151
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Bharadwaj HM, Mai AR, Simpson JM, Choi I, Heinz MG, Shinn-Cunningham BG. Non-Invasive Assays of Cochlear Synaptopathy - Candidates and Considerations. Neuroscience 2019; 407:53-66. [PMID: 30853540 DOI: 10.1016/j.neuroscience.2019.02.031] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Revised: 02/21/2019] [Accepted: 02/25/2019] [Indexed: 12/31/2022]
Abstract
Studies in multiple species, including in post-mortem human tissue, have shown that normal aging and/or acoustic overexposure can lead to a significant loss of afferent synapses innervating the cochlea. Hypothetically, this cochlear synaptopathy can lead to perceptual deficits in challenging environments and can contribute to central neural effects such as tinnitus. However, because cochlear synaptopathy can occur without any measurable changes in audiometric thresholds, synaptopathy can remain hidden from standard clinical diagnostics. To understand the perceptual sequelae of synaptopathy and to evaluate the efficacy of emerging therapies, sensitive and specific non-invasive measures at the individual patient level need to be established. Pioneering experiments in specific mice strains have helped identify many candidate assays. These include auditory brainstem responses, the middle-ear muscle reflex, envelope-following responses, and extended high-frequency audiograms. Unfortunately, because these non-invasive measures can be also affected by extraneous factors other than synaptopathy, their application and interpretation in humans is not straightforward. Here, we systematically examine six extraneous factors through a series of interrelated human experiments aimed at understanding their effects. Using strategies that may help mitigate the effects of such extraneous factors, we then show that these suprathreshold physiological assays exhibit across-individual correlations with each other indicative of contributions from a common physiological source consistent with cochlear synaptopathy. Finally, we discuss the application of these assays to two key outstanding questions, and discuss some barriers that still remain. This article is part of a Special Issue entitled: Hearing Loss, Tinnitus, Hyperacusis, Central Gain.
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Affiliation(s)
- Hari M Bharadwaj
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN.
| | - Alexandra R Mai
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN
| | - Jennifer M Simpson
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN
| | - Inyong Choi
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA
| | - Michael G Heinz
- Department of Speech, Language, and Hearing Sciences, Purdue University, West Lafayette, IN; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN
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152
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Vercammen C, Goossens T, Undurraga J, Wouters J, van Wieringen A. Electrophysiological and Behavioral Evidence of Reduced Binaural Temporal Processing in the Aging and Hearing Impaired Human Auditory System. Trends Hear 2019; 22:2331216518785733. [PMID: 30022734 PMCID: PMC6053861 DOI: 10.1177/2331216518785733] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A person’s ability to process temporal fine structure information is
indispensable for speech understanding. As speech understanding typically
deteriorates throughout adult life, this study aimed to disentangle age and
hearing impairment (HI)-related changes in binaural temporal processing. This
was achieved by examining neural and behavioral processing of interaural phase
differences (IPDs). Neural IPD processing was studied electrophysiologically
through steady-state activity in the electroencephalogram evoked by periodic
changes in IPDs over time, embedded in the temporal fine structure of acoustic
stimulation. In addition, behavioral IPD discrimination thresholds were
determined for the same stimuli. To disentangle potential effects of age from
those of HI, both measures were applied to six participant groups: young,
middle-aged, and older persons, with either normal hearing or sensorineural HI.
All participants passed a cognitive screening, and stimulus audibility was
controlled for in participants with HI. The results demonstrated that HI changes
neural processing of binaural temporal information for all age-groups included
in this study. These outcomes were revealed, superimposed on age-related changes
that emerge between young adulthood and middle age. Poorer neural outcomes were
also associated with poorer behavioral performance, even though the behavioral
IPD discrimination thresholds were affected by age rather than by HI. The neural
outcomes of this study are the first to evidence and disentangle the dual load
of age and HI on binaural temporal processing. These results could be a valuable
first step toward future research on rehabilitation.
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Affiliation(s)
- Charlotte Vercammen
- 1 Department of Neurosciences, Research Group Experimental Oto-Rhino-Laryngology, KU Leuven-University of Leuven, Belgium
| | - Tine Goossens
- 1 Department of Neurosciences, Research Group Experimental Oto-Rhino-Laryngology, KU Leuven-University of Leuven, Belgium
| | - Jaime Undurraga
- 2 Department of Linguistics, The Australian Hearing Hub, Macquarie University, Sydney, Australia.,3 Ear Institute, University College London, London, UK
| | - Jan Wouters
- 1 Department of Neurosciences, Research Group Experimental Oto-Rhino-Laryngology, KU Leuven-University of Leuven, Belgium
| | - Astrid van Wieringen
- 1 Department of Neurosciences, Research Group Experimental Oto-Rhino-Laryngology, KU Leuven-University of Leuven, Belgium
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153
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Heeringa AN, Köppl C. The aging cochlea: Towards unraveling the functional contributions of strial dysfunction and synaptopathy. Hear Res 2019; 376:111-124. [PMID: 30862414 DOI: 10.1016/j.heares.2019.02.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 02/01/2019] [Accepted: 02/26/2019] [Indexed: 10/27/2022]
Abstract
Strial dysfunction is commonly observed as a key consequence of aging in the cochlea. A large body of animal research, especially in the quiet-aged Mongolian gerbil, shows specific histopathological changes in the cochlear stria vascularis and the putatively corresponding effects on endocochlear potential and auditory nerve responses. However, recent work suggests that synaptopathy, or the loss of inner hair cell-auditory nerve fiber synapses, also presents as a consequence of aging. It is now believed that the loss of synapses is the earliest age-related degenerative event. The present review aims to integrate classic and novel research on age-related pathologies of the inner ear. First, we summarize current knowledge on age-related strial dysfunction and synaptopathy. We describe how these cochlear pathologies fit into the categories for presbyacusis, as first defined by Schuknecht in the '70s. Further, we discuss how strial dysfunction and synaptopathy affect sound coding by the auditory nerve and how they can be experimentally induced to study their specific contributions to age-related hearing deficits. As such, we aim to give an overview of the current literature on age-related cochlear pathologies and hope to inspire further research on the role of cochlear aging in age-related hearing deficits.
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Affiliation(s)
- Amarins N Heeringa
- Cluster of Excellence 'Hearing4all' and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany
| | - Christine Köppl
- Cluster of Excellence 'Hearing4all' and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany.
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154
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Evidence for age-related cochlear synaptopathy in humans unconnected to speech-in-noise intelligibility deficits. Hear Res 2019; 374:35-48. [DOI: 10.1016/j.heares.2019.01.017] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/18/2019] [Accepted: 01/22/2019] [Indexed: 12/20/2022]
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155
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Grose JH, Buss E, Elmore H. Age-Related Changes in the Auditory Brainstem Response and Suprathreshold Processing of Temporal and Spectral Modulation. Trends Hear 2019; 23:2331216519839615. [PMID: 30977442 PMCID: PMC6463337 DOI: 10.1177/2331216519839615] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 02/21/2019] [Accepted: 02/22/2019] [Indexed: 01/05/2023] Open
Abstract
The purpose of this study was to determine whether cochlear synaptopathy can be shown to be a viable basis for age-related hearing difficulties in humans and whether it manifests as deficient suprathreshold processing of temporal and spectral modulation. Three experiments were undertaken evaluating the effects of age on (a) the auditory brainstem response as a function of level, (b) temporal modulation detection as a function of level and background noise, and (c) spectral modulation as a function of level. Across the three experiments, a total of 21 older listeners with near-normal audiograms and 29 young listeners with audiometrically normal hearing participated. The auditory brainstem response experiment demonstrated reduced Wave I amplitudes and concomitant reductions in the amplitude ratios of Wave I to Wave V in the older listener group. These findings were interpreted as consistent with an electrophysiological profile of cochlear synaptopathy. The temporal and spectral modulation detection experiments, however, provided no support for the hypothesis of compromised suprathreshold processing in these domains. This pattern of results suggests that even if cochlear synaptopathy can be shown to be a viable basis for age-related hearing difficulties, then temporal and spectral modulation detection paradigms are not sensitive to its presence.
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Affiliation(s)
- John H. Grose
- Department of Otolaryngology – Head and Neck Surgery, University of North Carolina at Chapel Hill, NC, USA
| | - Emily Buss
- Department of Otolaryngology – Head and Neck Surgery, University of North Carolina at Chapel Hill, NC, USA
| | - Hollis Elmore
- Department of Otolaryngology – Head and Neck Surgery, University of North Carolina at Chapel Hill, NC, USA
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156
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Moore BCJ, Mariathasan S, Sęk AP. Effects of Age and Hearing Loss on the Discrimination of Amplitude and Frequency Modulation for 2- and 10-Hz Rates. Trends Hear 2019; 23:2331216519853963. [PMID: 31250705 PMCID: PMC6600487 DOI: 10.1177/2331216519853963] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/07/2019] [Accepted: 05/08/2019] [Indexed: 11/16/2022] Open
Abstract
Detection of frequency modulation (FM) with rate = 10 Hz may depend on conversion of FM to amplitude modulation (AM) in the cochlea, while detection of 2-Hz FM may depend on the use of temporal fine structure (TFS) information. TFS processing may worsen with greater age and hearing loss while AM processing probably does not. A two-stage experiment was conducted to test these ideas while controlling for the effects of detection efficiency. Stage 1 measured psychometric functions for the detection of AM alone and FM alone imposed on a 1-kHz carrier, using 2- and 10-Hz rates. Stage 2 assessed the discrimination of AM from FM at the same modulation rate when the detectability of the AM alone and FM alone was equated. Discrimination was better for the 2-Hz than for the 10-Hz rate for all young normal-hearing subjects and for some older subjects with normal hearing at 1 kHz. Other older subjects with normal hearing showed no clear difference in AM-FM discrimination for the 2- and 10-Hz rates, as was the case for most older hearing-impaired subjects. The results suggest that the ability to use TFS cues is reduced for some older people and most hearing-impaired people.
