The diversity of speech-perception difficulties among autistic individuals.

Background & aims: Communicative and sensory differences are core autistic traits, yet speech-perception abilities and difficulties among autistic individuals remain poorly understood. Laboratory studies have produced mixed and inconclusive results, in part because of the lack of input from autistic individuals in defining the hypotheses and shaping the methods used in this field of research. Little in-depth qualitative research on autistic experiences of speech perception has been published, yet such research could form the basis for better laboratory research, for improved understanding of autistic experiences, and for the development of interventions. Existing qualitative research describes widespread autistic listening differences with significant impacts, but these results rely on data gathered via oral interviews in a small sample. The present study addresses these limitations and employs a mixed-methods approach to explore autistic listening experiences. Methods: We gathered survey data from 79 autistic individuals aged 18-55 without diagnosed hearing loss. The questionnaire included 20 closed-set questions on listening abilities and difficulties and three free-text questions on listening experiences. The free-text questions underwent deductive content analysis using a framework composed of themes from previous interview data on listening experiences (including auditory differences, contributing factors, impacts, and coping strategies). Concepts in the free-text data that were not part of the analysis framework were analyzed inductively. Results: In the closed-set data, participants reported listening difficulties in most specified environments, but complex background sounds and particularly background voices caused the most difficulty. Those who reported listening difficulties expressed having substantially greater difficulties than other people the same age. Participants indicated multiple impacts from listening difficulties, most prominently in their social lives. Concepts in the free-text data strongly supported previous interview data on listening differences and factors that affect listening ability, especially the diversity of types of listening difficulties. Consistent with the closed-set data, background-sound complexity and concurrent voices were especially troubling. Some concepts in the free-text data were novel, particularly difficulties with remote, broadcast, and recorded audio, prompting the creation of new themes. Conclusions: Both forms of data indicate widespread listening differences-predominantly listening difficulties-affecting most autistic adults. Diverse types of listening difficulty are evident, potentially indicating heterogeneous underlying mechanisms, and complexity of background noise is consistently identified as an important factor. Listening difficulties are said to have substantial and varied impacts. Autistic adults are keen to share coping strategies, which are varied and usually self-devised. Implications: Based on both the quantitative and qualitative results, we provide recommendations to improve future research and support the autistic community. The data-revealing types of listening difficulties can guide better quantitative research into underlying mechanisms. Such research should take into account potential heterogeneity in listening difficulties. Suggestions for optimized collection of self-report data are also offered. Additionally, our results could be used to improve societal understanding of autistic listening differences and to create beneficial interventions for and with autistic individuals. Moreover, given the willingness of the autistic community to share coping strategies, systematic collation of these strategies could form the basis for self-help and clinical guidance.

Corrigendum: The effect of lifetime noise exposure and aging on speech-perception-in-noise ability and self-reported hearing symptoms: an online study.

[This corrects the article DOI: 10.3389/fnagi.2022.890010.].

Noise Exposure in Palestinian Workers Without a Diagnosis of Hearing Impairment: Relations to Speech-Perception-in-Noise Difficulties, Tinnitus, and Hyperacusis.

PURPOSE: Many workers in developing countries are exposed to unsafe occupational noise due to inadequate health and safety practices. We tested the hypotheses that occupational noise exposure and aging affect speech-perception-in-noise (SPiN) thresholds, self-reported hearing ability, tinnitus presence, and hyperacusis severity among Palestinian workers. METHOD: Palestinian workers (N = 251, aged 18-70 years) without diagnosed hearing or memory impairments completed online instruments including a noise exposure questionnaire; forward and backward digit span tests; hyperacusis questionnaire; the short-form Speech, Spatial and Qualities of Hearing Scale (SSQ12); the Tinnitus Handicap Inventory; and a digits-in-noise (DIN) test. Hypotheses were tested via multiple linear and logistic regression models, including age and occupational noise exposure as predictors, and with sex, recreational noise exposure, cognitive ability, and academic attainment as covariates. Familywise error rate was controlled across all 16 comparisons using the Bonferroni-Holm method. Exploratory analyses evaluated effects on tinnitus handicap. A comprehensive study protocol was preregistered. RESULTS: Nonsignificant trends of poorer SPiN performance, poorer self-reported hearing ability, greater prevalence of tinnitus, greater tinnitus handicap, and greater severity of hyperacusis as a function of higher occupational noise exposure were observed. Greater hyperacusis severity was significantly predicted by higher occupational noise exposure. Aging was significantly associated with higher DIN thresholds and lower SSQ12 scores, but not with tinnitus presence, tinnitus handicap, or hyperacusis severity. CONCLUSIONS: Workers in Palestine may suffer from auditory effects of occupational noise and aging despite no formal diagnosis. These findings highlight the importance of occupational noise monitoring and hearing-related health and safety practices in developing countries. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.22056701.

