Title: Chaotic Dynamics Enhance the Sensitivity of Inner Ear Hair Cells,
Abstract: 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.