Auditory Adaptation and Fatigue in Cochlear Potentials

Abstract

Urethane-anaesthetized guinea pigs -were exposed to noise and pure-tone stimulation. Cochlear potentials were recorded immediately after the exposure through electrodes cemented into the third turn. Stimulation with low intensities did not show any influence on the amplitude of the cochlear potentials. Only by exposure to intensities exceeding 95 db (re human threshold) was it possible to demonstrate a decrease in amplitude.1 This decrease is assumed to be due to fatigue, not to adaptation. The recovery time after high-intensity stimulation for less than 1 minute was 1 to 5 minutes. Longer stimulation resulted in a considerable increase in the recovery time. The effect on the cochlear potentials was found to be independent of the stimulus frequency on stimulation with pure tones of the frequencies 500, 1000 and 2000 cps. Stimulation with white noise affected, in particular, the low frequencies. Stimulation with noise containing the frequencies 5000-20,000 cps exerted a greater influence on the cochlear potentials than white noise of the same intensity.