Interaural Pitch-Discrimination Range Effects for Bilateral and Single-Sided-Deafness Cochlear-Implant Users

Abstract

By allowing bilateral access to sound, bilateral cochlear implants (BI-CIs) or unilateral CIs for individuals with single-sided deafness (SSD; i.e., normal or near-normal hearing in one ear) can improve sound localization and speech understanding in noise. Spatial hearing in the horizontal plane is primarily conveyed by interaural time and level differences computed from neurons in the superior olivary complex that receive frequency-matched inputs. Because BI-CIs and SSD-CIs do not necessarily convey frequency-matched information, it is critical to understand how to align the inputs to CI users. Previous studies show that interaural pitch discrimination for SSD-CI listeners is highly susceptible to contextual biases, questioning its utility for establishing interaural frequency alignment. Here, we replicate this finding for SSD-CI listeners and show that these biases also extend to BI-CI listeners. To assess the testing-range bias, three ranges of comparison electrodes (BI-CI) or pure-tone frequencies (SSD-CI) were tested: full range, apical/ lower half, or basal/upper half. To assess the reference bias, the reference electrode was either held fixed throughout a testing block or randomly chosen from three electrodes (basal end, middle, or apical end of the array). Results showed no effect of reference electrode randomization, but a large testing range bias; changing the center of the testing-range shifted the pitch match by an average

Evaluating the Impact of Age, Acoustic Exposure, and Electrical Stimulation on Binaural Sensitivity in Adult Bilateral Cochlear Implant Patients

“…Other methods exist for place matching, including finding the interaural electrode pair that yields the “best ITD” sensitivity using psychophysical testing and measurement of the binaural interaction component in the brainstem [ 43 , 44 ]. Although pitch-matching can be influenced by conditions tested and the task parameters [ 45 ], our approach usually leads to an interaural pair of electrodes that has relatively good ITD sensitivity in adults [ 41 , 44 , 46 ].…”

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

“…One way to achieve this is to perform electric-acoustic pitch matching experiments where subjects compare the pitch of a CI electrode with that evoked by acoustic stimuli differing in their spectral content. Previous pitch matching studies have shown that such measurements are difficult to conduct and usually produce very variable data (Carlyon et al, 2010; Goupell et al, 2019). This variability may have several causes, including methodological limitations as well as the choice of the acoustic stimulus type.…”

“…A wide range of methods have been used in the literature to compare the pitches of electric and acoustic stimuli. These include magnitude estimation (Vermeire et al, 2008; Plant et al, 2014), the method of constant stimuli (Boex et al, 2006; Reiss et al, 2007, 2015; Goupell et al, 2019), the method of adjustment (Green et al, 2012; Rader et al, 2016; Maarefvand et al, 2017; Tan et al, 2017) and various kinds of adaptive forced-choice procedures (Reiss et al, 2007; Schatzer et al, 2014; Vermeire et al, 2015; Peters et al, 2016). Carlyon et al (2010) tested several of these methods and showed they could all be potentially contaminated by different kinds of non-sensory biases.…”

“…Carlyon et al (2010) showed that the choice of this acoustic frequency range could have a large influence on the results. For example, in one subject, the same electrode could be matched to frequencies separated by more than two thirds of an octave for two different acoustic ranges, suggesting that the subjects were not performing real pitch comparisons but rather, and perhaps unconsciously, were basing their judgments on the frequency of the acoustic stimuli only: when the acoustic frequency was high relative to the range, they decided to judge it as “higher” than the electric stimulus, whereas when it was low relative to the range, they judged it as “lower” than the electric stimulus (see also Goupell et al, 2019). This range bias may be very problematic because the range of acoustic frequencies is usually dictated either by the amount of residual hearing of the subjects or by a priori estimation of the electric pitch by the experimenter, inferred from radiological findings or from preliminary pitch matches obtained before the experiment.…”

Pleasantness Ratings for Harmonic Intervals With Acoustic and Electric Hearing in Unilaterally Deaf Cochlear Implant Patients

“…Landsberger et al (2019) reported significantly higher musical sound quality ratings when SSD-CI participants listened with acoustic and electric hearing than with acoustic hearing alone. SSD-CI patients represent a unique patient population with which to compare auditory perception between acoustic and electric hearing within participants [e.g., inter-aural pitch matching (Vermeire et al, 2008, 2015; Goupell et al, 2019); sound quality differences between acoustic and electric hearing (Vermeire et al, 2013; Dorman et al, 2017); melodic interval distortion (Todd et al, 2017)]. SSD-CI patients would be similarly valuable for comparing harmonic interval perception between acoustic and electric hearing.…”