Listening effort and downstream effects due to hearing loss in children and young people: an online quantitative questionnaire-based observational study.

INTRODUCTION: The clinical application of listening effort (LE) is challenging due to the lack of consensus regarding measuring the concept. Correlational analysis between different measuring instruments shows conditional and weak relationships, indicating they capture different dimensions of LE. Current research has suggested possible links between LE and downstream consequences such as fatigue, stress and confidence. One way to clinically measure LE would be to focus on its corollaries. Further research is needed to explore whether tools used to measure these downstream effects can be applied to capture LE. This study explores using existing questionnaire-based outcome instruments to evaluate LE and its associated consequences in children and young people (CYP), with and without hearing loss. METHODS AND ANALYSIS: One hundred CYP aged 12-17 years with normal hearing and a range of hearing loss levels will be invited to complete a series of online questionnaires (Speech, Spatial and Qualities, Vanderbilt Fatigue Scale-Child, Perceived Stress Scale and Rosenberg Self-Esteem Scale) and a hearing test (Digits in Noise). They will complete the questionnaires at two time points (1) at the end of a rest day and (2) at the end of a workday. Standard demographic and hearing health information will be collected. The sample size was determined pragmatically due to a lack of comparable published data to power the study. Tests are exploratory and for generating hypotheses; therefore, the standard criterion of p<0.05 will be used. ETHICS AND DISSEMINATION: This study has been reviewed within the funding organisation (Cochlear Research and Development Limited) by an independent and relevant peer reviewer/committee. This study has had a favourable ethics committee review by both NHS ethics and University of Manchester ethics. The study will be disseminated through newsletters, publication and presentations at conferences. The results will be made available to participants on request.

Binaural temporal coding and the middle ear muscle reflex in audiometrically normal young adults.

Noise exposure may damage the synapses that connect inner hair cells with auditory nerve fibers, before outer hair cells are lost. In humans, this cochlear synaptopathy (CS) is thought to decrease the fidelity of peripheral auditory temporal coding. In the current study, the primary hypothesis was that higher middle ear muscle reflex (MEMR) thresholds, as a proxy measure of CS, would be associated with smaller values of the binaural intelligibility level difference (BILD). The BILD, which is a measure of binaural temporal coding, is defined here as the difference in thresholds between the diotic and the antiphasic versions of the digits in noise (DIN) test. This DIN BILD may control for factors unrelated to binaural temporal coding such as linguistic, central auditory, and cognitive factors. Fifty-six audiometrically normal adults (34 females) aged 18 - 30 were tested. The test battery included standard pure tone audiometry, tympanometry, MEMR using a 2 kHz elicitor and 226 Hz and 1 kHz probes, the Noise Exposure Structured Interview, forward digit span test, extended high frequency (EHF) audiometry, and diotic and antiphasic DIN tests. The study protocol was pre-registered prior to data collection. MEMR thresholds did not predict the DIN BILD. Secondary analyses showed no association between MEMR thresholds and the individual diotic and antiphasic DIN thresholds. Greater lifetime noise exposure was non-significantly associated with higher MEMR thresholds, larger DIN BILD values, and lower (better) antiphasic DIN thresholds, but not with diotic DIN thresholds, nor with EHF thresholds. EHF thresholds were associated with neither MEMR thresholds nor any of the DIN outcomes, including the DIN BILD. Results provide no evidence that young, audiometrically normal people incur CS with impacts on binaural temporal processing.

Patient and public involvement in hearing research: opportunities, impact and reflections with case studies from the Manchester Centre for Audiology and Deafness.

