Voltage noise power spectra reflect ciliary movement frequencies in statocyst hair cells

Voltage noise from statocyst hair cells of Hermissenda crassicornis was analyzed. In 40% of the cells the power spectrum was non-regular with a hump (broad peak) near 7 Hz, which is the mean frequency of the inherent movement of the hairs. When the cells were cooled or heated with chloral hydrate, treatments known to slow or stop hair movement, the hump either was shifted towards lower frequencies and greatly reduced, or it disappeared entirely. Removal of extracellular sodium, an ion that carried much of the current which produced voltage noise, also eliminated the hump, but did not affect hair movement. The results indicate that most of the voltage noise is due not to hair movement itself, but to collision of statoconia with the motile hairs. Thus, the power spectra reflect the frequency of these events.