Hair cells of the auditory and vestibular systems are capable of detecting sounds that induce sub-nanometer vibrations of the hair bundle, below the stochastic noise levels of the surrounding fluid. Hair cells of certain species are also known to oscillate without external stimulation, indicating the presence of an underlying active mechanism. We previously demonstrated that these spontaneous oscillations exhibit chaotic dynamics . By varying the Calcium concentration and the viscosity of the Endolymph solution , we are able to modulate the degree of chaos  in the hair cell dynamics . We find that the hair cell is most sensitive to a stimulus of small amplitude when it is poised in the weakly chaotic regime. Further, we show that the response time to a force step decreases with increasing levels of chaos. These results agree well with our numerical simulations of a chaotic Hopf oscillator and suggest that chaos may be responsible for the extreme sensitivity and temporal resolution of hair cells.
Hair cells of the auditory and vestibular systems are capable of detecting sounds that induce sub-nanometer vibrations of the hair bundle, below the stochastic noise levels of the surrounding fluid. Hair bundles of certain species are also known to oscillate without external stimulation, indicating the presence of an underlying active mechanism. We propose that chaotic dynamics enhance the sensitivity and temporal resolution of the hair bundle response, and provide experimental and theoretical evidence for this effect . By varying the viscosity and ionic composition of the surrounding fluid , we are able to modulate the degree of chaos observed in the hair bundle dynamics in vitro. We consistently find that the hair bundle is most sensitive to a stimulus of small amplitude when it is poised in the weakly chaotic regime. Further, we show that the response time to a force step decreases with increasing levels of chaos. These results agree well with our numerical simulations of a chaotic Hopf oscillator and suggest that chaos may be responsible for the sensitivity and temporal resolution of hair cells.
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cells
bundles
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previously demonstrated that these spontaneous oscillations exhibit chaotic dynamics
propose that chaotic dynamics enhance the sensitivity and temporal resolution of the hair bundle response, and provide experimental and theoretical evidence for this effect
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Calcium concentration and the viscosity of the Endolymph solution
viscosity and ionic composition of the surrounding fluid
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observed
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cell dynamics . We
bundle dynamics in vitro. We consistently
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cell
bundle
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extreme