Electrophysiologic effects following acute intracochlear direct current stimulation of the guinea pig cochlea.

Auditory brain stem responses to both acoustic (auditory brain stem response [ABR]) and electrical (electrically evoked auditory brain stem response [EABR]) stimuli, as well as the frequency-specific compound action potential (CAP), were recorded before and periodically following continuous intracochlear DC stimulation (2, 7, and 12 microA) for 2 hours in normal-hearing guinea pigs, by means of a banded intracochlear electrode array. Click-evoked ABR, frequency-specific CAP, and the EABR input-output function remained generally unchanged following stimulation at 2 microA DC. However, following stimulation at 7 and 12 microA, a significant decrement of the amplitude of the click-evoked ABR, frequency-specific CAP, and electrophonic component of the EABR was observed, while there was an increase in the amplitude of the EABR, associated with direct electrical stimulation of the auditory nerve.