Abstract
Experimental records of active bundle motility are used to demonstrate the presence of a low-dimensional chaotic attractor in hair cell dynamics. Dimensionality tests from dynamic systems theory are applied to estimate the number of independent variables sufficient for modelling the hair cell response. Poincaré maps are constructed to observe a quasiperiodic transition from chaos to order with increasing amplitudes of mechanical forcing. The onset of this transition is accompanied by a reduction of Kolmogorov entropy in the system and an increase in transfer entropy between the stimulus and the hair bundle, indicative of signal detection. A simple theoretical model is used to describe the observed chaotic dynamics. The model exhibits an enhancement of sensitivity to weak stimuli when the system is poised in the chaotic regime. We propose that chaos may play a role in the hair cell’s ability to detect low-amplitude sounds.
Highlights
The auditory system exhibits remarkable sensitivity, for it is capable of detecting sounds that elicit motions in the Å regime, below the stochastic noise levels in the inner ear[1]
Numerical simulations predicted a small positive Lyapunov exponent, indicative of weak chaos in the innate bundle motion[12]. Another numerical study that explored a 12-dimensional model of hair cell dynamics showed the presence of chaos and proposed that the sensitivity of detection to very low-frequency stimuli would be optimal in a chaotic regime[13]
The theoretical models have mostly focused on stable dynamics, exploring either the limit cycle regime, or the quiescent regime in the vicinity of a bifurcation
Summary
The auditory system exhibits remarkable sensitivity, for it is capable of detecting sounds that elicit motions in the Å regime, below the stochastic noise levels in the inner ear[1]. The innate motility has been proposed to play a role in amplifying incoming signals, aiding in the sensitivity of detection While their role in vivo has not been fully established, spontaneous oscillations constitute an important signature of the active processes operant in a hair cell, and provide an experimental probe for studying the underlying biophysical mechanisms[6]. Numerical simulations predicted a small positive Lyapunov exponent, indicative of weak chaos in the innate bundle motion[12] Another numerical study that explored a 12-dimensional model of hair cell dynamics showed the presence of chaos and proposed that the sensitivity of detection to very low-frequency stimuli would be optimal in a chaotic regime[13]. Use the theoretical model to demonstrate that a system poised in the chaotic regime shows an enhanced sensitivity to weak stimuli
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