Weighting of Spectral and Temporal Cues with n-of-m Cochlear Implant Strategies Depends on Voice Pitch.

Purpose: The relative contributions of spectral and temporal cues to voice pitch perception in cochlear implant (CI) users remain unclear. This study aimed to directly quantify these contributions in dynamic speech stimuli with clinical n-of-m processors.

Methods: Fundamental frequency (F0) discrimination was measured using consonant-vowel triplets in two experiments. Sixteen (eight female) postlingually deaf adult CI users with n-of-m strategies participated in experiment 1 (F0 range 76-242 Hz). Five (three female) also participated in experiment 2 (F0 range 242-768 Hz). Stimuli were presented acoustically or via direct stimulation. For the latter, pulse patterns were recorded in advance using the participants' own settings and modified to suppress temporal or spectral cues.

Results: In experiment 1, temporal suppression drastically decreased F0 discrimination. Spectral suppression decreased the F0 discrimination of only some participants, while spectral and temporal suppression combined decreased performance further. Conversely, in experiment 2, spectral suppression caused a drop in F0 discrimination while temporal suppression had no effect. Analysis of the unaltered stimuli showed that with increasing F0, temporal cues decreased and spectral cues increased in availability.

Conclusion: The novel prerecording and streaming method effectively combines realistic stimulation patterns with precise control at the pulse level. Our results indicate that in voice pitch discrimination, postlingually deafened adult CI users rely predominantly on the most available cue, which depends on the F0. Temporal cues dominate when discriminating F0s within the typical male to female voice range, while spectral cues tend to dominate within the typical female to child voice range.