An exploratory Study of EEG Alpha Oscillation and Pupil Dilation in Hearing-Aid Users During Effortful listening to Continuous Speech

Abstract

Individuals with hearing loss allocate cognitive resources to comprehend noisy speech in everyday life scenarios. Such a scenario could be when they are exposed to ongoing speech and need to sustain their attention for a rather long period of time, which requires listening effort. Two well-established physiological methods that have been found to be sensitive to identify changes in listening effort are pupillometry and electroencephalography (EEG). However, these measurements have been used mainly for momentary, evoked or episodic effort. The aim of this study was to investigate how sustained effort manifests in pupillometry and EEG, using continuous speech with varying signal-to-noise ratio (SNR). Eight hearing-aid users participated in this exploratory study and performed a continuous speech-in-noise task. The speech material consisted of 30-second continuous streams that were presented from loudspeakers to the right and left side of the listener (±30˚azimuth) in the presence of 4-talker background noise (+180˚azimuth). The participants were instructed to attend either to the right or left speaker and ignore the other in a randomized order with two different SNR conditions: 0 dB and-5 dB (the difference between the target and the competing talker). The effects of SNR on listening effort were explored objectively using pupillometry and EEG. The results showed larger mean pupil dilation and decreased EEG alpha power in the parietal lobe during the more effortful condition. This study demonstrates that both measures are sensitive to changes in SNR during continuous speech.

EEG Alpha Power and Pupil Diameter Reflect Endogenous Auditory Attention Switching and Listening Effort

“…Our alpha power results are consistent with previous sustained attention effort characterization (Seifi Ala et al, 2020). Where a lower magnitude alpha ERSP was associated with greater listening effort, we found a similar result in our most difficult experimental condition (at-will).…”

“…These states 30 can then be used to control stimuli enhancement which can improve the listener's experience. Altering the relative levels of attended and ignored stimuli can reduce listening effort and enhance attended stimuli entrainment (Seifi Ala et al, 2020;Presacco et al, 2019;Mirkovic et al, 2019). Speech enhancement has the capacity to improve listener quality of life in individuals of all ages and levels of hearing loss (Griffin et al, 2019;Liberman et al, 2016;Ciorba et al, 2012;Griffin et al, 2019).…”

Cortical alpha oscillations in cochlear implant users reflect subjective listening effort during speech-in-noise perception

“…As discussed, the “functional inhibition” hypothesis describes increased alpha power as consequence of inhibition in neural circuits, and decreased alpha power reflects neural engagement by reducing suppression [ 29 , 30 ]. Across studies, there have been observations of both an increase in in alpha power with speech listening difficulty (e.g., [ 27 , 28 , 32 , 56 ]) as well as decreases [ 33 , 57 ]. The difference in directions between these studies may be due to task-based differences or variability in listener strategies to complete the task, in line with the view that alpha power in auditory experiments changes as a function of the goals of the listeners, including selection of task-relevant stimuli [ 31 , 58 , 59 ].…”

EEG power spectral dynamics associated with listening in adverse conditions

“…Though many studies have pointed to more difficult conditions showing an increase in alpha power with more difficult listening conditions (Alhanbali et al, 2019;Dimitrijevic et al, 2019;Petersen et al, 2015;Winneke et al, 2020;Wisniewski et al, 2017;Wöstmann et al, 2015Wöstmann et al, , 2017, there are a number of other studies showing greater suppression of alpha power while listening to speech in a difficult compared to an easy condition. For instance, Hauswald et al (2020) found that parietal alpha power decreased with increased degradation to sentences through vocoding (also, see Hjortkjaer et al, 2020;Hunter, 2020;Seifi Ala et al, 2020). Part of the reason for between study differences may stem from differences in stimulus materials and the task.…”