Kevin J. Munro

Listening effort and fatigue: what exactly are we measuring? A British Society of Audiology Cognition in Hearing Special Interest Group 'white paper'.

Abstract Objective: There is growing interest in the concepts of listening effort and fatigue associated with hearing loss. However, the theoretical underpinnings and clinical meaning of these concepts are unclear. This lack of clarity reflects both the relative immaturity of the field and the fact that research studies investigating listening effort and fatigue have used a variety of methodologies including self-report, behavioural, and physiological measures. Design: This discussion paper provides working definitions for listening effort and listening-related fatigue. Using these definitions as a framework, methodologies to assess these constructs are reviewed. Results: Although each technique attempts to characterize the same construct (i.e. the clinical presentation of listening effort and fatigue), different assumptions are often made about the nature of these phenomena and their behavioural and physiological manifestations. Conclusion: We suggest that researchers consider these assumptions when interpreting their data and, where possible, make predictions based on current theoretical knowledge to add to our understanding of the underlying mechanisms of listening effort and listening-related fatigue. Foreword Following recent interest in the cognitive involvement in hearing, the British Society of Audiology (BSA) established a Special Interest Group on Cognition in Hearing in May 2013. In an exploratory group meeting, the ambiguity surrounding listening effort and fatigue was discussed. To address this problem, the group decided to develop a ‘white paper’ on listening effort and fatigue. This is a discussion document followed by an international set of commentaries from leading researchers in the field. An approach was made to the editor of the International Journal of Audiology who agreed to this suggestion. This paper, and the associated commentaries that follow, are the result.

Hearing loss and cognition: the role of hearing AIDS, social isolation and depression.

Hearing loss is associated with poor cognitive performance and incident dementia and may contribute to cognitive decline. Treating hearing loss with hearing aids may ameliorate cognitive decline. The purpose of this study was to test whether use of hearing aids was associated with better cognitive performance, and if this relationship was mediated via social isolation and/or depression. Structural equation modelling of associations between hearing loss, cognitive performance, social isolation, depression and hearing aid use was carried out with a subsample of the UK Biobank data set (n = 164,770) of UK adults aged 40 to 69 years who completed a hearing test. Age, sex, general health and socioeconomic status were controlled for as potential confounders. Hearing aid use was associated with better cognition, independently of social isolation and depression. This finding was consistent with the hypothesis that hearing aids may improve cognitive performance, although if hearing aids do have a positive effect on cognition it is not likely to be via reduction of the adverse effects of hearing loss on social isolation or depression. We suggest that any positive effects of hearing aid use on cognition may be via improvement in audibility or associated increases in self-efficacy. Alternatively, positive associations between hearing aid use and cognition may be accounted for by more cognitively able people seeking and using hearing aids. Further research is required to determine the direction of association, if there is any direct causal relationship between hearing aid use and better cognition, and whether hearing aid use results in reduction in rates of cognitive decline measured longitudinally.

The effect of speech presentation level on measurement of auditory acclimatization to amplified speech

A systematic improvement in auditory performance over time, following a change in the acoustic information available to the listener (that cannot be attributed to task, procedural or training effects) is known as auditory acclimatization. However, there is conflicting evidence concerning the existence of auditory acclimatization; some studies show an improvement in performance over time while other studies show no change. In an attempt to resolve this conflict, speech recognition abilities of 16 subjects with bilateral sensorineural hearing impairments were measured over a 12-week period following provision of a monaural hearing instrument for the first time. The not-fitted ear was used as the control. Three presentation levels were used representing quiet, normal, and raised speech. The results confirm the presence of acclimatization. In addition, the results show that acclimatization is evident at the higher presentation levels but not at the lowest.

Listening effort at signal-to-noise ratios that are typical of the school classroom

