Electrically evoked whole-nerve action potentials: parametric data from the cat

In a companion paper Brown et al., J. Acoust. Soc. Am. 88, 1385-1391 (1990)], a method for recording the electrically evoked whole-nerve action potential in human cochlear implant users was reported. The procedure for recording the response requires that two biphasic current pulses, a "masker" and a "probe," be presented at a rate and level sufficient to drive the auditory nerve into a refractory state. The present study was designed to assess the sensitivity of that recording technique to variations in stimulation parameters. The experiments described in this paper demonstrate that: (1) the EAP as recorded in the cat is triphasic and is defined by two negative peaks occurring at latencies of approximately 0.26 and 0.82 ms; (2) EAP amplitude is independent of the level of the masker stimulus for current levels equal to or greater than the current level of the probe stimulus; and (3) the time course of recovery of the EAP from the refractory state is stable over a range of both probe and masker current levels.