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Affiliation(s)
- Brian C. J. Moore
- Department of Experimental
Psychology, University of Cambridge, England
| | - Sashi Mariathasan
- Department of Experimental
Psychology, University of Cambridge, England
| | - Aleksander P. Sęk
- Faculty of Physics, Institute of
Acoustics, Adam Mickiewicz University, Poznań, Poland
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157
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Jahn KN, Arenberg JG. Polarity Sensitivity in Pediatric and Adult Cochlear Implant Listeners. Trends Hear 2019; 23:2331216519862987. [PMID: 31373266 PMCID: PMC6681263 DOI: 10.1177/2331216519862987] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 06/04/2019] [Accepted: 06/19/2019] [Indexed: 12/02/2022] Open
Abstract
Modeling data suggest that sensitivity to the polarity of an electrical stimulus may reflect the integrity of the peripheral processes of the spiral ganglion neurons. Specifically, better sensitivity to anodic (positive) current than to cathodic (negative) current could indicate peripheral process degeneration or demyelination. The goal of this study was to characterize polarity sensitivity in pediatric and adult cochlear implant listeners (41 ears). Relationships between polarity sensitivity at threshold and (a) polarity sensitivity at suprathreshold levels, (b) age-group, (c) preimplantation duration of deafness, and (d) phoneme perception were determined. Polarity sensitivity at threshold was defined as the difference in single-channel behavioral thresholds measured in response to each of two triphasic pulses, where the central high-amplitude phase was either cathodic or anodic. Lower thresholds in response to anodic than to cathodic pulses may suggest peripheral process degeneration. On the majority of electrodes tested, threshold and suprathreshold sensitivity was lower for anodic than for cathodic stimulation; however, dynamic range was often larger for cathodic than for anodic stimulation. Polarity sensitivity did not differ between child- and adult-implanted listeners. Adults with long preimplantation durations of deafness tended to have better sensitivity to anodic pulses on channels that were estimated to interface poorly with the auditory nerve; this was not observed in the child-implanted group. Across subjects, duration of deafness predicted phoneme perception performance. The results of this study suggest that subject- and electrode-dependent differences in polarity sensitivity may assist in developing customized cochlear implant programming interventions for child- and adult-implanted listeners.
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Affiliation(s)
- Kelly N. Jahn
- Department of Speech and Hearing
Sciences,
University
of Washington, Seattle, WA, USA
| | - Julie G. Arenberg
- Massachusetts Eye and Ear, Department of
Otolaryngology, Harvard Medical School, Boston, MA, USA
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158
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Prendergast G, Couth S, Millman RE, Guest H, Kluk K, Munro KJ, Plack CJ. Effects of Age and Noise Exposure on Proxy Measures of Cochlear Synaptopathy. Trends Hear 2019; 23:2331216519877301. [PMID: 31558119 PMCID: PMC6767746 DOI: 10.1177/2331216519877301] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 12/15/2022] Open
Abstract
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.
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Affiliation(s)
- Garreth Prendergast
- Manchester Centre for Audiology and
Deafness, The University of Manchester, Manchester Academic Health Science Centre,
UK
| | - Samuel Couth
- Manchester Centre for Audiology and
Deafness, The University of Manchester, Manchester Academic Health Science Centre,
UK
| | - Rebecca E. Millman
- Manchester Centre for Audiology and
Deafness, The University of Manchester, Manchester Academic Health Science Centre,
UK
- NIHR Manchester Biomedical Research
Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester
Academic Health Science Centre, Manchester, UK
| | - Hannah Guest
- Manchester Centre for Audiology and
Deafness, The University of Manchester, Manchester Academic Health Science Centre,
UK
| | - Karolina Kluk
- Manchester Centre for Audiology and
Deafness, The University of Manchester, Manchester Academic Health Science Centre,
UK
- NIHR Manchester Biomedical Research
Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester
Academic Health Science Centre, Manchester, UK
| | - Kevin J. Munro
- Manchester Centre for Audiology and
Deafness, The University of Manchester, Manchester Academic Health Science Centre,
UK
- NIHR Manchester Biomedical Research
Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester
Academic Health Science Centre, Manchester, UK
| | - Christopher J. Plack
- Manchester Centre for Audiology and
Deafness, The University of Manchester, Manchester Academic Health Science Centre,
UK
- NIHR Manchester Biomedical Research
Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester
Academic Health Science Centre, Manchester, UK
- Department of Psychology, Lancaster
University, UK
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159
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Le Prell CG. Effects of noise exposure on auditory brainstem response and speech-in-noise tasks: a review of the literature. Int J Audiol 2018; 58:S3-S32. [DOI: 10.1080/14992027.2018.1534010] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Colleen G. Le Prell
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, TX, USA
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160
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In vivo Assessment of an Endolymphatic Hydrops Gradient Along the Cochlea in Patients With Menière's Disease by Magnetic Resonance Imaging—A Pilot Study. Otol Neurotol 2018; 39:e1091-e1099. [DOI: 10.1097/mao.0000000000002016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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161
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Investigating peripheral sources of speech-in-noise variability in listeners with normal audiograms. Hear Res 2018; 371:66-74. [PMID: 30504092 DOI: 10.1016/j.heares.2018.11.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 10/25/2018] [Accepted: 11/19/2018] [Indexed: 12/19/2022]
Abstract
A current initiative in auditory neuroscience research is to better understand why some listeners struggle to perceive speech-in-noise (SIN) despite having normal hearing sensitivity. Various hypotheses regarding the physiologic bases of this disorder have been proposed. Notably, recent work has suggested that the site of lesion underlying SIN deficits in normal hearing listeners may be either in "sub-clinical" outer hair cell damage or synaptopathic degeneration at the inner hair cell-auditory nerve fiber synapse. In this study, we present a retrospective investigation of these peripheral sources and their relationship with SIN performance variability in one of the largest datasets of young normal-hearing listeners presented to date. 194 participants completed detailed case history questionnaires assessing noise exposure, SIN complaints, tinnitus, and hyperacusis. Standard and extended high frequency audiograms, distortion product otoacoustic emissions, click-evoked auditory brainstem responses, and SIN performance measures were also collected. We found that: 1) the prevalence of SIN deficits in normal hearing listeners was 42% when based on subjective report and 8% when based on SIN performance, 2) hearing complaints and hyperacusis were more common in listeners with self-reported noise exposure histories than controls, 3) neither extended high frequency thresholds nor compound action potential amplitudes differed between noise-exposed and control groups, 4) extended high frequency hearing thresholds and compound action potential amplitudes were not predictive of SIN performance. These results suggest an association between noise exposure and hearing complaints in young, normal hearing listeners; however, SIN performance variability is not explained by peripheral auditory function to the extent that these measures capture subtle physiologic differences between participants.
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162
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Ji L, Zhai S. Aging and the peripheral vestibular system. J Otol 2018; 13:138-140. [PMID: 30671091 PMCID: PMC6335476 DOI: 10.1016/j.joto.2018.11.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 11/13/2018] [Accepted: 11/13/2018] [Indexed: 11/28/2022] Open
Abstract
Whereas much has been learned about age-related auditory changes in the inner ear, relatively little is known about the aging effects on the vestibular part of the inner ear-the peripheral vestibular system. Here we review relevant literature with regard to the prevalence of vestibular dysfunction, vestibular functional and structural changes in the elderly. The prevalence of vestibular dysfunction increases with age. Functionally, as age increases, VEMP amplitudes decrease, VEMP thresholds increase, VOR gain of HIT decreases. Due to the complexity of the vestibular system, variations in subject age and measurement techniques, findings in VEMP latency and caloric tests are conflicting. To address this, a direct measure of the peripheral vestibular system should be applied. Structurally, age-related loss in vestibular ganglion and otoconia have been noted; hair cell changes are not well defined; while subcellular changes remain to be explored. Defining how the onset of vestibular dysfunction correlates with structural degeneration will offer insights into the mechanisms underlying vestibular aging.
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Affiliation(s)
- Lingchao Ji
- Medical School of Chinese PLA, Beijing, China
| | - Suoqiang Zhai
- Medical School of Chinese PLA, Beijing, China.,Chinese PLA General Hospital, Beijing, China
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163
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Kaur C, Pal I, Saini S, Jacob T, Nag T, Thakar A, Bhardwaj D, Roy T. Comparison of unbiased stereological estimation of total number of cresyl violet stained neurons and parvalbumin positive neurons in the adult human spiral ganglion. J Chem Neuroanat 2018. [DOI: 10.1016/j.jchemneu.2017.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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164
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Bakay WMH, Anderson LA, Garcia-Lazaro JA, McAlpine D, Schaette R. Hidden hearing loss selectively impairs neural adaptation to loud sound environments. Nat Commun 2018; 9:4298. [PMID: 30327471 PMCID: PMC6191434 DOI: 10.1038/s41467-018-06777-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 09/25/2018] [Indexed: 11/09/2022] Open
Abstract
Exposure to even a single episode of loud noise can damage synapses between cochlear hair cells and auditory nerve fibres, causing hidden hearing loss (HHL) that is not detected by audiometry. Here we investigate the effects of noise-induced HHL on functional hearing by measuring the ability of neurons in the auditory midbrain of mice to adapt to sound environments containing quiet and loud periods. Neurons from noise-exposed mice show less capacity for adaptation to loud environments, convey less information about sound intensity in those environments, and adaptation to the longer-term statistical structure of fluctuating sound environments is impaired. Adaptation comprises a cascade of both threshold and gain adaptation. Although noise exposure only impairs threshold adaptation directly, the preserved function of gain adaptation surprisingly aggravates coding deficits for loud environments. These deficits might help to understand why many individuals with seemingly normal hearing struggle to follow a conversation in background noise. Hidden hearing loss (HHL) arises through subtle damage to the synapses of hair cells in the inner ear before audiograms reveal hearing threshold shifts. Here, the authors report that HHL in a mouse model disrupts the neural encoding of loud sound environments in the central auditory system.
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Affiliation(s)
- Warren Michael Henry Bakay
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.,Manchester Centre for Audiology and Deafness (ManCAD), A3.16, University of Manchester, Ellen Wilkinson Building, Manchester, M13 9PL, UK
| | | | | | - David McAlpine
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.,Department of Linguistics, The Australian Hearing Hub, Macquarie University, 16 University Avenue, Sydney, NSW, 2109, Australia
| | - Roland Schaette
- UCL Ear Institute, 332 Gray's Inn Road, London, WC1X 8EE, UK.
