Outer hair cell receptor potentials reveal a local resonance in the mammalian cochlea

Sensory hair cells, including the sensorimotor outer hair cells, which enable the sensitive, sharply tuned responses of the mammalian cochlea, are excited by radial shear between the organ of Corti and the overlying tectorial membrane. It is not currently possible to measure directly in vivo mechanical responses in the narrow cleft between the tectorial membrane and organ of Corti over a wide range of stimulus frequencies and intensities. The mechanical responses can, however, be derived by measuring hair cell receptor potentials. We demonstrate that the seemingly complex frequency and intensity dependent behaviour of outer hair cell receptor potentials could be qualitatively explained by a two-degrees of freedom system with a local cochlear partition and tectorial membrane resonances strongly coupled by the outer hair cell stereocilia. A local minimum in the receptor potential below the characteristic frequency is always observed at the tectorial membrane resonance frequency which, however, might shift with stimulus intensity.