OBJECTIVE: Patient and public involvement (PPI) in research improves relevance to end users and improves processes including recruitment participants. PPI in our research has gone from being non-existent to ubiquitous over a few years. We provide critical reflections on the benefits and challenges of PPI. DESIGN: Case studies are reported according to a modified GRIP2 framework; the aims, methodology, impact of PPI and critical reflections on each case and our experiences with PPI in general. STUDY SAMPLE: We report five UK projects that included PPI from teenagers, families, people living with dementia, autistic people, and people from South Asian and d/Deaf communities. RESULTS: Our experience has progressed from understanding the rationale to grappling methodologies and integrating PPI in our research. PPI took place at all stages of research, although commonly involved input to design including recruitment and development of study materials. Methodologies varied between projects, including PPI co-investigators, advisory panels and online surveys. CONCLUSION: On-going challenges include addressing social exclusion from research for people that lack digital access following increasing on-line PPI and involvement from underserved communities. PPI was initially motivated by funders; however the benefits have driven widespread PPI, ensuring our research is relevant to people living with hearing loss.

Chasing the conversation: Autistic experiences of speech perception.

Background and aims: Humans communicate primarily through spoken language and speech perception is a core function of the human auditory system. Among the autistic community, atypical sensory reactivity and social communication difficulties are pervasive, yet the research literature lacks in-depth self-report data on speech perception in this population. The present study aimed to elicit detailed first-person accounts of autistic individuals' abilities and difficulties perceiving the spoken word. Methods: Semi-structured interviews were conducted with nine autistic adults. The interview schedule addressed interviewees' experiences of speech perception, factors influencing those experiences, and responses to those experiences. Resulting interview transcripts underwent thematic analysis. The six-person study team included two autistic researchers, to reduce risk of neurotypical 'overshadowing' of autistic voices. Results: Most interviewees reported pronounced difficulties perceiving speech in the presence of competing sounds. They emphasised that such listening difficulties are distinct from social difficulties, though the two can add and interact. Difficulties were of several varieties, ranging from powerful auditory distraction to drowning out of voices by continuous sounds. Contributing factors encompassed not only features of the soundscape but also non-acoustic factors such as multisensory processing and social cognition. Participants also identified compounding factors, such as lack of understanding of listening difficulties. Impacts were diverse and sometimes disabling, affecting socialising, emotions, fatigue, career, and self-image. A wide array of coping mechanisms was described. Conclusions: The first in-depth qualitative investigation of autistic speech-perception experiences has revealed diverse and widespread listening difficulties. These can combine with other internal, interpersonal, and societal factors to induce profound impacts. Lack of understanding of such listening difficulties - by the self, by communication partners, by institutions, and especially by clinicians - appears to be a crucial exacerbating factor. Many autistic adults have developed coping strategies to lessen speech-perception difficulties or mitigate their effects, and these are generally self-taught due to lack of clinical support. Implications: There is a need for carefully designed, adequately powered confirmatory research to verify, quantify, and disentangle the various forms of listening difficulty, preferably using large samples to explore heterogeneity. More immediate benefit might be obtained through development of self-help and clinical guidance materials, and by raising awareness of autistic listening experiences and needs, among the autistic community, communication partners, institutions, and clinicians.

The Effect of Lifetime Noise Exposure and Aging on Speech-Perception-in-Noise Ability and Self-Reported Hearing Symptoms: An Online Study.