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165
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Liebscher T, Alberter K, Hoppe U. Cortical auditory evoked potentials in cochlear implant listeners via single electrode stimulation in relation to speech perception. Int J Audiol 2018; 57:933-940. [DOI: 10.1080/14992027.2018.1514469] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Tim Liebscher
- Department of Audiology, ENT-Clinic, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Katrin Alberter
- Department of Audiology, ENT-Clinic, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Ulrich Hoppe
- Department of Audiology, ENT-Clinic, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
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166
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Wu PZ, Liberman LD, Bennett K, de Gruttola V, O'Malley JT, Liberman MC. Primary Neural Degeneration in the Human Cochlea: Evidence for Hidden Hearing Loss in the Aging Ear. Neuroscience 2018; 407:8-20. [PMID: 30099118 DOI: 10.1016/j.neuroscience.2018.07.053] [Citation(s) in RCA: 243] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 07/25/2018] [Accepted: 07/30/2018] [Indexed: 01/18/2023]
Abstract
The noise-induced and age-related loss of synaptic connections between auditory-nerve fibers and cochlear hair cells is well-established from histopathology in several mammalian species; however, its prevalence in humans, as inferred from electrophysiological measures, remains controversial. Here we look for cochlear neuropathy in a temporal-bone study of "normal-aging" humans, using autopsy material from 20 subjects aged 0-89 yrs, with no history of otologic disease. Cochleas were immunostained to allow accurate quantification of surviving hair cells in the organ Corti and peripheral axons of auditory-nerve fibers. Mean loss of outer hair cells was 30-40% throughout the audiometric frequency range (0.25-8.0 kHz) in subjects over 60 yrs, with even greater losses at both apical (low-frequency) and basal (high-frequency) ends. In contrast, mean inner hair cell loss across audiometric frequencies was rarely >15%, at any age. Neural loss greatly exceeded inner hair cell loss, with 7/11 subjects over 60 yrs showing >60% loss of peripheral axons re the youngest subjects, and with the age-related slope of axonal loss outstripping the age-related loss of inner hair cells by almost 3:1. The results suggest that a large number of auditory neurons in the aging ear are disconnected from their hair cell targets. This primary neural degeneration would not affect the audiogram, but likely contributes to age-related hearing impairment, especially in noisy environments. Thus, therapies designed to regrow peripheral axons could provide clinically meaningful improvement in the aged ear.
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Affiliation(s)
- P Z Wu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA; Department of Otorhinolaryngology Head and Neck Surgery, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China
| | - L D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - K Bennett
- Department of Biostatistics, Harvard TH Chan School of Public Health, Boston, MA 02115, USA
| | - V de Gruttola
- Department of Biostatistics, Harvard TH Chan School of Public Health, Boston, MA 02115, USA
| | - J T O'Malley
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - M C Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA.
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167
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Glueckert R, Johnson Chacko L, Rask-Andersen H, Liu W, Handschuh S, Schrott-Fischer A. Anatomical basis of drug delivery to the inner ear. Hear Res 2018; 368:10-27. [PMID: 30442227 DOI: 10.1016/j.heares.2018.06.017] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 06/16/2018] [Accepted: 06/25/2018] [Indexed: 12/19/2022]
Abstract
The isolated anatomical position and blood-labyrinth barrier hampers systemic drug delivery to the mammalian inner ear. Intratympanic placement of drugs and permeation via the round- and oval window are established methods for local pharmaceutical treatment. Mechanisms of drug uptake and pathways for distribution within the inner ear are hard to predict. The complex microanatomy with fluid-filled spaces separated by tight- and leaky barriers compose various compartments that connect via active and passive transport mechanisms. Here we provide a review on the inner ear architecture at light- and electron microscopy level, relevant for drug delivery. Focus is laid on the human inner ear architecture. Some new data add information on the human inner ear fluid spaces generated with high resolution microcomputed tomography at 15 μm resolution. Perilymphatic spaces are connected with the central modiolus by active transport mechanisms of mesothelial cells that provide access to spiral ganglion neurons. Reports on leaky barriers between scala tympani and the so-called cortilymph compartment likely open the best path for hair cell targeting. The complex barrier system of tight junction proteins such as occludins, claudins and tricellulin isolates the endolymphatic space for most drugs. Comparison of relevant differences of barriers, target cells and cell types involved in drug spread between main animal models and humans shall provide some translational aspects for inner ear drug applications.
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Affiliation(s)
- R Glueckert
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria; University Clinics Innsbruck, Tirol Kliniken, University Clinic for Ear, Nose and Throat Medicine Innsbruck, Austria.
| | - L Johnson Chacko
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - H Rask-Andersen
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, SE-751 85, Uppsala, Sweden
| | - W Liu
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, SE-751 85, Uppsala, Sweden
| | - S Handschuh
- VetImaging, VetCore Facility for Research, University of Veterinary Medicine, Vienna, Austria
| | - A Schrott-Fischer
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
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168
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Spiegel R, Kalla R, Mantokoudis G, Maire R, Mueller H, Hoerr R, Ihl R. Ginkgo biloba extract EGb 761 ® alleviates neurosensory symptoms in patients with dementia: a meta-analysis of treatment effects on tinnitus and dizziness in randomized, placebo-controlled trials. Clin Interv Aging 2018; 13:1121-1127. [PMID: 29942120 PMCID: PMC6005330 DOI: 10.2147/cia.s157877] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Background Tinnitus and dizziness are frequent in old age and often seen as concomitant symptoms in patients with dementia. In earlier clinical trials, Ginkgo biloba extract EGb 761® was found to alleviate tinnitus and dizziness in elderly patients. Consequently, a meta-analysis was conducted to evaluate the effects of EGb 761® at a daily dose of 240 mg on tinnitus and dizziness associated with dementia. Methods Randomized, placebo-controlled clinical trials of G. biloba extract EGb 761® identified by a systematic database search were included in a meta-analysis if they met all of the following selection criteria: 1) diagnosis of dementia according to generally accepted criteria, 2) treatment period of at least 20 weeks, 3) outcome measures covering at least two of the three conventional domains of assessment, 4) presence and severity of dizziness and tinnitus were assessed, and 5) assessment was done before and after randomized treatment. Results Five trials that met the inclusion criteria were included in the meta-analysis. The risk of bias was judged as low, with Jadad scores of 3 and 5. In all trials, 11-point box scales were used to assess the severity of tinnitus and dizziness. Overall, EGb 761® was superior to placebo, with weighted mean differences for change from baseline, calculated in meta-analyses using random effects models, of -1.06 (95% CI: -1.77, -0.36) for tinnitus (p = 0.003) and -0.77 (95% CI: -1.44, -0.09) for dizziness (p = 0.03). Conclusion Our findings support the notion that EGb 761® is also effective in alleviating concomitant neurosensory symptoms in patients with dementia.
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Affiliation(s)
- Rainer Spiegel
- Division of Internal Medicine, Basel University Hospital, University of Basel, Basel, Switzerland
| | - Roger Kalla
- Department of Neurology, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Georgios Mantokoudis
- Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, Bern University Hospital, Bern, Switzerland
| | | | - Heiko Mueller
- Clinical Research Department, Dr Willmar Schwabe GmbH & Co. KG, Karlsruhe, Germany
| | - Robert Hoerr
- Clinical Research Department, Dr Willmar Schwabe GmbH & Co. KG, Karlsruhe, Germany
| | - Ralf Ihl
- Department of Psychiatry, University of Duesseldorf, Alexian Research Center Krefeld, Krefeld, Germany
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169
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Henry KS, Abrams KS. Persistent Auditory Nerve Damage Following Kainic Acid Excitotoxicity in the Budgerigar (Melopsittacus undulatus). J Assoc Res Otolaryngol 2018; 19:435-449. [PMID: 29744730 DOI: 10.1007/s10162-018-0671-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 04/22/2018] [Indexed: 11/30/2022] Open
Abstract
Permanent loss of auditory nerve (AN) fibers occurs with increasing age and sound overexposure, sometimes without hair cell damage or associated audiometric threshold elevation. Rodent studies suggest effects of AN damage on central processing and behavior, but these species have limited capacity to discriminate low-frequency speech-like sounds. Here, we introduce a new animal model of AN damage in an avian communication specialist, the budgerigar (Melopsittacus undulatus). The budgerigar is a vocal learner and speech mimic with sensitive low-frequency hearing and human-like behavioral sensitivity to many complex signals including speech components. Excitotoxic AN damage was induced through bilateral cochlear infusions of kainic acid (KA). Acute KA effects on cochlear function were assessed using AN compound action potentials (CAPs) and hair cell cochlear microphonics (CMs). Long-term KA effects were assessed using auditory brainstem response (ABR) measurements for up to 31 weeks post-KA exposure. KA infusion immediately abolished AN CAPs while having mild impact on the CM. ABR wave I, the far-field AN response, showed a pronounced 40-75 % amplitude reduction at moderate-to-high sound levels that persisted for the duration of the study. In contrast, wave I latency and the amplitude of wave V were nearly unaffected by KA, and waves II-IV were less reduced than wave I. ABR thresholds, calculated based on complete response waveforms, showed no impairment following KA. These results demonstrate that KA exposure in the budgerigar causes irreversible AN damage, most likely through excitotoxic injury to afferent fibers or synapses as in other species, while sparing ABR thresholds. Normal wave V amplitude, assumed to originate centrally, may persist through compensatory mechanisms that restore central response amplitude by downregulating inhibition. Future studies in this new animal model of AN damage can explore effects of this neural lesion, in isolation from hair cell trauma and threshold elevation, on central processing and perception of complex sounds.
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Affiliation(s)
- Kenneth S Henry
- Department of Otolaryngology, University of Rochester, 601 Elmwood Ave., Box 629, Rochester, NY, 14642, USA.
| | - Kristina S Abrams
- Department of Otolaryngology, University of Rochester, 601 Elmwood Ave., Box 629, Rochester, NY, 14642, USA.,Department of Neuroscience, University of Rochester, Rochester, NY, USA
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170
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Tu NC, Friedman RA. Age-related hearing loss: Unraveling the pieces. Laryngoscope Investig Otolaryngol 2018; 3:68-72. [PMID: 29721536 PMCID: PMC5915820 DOI: 10.1002/lio2.134] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 11/06/2017] [Accepted: 12/04/2017] [Indexed: 01/23/2023] Open
Abstract
Age-related hearing loss (ARHL) is the most common cause of hearing loss in the world. The development of ARHL in each individual is multifactorial, involving both intrinsic and extrinsic factors. This review highlights several of the key findings in the ARHL literature and discusses future directions. LEVEL OF EVIDENCE NA.
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Affiliation(s)
- Nathan C. Tu
- Tina and Rick Caruso Department of Otolaryngology–Head and Neck Surgery (N.C.T., R.A.F.)Keck School of Medicine of the University of Southern CaliforniaLos AngelesCaliforniaU.S.A.
| | - Rick A. Friedman
- Tina and Rick Caruso Department of Otolaryngology–Head and Neck Surgery (N.C.T., R.A.F.)Keck School of Medicine of the University of Southern CaliforniaLos AngelesCaliforniaU.S.A.
