Individual Variations in Effort: Assessing Pupillometry for the Hearing Impaired

Abstract

Assessing effort in speech comprehension for hearing-impaired (HI) listeners is important, as effortful processing of speech can limit their hearing rehabilitation. We examined the measure of pupil dilation in its capacity to accommodate the heterogeneity that is present within clinical populations by studying lexical access in users with sensorineural hearing loss, who perceive speech via cochlear implants (CIs). We compared the pupillary responses of 15 experienced CI users and 14 age-matched normal-hearing (NH) controls during auditory lexical decision. A growth curve analysis was applied to compare the responses between the groups. NH listeners showed a coherent pattern of pupil dilation that reflects the task demands of the experimental manipulation and a homogenous time course of dilation. CI listeners showed more variability in the morphology of pupil dilation curves, potentially reflecting variable sources of effort across individuals. In follow-up analyses, we examined how speech perception, a task that relies on multiple stages of perceptual analyses, poses multiple sources of increased effort for HI listeners, wherefore we might not be measuring the same source of effort for HI as for NH listeners. We argue that interindividual variability among HI listeners can be clinically meaningful in attesting not only the magnitude but also the locus of increased effort. The understanding of individual variations in effort requires experimental paradigms that (a) differentiate the task demands during speech comprehension, (b) capture pupil dilation in its time course per individual listeners, and (c) investigate the range of individual variability present within clinical and NH populations.

Pupillometry Assessment of Speech Recognition and Listening Experience in Adult Cochlear Implant Patients

“…Percent change in event-related pupil dilation (ERPD) were then calculated, per each individual trial and participant, according to the formula described in Wagner et al (2019), % change ERPD = 100x (observation -baseline)/baseline. Baseline was defined as the one-second period preceding the onset of the noise (i.e., time 0 in all graphical representations).…”

“…They further showed that this later-occurring, and longer-lasting “repair” process observed in CI users, could easily be perturbed, and even canceled by later-occurring sounds, especially when these were intelligible utterances ( Winn and Moore, 2018 ). More recently, Wagner et al (2019) reported that CI users showed increased variability in their evoked pupil responses compared to matched normal-hearing participants, suggesting that this variability could be clinically meaningful and could be an index of processing load in individual patients. Even if these first studies highlight the interest of pupillometry to explore cognitive processing involved during listening tasks in CI users, the potential of pupillary responses as a clinical objective tool to evaluate CI performance remains to be explored.…”

Anticipatory Baseline Pupil Diameter Is Sensitive to Differences in Hearing Thresholds

“…In studies such as these, task-related changes in pupil diameter are typically expressed as a difference from a prestimulus baseline in the form of a brief silent period prior to presentation of the speech stimulus. The pupil size measured in this pre-stimulus window is referred to as the baseline pupil diameter (BPD; Kuchinsky et al, 2013;Koelewijn et al, 2015;Winn and Moore, 2018;Wagner et al, 2019).…”

The relationship between talker acoustics, intelligibility, and effort in degraded listening conditions

“…We observed that mean pupil dilation and baseline pupil size generally declined over the course of a block (48 sentences). This decline might reflect task familiarization, but also fatigue (Wagner et al, 2019). Given the role of attention in adapting to noise-vocoded speech (Huyck and Johnsrude, 2012), we expected to see a more sustained baseline pupil size across trials.…”