Auditory Adaptation in Nerve Action Potentials Recorded from the Cochlea in Guinea Pigs

Abstract

Urethane-anaesthetised guinea pigs were exposed to noise and pure-tone stimulation of low intensity (35-80 db). The effect of the exposure was measured on neural click responses recorded with gross electrodes from the basal turn of the cochlea. A depression of the neural activity, evidenced by a reduction of the amplitude of the click response, was demonstrated when the clicks were masked by white noise of moderate intensity. The poststimulatory effect was recorded after exposure to white noise or pure tones of varying frequencies. The recovery time was measured. The recovery time for the second of a pair of clicks was also recorded. A depression could not be provoked by stimulation of the contralateral ear, for which reason central inhibition could be excluded. The phenomenon is assumed to be the electrophysiological equivalent to auditory adaptation.