Animal research shows that aging and excessive noise exposure damage cochlear outer hair cells, inner hair cells, and the synapses connecting inner hair cells with the auditory nerve. This may translate into auditory symptoms such as difficulty understanding speech in noise, tinnitus, and hyperacusis. The current study, using a novel online approach, assessed and quantified the effects of lifetime noise exposure and aging on (i) speech-perception-in-noise (SPiN) thresholds, (ii) self-reported hearing ability, and (iii) the presence of tinnitus. Secondary aims involved documenting the effects of lifetime noise exposure and aging on tinnitus handicap and the severity of hyperacusis. Two hundred and ninety-four adults with no past diagnosis of hearing or memory impairments were recruited online. Participants were assigned into two groups: 217 "young" (age range: 18-35 years, females: 151) and 77 "older" (age range: 50-70 years, females: 50). Participants completed a set of online instruments including an otologic health and demographic questionnaire, a dementia screening tool, forward and backward digit span tests, a noise exposure questionnaire, the Khalfa hyperacusis questionnaire, the short-form of the Speech, Spatial, and Qualities of Hearing scale, the Tinnitus Handicap Inventory, a digits-in-noise test, and a Coordinate Response Measure speech-perception test. Analyses controlled for sex and cognitive function as reflected by the digit span. A detailed protocol was pre-registered, to guard against "p-hacking" of this extensive dataset. Lifetime noise exposure did not predict SPiN thresholds, self-reported hearing ability, or the presence of tinnitus in either age group. Exploratory analyses showed that worse hyperacusis scores, and a greater prevalence of tinnitus, were associated significantly with high lifetime noise exposure in the young, but not in the older group. Age was a significant predictor of SPiN thresholds and the presence of tinnitus, but not of self-reported hearing ability, tinnitus handicap, or severity of hyperacusis. Consistent with several lab studies, our online-derived data suggest that older adults with no diagnosis of hearing impairment have a poorer SPiN ability and a higher risk of tinnitus than their younger counterparts. Moreover, lifetime noise exposure may increase the risk of tinnitus and the severity of hyperacusis in young adults with no diagnosis of hearing impairment.

Estimation of the burden of shielding among a cross-section of patients attending rheumatology clinics with SLE-data from the BSR audit of systemic lupus erythematosus.

OBJECTIVES: We aimed to estimate what proportion of people with SLE attending UK rheumatology clinics would be categorized as being at high risk from coronavirus disease 2019 (COVID-19) and therefore asked to shield, and explore what implications this has for rheumatology clinical practice. METHODS: We used data from the British Society for Rheumatology multicentre audit of SLE, which included a large, representative cross-sectional sample of patients attending UK Rheumatology clinics with SLE. We calculated who would receive shielding advice using the British Society for Rheumatology's risk stratification guidance and accompanying scoring grid, and assessed whether ethnicity and history of nephritis were over-represented in the shielding group. RESULTS: The audit included 1003 patients from 51 centres across all 4 nations of the UK. Overall 344 (34.3%) patients had a shielding score ≥3 and would have been advised to shield. People with previous or current LN were 2.6 (1.9-3.4) times more likely to be in the shielding group than people with no previous LN (P < 0.001). Ethnicity was not evenly distributed between the groups (chi-squared P < 0.001). Compared with White people, people of Black ethnicity were 1.9 (1.3-2.8) and Asian 1.9 (1.3-2.7) times more likely to be in the shielding group. Increased risk persisted after controlling for LN. CONCLUSION: Our study demonstrates the large number of people with SLE who are likely to be shielding. Implications for clinical practice include considering communication across language and cultural differences, and ways to conduct renal assessment including urinalysis, during telephone and video consultations for patients who are shielding.

BSR guideline on the management of adults with systemic lupus erythematosus (SLE) 2018: baseline multi-centre audit in the UK.

OBJECTIVES: To assess the baseline care provided to patients with SLE attending UK Rheumatology units, audited against standards derived from the recently published BSR guideline for the management of adults with SLE, the NICE technology appraisal for belimumab, and NHS England's clinical commissioning policy for rituximab. METHODS: SLE cases attending outpatient clinics during any 4-week period between February and June 2018 were retrospectively audited to assess care at the preceding visit. The effect of clinical environment (general vs dedicated CTD/vasculitis clinic and specialized vs non-specialized centre) were tested. Bonferroni's correction was applied to the significance level. RESULTS: Fifty-one units participated. We audited 1021 episodes of care in 1003 patients (median age 48 years, 74% diagnosed >5 years ago). Despite this disease duration, 286 (28.5%) patients had active disease. Overall in 497 (49%) clinic visits, it was recorded that the patient was receiving prednisolone, including in 28.5% of visits where disease was assessed as inactive. Low documented compliance (<60% clinic visits) was identified for audit standards relating to formal disease-activity assessment, reduction of drug-related toxicity and protection against comorbidities and damage. Compared with general clinics, dedicated clinics had higher compliance with standards for appropriate urine protein quantification (85.1% vs 78.1%, P ≤ 0.001). Specialized centres had higher compliance with BILAG Biologics Register recruitment (89.4% vs 44.4%, P ≤ 0.001) and blood pressure recording (95.3% vs 84.1%). CONCLUSIONS: This audit highlights significant unmet need for better disease control and reduction in corticosteroid toxicity and is an opportunity to improve compliance with national guidelines. Higher performance with nephritis screening in dedicated clinics supports wider adoption of this service-delivery model.

