EEG power spectral dynamics associated with listening in adverse conditions

Wearing Hearing Protection Makes Me Worse at My Job: Impacts of Hearing Protection Use on Sensorimotor Tracking Performance

OBJECTIVES

Occupational hearing loss is a significant problem worldwide despite the fact that it can be mitigated by the wearing of hearing protection devices (HPDs). When surveyed, workers frequently report that worsened work performance while wearing HPDs is one reason why they choose not to wear them. However, there have been few studies to supplement these subjective reports with objective measures. Where they do exist, assessed performance measures have mostly characterized auditory situational awareness in gross terms (e.g., average speech comprehension scores over an entire session). The temporal dynamics of performance and HPD impacts on nonauditory aspects of work performance are largely unknown. In the present study, we aimed to fill this gap in the literature by measuring how HPD usage impacted sensorimotor tracking performance in relation to ongoing auditory events.

DESIGN

In two experiments, listeners heard commands sourced from the coordinate response measure (CRM) corpus (i.e., sentences of the form "Ready go to now"). These commands informed listeners of which of nine moving on-screen objects to track with a computer mouse (e.g., "blue four" refers the listener to a blue square). The commands were presented in background street noise and were heard under either "No HPD" or "HPD" conditions. In experiment 1, HPD wearing was simulated with a digital filter designed to mimic the attenuation profile of a passive HPD. In experiment 2, actual HPDs were worn by listeners. Continuous recording of tracking error allowed us to simultaneously examine how HPD wearing impacted speech comprehension, the accuracy of tracking, and how tracking accuracy varied as a function of time on task and ongoing auditory events (e.g., the presentation of a critical CRM sentence).

RESULTS

In both experiments, listeners spent less time tracking the correct object in the HPD condition. After trimming data to those time points in which the target object was known, worse performance was exhibited by the HPD condition than the No HPD condition. In the examination of the temporal dynamics of tracking error, it was apparent that differences arose strongly during the presentation of CRM sentences.

CONCLUSIONS

Workers' complaints of poorer performance while wearing HPDs are justified and extend beyond just diminished auditory situational awareness. The negative impact on nonauditory aspects of work performance may be strongest around critical listening periods. Addressing these aspects of performance will be an important part of addressing HPD nonuse in occupational settings.

The Effort of Repairing a Misperceived Word Can Impair Perception of Following Words, Especially for Listeners With Cochlear Implants

OBJECTIVES

In clinical and laboratory settings, speech recognition is typically assessed in a way that cannot distinguish accurate auditory perception from misperception that was mentally repaired or inferred from context. Previous work showed that the process of repairing misperceptions elicits greater listening effort, and that this elevated effort lingers well after the sentence is heard. That result suggests that cognitive repair strategies might appear successful when testing a single utterance but fail for everyday continuous conversational speech. The present study tested the hypothesis that the effort of repairing misperceptions has the consequence of carrying over to interfere with perception of later words after the sentence.

DESIGN

Stimuli were open-set coherent sentences that were presented intact or with a word early in the sentence replaced with noise, forcing the listener to use later context to mentally repair the missing word. Sentences were immediately followed by digit triplets, which served to probe carryover effort from the sentence. Control conditions allowed for the comparison to intact sentences that did not demand mental repair, as well as to listening conditions that removed the need to attend to the post-sentence stimuli, or removed the post-sentence digits altogether. Intelligibility scores for the sentences and digits were accompanied by time-series measurements of pupil dilation to assess cognitive load during the task, as well as subjective rating of effort. Participants included adults with cochlear implants (CIs), as well as an age-matched group and a younger group of listeners with typical hearing for comparison.

RESULTS

For the CI group, needing to repair a missing word during a sentence resulted in more errors on the digits after the sentence, especially when the repair process did not result in a coherent sensible perception. Sentences that needed repair also contained more errors on the words that were unmasked. All groups showed substantial increase of pupil dilation when sentences required repair, even when the repair was successful. Younger typical hearing listeners showed clear differences in moment-to-moment allocation of effort in the different conditions, while the other groups did not.

