dissipation theorem holds for active biological oscillators when the correct degrees of freedom are considered.

Findings

Violation of the standard fluctuation-dissipation theorem observed.

Generalized fluctuation-dissipation theorem validated within experimental accuracy.

Active processes maintain the system out of equilibrium.

Abstract

The hair bundle of sensory cells in the vertebrate ear provides an example of a noisy oscillator close to a Hopf bifurcation. The analysis of the data from both spontaneous and forced oscillations shows a strong violation of the fluctuation-dissipation theorem, revealing the presence of an underlying active process that keeps the system out of equilibrium. Nevertheless, we show that a generalized fluctuation-dissipation theorem, valid for non-equilibrium steady states, is fulfilled within the limits of our experimental accuracy and computational approximations, when the adequate conjugate degrees of freedom are chosen.