Listening Effort in Cochlear Implant Users: The Effect of Speech Intelligibility, Noise Reduction Processing, and Working Memory Capacity on the Pupil Dilation Response

Abstract

Purpose: This study aimed to evaluate the effect of speech recognition performance, working memory capacity (WMC), and a noise reduction algorithm (NRA) on listening effort as measured with pupillometry in cochlear implant (CI) users while listening to speech in noise. Method: Speech recognition and pupil responses (peak dilation, peak latency, and release of dilation) were measured during a speech recognition task at three speech-to-noise ratios (SNRs) with an NRA in both on and off conditions. WMC was measured with a reading span task. Twenty experienced CI users participated in this study. Results: With increasing SNR and speech recognition performance, (a) the peak pupil dilation decreased by only a small amount, (b) the peak latency decreased, and (c) the release of dilation after the sentences increased. The NRA had no effect on speech recognition in noise or on the peak or latency values of the pupil response but caused less release of dilation after the end of the sentences. A lower reading span score was associated with higher peak pupil dilation but was not associated with peak latency, release of dilation, or speech recognition in noise. Conclusions: In CI users, speech perception is effortful, even at higher speech recognition scores and high SNRs, indicating that CI users are in a chronic state of increased effort in communication situations. The application of a clinically used NRA did not improve speech perception, nor did it reduce listening effort. Participants with a relatively low WMC exerted relatively more listening effort but did not have better speech reception thresholds in noise.

Impact of SNR, peripheral auditory sensitivity, and central cognitive profile on the psychometric relation between pupillary response and speech performance in CI users

“…It is no news that the same SNR level does not yield same speech recognition scores among NH, HI, and CI listeners, so comparing directly 'tipping points' in terms of their corresponding SNR levels is not thorough enough. Regardless of the difference in SNR levels, NH and HI listeners typically showed the 'tipping point' on their pupillometry psychometric curves at around 40-50% speech intelligibility (Ohlenforst et al, 2017;Wendt et al, 2017;Dingemanse and Goedegebure, 2022). This suggests that even though NH and HI listeners have different speech recognition, they tend to disengage from the task at similar intelligibility level.…”

“…This study is motivated by the authors intending to resolve anecdotal reports on using pupillometry with CI users in the clinical settings. Past studies have examined CI users' pupillary response at various points on the psychometric curve (Russo et al, 2020;Stronks et al, 2021;Dingemanse and Goedegebure, 2022), however our study is the first to date to approximate a more complete curve by testing multiple points and considering a wide range of individual differences.…”

“…Such variability may be due to many factors including, but not limited to, the age of implantation, duration of deafness, duration of CI use, the limited spectral and temporal resolution of the signal, quality of the electrode-neural interface, and the narrow electric dynamic range of the output signals codified at the stimulation electrodes (Blamey et al, 2012;Holden et al, 2013;Dorman and Gifford, 2017;Boisvert et al, 2020). CI users often complain of the high listening effort required in those situations, even when speech communication is successful (Hughes and Galvin, 2013;Winn et al, 2015;Pichora-Fuller et al, 2016;Winn, 2016;Rapport et al, 2020;Dingemanse and Goedegebure, 2022;Winn and Teece, 2022). Eventually, this sustained and unresolved high effort status associated with hearing could have negative consequence on social communication and cognitive health for CI users (Nachtegaal et al, 2009;Pichora-Fuller et al, 2015;Herrmann and Johnsrude, 2020;Shukla et al, 2020).…”

“…In addition to biological and audiological factors, individual cognitive capacities, i.e., top-down abilities, have been shown to affct both the speech and listening effort outcomes in CI users (Pisoni, 2000;Amini et al, 10.3389/fnins.2023.1307777 Frontiers in Neuroscience 03 frontiersin.org 2023; Beckers et al, 2023). Working memory (WM) is a factor of most interest due to its association with speech performance in pediatric and adult CI users, HI and old NH listeners (Pisoni and Cleary, 2003;Akeroyd, 2008;Rudner et al, 2011;Besser et al, 2013;Füllgrabe and Rosen, 2016;Kestens et al, 2021;Dingemanse and Goedegebure, 2022). WM is a limited-capacity system with simultaneous storage and processing mechanisms whereby encoded information is analyzed and manipulated (Daneman and Carpenter, 1980).…”

Listening effort and fatigue among cochlear implant users: a scoping review

“…On the other hand, it has already been suggested that a slower speaking rate and the availability of a relevant semantic context may reduce listening effort in CI users (58,59). Furthermore, listening effort seems to decrease with increasing SNR levels (12,42,60) although, even in favorable listening conditions, listening is still an effort for CI users (60). Considering that listening remains an effort for CI users and the higher listening effort reported in CI compared to controls with normal hearing, it is interesting to further explore the influencing factors as there is still much ambiguity about it.…”