CONCLUSIONS

For CI listeners, the effort of needing to repair misperceptions in a sentence can last long enough to interfere with words that follow the sentence. This pattern could pose a serious problem for regular communication but would go overlooked in typical testing with single utterances, where a listener has a chance to repair misperceptions before responding. Carryover effort was not predictable by basic intelligibility scores, but can be revealed in behavioral data when sentences are followed immediately by extra probe words such as digits.

Alpha and theta oscillations on a visual strategic processing task in age-related hearing loss

Introduction

Emerging evidence suggests changes in several cognitive control processes in individuals with age-related hearing loss (ARHL). However, value-directed strategic processing, which involves selectively processing salient information based on high value, has been relatively unexplored in ARHL. Our previous work has shown behavioral changes in strategic processing in individuals with ARHL. The current study examined event-related alpha and theta oscillations linked to a visual, value-directed strategic processing task in 19 individuals with mild untreated ARHL and 17 normal hearing controls of comparable age and education.

Methods

Five unique word lists were presented where words were assigned high- or low-value based on the letter case, and electroencephalography (EEG) data was recorded during task performance.

Results

The main effect of the group was observed in early time periods. Specifically, greater theta synchronization was seen in the ARHL group relative to the control group. Interaction between group and value was observed at later time points, with greater theta synchronization for high- versus low-value information in those with ARHL.

Discussion

Our findings provide evidence for oscillatory changes tied to a visual task of value-directed strategic processing in individuals with mild untreated ARHL. This points towards modality-independent neurophysiological changes in cognitive control in individuals with mild degrees of ARHL and adds to the rapidly growing literature on the cognitive consequences of ARHL.

Effects of Background Noise and Linguistic Violations on Frontal Theta Oscillations During Effortful Listening

OBJECTIVES

Background noise and linguistic violations have been shown to increase the listening effort. The present study aims to examine the effects of the interaction between background noise and linguistic violations on subjective listening effort and frontal theta oscillations during effortful listening.

DESIGN

Thirty-two normal-hearing listeners participated in this study. The linguistic violation was operationalized as sentences versus random words (strings). Behavioral and electroencephalography data were collected while participants listened to sentences and strings in background noise at different signal to noise ratios (SNRs) (-9, -6, -3, 0 dB), maintained them in memory for about 3 sec in the presence of background noise, and then chose the correct sequence of words from a base matrix of words.

RESULTS

Results showed the interaction effects of SNR and speech type on effort ratings. Although strings were inherently more effortful than sentences, decreasing SNR from 0 to -9 dB (in 3 dB steps), increased effort rating more for sentences than strings in each step, suggesting the more pronounced effect of noise on sentence processing that strings in low SNRs. Results also showed a significant interaction between SNR and speech type on frontal theta event-related synchronization during the retention interval. This interaction indicated that strings exhibited higher frontal theta event-related synchronization than sentences at SNR of 0 dB, suggesting increased verbal working memory demand for strings under challenging listening conditions.

CONCLUSIONS

The study demonstrated that the interplay between linguistic violation and background noise shapes perceived effort and cognitive load during speech comprehension under challenging listening conditions. The differential impact of noise on processing sentences versus strings highlights the influential role of context and cognitive resource allocation in the processing of speech.

Theta and alpha oscillatory signatures of auditory sensory and cognitive loads during complex listening