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171
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Meas SJ, Zhang CL, Dabdoub A. Reprogramming Glia Into Neurons in the Peripheral Auditory System as a Solution for Sensorineural Hearing Loss: Lessons From the Central Nervous System. Front Mol Neurosci 2018; 11:77. [PMID: 29593497 PMCID: PMC5861218 DOI: 10.3389/fnmol.2018.00077] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 02/26/2018] [Indexed: 12/12/2022] Open
Abstract
Disabling hearing loss affects over 5% of the world’s population and impacts the lives of individuals from all age groups. Within the next three decades, the worldwide incidence of hearing impairment is expected to double. Since a leading cause of hearing loss is the degeneration of primary auditory neurons (PANs), the sensory neurons of the auditory system that receive input from mechanosensory hair cells in the cochlea, it may be possible to restore hearing by regenerating PANs. A direct reprogramming approach can be used to convert the resident spiral ganglion glial cells into induced neurons to restore hearing. This review summarizes recent advances in reprogramming glia in the CNS to suggest future steps for regenerating the peripheral auditory system. In the coming years, direct reprogramming of spiral ganglion glial cells has the potential to become one of the leading biological strategies to treat hearing impairment.
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Affiliation(s)
- Steven J Meas
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.,Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Chun-Li Zhang
- Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Alain Dabdoub
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.,Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada.,Department of Otolaryngology - Head & Neck Surgery, University of Toronto, Toronto, ON, Canada
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172
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Guest H, Munro KJ, Prendergast G, Millman RE, Plack CJ. Impaired speech perception in noise with a normal audiogram: No evidence for cochlear synaptopathy and no relation to lifetime noise exposure. Hear Res 2018; 364:142-151. [PMID: 29680183 PMCID: PMC5993872 DOI: 10.1016/j.heares.2018.03.008] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 02/26/2018] [Accepted: 03/06/2018] [Indexed: 02/01/2023]
Abstract
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. Study of adults with impaired speech perception in noise (SPiN) and normal audiograms. A subset of those with reported SPiN impairment exhibited measurable SPiN deficits. SPiN-impaired participants were matched with controls for age, sex, and audiogram. Impaired SPiN was not associated with ABR or EFR measures of cochlear synaptopathy. Impaired SPiN was not associated with a detailed measure of lifetime noise exposure.
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Affiliation(s)
- Hannah Guest
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK; NIHR Manchester Biomedical Research Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, UK.
| | - Kevin J Munro
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK; NIHR Manchester Biomedical Research Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, UK
| | - Garreth Prendergast
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK; NIHR Manchester Biomedical Research Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, UK
| | - Rebecca E Millman
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK; NIHR Manchester Biomedical Research Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, UK
| | - Christopher J Plack
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK; NIHR Manchester Biomedical Research Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, UK; Department of Psychology, Lancaster University, UK
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173
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Auditory Brainstem Response Altered in Humans With Noise Exposure Despite Normal Outer Hair Cell Function. Ear Hear 2018; 38:e1-e12. [PMID: 27992391 DOI: 10.1097/aud.0000000000000370] [Citation(s) in RCA: 140] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Recent animal studies demonstrated that cochlear synaptopathy, a partial loss of inner hair cell-auditory nerve fiber synapses, can occur in response to noise exposure without any permanent auditory threshold shift. In animal models, this synaptopathy is associated with a reduction in the amplitude of wave I of the auditory brainstem response (ABR). The goal of this study was to determine whether higher lifetime noise exposure histories in young people with clinically normal pure-tone thresholds are associated with lower ABR wave I amplitudes. DESIGN Twenty-nine young military Veterans and 35 non Veterans (19 to 35 years of age) with normal pure-tone thresholds were assigned to 1 of 4 groups based on their self-reported lifetime noise exposure history and Veteran status. Suprathreshold ABR measurements in response to alternating polarity tone bursts were obtained at 1, 3, 4, and 6 kHz with gold foil tiptrode electrodes placed in the ear canal. Wave I amplitude was calculated from the difference in voltage at the positive peak and the voltage at the following negative trough. Distortion product otoacoustic emission input/output functions were collected in each participant at the same four frequencies to assess outer hair cell function. RESULTS After controlling for individual differences in sex and distortion product otoacoustic emission amplitude, the groups containing participants with higher reported histories of noise exposure had smaller ABR wave I amplitudes at suprathreshold levels across all four frequencies compared with the groups with less history of noise exposure. CONCLUSIONS Suprathreshold ABR wave I amplitudes were reduced in Veterans reporting high levels of military noise exposure and in non Veterans reporting any history of firearm use as compared with Veterans and non Veterans with lower levels of reported noise exposure history. The reduction in ABR wave I amplitude in the groups with higher levels of noise exposure cannot be accounted for by sex or variability in outer hair cell function. This change is similar to the decreased ABR wave I amplitudes observed in animal models of noise-induced cochlear synaptopathy. However, without post mortem examination of the temporal bone, no direct conclusions can be drawn concerning the presence of synaptopathy in the study groups with higher noise exposure histories.
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174
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Abstract
Many people with difficulties following conversations in noisy settings have “clinically normal” audiograms, that is, tone thresholds better than 20 dB HL from 0.1 to 8 kHz. This review summarizes the possible causes of such difficulties, and examines established as well as promising new psychoacoustic and electrophysiologic approaches to differentiate between them. Deficits at the level of the auditory periphery are possible even if thresholds remain around 0 dB HL, and become probable when they reach 10 to 20 dB HL. Extending the audiogram beyond 8 kHz can identify early signs of noise-induced trauma to the vulnerable basal turn of the cochlea, and might point to “hidden” losses at lower frequencies that could compromise speech reception in noise. Listening difficulties can also be a consequence of impaired central auditory processing, resulting from lesions affecting the auditory brainstem or cortex, or from abnormal patterns of sound input during developmental sensitive periods and even in adulthood. Such auditory processing disorders should be distinguished from (cognitive) linguistic deficits, and from problems with attention or working memory that may not be specific to the auditory modality. Improved diagnosis of the causes of listening difficulties in noise should lead to better treatment outcomes, by optimizing auditory training procedures to the specific deficits of individual patients, for example.
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175
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Temporal Response Properties of the Auditory Nerve in Implanted Children with Auditory Neuropathy Spectrum Disorder and Implanted Children with Sensorineural Hearing Loss. Ear Hear 2018; 37:397-411. [PMID: 26655913 DOI: 10.1097/aud.0000000000000254] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE This study aimed to (1) characterize temporal response properties of the auditory nerve in implanted children with auditory neuropathy spectrum disorder (ANSD), and (2) compare results recorded in implanted children with ANSD with those measured in implanted children with sensorineural hearing loss (SNHL). DESIGN Participants included 28 children with ANSD and 29 children with SNHL. All subjects used cochlear nucleus devices in their test ears. Both ears were tested in 6 children with ANSD and 3 children with SNHL. For all other subjects, only one ear was tested. The electrically evoked compound action potential (ECAP) was measured in response to each of the 33 pulses in a pulse train (excluding the second pulse) for one apical, one middle-array, and one basal electrode. The pulse train was presented in a monopolar-coupled stimulation mode at 4 pulse rates: 500, 900, 1800, and 2400 pulses per second. Response metrics included the averaged amplitude, latencies of response components and response width, the alternating depth and the amount of neural adaptation. These dependent variables were quantified based on the last six ECAPs or the six ECAPs occurring within a time window centered around 11 to 12 msec. A generalized linear mixed model was used to compare these dependent variables between the 2 subject groups. The slope of the linear fit of the normalized ECAP amplitudes (re. amplitude of the first ECAP response) over the duration of the pulse train was used to quantify the amount of ECAP increment over time for a subgroup of 9 subjects. RESULTS Pulse train-evoked ECAPs were measured in all but 8 subjects (5 with ANSD and 3 with SNHL). ECAPs measured in children with ANSD had smaller amplitude, longer averaged P2 latency and greater response width than children with SNHL. However, differences in these two groups were only observed for some electrodes. No differences in averaged N1 latency or in the alternating depth were observed between children with ANSD and children with SNHL. Neural adaptation measured in these 2 subject groups was comparable for relatively short durations of stimulation (i.e., 11 to 12 msec). Children with ANSD showed greater neural adaptation than children with SNHL for a longer duration of stimulation. Amplitudes of ECAP responses rapidly declined within the first few milliseconds of stimulation, followed by a gradual decline up to 64 msec after stimulus onset in the majority of subjects. This decline exhibited an alternating pattern at some pulse rates. Further increases in pulse rate diminished this alternating pattern. In contrast, ECAPs recorded from at least one stimulating electrode in six ears with ANSD and three ears with SNHL showed a clear increase in amplitude over the time course of stimulation. The slope of linear regression functions measured in these subjects was significantly greater than zero. CONCLUSIONS Some but not all aspects of temporal response properties of the auditory nerve measured in this study differ between implanted children with ANSD and implanted children with SNHL. These differences are observed for some but not all electrodes. A new neural response pattern is identified. Further studies investigating its underlying mechanism and clinical relevance are warranted.
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176
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Füllgrabe C, Sęk AP, Moore BCJ. Senescent Changes in Sensitivity to Binaural Temporal Fine Structure. Trends Hear 2018; 22:2331216518788224. [PMID: 30027803 PMCID: PMC6055238 DOI: 10.1177/2331216518788224] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 06/11/2018] [Accepted: 06/12/2018] [Indexed: 11/26/2022] Open
Abstract
Differences in the temporal fine structure (TFS) of sounds at the two ears are used for sound localization and for the perceptual analysis of complex auditory scenes. The ability to process this binaural TFS information is poorer for older than for younger participants, and this may contribute to age-related declines in the ability to understand speech in noisy situations. However, it is unclear how sensitivity to binaural TFS changes across the older age range. This article presents data for a test of binaural sensitivity to TFS, the "TFS-adaptive frequency" (AF) test, for 118 listeners aged 60 to 96 years with normal or near-normal low-frequency hearing, but a variety of patterns of hearing loss at higher frequencies. TFS-AF scores were significantly lower (i.e., poorer) than those for young adults. On average, scores decreased by about 162 Hz for each 10-year increase in age over the range 60 to 85 years. Individual variability increased with increasing age. Scores also declined as low-frequency audiometric thresholds worsened. The results illustrate the range of scores that can be obtained as a function of age and may be useful for the diagnosis and management of age-related hearing difficulties.