Abstract Objective: The aim of the study was to measure listening effort at typical classroom signal-to-noise ratios (SNRs). Design: Listening effort was measured using a dual task paradigm. Participants repeated monosyllabic words presented in a background of childrens chatter (primary task) at SNRs that are considered typical of the school classroom environment (quiet, +4, 0, −4 dB) while simultaneously rehearsing sets of five digits for recall (secondary task). High listening effort requires greater cognitive resources and is associated with reduced performance on the secondary task. Study sample: Thirty one normal-hearing children (9-12 years). Results: Performance was generally maintained on the listening task when multitasking; however, performance decreased on the secondary recall task, especially at the more negative SNRs. Conclusions: This demonstrates that considerable listening effort is required when listening at SNRs that are typical of the school classroom. Sumario Objetivo: El propósito de este estudio fue medir el esfuerzo para escuchar en un salón de clases con un nivel señal/ruido típico Diseño: Se midió el esfuerzo para escuchar utilizando un paradigma de doble tarea. Los participantes repitieron palabras monosilábicas presentadas sobre un ruido de fondo de niños hablando (tarea primaria) con una tasa señal/ruido considerada como típica del ambiente en un salón de clases (silencio, +4, 0, −4 dB) mientras que simultáneamente se ejercitaba la memorización de grupos de cinco dígitos (tarea secundaria). El esfuerzo elevado requiere grandes habilidades cognitivas y se asocia con un desempeño pobre en la tarea secundaria. Muestra: Treinta y un niños normoyentes (9 a 11 años de edad) Resultados: El desempeño generalmente se mantuvo en la tarea de escuchar durante la realización de varias tareas; sin embargo, el desempeño disminuyó en la tarea de recordar, especialmente en el extremo negativo de SNR. Conclusiones: Esto demuestra que se requiere un esfuerzo considerable para escuchar cuando hay un SNR típico del salón de clases.

Adaptive plasticity in brainstem of adult listeners following earplug-induced deprivation

Previous research has shown that loudness perception is modified in adult listeners following 2 weeks of continuous sensory deprivation or stimulation [Formby, C. et al. (2003). J. Acoust. Soc. Am. 114, 55-58]. However, it is not known if the auditory system undergoes physiological changes or if the listeners simply recalibrate their behavioral criteria such that they become more, or less, conservative following sensory deprivation and stimulation, respectively. The results of this study, comparing threshold of the middle ear acoustic reflex in the two ears of adult listeners after use of a unilateral earplug, are consistent with adaptive plasticity. Acoustic reflexes were measured at a lower sound pressure level in the ear that had been plugged for 7 days. Thus, the effect is consistent with a central gain mechanism mediated by a process within the brainstem.

Reorganization of the Adult Auditory System: Perceptual and Physiological Evidence From Monaural Fitting of Hearing Aids

Changes in the sensory environment modify our sensory experience and may result in experience-related or learning-induced reorganization within the central nervous system. Hearing aids change the sensory environment by stimulating a deprived auditory system; therefore, they may be capable of inducing changes within the central auditory system. Examples of studies that have shown hearing aid induced perceptual and/or physiological changes in the adult human auditory system are discussed. Evidence in the perceptual domain is provided by studies that have investigated (a) speech perception, (b) intensity discrimination, and (c) loudness perception. Evidence in the physiological domain is provided by studies that have investigated acoustic reflex thresholds and event-related potentials. Despite the controversy in the literature concerning the rate, extent, and clinical significance of the acclimatization effect, there is irrefutable evidence that the deprived auditory system of some listeners can be modified with hearing aid experience.

Relation between Speech-in-Noise Threshold, Hearing Loss and Cognition from 40–69 Years of Age

Background Healthy hearing depends on sensitive ears and adequate brain processing. Essential aspects of both hearing and cognition decline with advancing age, but it is largely unknown how one influences the other. The current standard measure of hearing, the pure-tone audiogram is not very cognitively demanding and does not predict well the most important yet challenging use of hearing, listening to speech in noisy environments. We analysed data from UK Biobank that asked 40–69 year olds about their hearing, and assessed their ability on tests of speech-in-noise hearing and cognition. Methods and Findings About half a million volunteers were recruited through NHS registers. Respondents completed ‘whole-body’ testing in purpose-designed, community-based test centres across the UK. Objective hearing (spoken digit recognition in noise) and cognitive (reasoning, memory, processing speed) data were analysed using logistic and multiple regression methods. Speech hearing in noise declined exponentially with age for both sexes from about 50 years, differing from previous audiogram data that showed a more linear decline from <40 years for men, and consistently less hearing loss for women. The decline in speech-in-noise hearing was especially dramatic among those with lower cognitive scores. Decreasing cognitive ability and increasing age were both independently associated with decreasing ability to hear speech-in-noise (0.70 and 0.89 dB, respectively) among the population studied. Men subjectively reported up to 60% higher rates of difficulty hearing than women. Workplace noise history associated with difficulty in both subjective hearing and objective speech hearing in noise. Leisure noise history was associated with subjective, but not with objective difficulty hearing. Conclusions Older people have declining cognitive processing ability associated with reduced ability to hear speech in noise, measured by recognition of recorded spoken digits. Subjective reports of hearing difficulty generally show a higher prevalence than objective measures, suggesting that current objective methods could be extended further.

