Multiple-Timescale Dynamics Underlying Spontaneous Oscillations of Saccular Hair Bundles

Spontaneous oscillations displayed by hair bundles of the bullfrog sacculus have complex temporal profiles, not fully captured by single limit-cycle descriptions. Quiescent intervals are typically interspersed with oscillations, leading to a bursting-type behavior. Temporal characteristics of the oscillation are strongly affected by imposing a mechanical load or by the application of a steady-state deflection to the resting position of the bundle. Separate spectral components of the spontaneous motility are differently affected by increases in the external calcium concentration. We use numerical modeling to explore the effects of internal parameters on the oscillatory profiles, and to reproduce the experimental modulation induced by mechanical or ionic manipulation.