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Affiliation(s)
- Christian Füllgrabe
- Medical Research Council Institute of Hearing Research, School of Medicine, University of Nottingham, UK
| | - Aleksander P. Sęk
- Institute of Acoustics, Faculty of Physics, Adam Mickiewicz University, Poznan, Poland
- Department of Psychology, University of Cambridge, UK
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177
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Chambers AR, Pilati N, Balaram P, Large CH, Kaczmarek LK, Polley DB. Pharmacological modulation of Kv3.1 mitigates auditory midbrain temporal processing deficits following auditory nerve damage. Sci Rep 2017; 7:17496. [PMID: 29235497 PMCID: PMC5727503 DOI: 10.1038/s41598-017-17406-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 11/20/2017] [Indexed: 12/12/2022] Open
Abstract
Higher stages of central auditory processing compensate for a loss of cochlear nerve synapses by increasing the gain on remaining afferent inputs, thereby restoring firing rate codes for rudimentary sound features. The benefits of this compensatory plasticity are limited, as the recovery of precise temporal coding is comparatively modest. We reasoned that persistent temporal coding deficits could be ameliorated through modulation of voltage-gated potassium (Kv) channels that regulate temporal firing patterns. Here, we characterize AUT00063, a pharmacological compound that modulates Kv3.1, a high-threshold channel expressed in fast-spiking neurons throughout the central auditory pathway. Patch clamp recordings from auditory brainstem neurons and in silico modeling revealed that application of AUT00063 reduced action potential timing variability and improved temporal coding precision. Systemic injections of AUT00063 in vivo improved auditory synchronization and supported more accurate decoding of temporal sound features in the inferior colliculus and auditory cortex in adult mice with a near-complete loss of auditory nerve afferent synapses in the contralateral ear. These findings suggest modulating Kv3.1 in central neurons could be a promising therapeutic approach to mitigate temporal processing deficits that commonly accompany aging, tinnitus, ototoxic drug exposure or noise damage.
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Affiliation(s)
- Anna R Chambers
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.,Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Nadia Pilati
- Autifony SRL, Verona, Italy; and Autifony Therapeutics Limited, Imperial College Incubator, London, UK
| | - Pooja Balaram
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA, USA.,Department of Otolaryngology, Harvard Medical School, Boston, MA, USA
| | - Charles H Large
- Autifony SRL, Verona, Italy; and Autifony Therapeutics Limited, Imperial College Incubator, London, UK
| | - Leonard K Kaczmarek
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
| | - Daniel B Polley
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA, USA. .,Department of Otolaryngology, Harvard Medical School, Boston, MA, USA.
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178
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Zhang W, Zheng J, Meng J, Neng L, Chen X, Qin Z. Macrophage migration inhibitory factor knockdown inhibit viability and induce apoptosis of PVM/Ms. Mol Med Rep 2017; 16:8643-8648. [PMID: 28990052 PMCID: PMC5779918 DOI: 10.3892/mmr.2017.7684] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 07/03/2017] [Indexed: 12/20/2022] Open
Abstract
Previous studies have suggested that macrophage migration inhibitory factor (MIF) serves an important role in hearing function; however, the underlying mechanism remains unclear. In the present study, perivascular‑resident macrophage‑like melanocytes (PVM/Ms) from the stria vascularis of the lateral cochlear wall in young and aged mice were isolated. The mRNA and protein expression levels of MIF were determined using reverse transcription‑quantitative polymerase chain reaction analysis, and western blotting, respectively. MIF expression was knocked down in vitro and in vivo using small interfering RNA. Cell viability was determined using an MTT assay and cell apoptosis was determined using flow cytometry analysis. The hearing ability was assessed through the auditory brain stem response in vivo. The results of the current study demonstrated that the expression of MIF was significantly downregulated in aged mice compared with in young mice. Furthermore, the viability of PVM/Ms in aged mice was significantly decreased and the number of apoptotic PVM/Ms was significantly increased compared with that in young mice. Further studies demonstrated that the MIF knockdown accentuated hearing loss in young mice as compared with the scramble control group. In addition, the MIF knockdown in PVM/Ms significantly inhibited cell viability and lead to a significant increase in the apoptotic cell number as compared with the control group. In summary, these results revealed that the MIF knockdown significantly accentuates hearing loss in young mice in vivo, and significantly inhibits the viability and induces the apoptosis of PVM/Ms in vitro. Thus, the results of the present study may provide a novel potential therapeutic approach and prevention method for presbycusis.
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Affiliation(s)
- Wenjing Zhang
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, P.R. China
| | - Jian Zheng
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, P.R. China
| | - Juan Meng
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, P.R. China
| | - Lingling Neng
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, P.R. China
| | - Xiaohua Chen
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, P.R. China
| | - Zhaobing Qin
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450000, P.R. China
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179
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Abstract
OBJECTIVES The long-term goal of this research is to determine whether the middle ear muscle reflex can be used to predict the number of healthy auditory nerve fibers in hearing-impaired ears. In this study, we develop a high-impedance source and an animal model of the middle ear muscle reflex and explore the influence of signal frequency and level on parameters of the reflex to determine an optimal signal to examine auditory nerve fiber survival. DESIGN A high-impedance source was developed using a hearing aid receiver attached to a 0.06 diameter 10.5-cm length tube. The impedance probe consisted of a microphone probe placed near the tip of a tube coupled to a sound source. The probe was calibrated by inserting it into a syringe of known volumes and impedances. The reflex in the anesthetized rat was measured with elicitor stimuli ranging from 3 to 16 kHz presented at levels ranging from 35 to 100 dB SPL to one ear while the reflex was measured in the opposite ear containing the probe and probe stimulus. RESULTS The amplitude of the reflex increased with elicitor level and was largest at 3 kHz. The lowest threshold was approximately 54 dB SPL for the 3-kHz stimulus. The rate of decay of the reflex was greatest at 16 kHz followed by 10 and 3 kHz. The rate of decay did not change significantly with elicitor signal level for 3 and 16 kHz, but decreased as the level of the 10-kHz elicitor increased. A negative feedback model accounts for the reflex decay by having the strength of feedback dependent on auditory nerve input. The rise time of the reflex varied with frequency and changed with level for the 10- and 16-kHz signals but not significantly for the 3-kHz signal. The latency of the reflex increased with a decrease in elicitor level, and the change in latency with level was largest for the 10-kHz stimulus. CONCLUSIONS Because the amplitude of the reflex in rat was largest with an elicitor signal at 3 kHz, had the lowest threshold, and yielded the least amount of decay, this may be the ideal frequency to estimate auditory nerve survival in hearing-impaired ears.
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180
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Shinn-Cunningham B. Cortical and Sensory Causes of Individual Differences in Selective Attention Ability Among Listeners With Normal Hearing Thresholds. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2017; 60:2976-2988. [PMID: 29049598 PMCID: PMC5945067 DOI: 10.1044/2017_jslhr-h-17-0080] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 06/23/2017] [Accepted: 07/05/2017] [Indexed: 05/28/2023]
Abstract
PURPOSE This review provides clinicians with an overview of recent findings relevant to understanding why listeners with normal hearing thresholds (NHTs) sometimes suffer from communication difficulties in noisy settings. METHOD The results from neuroscience and psychoacoustics are reviewed. RESULTS In noisy settings, listeners focus their attention by engaging cortical brain networks to suppress unimportant sounds; they then can analyze and understand an important sound, such as speech, amidst competing sounds. Differences in the efficacy of top-down control of attention can affect communication abilities. In addition, subclinical deficits in sensory fidelity can disrupt the ability to perceptually segregate sound sources, interfering with selective attention, even in listeners with NHTs. Studies of variability in control of attention and in sensory coding fidelity may help to isolate and identify some of the causes of communication disorders in individuals presenting at the clinic with "normal hearing." CONCLUSIONS How well an individual with NHTs can understand speech amidst competing sounds depends not only on the sound being audible but also on the integrity of cortical control networks and the fidelity of the representation of suprathreshold sound. Understanding the root cause of difficulties experienced by listeners with NHTs ultimately can lead to new, targeted interventions that address specific deficits affecting communication in noise. PRESENTATION VIDEO http://cred.pubs.asha.org/article.aspx?articleid=2601617.
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Affiliation(s)
- Barbara Shinn-Cunningham
- Center for Research in Sensory Communication and Emerging Neural Technology, Boston University, MA
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181
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Lai J, Sommer AL, Bartlett EL. Age-related changes in envelope-following responses at equalized peripheral or central activation. Neurobiol Aging 2017; 58:191-200. [PMID: 28753474 PMCID: PMC5581704 DOI: 10.1016/j.neurobiolaging.2017.06.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 06/18/2017] [Accepted: 06/18/2017] [Indexed: 11/20/2022]
Abstract
Previous work has debated about the comparisons of hearing abilities faced with alterations in hearing thresholds and evoked potentials between groups following acoustic trauma- or age-related changes. This study compares envelope-following responses (EFRs) of young and aged rats when sound levels were matched according to (1) wave I amplitudes of auditory brainstem responses (ABRs) elicited by 8-kHz tones or (2) EFR amplitudes evoked by sinusoidally amplitude-modulated (SAM) tones at 100% depth. Matched wave I amplitudes across age corresponded to approximately 20-dB sound level differences. For matched wave I, no age-related differences were observed in wave V amplitudes. However, EFRs recorded in silence were enhanced with aging at 100% but not at 25% depth, consistent with enhanced central gain in aging. For matched EFRs, there were no age-related differences in EFRs of amplitude modulation (AM) depth and AM frequency processing. These results suggest novel, objective measures beyond threshold to compensate for differences in auditory nerve activation and to differentiate peripheral and central contributions of EFRs.
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Affiliation(s)
- Jesyin Lai
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Alexandra L Sommer
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Edward L Bartlett
- Department of Biological Sciences and the Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
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182
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Grinn SK, Wiseman KB, Baker JA, Le Prell CG. Hidden Hearing Loss? No Effect of Common Recreational Noise Exposure on Cochlear Nerve Response Amplitude in Humans. Front Neurosci 2017; 11:465. [PMID: 28919848 PMCID: PMC5585187 DOI: 10.3389/fnins.2017.00465] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Accepted: 08/07/2017] [Indexed: 11/22/2022] Open
Abstract
This study tested hypothesized relationships between noise exposure and auditory deficits. Both retrospective assessment of potential associations between noise exposure history and performance on an audiologic test battery and prospective assessment of potential changes in performance after new recreational noise exposure were completed. Methods: 32 participants (13M, 19F) with normal hearing (25-dB HL or better, 0.25–8 kHz) were asked to participate in 3 pre- and post-exposure sessions including: otoscopy, tympanometry, distortion product otoacoustic emissions (DPOAEs) (f2 frequencies 1–8 kHz), pure-tone audiometry (0.25–8 kHz), Words-in-Noise (WIN) test, and electrocochleography (eCochG) measurements at 70, 80, and 90-dB nHL (click and 2–4 kHz tone-bursts). The first session was used to collect baseline data, the second session was collected the day after a loud recreational event, and the third session was collected 1-week later. Of the 32 participants, 26 completed all 3 sessions. Results: The retrospective analysis did not reveal statistically significant relationships between noise exposure history and any auditory deficits. The day after new exposure, there was a statistically significant correlation between noise “dose” and WIN performance overall, and within the 4-dB signal-to-babble ratio. In contrast, there were no statistically significant correlations between noise dose and changes in threshold, DPOAE amplitude, or AP amplitude the day after new noise exposure. Additional analyses revealed a statistically significant relationship between TTS and DPOAE amplitude at 6 kHz, with temporarily decreased DPOAE amplitude observed with increasing TTS. Conclusions: There was no evidence of auditory deficits as a function of previous noise exposure history, and no permanent changes in audiometric, electrophysiologic, or functional measures after new recreational noise exposure. There were very few participants with TTS the day after exposure - a test time selected to be consistent with previous animal studies. The largest observed TTS was approximately 20-dB. The observed pattern of small TTS suggests little risk of synaptopathy from common recreational noise exposure, and that we should not expect to observe changes in evoked potentials for this reason. No such changes were observed in this study. These data do not support suggestions that common, recreational noise exposure is likely to result in “hidden hearing loss”.
