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Khanna S.M., and Hao L.F.

Nonlinear vibrations of sensory cells in the inner ear
S.M. Khanna, and L.F. Hao
Columbia University, New York, USA

The apical turn of the cochlea was approached through the floor of the mouth. The bulla was opened. Access to the apex of the cochlea was obtained by removing the cochlear bone over about 1/3 of the turn,leaving the Reissner's membrane intact. The cochlea was coupled to the objective lens of a microscope interferometer with a thin rubber tube filled with tissue culture medium, thus forming a completely sealed system. The reticular lamina was visualized in the apical turn of a living guinea pig cochlea through the intact Reissner's membrane using a slit confocal microscope. Vibrations were measured with a confocal heterodyne interferometer,at selected locations. The position coordinates of each location were recorded. Vibration measurements in response to sound applied to the ear were made at Hensen's cells, outer hair cells,inner hair cells, and at the osseus spiral lamina, over a wide frequency and intensity range. Although the acoustical signal was a pure sinusoid, the response waveform was distorted. FFT of the time waveform showed a large array of harmonics. Dependance of the harmonics on the sound pressure and the cellular location is examined. The shape of the tuning curves is analysed at the fundamantal and the harmonic frequencies, to determine the position where the nonlinearity is most pronounced.

Research supported by Emil Capita fund, DRF and NOHR.



Book of abstracts
ICND-96