Wave propagation in the mammalian cochlea

Using optical coherence tomography (OCT) we recorded the 3D spatial variation of cochlear partition vibration with unprecedented spatial resolution over a wide frequency span. The spatial vibration pattern varied systematically with both stimulus frequency and intensity. The longitudinal gradients in magnitude and phase yielded an accurate description of wave propagation in the cochlear partition, including the growth and decay of the wave, its wavelength, phase velocity and group velocity, and their variation with position and stimulus intensity. Especially at low intensities the wave had unusual dispersion characteristics. We interpret our findings in terms of fluid dynamics and discuss their contribution towards understanding cochlear frequency selectivity and dynamic range compression.

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