The neuronal signatures of sensory and cognitive load provide access to brain activities related to complex listening situations. Sensory and cognitive loads are typically reflected in measures like response time (RT) and event-related potentials (ERPs) components. It's, however, strenuous to distinguish the underlying brain processes solely from these measures. In this study, along with RT- and ERP-analysis, we performed time-frequency analysis and source localization of oscillatory activity in participants performing two different auditory tasks with varying degrees of complexity and related them to sensory and cognitive load. We studied neuronal oscillatory activity in both periods before the behavioral response (pre-response) and after it (post-response). Robust oscillatory activities were found in both periods and were differentially affected by sensory and cognitive load. Oscillatory activity under sensory load was characterized by decrease in pre-response (early) theta activity and increased alpha activity. Oscillatory activity under cognitive load was characterized by increased theta activity, mainly in post-response (late) time. Furthermore, source localization revealed specific brain regions responsible for processing these loads, such as temporal and frontal lobe, cingulate cortex and precuneus. The results provide evidence that in complex listening situations, the brain processes sensory and cognitive loads differently. These neural processes have specific oscillatory signatures and are long lasting, extending beyond the behavioral response.

Finding tau rhythms in EEG: An independent component analysis approach

Tau rhythms are largely defined by sound responsive alpha band (~8-13 Hz) oscillations generated largely within auditory areas of the superior temporal gyri. Studies of tau have mostly employed magnetoencephalography or intracranial recording because of tau's elusiveness in the electroencephalogram. Here, we demonstrate that independent component analysis (ICA) decomposition can be an effective way to identify tau sources and study tau source activities in EEG recordings. Subjects (N = 18) were passively exposed to complex acoustic stimuli while the EEG was recorded from 68 electrodes across the scalp. Subjects' data were split into 60 parallel processing pipelines entailing use of five levels of high-pass filtering (passbands of 0.1, 0.5, 1, 2, and 4 Hz), three levels of low-pass filtering (25, 50, and 100 Hz), and four different ICA algorithms (fastICA, infomax, adaptive mixture ICA [AMICA], and multi-model AMICA [mAMICA]). Tau-related independent component (IC) processes were identified from this data as being localized near the superior temporal gyri with a spectral peak in the 8-13 Hz alpha band. These "tau ICs" showed alpha suppression during sound presentations that was not seen for other commonly observed IC clusters with spectral peaks in the alpha range (e.g., those associated with somatomotor mu, and parietal or occipital alpha). The choice of analysis parameters impacted the likelihood of obtaining tau ICs from an ICA decomposition. Lower cutoff frequencies for high-pass filtering resulted in significantly fewer subjects showing a tau IC than more aggressive high-pass filtering. Decomposition using the fastICA algorithm performed the poorest in this regard, while mAMICA performed best. The best combination of filters and ICA model choice was able to identify at least one tau IC in the data of ~94% of the sample. Altogether, the data reveal close similarities between tau EEG IC dynamics and tau dynamics observed in MEG and intracranial data. Use of relatively aggressive high-pass filters and mAMICA decomposition should allow researchers to identify and characterize tau rhythms in a majority of their subjects. We believe adopting the ICA decomposition approach to EEG analysis can increase the rate and range of discoveries related to auditory responsive tau rhythms.

Validity and reliability of self-reported and neural measures of listening effort

Listening effort can be defined as a measure of cognitive resources used by listeners to perform a listening task. Various methods have been proposed to measure this effort, yet their reliability remains unestablished, a crucial step before their application in research or clinical settings. This study encompassed 32 participants undertaking speech-in-noise tasks across two sessions, approximately a week apart. They listened to sentences and word lists at varying signal-to-noise ratios (SNRs) (-9, -6, -3 and 0 dB), then retaining them for roughly 3 s. We evaluated the test-retest reliability of self-reported effort ratings, theta (4-7 Hz) and alpha (8-13 Hz) oscillatory power, suggested previously as neural markers of listening effort. Additionally, we examined the reliability of correct word percentages. Both relative and absolute reliability were assessed using intraclass correlation coefficients (ICC) and Bland-Altman analysis. We also computed the standard error of measurement (SEM) and smallest detectable change (SDC). Our findings indicated heightened frontal midline theta power for word lists compared to sentences during the retention phase under high SNRs (0 dB, -3 dB), likely indicating a greater memory load for word lists. We observed SNR's impact on alpha power in the right central region during the listening phase and frontal theta power during the retention phase in sentences. Overall, the reliability analysis demonstrated satisfactory between-session variability for correct words and effort ratings. However, neural measures (frontal midline theta power and right central alpha power) displayed substantial variability, even though group-level outcomes appeared consistent across sessions.

