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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Neurosci. | doi: 10.3389/fnins.2019.01119

Pitch Matching in Cochlear Implant Users with Single-Sided Deafness: Effects of Electrode Position and Acoustic Stimulus Type

  • 1Audiological Acoustics, Department of Otorhinolaryngology, University Hospital Frankfurt, Germany
  • 2Aix-Marseille University, Centrale Marseille, CNRS, UPR7051 Laboratoire de mécanique et d'acoustique (LMA), France

Previous studies in patients with single-sided deafness (SSD) have reported results of pitch comparisons between electric stimulation of their cochlear implant (CI) and acoustic stimulation presented to their near-normal hearing contralateral ear. These comparisons typically used sinusoids, although the percept elicited by electric stimulation may be closer to a wideband stimulus. Furthermore, it has been shown that pitch comparisons between sounds with different timbres is a difficult task and subjected to various types of range biases. The present study aims to introduce a method to minimize non-sensory bias, and to investigate the effect of different acoustic stimulus types on the frequency and variability of the electric-acoustic pitch matches.
Pitch matches were collected from 13 CI users with SSD using the binary search procedure. Electric stimulation was presented at either an apical or a middle electrode position, at a rate of 800 pps. Acoustic stimulus types were sinusoids (SINE), 1/3-octave wide narrow bands of Gaussian noises (NBN), or 1/3-octave wide pulse spreading harmonic complexes (PSHC). On the one hand, NBN and PSHC are presumed to better mimic the spread of excitation produced by a single-electrode stimulation than SINE. On the other hand, SINE and PSHC contain less inherent fluctuations than NBN and may therefore provide a temporal pattern closer to that produced by a constant-amplitude electric pulse train.
Analysis of mean pitch match variance showed no differences between stimulus types. However, mean pitch matches showed effects of electrode position and stimulus type, with the middle electrode always matched to a higher frequency than the apical one (p < .001), and significantly higher across-subject pitch matches for PSHC compared with SINE (p = .017). Mean pitch matches for all stimulus types were better predicted by place-dependent characteristic frequencies (CFs) based on an organ of Corti map compared with a spiral ganglion map. CF predictions were closest to pitch matches with SINE for the apical electrode position, and conversely with NBN or PSHC for the middle electrode position. These results provide evidence that the choice of acoustic stimulus type can have a significant effect on electric-acoustic pitch matching.

Keywords: cochlear implant, Pitch Perception, single-sided deafness, simulation, pulse-spreading harmonic complex, Binary Search Procedure, non-sensory bias

Received: 03 May 2019; Accepted: 03 Oct 2019.

Copyright: © 2019 Adel, Nagel, Weissgerber, Baumann and Macherey. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mr. Youssef Adel, University Hospital Frankfurt, Audiological Acoustics, Department of Otorhinolaryngology, Frankfurt, Germany, youssef.adel@uni-tuebingen.de