Average spectrum of spontaneous activity at the round window modified by sedation, anesthesia and salicylate

Abstract
The electrophysiological signal recorded at the round window of the cochlea reflects sensory and neural activity of the inner ear. Besides acoustically evoked responses, sometimes temporally averaged, which are usual means of functional assessement ; recordings obtained in silent conditions and spectrally averaged reflect spontaneous auditory nerve activity as recently demonstrated. In this paper it is shown that averaged spectrum of spontaneous activity (ASSA) at the round window of guinea pigs, with permanently implanted electrodes, differs in awake versus sedated or anesthetized conditions. This casts some doubt upon the physiological significance of single-unit analyses of spontaneous auditory nerve activity. It is ago shown in this paper that ASSA is modified by administration of salicylate even at a dose which does not induce threshold elevation. These observations set ASSA at the round window as a convenient and very sensitive physiological measure of spontaneous sensory-neural activity and provide much more convicing foundations for physiological exploration of tinnitus in animal models.