[Suppression of spontaneous AC potentials in guinea pig cochlea by external tones]

Spontaneous electrical oscillations (AC potentials) were observed in the cochlea of three guinea pigs without any exposure to noise or drugs. The AC potentials disappeared completely within one minute after the cessation of artificial ventilation, and were suppressed by presenting external tones to the ear. As the frequency of the external tone was displaced toward that of the spontaneous oscillation, the signals were increasingly suppressed. Exposure to intense tone produced residual suppression of the AC potentials for several minutes. The time course of recovery from the suppression appeared to be similar to that in the noise induced temporary threshold shift measured psychoacoustically. From these results, it was concluded that the spontaneous AC potentials in the guinea pig cochlea were generated by the active mechanical vibration system at the area on the basilar membrane where the characteristic frequency corresponded to that of the AC potentials.