The Effect of Stimulus Polarity on the Relation Between Pitch Ranking and ECAP Spread of Excitation in Cochlear Implant Users

Abstract

Although modern cochlear implants (CIs) use cathodic-leading symmetrical biphasic pulses to stimulate the auditory nerve, a growing body of evidence suggests that anodic-leading pulses may be more effective. The positive polarity has been shown to produce larger electrically evoked compound action potential (ECAP) amplitudes, steeper slope of the amplitude growth function, and broader spread of excitation (SOE) patterns. Polarity has also been shown to influence pitch perception. It remains unclear how polarity affects the relation between physiological SOE and psychophysical pitch perception. Using a within-subject design, we examined the correlation between performance on a pitch-ranking task and spatial separation between SOE patterns for anodic and cathodic-leading symmetric biphasic pulses for 14 CI ears. Overall, there was no effect of polarity on either ECAP SOE patterns, pitch ranking performance, or the relation between the two. This result is likely due the use of symmetric biphasic pulses, which may have reduced the size of the effect previously observed for pseudomonophasic pulses. Further research is needed to determine if a pseudomonophasic stimulus might further improve the relation between physiology and pitch perception.