[An experimental study on the auditory brainstem response to electrical stimulation of the cochlea]

This animal research was undertaken to study some important issues for cochlear implantation. This included investigations of 1) the difference in the auditory brainstem responses (ABRs) to extra- and intracochlear electrical stimulations. 2) stimulus parameters and ABRs to a bipolar intracochlear stimulation, and 3) electrode placements and ABRs. There were no distinct differences in waveforms and input-output curves of ABRs between extracochlear electrical stimulation and intracochlear bipolar stimulation of the cochlea. Changes in amplitude and latency of ABRs were investigated at changes of the pulse amplitude or the pulse width of stimulating electric rectangular waves. Increase in the pulse amplitude or the pulse width resulted in increase of the amplitude of ABRs and no increase in the ABR latency. This results showed the amplitude of ABR was dependent on the amount of electricity; coulomb. Electrically evoked ABRs were studied for stimulations at different sites of the cochlea. The ABR elicited with a bipolar electrode placed at the third turn of the cochlea had a longer latency of each peak of ABR waves than the one at the basal turn. This indicates that electrical stimulation with a bipolar electrode can give rise to a localized excitation in the cochlea and a latency change along the longitudinal axis of the cochlea, so that it suggests a multichannel cochlea implant system can transmit more information as a spacious pattern than a single channel system.