Investigating the effects of noise exposure on self-report, behavioral and electrophysiological indices of hearing damage in musicians with normal audiometric thresholds.

Musicians are at risk of hearing loss due to prolonged noise exposure, but they may also be at risk of early sub-clinical hearing damage, such as cochlear synaptopathy. In the current study, we investigated the effects of noise exposure on electrophysiological, behavioral and self-report correlates of hearing damage in young adult (age range = 18-27 years) musicians and non-musicians with normal audiometric thresholds. Early-career musicians (n = 76) and non-musicians (n = 47) completed a test battery including the Noise Exposure Structured Interview, pure-tone audiometry (PTA; 0.25-8 kHz), extended high-frequency (EHF; 12 and 16 kHz) thresholds, otoacoustic emissions (OAEs), auditory brainstem responses (ABRs), speech perception in noise (SPiN), and self-reported tinnitus, hyperacusis and hearing in noise difficulties. Total lifetime noise exposure was similar between musicians and non-musicians, the majority of which could be accounted for by recreational activities. Musicians showed significantly greater ABR wave I/V ratios than non-musicians and were also more likely to report experience of - and/or more severe - tinnitus, hyperacusis and hearing in noise difficulties, irrespective of noise exposure. A secondary analysis revealed that individuals with the highest levels of noise exposure had reduced outer hair cell function compared to individuals with the lowest levels of noise exposure, as measured by OAEs. OAE level was also related to PTA and EHF thresholds. High levels of noise exposure were also associated with a significant increase in ABR wave V latency, but only for males, and a higher prevalence and severity of hyperacusis. These findings suggest that there may be sub-clinical effects of noise exposure on various hearing metrics even at a relatively young age, but do not support a link between lifetime noise exposure and proxy measures of cochlear synaptopathy such as ABR wave amplitudes and SPiN. Closely monitoring OAEs, PTA and EHF thresholds when conventional PTA is within the clinically 'normal' range could provide a useful early metric of noise-induced hearing damage. This may be particularly relevant to early-career musicians as they progress through a period of intensive musical training, and thus interventions to protect hearing longevity may be vital.

The association between subcortical and cortical fMRI and lifetime noise exposure in listeners with normal hearing thresholds.

In animal models, exposure to high noise levels can cause permanent damage to hair-cell synapses (cochlear synaptopathy) for high-threshold auditory nerve fibers without affecting sensitivity to quiet sounds. This has been confirmed in several mammalian species, but the hypothesis that lifetime noise exposure affects auditory function in humans with normal audiometric thresholds remains unconfirmed and current evidence from human electrophysiology is contradictory. Here we report the auditory brainstem response (ABR), and both transient (stimulus onset and offset) and sustained functional magnetic resonance imaging (fMRI) responses throughout the human central auditory pathway across lifetime noise exposure. Healthy young individuals aged 25-40 years were recruited into high (n = 32) and low (n = 30) lifetime noise exposure groups, stratified for age, and balanced for audiometric threshold up to 16 kHz fMRI demonstrated robust broadband noise-related activity throughout the auditory pathway (cochlear nucleus, superior olivary complex, nucleus of the lateral lemniscus, inferior colliculus, medial geniculate body and auditory cortex). fMRI responses in the auditory pathway to broadband noise onset were significantly enhanced in the high noise exposure group relative to the low exposure group, differences in sustained fMRI responses did not reach significance, and no significant group differences were found in the click-evoked ABR. Exploratory analyses found no significant relationships between the neural responses and self-reported tinnitus or reduced sound-level tolerance (symptoms associated with synaptopathy). In summary, although a small effect, these fMRI results suggest that lifetime noise exposure may be associated with central hyperactivity in young adults with normal hearing thresholds.

