Nonequilibrium limit cycle oscillators: fluctuations in hair bundle dynamics

TL;DR

This paper presents a theoretical framework for understanding stochastic fluctuations in limit cycle oscillators, with applications to hair cell dynamics in the inner ear, highlighting phase diffusion and spectral properties under noise.

Contribution

It introduces a general interpretation method for stochastic limit cycle oscillators and applies it to biological hair cell data, revealing noise-induced spectral features and cycle deformation.

Findings

Phase of the oscillator diffuses under noise.

Deviations orthogonal to the cycle show Lorentzian spectra.

Application to hair cell data confirms theoretical predictions.

Abstract

We develop a framework for the general interpretation of the stochastic dynamical system near a limit cycle. Such quasi-periodic dynamics are commonly found in a variety of nonequilibrium systems, including the spontaneous oscillations of hair cells in the inner ear. We demonstrate quite generally that in the presence of noise, the phase of the limit cycle oscillator will diffuse while deviations in the directions locally orthogonal to that limit cycle will display the Lorentzian power spectrum of a damped oscillator. We identify two mechanisms by which these stochastic dynamics can acquire a complex frequency dependence, and discuss the deformation of the mean limit cycle as a function of temperature. The theoretical ideas are applied to data obtained from spontaneously oscillating hair cells of the amphibian sacculus.