Hair cells in the inner ear displayed remarkable sensitivity, frequency-tuning, and active amplifying characteristics. Spontaneous oscillations of hair cell bundles observed in several species were hypothesized to be a signature of the amplifying mechanism. Here we brought the system away from its natural state by mechanically overstimulating the hair cell bundle, then observe its recovery. Temporary suppression of spontaneous oscillations after stimulation indicates that there is a negative feedback. Characteristics of the recovery showed that there are two feedback mechanisms working on two different timescales. The shorter timescale, on the order of tens of milliseconds, is consistent with the myosin-based adaptation. The longer timescale, on the order of hundreds of milliseconds, is a feedback mechanism correlated to calcium concentration near the transduction complex. Bundle offset position induced and suppression of active motility are consistent with the variable gating spring model proposed previously.
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