No Effect of Interstimulus Interval on Acoustic Reflex Thresholds.

The acoustic reflex (AR), a longstanding component of the audiological test battery, has received renewed attention in the context of noise-induced cochlear synaptopathy-the destruction of synapses between inner hair cells and auditory nerve fibers. Noninvasive proxy measures of synaptopathy are widely sought, and AR thresholds (ARTs) correlate closely with synaptic survival in rodents. However, measurement in humans at high stimulus frequencies-likely important when testing for noise-induced pathology-can be challenging; reflexes at 4 kHz are frequently absent or occur only at high stimulus levels, even in young people with clinically normal audiograms. This phenomenon may partly reflect differences across stimulus frequency in the temporal characteristics of the response; later onset of the response, earlier onset of adaptation, and higher rate of adaptation have been observed at 4 kHz than at 1 kHz. One temporal aspect of the response that has received little attention is the interstimulus interval (ISI); inadequate duration of ISI might lead to incomplete recovery of the response between successive presentations and consequent response fatigue. This research aimed to test for effects of ISI on ARTs in normally hearing young humans, measured at 1 and 4 kHz. Contrary to our hypotheses, increasing ISIs from 2.5 to 8.5 s did not reduce ART level, nor raise ART reliability. Results confirm that clinically measured ARTs-including those at 4 kHz-can exhibit excellent reliability and that relatively short (2.5 s) ISIs are adequate for the measurement of sensitive and reliable ARTs.

Effects of Age and Noise Exposure on Proxy Measures of Cochlear Synaptopathy.

Although there is strong histological evidence for age-related synaptopathy in humans, evidence for the existence of noise-induced cochlear synaptopathy in humans is inconclusive. Here, we sought to evaluate the relative contributions of age and noise exposure to cochlear synaptopathy using a series of electrophysiological and behavioral measures. We extended an existing cohort by including 33 adults in the age range 37 to 60, resulting in a total of 156 participants, with the additional older participants resulting in a weakening of the correlation between lifetime noise exposure and age. We used six independent regression models (corrected for multiple comparisons), in which age, lifetime noise exposure, and high-frequency audiometric thresholds were used to predict measures of synaptopathy, with a focus on differential measures. The models for auditory brainstem responses, envelope-following responses, interaural phase discrimination, and the co-ordinate response measure of speech perception were not statistically significant. However, both age and noise exposure were significant predictors of performance on the digit triplet test of speech perception in noise, with greater noise exposure (unexpectedly) predicting better performance in the 80 dB sound pressure level (SPL) condition and greater age predicting better performance in the 40 dB SPL condition. Amplitude modulation detection thresholds were also significantly predicted by age, with older listeners performing better than younger listeners at 80 dB SPL. Overall, the results are inconsistent with the predicted effects of synaptopathy.

Reliability and interrelations of seven proxy measures of cochlear synaptopathy.

Investigations of cochlear synaptopathy in living humans rely on proxy measures of auditory nerve function. Numerous procedures have been developed, typically based on the auditory brainstem response (ABR), envelope-following response (EFR), or middle-ear-muscle reflex (MEMR). Validation is challenging, due to the absence of a gold-standard measure in humans. Some metrics correlate with synaptic survival in animal models, but translation between species is not straightforward; measurements in humans are likely to reflect greater error and greater variability from non-synaptopathic sources. The present study assessed the reliability of seven measures, as well as testing for correlations between them. Thirty-one young women with normal audiograms underwent repeated measurements of ABR wave I amplitude, ABR wave I growth, ABR wave V latency shift in noise, EFR amplitude, EFR growth with stimulus modulation depth, MEMR threshold, and an MEMR across-frequency difference measure. Intraclass correlation coefficients for ABR wave I amplitude, EFR amplitude, and MEMR threshold ranged from 0.85 to 0.93, suggesting that such tests can yield highly reliable results, given careful measurement techniques. The ABR and EFR difference measures exhibited only poor-to-moderate reliability. No significant correlations, nor any consistent trends, were observed between the various measures, providing no indication that these metrics reflect the same underlying physiological processes. Findings suggest that many proxy measures of cochlear synaptopathy should be regarded with caution, at least when employed in young adults with normal audiograms.