Music in noise recognition: An EEG study of listening effort in cochlear implant users and normal hearing controls

Despite the plethora of studies investigating listening effort and the amount of research concerning music perception by cochlear implant (CI) users, the investigation of the influence of background noise on music processing has never been performed. Given the typical speech in noise recognition task for the listening effort assessment, the aim of the present study was to investigate the listening effort during an emotional categorization task on musical pieces with different levels of background noise. The listening effort was investigated, in addition to participants' ratings and performances, using EEG features known to be involved in such phenomenon, that is alpha activity in parietal areas and in the left inferior frontal gyrus (IFG), that includes the Broca's area. Results showed that CI users performed worse than normal hearing (NH) controls in the recognition of the emotional content of the stimuli. Furthermore, when considering the alpha activity corresponding to the listening to signal to noise ratio (SNR) 5 and SNR10 conditions subtracted of the activity while listening to the Quiet condition-ideally removing the emotional content of the music and isolating the difficulty level due to the SNRs- CI users reported higher levels of activity in the parietal alpha and in the homologous of the left IFG in the right hemisphere (F8 EEG channel), in comparison to NH. Finally, a novel suggestion of a particular sensitivity of F8 for SNR-related listening effort in music was provided.

Energetic and informational masking place dissociable demands on listening effort: Evidence from simultaneous electroencephalography and pupillometrya)

The task of processing speech masked by concurrent speech/noise can pose a substantial challenge to listeners. However, performance on such tasks may not directly reflect the amount of listening effort they elicit. Changes in pupil size and neural oscillatory power in the alpha range (8-12 Hz) are prominent neurophysiological signals known to reflect listening effort; however, measurements obtained through these two approaches are rarely correlated, suggesting that they may respond differently depending on the specific cognitive demands (and, by extension, the specific type of effort) elicited by specific tasks. This study aimed to compare changes in pupil size and alpha power elicited by different types of auditory maskers (highly confusable intelligible speech maskers, speech-envelope-modulated speech-shaped noise, and unmodulated speech-shaped noise maskers) in young, normal-hearing listeners. Within each condition, the target-to-masker ratio was set at the participant's individually estimated 75% correct point on the psychometric function. The speech masking condition elicited a significantly greater increase in pupil size than either of the noise masking conditions, whereas the unmodulated noise masking condition elicited a significantly greater increase in alpha oscillatory power than the speech masking condition, suggesting that the effort needed to solve these respective tasks may have different neural origins.

Effortful listening produces both enhancement and suppression of alpha in the EEG

Introduction

Adverse listening conditions can drive increased mental effort during listening. Neuromagnetic alpha oscillations (8-13 Hz) may index this listening effort, but inconsistencies regarding the direction of the relationship are abundant. We performed source analyses on high-density EEG data collected during a speech-on-speech listening task to address the possibility that opposing alpha power relationships among alpha producing brain sources drive this inconsistency.

Methods

Listeners (N=20) heard two simultaneously presented sentences of the form: Ready go to now. They either reported the color/number pair of a "Baron" call sign sentence (active: high effort), or ignored the stimuli (passive: low effort). Independent component analysis (ICA) was used to segregate temporally distinct sources in the EEG.

Results

Analysis of independent components (ICs) revealed simultaneous alpha enhancements (e.g., for somatomotor mu ICs) and suppressions (e.g., for left temporal ICs) for different brain sources. The active condition exhibited stronger enhancement for left somatomotor mu rhythm ICs, but stronger suppression for central occipital ICs.

Discussion

This study shows both alpha enhancement and suppression to be associated with increases in listening effort. Literature inconsistencies could partially relate to some source activities overwhelming others in scalp recordings.

