Polarity Effects on Neural Responses of the Electrically Stimulated Auditory Nerve at Different Cochlear Sites

摘要

Three experiments studied the effect of stimulus polarity on the Electrically Evoked Compound Action Potential (ECAP) obtained with the masker-probe paradigm on different sites along the cochlea in cochlear implant (CI) users. Experiment 1 which used a biphasic cathodic-1st (BIC) masker showed that ECAP N1 peak latencies were longer for BIC than for anodic-1st (BIA) probes on all electrodes under test. Relative differences in latency between BIA and BIC probes as well as absolute latencies increased when the phase duration (PD) of both masker and probe increased. Experiment 2 used maskers with long inter-phase gaps, and, by manipulating the polarity of the second phase (closest in time to the biphasic probe), showed that only an anodic phase could mask the probe response. Experiment 3 used both masker and probe with the same polarity. ECAP responses were only obtained when the polarity was anodic. Results of all experiments suggest that the anodic polarity is the most effective one and that its effectiveness can be generalized to different sites along the cochlea.