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Tripolar Stimulation Improves Polyphonic Pitch Detection in Cochlear Implant Users

Chari, Divya A.; Jiradejvong, Patpong; Limb, Charles J.

doi: 10.1097/MAO.0000000000002061
COCHLEAR IMPLANTS

Objective: Cochlear implant (CI) users struggle with pitch perception, particularly for polyphonic stimuli. Tripolar (TP) stimulation has been proposed as a way to mitigate the broad spread of neural excitation observed in traditional monopolar (MP) stimulation, thereby potentially improving perception of polyphony.

Study Design: Prospective cohort study.

Setting: Tertiary academic center.

Patients: Eleven postlingually deafened adults with Advanced Bionics HiRes 90K CIs.

Intervention(s): We performed pitch ranking and polyphonic pitch detection testing under MP and TP configurations. To assess pitch ranking, users were asked to identify the higher pitch between two notes. In polyphonic pitch detection, users were asked to distinguish between single-pitch tones and two-pitch tones. Two-pitch stimuli consisted of one pitch of three base frequencies (392, 523, 740 Hz) and a second pitch between 1 and 12 semitones above the base frequency.

Main Outcome Measure: Pitch performance was analyzed as a function of current delivery mode (tripolar vs. monopolar), with smaller semitone interval pitch resolution indicating better performance.

Results: In pitch ranking tasks, TP configuration did not confer an advantage over MP stimulation. In polyphonic perception, however, tripolar stimulation improved performance in lower frequencies and resulted in statistically significant (p < 0.05) improvement at the highest base frequency, 740 Hz.

Conclusions: These data suggest that TP configuration may confer an advantage in the perception of polyphonic pitch, which may not be observed in monophonic pitch ranking tasks. Since music is typically polyphonic, such data offer approaches toward improving perception of real-world musical stimuli.

Department of Otolaryngology – Head and Neck Surgery, University of California San Francisco, San Francisco, California

Address correspondence and reprint requests to Charles J. Limb, M.D., Department of Otolaryngology, University of California, San Francisco, 2233 Post Street, 3rd floor, San Francisco, CA 94115; E-mail: Charles.Limb@ucsf.edu

This study was supported scientifically by Advanced Bionics.

C.L. serves as a consultant for and received research support from Advanced Bionics, Med El and Oticon Medical. C.L. also serves as the Chief Medical Officer of Spiral Therapeutics. The remaining authors disclose no conflicts of interest.

Copyright © 2019 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company