Neural α Oscillations and Pupil Size Differentially Index Cognitive Demand under Competing Audiovisual Task Conditions

Cognitive demand is thought to modulate two often used, but rarely combined, measures: pupil size and neural α (8-12 Hz) oscillatory power. However, it is unclear whether these two measures capture cognitive demand in a similar way under complex audiovisual-task conditions. Here we recorded pupil size and neural α power (using electroencephalography), while human participants of both sexes concurrently performed a visual multiple object-tracking task and an auditory gap detection task. Difficulties of the two tasks were manipulated independent of each other. Participants' performance decreased in accuracy and speed with increasing cognitive demand. Pupil size increased with increasing difficulty for both the auditory and the visual task. In contrast, α power showed diverging neural dynamics: parietal α power decreased with increasing difficulty in the visual task, but not with increasing difficulty in the auditory task. Furthermore, independent of task difficulty, within-participant trial-by-trial fluctuations in pupil size were negatively correlated with α power. Difficulty-induced changes in pupil size and α power, however, did not correlate, which is consistent with their different cognitive-demand sensitivities. Overall, the current study demonstrates that the dynamics of the neurophysiological indices of cognitive demand and associated effort are multifaceted and potentially modality-dependent under complex audiovisual-task conditions.SIGNIFICANCE STATEMENT Pupil size and oscillatory α power are associated with cognitive demand and effort, but their relative sensitivity under complex audiovisual-task conditions is unclear, as is the extent to which they share underlying mechanisms. Using an audiovisual dual-task paradigm, we show that pupil size increases with increasing cognitive demands for both audition and vision. In contrast, changes in oscillatory α power depend on the respective task demands: parietal α power decreases with visual demand but not with auditory task demand. Hence, pupil size and α power show different sensitivity to cognitive demands, perhaps suggesting partly different underlying neural mechanisms.

Combining Multiple Psychophysiological Measures of Listening Effort: Challenges and Recommendations

About one-third of all recently published studies on listening effort have used at least one physiological measure, providing evidence of the popularity of such measures in listening effort research. However, the specific measures employed, as well as the rationales used to justify their inclusion, vary greatly between studies, leading to a literature that is fragmented and difficult to integrate. A unified approach that assesses multiple psychophysiological measures justified by a single rationale would be preferable because it would advance our understanding of listening effort. However, such an approach comes with a number of challenges, including the need to develop a clear definition of listening effort that links to specific physiological measures, customized equipment that enables the simultaneous assessment of multiple measures, awareness of problems caused by the different timescales on which the measures operate, and statistical approaches that minimize the risk of type-I error inflation. This article discusses in detail the various obstacles for combining multiple physiological measures in listening effort research and provides recommendations on how to overcome them.

Speech to noise ratio improvement induces nonlinear parietal phase synchrony in hearing aid users

Objectives

Comprehension of speech in adverse listening conditions is challenging for hearing-impaired (HI) individuals. Noise reduction (NR) schemes in hearing aids (HAs) have demonstrated the capability to help HI to overcome these challenges. The objective of this study was to investigate the effect of NR processing (inactive, where the NR feature was switched off, vs. active, where the NR feature was switched on) on correlates of listening effort across two different background noise levels [+3 dB signal-to-noise ratio (SNR) and +8 dB SNR] by using a phase synchrony analysis of electroencephalogram (EEG) signals.

Design

The EEG was recorded while 22 HI participants fitted with HAs performed a continuous speech in noise (SiN) task in the presence of background noise and a competing talker. The phase synchrony within eight regions of interest (ROIs) and four conventional EEG bands was computed by using a multivariate phase synchrony measure.

Results

The results demonstrated that the activation of NR in HAs affects the EEG phase synchrony in the parietal ROI at low SNR differently than that at high SNR. The relationship between conditions of the listening task and phase synchrony in the parietal ROI was nonlinear.

Conclusion

We showed that the activation of NR schemes in HAs can non-linearly reduce correlates of listening effort as estimated by EEG-based phase synchrony. We contend that investigation of the phase synchrony within ROIs can reflect the effects of HAs in HI individuals in ecological listening conditions.