Mechanical tuning characteristics of the hearing organ measured at the sensory cells in the gerbil temporal bone preparation.

The micromechanical behaviour of the inner ear in response to sound stimulation was investigated in an in vitro preparation of the gerbil temporal bone. Using laser heterodyne interferometry it was possible to measure the vibration responses directly at the level of the sensory and supporting cells within the hearing organ rather than from the underlying basilar membrane as has been done in previous studies. There was a tuned mechanical response of the cellular structures within the hearing organ. The resonance frequency measured at cells in the apical (third) turn was around 200Hz. The frequency of the mechanical tuning varied along the length of the cochlea. In the second turn the resonance frequency was around 500-700Hz. The cellular response in the second turn was more sharply tuned as compared to the response in the apical turn. In both cochlear turns the amplitude of the vibratory response changed with the cellular location radially across the hearing organ.