On spontaneous oscillations of hair bundles in the amphibian papilla

Hair cells play a critical role in the auditory system, acting as key agents in active sound detection. Studying living hair cells ex vivo provides valuable insights into the mechanisms underlying sound detection. In this study, we investigated the nonlinear dynamics of hair bundle oscillations. We developed a robust ex vivo preparation of the amphibian papilla, a bullfrog's auditory organ, and observed spontaneous oscillations of hair bundles. These oscillations were classified into three distinct types: regular, bursting, and spiking. Regular oscillators demonstrated stable oscillations with a well-defined dominant frequency. Bursting oscillators alternated between periods of stable oscillatory activity and quiescence, while spiking oscillators were mostly quiescent, interrupted by brief oscillatory bursts. The oscillation frequencies ranged from 1 to 90 Hz, with approximately 95% of cells oscillating below 40 Hz.