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Affiliation(s)
- Sarah K Grinn
- School of Behavioral and Brain Sciences, University of Texas at DallasDallas, TX, United States.,College of Public Health and Health Professions, University of FloridaGainesville, FL, United States
| | - Kathryn B Wiseman
- School of Behavioral and Brain Sciences, University of Texas at DallasDallas, TX, United States
| | - Jason A Baker
- School of Behavioral and Brain Sciences, University of Texas at DallasDallas, TX, United States
| | - Colleen G Le Prell
- School of Behavioral and Brain Sciences, University of Texas at DallasDallas, TX, United States
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183
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Valero MD, Burton JA, Hauser SN, Hackett TA, Ramachandran R, Liberman MC. Noise-induced cochlear synaptopathy in rhesus monkeys (Macaca mulatta). Hear Res 2017; 353:213-223. [PMID: 28712672 PMCID: PMC5632522 DOI: 10.1016/j.heares.2017.07.003] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 06/02/2017] [Accepted: 07/06/2017] [Indexed: 12/21/2022]
Abstract
Cochlear synaptopathy can result from various insults, including acoustic trauma, aging, ototoxicity, or chronic conductive hearing loss. For example, moderate noise exposure in mice can destroy up to ∼50% of synapses between auditory nerve fibers (ANFs) and inner hair cells (IHCs) without affecting outer hair cells (OHCs) or thresholds, because the synaptopathy occurs first in high-threshold ANFs. However, the fiber loss likely impairs temporal processing and hearing-in-noise, a classic complaint of those with sensorineural hearing loss. Non-human primates appear to be less vulnerable to noise-induced hair-cell loss than rodents, but their susceptibility to synaptopathy has not been studied. Because establishing a non-human primate model may be important in the development of diagnostics and therapeutics, we examined cochlear innervation and the damaging effects of acoustic overexposure in young adult rhesus macaques. Anesthetized animals were exposed bilaterally to narrow-band noise centered at 2 kHz at various sound-pressure levels for 4 h. Cochlear function was assayed for up to 8 weeks following exposure via auditory brainstem responses (ABRs) and otoacoustic emissions (OAEs). A moderate loss of synaptic connections (mean of 12-27% in the basal half of the cochlea) followed temporary threshold shifts (TTS), despite minimal hair-cell loss. A dramatic loss of synapses (mean of 50-75% in the basal half of the cochlea) was seen on IHCs surviving noise exposures that produced permanent threshold shifts (PTS) and widespread hair-cell loss. Higher noise levels were required to produce PTS in macaques compared to rodents, suggesting that primates are less vulnerable to hair-cell loss. However, the phenomenon of noise-induced cochlear synaptopathy in primates is similar to that seen in rodents.
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Affiliation(s)
- M D Valero
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA.
| | - J A Burton
- Vanderbilt University Medical Center, Dept. of Hearing and Speech Sciences, Nashville, TN 37232, USA
| | - S N Hauser
- Vanderbilt University Medical Center, Dept. of Hearing and Speech Sciences, Nashville, TN 37232, USA
| | - T A Hackett
- Vanderbilt University Medical Center, Dept. of Hearing and Speech Sciences, Nashville, TN 37232, USA
| | - R Ramachandran
- Vanderbilt University Medical Center, Dept. of Hearing and Speech Sciences, Nashville, TN 37232, USA
| | - M C Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA; Department of Otolaryngology, Harvard Medical School, Boston, MA 02115, USA
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184
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Abstract
Noise levels are truly continuous in relatively few occupations, with some degree of intermittency the most common condition. The sound levels of intermittent noise are often referred to as non-Gaussian in that they are not normally distributed in the time domain. In some conditions, intermittent noise affects the ear differently from continuous noise, and it is this assumption that underlies the selection of the 5-dB exchange rate (ER). The scientific and professional communities have debated this assumption over recent decades. This monograph explores the effect of non-Gaussian noise on the auditory system. It begins by summarizing an earlier report by the same author concentrating on the subject of the ER. The conclusions of the earlier report supported the more conservative 3-dB ER with possible adjustments to the permissible exposure limit for certain working conditions. The current document has expanded on the earlier report in light of the relevant research accomplished in the intervening decades. Although some of the animal research has supported the mitigating effect of intermittency, a closer look at many of these studies reveals certain weaknesses, along with the fact that these noise exposures were not usually representative of the conditions under which people actually work. The more recent animal research on complex noise shows that intermittencies do not protect the cochlea and that many of the previous assumptions about the ameliorative effect of intermittencies are no longer valid, lending further support to the 3-dB ER. The neurologic effects of noise on hearing have gained increasing attention in recent years because of improvements in microscopy and immunostaining techniques. Animal experiments showing damage to auditory synapses from noise exposures previously considered harmless may signify the need for a more conservative approach to the assessment of noise-induced hearing loss and consequently the practice of hearing conservation programs.
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185
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Zhang W, Zheng J, Meng J, Neng L, Chen X, Qin Z. Macrophage migration inhibitory factor mediates viability and apoptosis of PVM/Ms through PI3K/Akt pathway. Neuroscience 2017; 360:220-229. [PMID: 28694172 DOI: 10.1016/j.neuroscience.2017.06.063] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 06/01/2017] [Accepted: 06/05/2017] [Indexed: 12/20/2022]
Abstract
Macrophage migration inhibitory factor (MIF) plays an important role in hearing function; however, the underlying mechanism remains indistinct. PVM/Ms from the stria vascularis of lateral wall of cochlea in young and aged mice were isolated, and the mRNA and protein expression levels were detected. MIF was knocked down or overexpresssed in vitro, and transfection was performed in vivo. Cell viability and apoptosis were determined by MTT assay and flow cytometry analysis, respectively. The hearing ability was tested by the auditory brain stem response. The results showed that MIF expression was significantly downregulated in aged mice. In aged mice, the viability of PVM/Ms significantly decreased, but the apoptotic number markedly increased. MIF knockdown in PVM/Ms in vitro significantly inhibited cell viability and induced cell apoptosis, but MIF overexpression showed contrasting results. Further studies showed that MIF knockdown in young mice resulted in serious hearing loss, but MIF overexpression in aged mice restored the hearing. Si-MIF inhibited the viability and induced apoptosis of PVM/Ms from young mice, whereas Ad-MIF induced the viability and inhibited apoptosis of PVM/Ms from aged mice. Moreover, MIF effectively altered the expression levels of CDK1, BRAF, p-ERK1/2, p-PI3K, and p-Akt. Furthermore, ERK inhibitor PD98059 or PI3K inhibitor LY294002 significantly reversed the effects of Si-MIF on PVM/Ms from young mice, whereas ERK activator EGF or PI3K activator IGF significantly reversed the effects of Ad-MIF on PVM/Ms from aged mice. Taken together, MIF mediates the viability and apoptosis of PVM/Ms, at least partially, through MAPK and/or PI3K/Akt pathway.
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Affiliation(s)
- Wenjing Zhang
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450000, China
| | - Jian Zheng
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450000, China
| | - Juan Meng
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450000, China
| | - Lingling Neng
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450000, China
| | - Xiaohua Chen
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450000, China
| | - Zhaobing Qin
- Department of Otology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450000, China.
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186
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Sagers JE, Landegger LD, Worthington S, Nadol JB, Stankovic KM. Human Cochlear Histopathology Reflects Clinical Signatures of Primary Neural Degeneration. Sci Rep 2017; 7:4884. [PMID: 28687782 PMCID: PMC5501826 DOI: 10.1038/s41598-017-04899-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 05/22/2017] [Indexed: 01/22/2023] Open
Abstract
Auditory neuropathy is a significant and understudied cause of human hearing loss, diagnosed in patients who demonstrate abnormal function of the cochlear nerve despite typical function of sensory cells. Because the human inner ear cannot be visualized during life, histopathological analysis of autopsy specimens is critical to understanding the cellular mechanisms underlying this pathology. Here we present statistical models of severe primary neuronal degeneration and its relationship to pure tone audiometric thresholds and word recognition scores in comparison to age-matched control patients, spanning every decade of life. Analysis of 30 ears from 23 patients shows that severe neuronal loss correlates with elevated audiometric thresholds and poor word recognition. For each ten percent increase in total neuronal loss, average thresholds across patients at each audiometric test frequency increase by 6.0 dB hearing level (HL). As neuronal loss increases, threshold elevation proceeds more rapidly in low audiometric test frequencies than in high frequencies. Pure tone average closely agrees with word recognition scores in the case of severe neural pathology. Histopathologic study of the human inner ear continues to emphasize the need for non- or minimally invasive clinical tools capable of establishing cellular-level diagnoses.
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Affiliation(s)
- Jessica E Sagers
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States.,Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, 02114, United States
| | - Lukas D Landegger
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States.,Department of Otolaryngology, Vienna General Hospital, Medical University of Vienna, Vienna, 1090, Austria.,Department of Otolaryngology, Harvard Medical School, Boston, MA, 02114, United States
| | - Steven Worthington
- Harvard Institute for Quantitative Social Science, Harvard University, Cambridge, MA, 02138, USA
| | - Joseph B Nadol
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States.,Department of Otolaryngology, Harvard Medical School, Boston, MA, 02114, United States
| | - Konstantina M Stankovic
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States. .,Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, 02114, United States. .,Department of Otolaryngology, Harvard Medical School, Boston, MA, 02114, United States.
