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

Abstract

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 biases, 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 < 0.001), and significantly higher across-subject pitch matches for PSHC compared with SINE (p = 0.017). 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.

Interaural place-of-stimulation mismatch estimates using CT scans and binaural perception, but not pitch, are consistent in cochlear-implant users

“…One possible reason for the disparate results across studies is that the procedures (Jensen et al, 2021) and stimuli (Adel et al, 2019) employed had a large impact on the observed results, which questions whether these measurements reflect place of stimulation. In the current study, the surprising tonotopic pattern of pitch-match estimates for SSD-CI listeners (positive at the apex, negative at the base, Fig.…”

“…To address the question of plasticity to interaural place mismatch more directly, the current study explicitly compared interaural place-pitch perception and tuning curves for interaural time-difference (ITD) sensitivity to estimates of electrode position derived from computed-tomography (CT) scans. Previous studies have compared pitch matching and ITD discrimination for BI-CI users (Hu and Dietz, 2015), or pitch matching and CT scans for SSD-CI users (Schatzer et al, 2014; Adel et al, 2019), but the three measurements have never been compared. We hypothesized that evidence for plasticity would differ between the two perceptual measures: binaural sensitivity would not show evidence of plasticity, with ITD-based estimates aligning closely with CT-based estimates of electrode location, while interaural place pitch would show evidence of plasticity, with pitch-based estimates aligning more closely with clinical center frequencies (CFs) in the CI map.…”

Temporal Pitch Perception in Cochlear-Implant Users: Channel Independence in Apical Cochlear Regions

“…Previous studies suggested that pitch matching of electric and contralateral acoustic stimuli can be a difficult task ( Adel et al., 2019 ; Carlyon et al., 2010 ; Schatzer et al., 2014 ). Carlyon et al.…”

“…In both loudness balancing and pitch matching experiments, pairs of stimuli were presented with a 300-ms gap. The suitability of different types of acoustic stimuli including pure tones, narrow band noise, and filtered harmonic stimuli in electric-acoustic pitch matching experiments has been analyzed in the literature ( Adel et al., 2019 ; Carlyon et al., 2010 ). Adel et al.…”

The sound sensation of a pure tone in cochlear implant recipients with single-sided deafness

“…The 250 Hz pure tone (es20) activated the most apical electrode only (electrode 20), while the 1050 Hz pure tone (es14) activated electrode 14 and 13. Such tasks have been performed in previous studies [7], [8], [17][18][19][20][21][22]. However, in these studies, the pulse rate was set to a level either below 40 or above 700 pps in order to minimize the temporal pitch cues.…”