Abstract
ObjectiveThe aim of the present study was to investigate the pupillary response to word identification in cochlear implant (CI) patients. Authors hypothesized that when task difficulty (i.e., addition of background noise) increased, pupil dilation markers such as the peak dilation or the latency of the peak dilation would increase in CI users, as already observed in normal-hearing and hearing-impaired subjects.MethodsPupillometric measures in 10 CI patients were combined to standard speech recognition scores used to evaluate CI outcomes, namely, speech audiometry in quiet and in noise at +10 dB signal-to-noise ratio (SNR). The main outcome measures of pupillometry were mean pupil dilation, maximal pupil dilation, dilation latency, and mean dilation during return to baseline or retention interval. Subjective hearing quality was evaluated by means of one self-reported fatigue questionnaire, and the Speech, Spatial, and Qualities (SSQ) of Hearing scale.ResultsAll pupil dilation data were transformed to percent change in event-related pupil dilation (ERPD, %). Analyses show that the peak amplitudes for both mean pupil dilation and maximal pupil dilation were higher during the speech-in-noise test. Mean peak dilation was measured at 3.47 ± 2.29% noise vs. 2.19 ± 2.46 in quiet and maximal peak value was detected at 9.17 ± 3.25% in noise vs. 8.72 ± 2.93% in quiet. Concerning the questionnaires, the mean pupil dilation during the retention interval was significantly correlated with the spatial subscale score of the SSQ Hearing scale [r(8) = −0.84, p = 0.0023], and with the global score [r(8) = −0.78, p = 0.0018].ConclusionThe analysis of pupillometric traces, obtained during speech audiometry in quiet and in noise in CI users, provided interesting information about the different processes engaged in this task. Pupillometric measures could be indicative of listening difficulty, phoneme intelligibility, and were correlated with general hearing experience as evaluated by the SSQ of Hearing scale. These preliminary results show that pupillometry constitutes a promising tool to improve objective quantification of CI performance in clinical settings.
Highlights
For hearing-impaired people, listening and understanding speech in noisy situations is a difficult task, requiring substantial cognitive effort and often associated with increased self-reported fatigue (Alhanbali et al, 2017)
Twelve patients were originally included in the study, one of them had to be excluded from further analyses because of the poor quality of its pupillometry measure, and one more patient could only perform two lists of words per conditions
Studies implicating normal-hearing and hearing-impaired participants were conducted by Kramer et al (1997), who reported an elevation of peak pupil dilation evoked by the presentation of sentences in noise at various signal-to-noise ratios (SNRs), showing that dilation was proportional to the difficulty of the listening situation
Summary
For hearing-impaired people, listening and understanding speech in noisy situations is a difficult task, requiring substantial cognitive effort and often associated with increased self-reported fatigue (Alhanbali et al, 2017). Patients with cochlear implants (CIs) often experience high levels of listening effort in everyday life listening situations due, among other causes, to the spectral reduction that CIs impose on incoming sounds (Winn et al, 2015) This constant subjective experience of effortful listening is correlated with degraded speech-innoise performance and experienced hearing handicap (Alhanbali et al, 2018). As the severity of hearing loss increases, or as the environment becomes more challenging, hearing-impaired individuals are forced to engage more cognitive resources to direct attention and focus on fine-acoustic details of speech This leads to increased mental load and concentration needed to identify, recognize, and understand auditory information, negatively affecting other cognitive functions such as memory abilities (Ng et al, 2013; Zekveld et al, 2013). The hypothesis of a chronic excessive cognitive load existing in hearing-impaired patients is sustained by several recent researches, in which it has been demonstrated that even moderate levels of hearing loss constitute a risk factor for dementia and cognitive decline (Lin, 2011; Lin et al, 2013; Deal et al, 2017)
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