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187
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Aazh H, Moore BCJ. Factors related to uncomfortable loudness levels for patients seen in a tinnitus and hyperacusis clinic. Int J Audiol 2017. [PMID: 28622055 DOI: 10.1080/14992027.2017.1335888] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVES The aims were as follows: (1) to explore patterns of uncomfortable loudness levels (ULLs) across frequency and their associated factors for patients with tinnitus and hyperacusis, and (2) to re-evaluate the criteria for diagnosing hyperacusis based on ULLs and scores for the Hyperacusis Questionnaire (HQ). DESIGN This was a retrospective cross-sectional study. STUDY SAMPLE 573 consecutive patients for whom ULLs had been measured were included. RESULTS A good correspondence between the diagnosis of hyperacusis based on the across-frequency average ULL for the ear with the lowest ULLs (ULLmin) and hyperacusis handicap based on HQ scores was obtained with cut-off values of ULLmin ≤77 dB HL and HQ score ≥ 22. A regression model showed significant relationships between ULLmin and the score on the HQ and age. The mean HQ score for patients with a large interaural asymmetry in ULLs was significantly higher than for the remainder. Hyperacusis handicap was associated with strong across-frequency variations in ULLs. CONCLUSIONS Appropriate cut-off values for diagnosing hyperacusis are ULLmin ≤77 dB HL and HQ score ≥22. Large interaural asymmetry and large across-frequency variations in ULLs are associated with higher HQ scores.
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Affiliation(s)
- Hashir Aazh
- a Audiology Department , Royal Surrey County Hospital NHS Foundation Trust , Guildford , UK and
| | - Brian C J Moore
- b Department of Experimental Psychology , University of Cambridge , Cambridge , UK
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188
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Mady LJ, Sukato DC, Fruit J, Palmer C, Raz Y, Hirsch BE, McCall AA. Hearing Preservation: Does Electrode Choice Matter? Otolaryngol Head Neck Surg 2017; 157:837-847. [PMID: 28608735 DOI: 10.1177/0194599817707167] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective Evaluate if electrode design affects hearing preservation (HP) following cochlear implantation (CI) with full-length electrodes. Study Design Case series with chart review. Setting Tertiary referral academic center. Subjects and Methods Forty-five adults with low-frequency hearing (≤85 dB at 250 and 500 Hz) who underwent unilateral CI with full-length electrode arrays made by 1 manufacturer were included. HP was calculated with (1) mean low-frequency pure-tone average (LFPTA) at 250 and 500 Hz (MEAN method), (2) a percentile method across the audiometric frequency spectrum generating an S-value (HEARRING method), and (3) functional if hearing remained ≤85 dB at 250 and 500 Hz. Audiometric testing was performed approximately 1 month and 1 year postoperatively, yielding short-term and long-term results, respectively. Results Of 45 patients who underwent CI, 46.7% received lateral wall (LW) and 53.3% received perimodiolar (PM) electrodes. At short-term follow-up, LW electrodes were associated with significantly better HP than PM (LFPTA method: 27.7 vs 39.3 dB, P < .05; S-value method: 48.2 vs 21.8%, P < .05). In multivariate regression of short-term outcomes, LW electrode use was a significant predictor of better HP ( P < .05). At long-term follow-up, electrode type was not associated with HP. Younger patient age was the only significant predictor of long-term HP on multivariate analysis ( P < .05). Conclusion The LW electrode is associated with short-term HP, suggesting its design is favorable for limiting trauma to the cochlea during and directly following CI. Other factors, including age, are relevant for maintaining HP over the long term. The data support further investigation into what modifiable factors may promote long-term HP.
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Affiliation(s)
- Leila J Mady
- 1 Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Daniel C Sukato
- 1 Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Jenifer Fruit
- 1 Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Catherine Palmer
- 1 Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.,2 Department of Communication Science and Disorders, University of Pittsburgh, Pennsylvania, USA
| | - Yael Raz
- 1 Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.,3 Department of Otolaryngology/Head and Neck Surgery, Oregon Health and Sciences University, Portland, Oregon, USA
| | - Barry E Hirsch
- 1 Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.,2 Department of Communication Science and Disorders, University of Pittsburgh, Pennsylvania, USA
| | - Andrew A McCall
- 1 Department of Otolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
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189
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Landegger LD, Dilwali S, Stankovic KM. Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research. J Vis Exp 2017. [PMID: 28654047 DOI: 10.3791/55704] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a condition that typically involves damage to or loss of the delicate mechanosensory structures of the inner ear. Sophisticated in vitro and ex vivo assays have emerged in recent years, enabling the screening of an increasing number of potentially therapeutic compounds while minimizing resources and accelerating efforts to develop cures for SNHL. Though homogenous cultures of certain cell types continue to play an important role in current research, many scientists now rely on more complex organotypic cultures of murine inner ears, also known as cochlear explants. The preservation of organized cellular structures within the inner ear facilitates the in situ evaluation of various components of the cochlear infrastructure, including inner and outer hair cells, spiral ganglion neurons, neurites, and supporting cells. Here we present the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The careful preparation of these explants facilitates the identification of mechanisms that contribute to SNHL and constitutes a valuable tool for the hearing research community.
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Affiliation(s)
- Lukas D Landegger
- Eaton Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear; Department of Otolaryngology, Harvard Medical School; Department of Otolaryngology, Vienna General Hospital, Medical University of Vienna
| | - Sonam Dilwali
- Eaton Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear; Harvard Program in Speech and Hearing Bioscience and Technology
| | - Konstantina M Stankovic
- Eaton Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear; Department of Otolaryngology, Harvard Medical School; Harvard Program in Speech and Hearing Bioscience and Technology;
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190
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Liberman MC, Kujawa SG. Cochlear synaptopathy in acquired sensorineural hearing loss: Manifestations and mechanisms. Hear Res 2017; 349:138-147. [PMID: 28087419 PMCID: PMC5438769 DOI: 10.1016/j.heares.2017.01.003] [Citation(s) in RCA: 435] [Impact Index Per Article: 62.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 12/19/2016] [Accepted: 01/05/2017] [Indexed: 12/20/2022]
Abstract
Common causes of hearing loss in humans - exposure to loud noise or ototoxic drugs and aging - often damage sensory hair cells, reflected as elevated thresholds on the clinical audiogram. Recent studies in animal models suggest, however, that well before this overt hearing loss can be seen, a more insidious, but likely more common, process is taking place that permanently interrupts synaptic communication between sensory inner hair cells and subsets of cochlear nerve fibers. The silencing of affected neurons alters auditory information processing, whether accompanied by threshold elevations or not, and is a likely contributor to a variety of perceptual abnormalities, including speech-in-noise difficulties, tinnitus and hyperacusis. Work described here will review structural and functional manifestations of this cochlear synaptopathy and will consider possible mechanisms underlying its appearance and progression in ears with and without traditional 'hearing loss' arising from several common causes in humans.
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MESH Headings
- Animals
- Auditory Perception
- Auditory Threshold
- Cochlear Nerve/metabolism
- Cochlear Nerve/pathology
- Cochlear Nerve/physiopathology
- Glutamic Acid/metabolism
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/pathology
- Hearing
- Hearing Loss, Noise-Induced/metabolism
- Hearing Loss, Noise-Induced/pathology
- Hearing Loss, Noise-Induced/physiopathology
- Hearing Loss, Noise-Induced/psychology
- Hearing Loss, Sensorineural/metabolism
- Hearing Loss, Sensorineural/pathology
- Hearing Loss, Sensorineural/physiopathology
- Hearing Loss, Sensorineural/psychology
- Humans
- Nerve Degeneration
- Noise/adverse effects
- Risk Factors
- Synapses/metabolism
- Synapses/pathology
- Synaptic Transmission
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Affiliation(s)
- M Charles Liberman
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary, Boston MA, USA
| | - Sharon G Kujawa
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary, Boston MA, USA.
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191
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Harris KC, Dubno JR. Age-related deficits in auditory temporal processing: unique contributions of neural dyssynchrony and slowed neuronal processing. Neurobiol Aging 2017; 53:150-158. [PMID: 28185661 PMCID: PMC5385299 DOI: 10.1016/j.neurobiolaging.2017.01.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 01/02/2017] [Accepted: 01/05/2017] [Indexed: 11/20/2022]
Abstract
This study was guided by the hypothesis that the aging central nervous system progressively loses its ability to process rapid acoustic changes that are important for speech recognition. Specifically, we hypothesized that age-related deficits in neural synchrony and neuronal oscillatory activity occur independently in older adults and disrupt auditory temporal processing. Neural synchrony is largely dependent on phase locking within the central auditory pathway, beginning at the auditory nerve. In contrast, the resonance characteristics of oscillatory activity are dependent on the integrity and structure of long range cortical connections. We tested our hypotheses by assessing age-related differences in electrophysiologic correlates of neural synchrony and peak oscillatory frequency in younger and older adults with normal hearing and determining their associations with a behavioral measure of gap detection. Phase-locking values were smaller (poorer neural synchrony) and peak alpha frequency was lower for older than younger adults and decreased as gap detection thresholds increased; variations in phase-locking values and peak alpha frequency uniquely predicted gap detection thresholds. These effects were driven, in large part, by associations in older adults. These results reveal dissociable neural mechanisms associated with distinct underlying pathology that may differentially be present in older adults and contribute to auditory processing declines.
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Affiliation(s)
- Kelly C Harris
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, USA.
| | - Judy R Dubno
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
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192
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Hoben R, Easow G, Pevzner S, Parker MA. Outer Hair Cell and Auditory Nerve Function in Speech Recognition in Quiet and in Background Noise. Front Neurosci 2017; 11:157. [PMID: 28439223 PMCID: PMC5383716 DOI: 10.3389/fnins.2017.00157] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 03/10/2017] [Indexed: 11/17/2022] Open
Abstract
The goal of this study was to describe the contribution of outer hair cells (OHCs) and the auditory nerve (AN) to speech understanding in quiet and in the presence of background noise. Fifty-three human subjects with hearing ranging from normal to moderate sensorineural hearing loss were assayed for both speech in quiet (Word Recognition) and speech in noise (QuickSIN test) performance. Their scores were correlated with OHC function as assessed via distortion product otoacoustic emissions, and AN function as measured by amplitude, latency, and threshold of the VIIIth cranial nerve Compound Action Potential (CAP) recorded during electrocochleography (ECochG). Speech and ECochG stimuli were presented at equivalent sensation levels in order to control for the degree of hearing sensitivity across patients. The results indicated that (1) OHC dysfunction was evident in the lower range of normal audiometric thresholds, which demonstrates that OHC damage can produce “Hidden Hearing Loss,” (2) AN dysfunction was evident beginning at mild levels of hearing loss, (3) when controlled for normal OHC function, persons exhibiting either high or low ECochG amplitudes exhibited no statistically significant differences in neither speech in quiet nor speech in noise performance, (4) speech in noise performance was correlated with OHC function, (5) hearing impaired subjects with OHC dysfunction exhibited better speech in quiet performance at or near threshold when stimuli were presented at equivalent sensation levels. These results show that OHC dysfunction contributes to hidden hearing loss, OHC function is required for optimum speech in noise performance, and those persons with sensorineural hearing loss exhibit better word discrimination in quiet at or near their audiometric thresholds than normal listeners.