Reversible Induction of Phantom Auditory Sensations through Simulated Unilateral Hearing Loss

Tinnitus, a phantom auditory sensation, is associated with hearing loss in most cases, but it is unclear if hearing loss causes tinnitus. Phantom auditory sensations can be induced in normal hearing listeners when they experience severe auditory deprivation such as confinement in an anechoic chamber, which can be regarded as somewhat analogous to a profound bilateral hearing loss. As this condition is relatively uncommon among tinnitus patients, induction of phantom sounds by a lesser degree of auditory deprivation could advance our understanding of the mechanisms of tinnitus. In this study, we therefore investigated the reporting of phantom sounds after continuous use of an earplug. 18 healthy volunteers with normal hearing wore a silicone earplug continuously in one ear for 7 days. The attenuation provided by the earplugs simulated a mild high-frequency hearing loss, mean attenuation increased from <10 dB at 0.25 kHz to >30 dB at 3 and 4 kHz. 14 out of 18 participants reported phantom sounds during earplug use. 11 participants presented with stable phantom sounds on day 7 and underwent tinnitus spectrum characterization with the earplug still in place. The spectra showed that the phantom sounds were perceived predominantly as high-pitched, corresponding to the frequency range most affected by the earplug. In all cases, the auditory phantom disappeared when the earplug was removed, indicating a causal relation between auditory deprivation and phantom sounds. This relation matches the predictions of our computational model of tinnitus development, which proposes a possible mechanism by which a stabilization of neuronal activity through homeostatic plasticity in the central auditory system could lead to the development of a neuronal correlate of tinnitus when auditory nerve activity is reduced due to the earplug.

Hearing in middle age: A population snapshot of 40- to 69-year olds in the united kingdom

Objectives: To report population-based prevalence of hearing impairment based on speech recognition in noise testing in a large and inclusive sample of U.K. adults aged 40 to 69 years. The present study is the first to report such data. Prevalence of tinnitus and use of hearing aids is also reported. Design: The research was conducted using the UK Biobank resource. The better-ear unaided speech reception threshold was measured adaptively using the Digit Triplet Test (n = 164,770). Self-report data on tinnitus, hearing aid use, noise exposure, as well as demographic variables were collected. Results: Overall, 10.7% of adults (95% confidence interval [CI] 10.5–10.9%) had significant hearing impairment. Prevalence of tinnitus was 16.9% (95%CI 16.6–17.1%) and hearing aid use was 2.0% (95%CI 1.9–2.1%). Odds of hearing impairment increased with age, with a history of work- and music-related noise exposure, for lower socioeconomic background and for ethnic minority backgrounds. Males were at no higher risk of hearing impairment than females. Conclusions: Around 1 in 10 adults aged 40 to 69 years have substantial hearing impairment. The reasons for excess risk of hearing impairment particularly for those from low socioeconomic and ethnic minority backgrounds require identification, as this represents a serious health inequality. The underuse of hearing aids has altered little since the 1980s, and is a major cause for concern.

Cognitive predictors of perceptual adaptation to accented speech

The present study investigated the effects of inhibition, vocabulary knowledge, and working memory on perceptual adaptation to accented speech. One hundred young, normal-hearing adults listened to sentences spoken in a constructed, unfamiliar accent presented in speech-shaped background noise. Speech Reception Thresholds (SRTs) corresponding to 50% speech recognition accuracy provided a measurement of adaptation to the accented speech. Stroop, vocabulary knowledge, and working memory tests were performed to measure cognitive ability. Participants adapted to the unfamiliar accent as revealed by a decrease in SRTs over time. Better inhibition (lower Stroop scores) predicted greater and faster adaptation to the unfamiliar accent. Vocabulary knowledge predicted better recognition of the unfamiliar accent, while working memory had a smaller, indirect effect on speech recognition mediated by vocabulary score. Results support a top-down model for successful adaptation to, and recognition of, accented speech; they add to recent theories that allocate a prominent role for executive function to effective speech comprehension in adverse listening conditions.