Acoustic Middle-Ear-Muscle-Reflex Thresholds in Humans with Normal Audiograms: No Relations to Tinnitus, Speech Perception in Noise, or Noise Exposure.

The acoustic middle-ear-muscle reflex (MEMR) has been suggested as a sensitive non-invasive measure of cochlear synaptopathy, the loss of synapses between inner hair cells and auditory nerve fibers. In the present study, clinical MEMR thresholds were measured for 1-, 2-, and 4-kHz tonal elicitors, using a procedure shown to produce thresholds with excellent reliability. MEMR thresholds of 19 participants with tinnitus and normal audiograms were compared to those of 19 age- and sex-matched controls. MEMR thresholds did not differ significantly between the two groups at any frequency. These 38 participants were included in a larger sample of 70 participants with normal audiograms. For this larger group, MEMR thresholds were compared to a measure of spatial speech perception in noise (SPiN) and a detailed self-report estimate of lifetime noise exposure. MEMR thresholds were unrelated to either SPiN or noise exposure, despite a wide range in both measures. It is possible that thresholds measured using a clinical paradigm are less sensitive to synaptopathy than those obtained using more sophisticated measurement techniques; however, we had good sensitivity at the group level, and even trends in the hypothesized direction were not observed. To the extent that MEMR thresholds are sensitive to cochlear synaptopathy, the present results provide no evidence that tinnitus, SPiN, or noise exposure are related to synaptopathy in the population studied.

The Noise Exposure Structured Interview (NESI): An Instrument for the Comprehensive Estimation of Lifetime Noise Exposure.

Lifetime noise exposure is generally quantified by self-report. The accuracy of retrospective self-report is limited by respondent recall but is also bound to be influenced by reporting procedures. Such procedures are of variable quality in current measures of lifetime noise exposure, and off-the-shelf instruments are not readily available. The Noise Exposure Structured Interview (NESI) represents an attempt to draw together some of the stronger elements of existing procedures and to provide solutions to their outstanding limitations. Reporting is not restricted to prespecified exposure activities and instead encompasses all activities that the respondent has experienced as noisy (defined based on sound level estimated from vocal effort). Changing exposure habits over time are reported by dividing the lifespan into discrete periods in which exposure habits were approximately stable, with life milestones used to aid recall. Exposure duration, sound level, and use of hearing protection are reported for each life period separately. Simple-to-follow methods are provided for the estimation of free-field sound level, the sound level emitted by personal listening devices, and the attenuation provided by hearing protective equipment. An energy-based means of combining the resulting data is supplied, along with a primarily energy-based method for incorporating firearm-noise exposure. Finally, the NESI acknowledges the need of some users to tailor the procedures; this flexibility is afforded, and reasonable modifications are described. Competency needs of new users are addressed through detailed interview instructions (including troubleshooting tips) and a demonstration video. Limited evaluation data are available, and future efforts at evaluation are proposed.

Supra-threshold auditory brainstem response amplitudes in humans: Test-retest reliability, electrode montage and noise exposure.

The auditory brainstem response (ABR) is a sub-cortical evoked potential in which a series of well-defined waves occur in the first 10 ms after the onset of an auditory stimulus. Wave V of the ABR, particularly wave V latency, has been shown to be remarkably stable over time in individual listeners. However, little attention has been paid to the reliability of wave I, which reflects auditory nerve activity. This ABR component has attracted interest recently, as wave I amplitude has been identified as a possible non-invasive measure of noise-induced cochlear synaptopathy. The current study aimed to determine whether ABR wave I amplitude has sufficient test-retest reliability to detect impaired auditory nerve function in an otherwise normal-hearing listener. Thirty normal-hearing females were tested, divided equally into low- and high-noise exposure groups. The stimulus was an 80 dB nHL click. ABR recordings were made from the ipsilateral mastoid and from the ear canal (using a tiptrode). Although there was some variability between listeners, wave I amplitude had high test-retest reliability, with an intraclass correlation coefficient (ICC) comparable to that for wave V amplitude. There were slight gains in reliability for wave I amplitude when recording from the ear canal (ICC of 0.88) compared to the mastoid (ICC of 0.85). The summating potential (SP) and ratio of SP to wave I were also quantified and found to be much less reliable than measures of wave I and V amplitude. Finally, we found no significant differences in the amplitude of any wave components between low- and high-noise exposure groups. We conclude that, if the other sources of between-subject variability can be controlled, wave I amplitude is sufficiently reliable to accurately characterize individual differences in auditory nerve function.

