| Abstract: | Objective:To study the electromotility of the basilar membrane (BM) of guinea pigs in vivo. Methods :A pair of platinum-iridium wire electrodes were deposited into the holes drilled into the scala vestibuli and scala tympani on the basal turn of cochlea. The organ of Corti was stimulated with rectangular, constant current pulses . The displacement and velocity of BM were measured with laser doppler velocimeter. Results: The electrically elicited displacement of BM moved toward the scala where the electrode was positively charged. The waveform of BM displacement generally corresponded to the shape of the rectangular pulse of electric current. Ringing responses could be seen at the onset and offset of current pulse reflecting transient responses of the organ of Corti. In the cochlea of hearing-impaired or dead animal, direct current (DC) could still elicit a BM displacement but the ringing response was attenuated or disappeared. This phenomenon was probably due to metabolic disturbance in the damaged outer hair cells. In the sensitive cochlea, the BM vibration induced with direct current was similar to that induced by acoustic stimulation, and the BM moves in a traveling wave pattern. Conclusion: The findings of this experiment implicated that the DC stimulation of the cochlea conduces the contraction or elongation of OHCs. The electromotility of OHCs provides sufficient force to displace the BM. In the electrically stimulated normal cochlea,transient response of OHCs can induce resonant vibration at the same frequency as that Of the characteristic frequency (CF) of a partition in the BM. The vibration should be an active process of energy depletion associated with the cochlear amplifier.The vibration of BM can propagate to other partition of BM according to the traveling wave theory. This characteristic has laid the foundation for the electromotile hearing and electrically evoked otoacoustic emission. |