Impaired speech perception in noise with a normal audiogram: No evidence for cochlear synaptopathy and no relation to lifetime noise exposure.

In rodents, noise exposure can destroy synapses between inner hair cells and auditory nerve fibers ("cochlear synaptopathy") without causing hair cell loss. Noise-induced cochlear synaptopathy usually leaves cochlear thresholds unaltered, but is associated with long-term reductions in auditory brainstem response (ABR) amplitudes at medium-to-high sound levels. This pathophysiology has been suggested to degrade speech perception in noise (SPiN), perhaps explaining why SPiN ability varies so widely among audiometrically normal humans. The present study is the first to test for evidence of cochlear synaptopathy in humans with significant SPiN impairment. Individuals were recruited on the basis of self-reported SPiN difficulties and normal pure tone audiometric thresholds. Performance on a listening task identified a subset with "verified" SPiN impairment. This group was matched with controls on the basis of age, sex, and audiometric thresholds up to 14 kHz. ABRs and envelope-following responses (EFRs) were recorded at high stimulus levels, yielding both raw amplitude measures and within-subject difference measures. Past exposure to high sound levels was assessed by detailed structured interview. Impaired SPiN was not associated with greater lifetime noise exposure, nor with any electrophysiological measure. It is conceivable that retrospective self-report cannot reliably capture noise exposure, and that ABRs and EFRs offer limited sensitivity to synaptopathy in humans. Nevertheless, the results do not support the notion that noise-induced synaptopathy is a significant etiology of SPiN impairment with normal audiometric thresholds. It may be that synaptopathy alone does not have significant perceptual consequences, or is not widespread in humans with normal audiograms.

The Physiological Bases of Hidden Noise-Induced Hearing Loss: Protocol for a Functional Neuroimaging Study.

BACKGROUND: Rodent studies indicate that noise exposure can cause permanent damage to synapses between inner hair cells and high-threshold auditory nerve fibers, without permanently altering threshold sensitivity. These demonstrations of what is commonly known as hidden hearing loss have been confirmed in several rodent species, but the implications for human hearing are unclear. OBJECTIVE: Our Medical Research Council-funded program aims to address this unanswered question, by investigating functional consequences of the damage to the human peripheral and central auditory nervous system that results from cumulative lifetime noise exposure. Behavioral and neuroimaging techniques are being used in a series of parallel studies aimed at detecting hidden hearing loss in humans. The planned neuroimaging study aims to (1) identify central auditory biomarkers associated with hidden hearing loss; (2) investigate whether there are any additive contributions from tinnitus or diminished sound tolerance, which are often comorbid with hearing problems; and (3) explore the relation between subcortical functional magnetic resonance imaging (fMRI) measures and the auditory brainstem response (ABR). METHODS: Individuals aged 25 to 40 years with pure tone hearing thresholds ≤20 dB hearing level over the range 500 Hz to 8 kHz and no contraindications for MRI or signs of ear disease will be recruited into the study. Lifetime noise exposure will be estimated using an in-depth structured interview. Auditory responses throughout the central auditory system will be recorded using ABR and fMRI. Analyses will focus predominantly on correlations between lifetime noise exposure and auditory response characteristics. RESULTS: This paper reports the study protocol. The funding was awarded in July 2013. Enrollment for the study described in this protocol commenced in February 2017 and was completed in December 2017. Results are expected in 2018. CONCLUSIONS: This challenging and comprehensive study will have the potential to impact diagnostic procedures for hidden hearing loss, enabling early identification of noise-induced auditory damage via the detection of changes in central auditory processing. Consequently, this will generate the opportunity to give personalized advice regarding provision of ear defense and monitoring of further damage, thus reducing the incidence of noise-induced hearing loss.