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Affiliation(s)
- Richard Hoben
- Department of Otolaryngology, Steward St. Elizabeth's Medical CenterBoston, MA, USA
| | - Gifty Easow
- Department of Otolaryngology, Steward St. Elizabeth's Medical CenterBoston, MA, USA
| | - Sofia Pevzner
- Department of Otolaryngology, Steward St. Elizabeth's Medical CenterBoston, MA, USA
| | - Mark A Parker
- Department of Otolaryngology, Steward St. Elizabeth's Medical CenterBoston, MA, USA.,Department of Otolaryngology, Head and Neck Surgery, Tufts University School of MedicineBoston, MA, USA
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193
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Mehraei G, Gallardo AP, Shinn-Cunningham BG, Dau T. Auditory brainstem response latency in forward masking, a marker of sensory deficits in listeners with normal hearing thresholds. Hear Res 2017; 346:34-44. [PMID: 28159652 PMCID: PMC5402043 DOI: 10.1016/j.heares.2017.01.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 01/19/2017] [Accepted: 01/25/2017] [Indexed: 12/17/2022]
Abstract
In rodent models, acoustic exposure too modest to elevate hearing thresholds can nonetheless cause auditory nerve fiber deafferentation, interfering with the coding of supra-threshold sound. Low-spontaneous rate nerve fibers, important for encoding acoustic information at supra-threshold levels and in noise, are more susceptible to degeneration than high-spontaneous rate fibers. The change in auditory brainstem response (ABR) wave-V latency with noise level has been shown to be associated with auditory nerve deafferentation. Here, we measured ABR in a forward masking paradigm and evaluated wave-V latency changes with increasing masker-to-probe intervals. In the same listeners, behavioral forward masking detection thresholds were measured. We hypothesized that 1) auditory nerve fiber deafferentation increases forward masking thresholds and increases wave-V latency and 2) a preferential loss of low-spontaneous rate fibers results in a faster recovery of wave-V latency as the slow contribution of these fibers is reduced. Results showed that in young audiometrically normal listeners, a larger change in wave-V latency with increasing masker-to-probe interval was related to a greater effect of a preceding masker behaviorally. Further, the amount of wave-V latency change with masker-to-probe interval was positively correlated with the rate of change in forward masking detection thresholds. Although we cannot rule out central contributions, these findings are consistent with the hypothesis that auditory nerve fiber deafferentation occurs in humans and may predict how well individuals can hear in noisy environments.
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Affiliation(s)
- Golbarg Mehraei
- Program in Speech and Hearing Bioscience and Technology, Harvard University-Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Center for Computational Neuroscience and Neural Technology, Boston University, Boston, MA, 02215, USA; Hearing Systems Group, Technical University of Denmark, Ørsteds Plads Building 352, 2800, Kongens Lyngby, Denmark.
| | - Andreu Paredes Gallardo
- Hearing Systems Group, Technical University of Denmark, Ørsteds Plads Building 352, 2800, Kongens Lyngby, Denmark
| | - Barbara G Shinn-Cunningham
- Program in Speech and Hearing Bioscience and Technology, Harvard University-Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Center for Computational Neuroscience and Neural Technology, Boston University, Boston, MA, 02215, USA; Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Torsten Dau
- Hearing Systems Group, Technical University of Denmark, Ørsteds Plads Building 352, 2800, Kongens Lyngby, Denmark
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194
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Rawool VW. Effect of age-related hearing loss on the click-rate-induced facilitation of acoustic reflex thresholds. Int J Audiol 2017. [DOI: 10.1080/14992027.2017.1288303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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195
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Prendergast G, Guest H, Munro KJ, Kluk K, Léger A, Hall DA, Heinz MG, Plack CJ. Effects of noise exposure on young adults with normal audiograms I: Electrophysiology. Hear Res 2017; 344:68-81. [PMID: 27816499 PMCID: PMC5256477 DOI: 10.1016/j.heares.2016.10.028] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 10/28/2016] [Accepted: 10/31/2016] [Indexed: 12/22/2022]
Abstract
Noise-induced cochlear synaptopathy has been demonstrated in numerous rodent studies. In these animal models, the disorder is characterized by a reduction in amplitude of wave I of the auditory brainstem response (ABR) to high-level stimuli, whereas the response at threshold is unaffected. The aim of the present study was to determine if this disorder is prevalent in young adult humans with normal audiometric hearing. One hundred and twenty six participants (75 females) aged 18-36 were tested. Participants had a wide range of lifetime noise exposures as estimated by a structured interview. Audiometric thresholds did not differ across noise exposures up to 8 kHz, although 16-kHz audiometric thresholds were elevated with increasing noise exposure for females but not for males. ABRs were measured in response to high-pass (1.5 kHz) filtered clicks of 80 and 100 dB peSPL. Frequency-following responses (FFRs) were measured to 80 dB SPL pure tones from 240 to 285 Hz, and to 80 dB SPL 4 kHz pure tones amplitude modulated at frequencies from 240 to 285 Hz (transposed tones). The bandwidth of the ABR stimuli and the carrier frequency of the transposed tones were chosen to target the 3-6 kHz characteristic frequency region which is usually associated with noise damage in humans. The results indicate no relation between noise exposure and the amplitude of the ABR. In particular, wave I of the ABR did not decrease with increasing noise exposure as predicted. ABR wave V latency increased with increasing noise exposure for the 80 dB peSPL click. High carrier-frequency (envelope) FFR signal-to-noise ratios decreased as a function of noise exposure in males but not females. However, these correlations were not significant after the effects of age were controlled. The results suggest either that noise-induced cochlear synaptopathy is not a significant problem in young, audiometrically normal adults, or that the ABR and FFR are relatively insensitive to this disorder in young humans, although it is possible that the effects become more pronounced with age.
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Affiliation(s)
- Garreth Prendergast
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, M13 9PL, UK
| | - Hannah Guest
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, M13 9PL, UK
| | - Kevin J Munro
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, M13 9PL, UK; Audiology Department, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, M13 9WL, UK
| | - Karolina Kluk
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, M13 9PL, UK
| | - Agnès Léger
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, M13 9PL, UK
| | - Deborah A Hall
- National Institute for Health Research (NIHR) Nottingham Hearing Biomedical Research Unit, Nottingham, NG1 5DU, UK; Otology and Hearing Group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Michael G Heinz
- Department of Speech, Language, & Hearing Sciences and Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Christopher J Plack
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, M13 9PL, UK; Department of Psychology, Lancaster University, Lancaster, LA1 4YF, UK
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196
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Hickox AE, Larsen E, Heinz MG, Shinobu L, Whitton JP. Translational issues in cochlear synaptopathy. Hear Res 2017; 349:164-171. [PMID: 28069376 DOI: 10.1016/j.heares.2016.12.010] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 12/15/2016] [Accepted: 12/16/2016] [Indexed: 10/20/2022]
Abstract
Understanding the biology of the previously underappreciated sensitivity of cochlear synapses to noise insult, and its clinical consequences, is becoming a mission for a growing number of auditory researchers. In addition, several research groups have become interested in developing therapeutic approaches that can reverse synaptopathy and restore hearing function. One of the major challenges to realizing the potential of synaptopathy rodent models is that current clinical audiometric approaches cannot yet reveal the presence of this subtle cochlear pathology in humans. This has catalyzed efforts, both from basic and clinical perspectives, to investigate novel means for diagnosing synaptopathy and to determine the main functional consequences for auditory perception and hearing abilities. Such means, and a strong concordance between findings in pre-clinical animal models and clinical studies in humans, are important for developing and realizing therapeutics. This paper frames the key outstanding translational questions that need to be addressed to realize this ambitious goal.
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Affiliation(s)
- Ann E Hickox
- Decibel Therapeutics, 215 First St, Cambridge, MA, 02142, USA.
| | - Erik Larsen
- Decibel Therapeutics, 215 First St, Cambridge, MA, 02142, USA.
| | - Michael G Heinz
- Speech, Language, and Hearing Sciences and Biomedical Engineering, Purdue University, 715 Clinic Drive, West Lafayette, IN, 47907, USA.
| | - Leslie Shinobu
- Decibel Therapeutics, 215 First St, Cambridge, MA, 02142, USA.
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197
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Communicating in Challenging Environments: Noise and Reverberation. THE FREQUENCY-FOLLOWING RESPONSE 2017. [DOI: 10.1007/978-3-319-47944-6_8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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198
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Lobarinas E, Spankovich C, Le Prell CG. Evidence of "hidden hearing loss" following noise exposures that produce robust TTS and ABR wave-I amplitude reductions. Hear Res 2016; 349:155-163. [PMID: 28003148 DOI: 10.1016/j.heares.2016.12.009] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/21/2016] [Accepted: 12/12/2016] [Indexed: 11/30/2022]
Abstract
In animals, noise exposures that produce robust temporary threshold shifts (TTS) can produce immediate damage to afferent synapses and long-term degeneration of low spontaneous rate auditory nerve fibers. This synaptopathic damage has been shown to correlate with reduced auditory brainstem response (ABR) wave-I amplitudes at suprathreshold levels. The perceptual consequences of this "synaptopathy" remain unknown but have been suggested to include compromised hearing performance in competing background noise. Here, we used a modified startle inhibition paradigm to evaluate whether noise exposures that produce robust TTS and ABR wave-I reduction but not permanent threshold shift (PTS) reduced hearing-in-noise performance. Animals exposed to 109 dB SPL octave band noise showed TTS >30 dB 24-h post noise and modest but persistent ABR wave-I reduction 2 weeks post noise despite full recovery of ABR thresholds. Hearing-in-noise performance was negatively affected by the noise exposure. However, the effect was observed only at the poorest signal to noise ratio and was frequency specific. Although TTS >30 dB 24-h post noise was a predictor of functional deficits, there was no relationship between the degree of ABR wave-I reduction and degree of functional impairment.
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Affiliation(s)
- Edward Lobarinas
- The University of Texas at Dallas, School of Behavioral and Brain Sciences, USA.
| | - Christopher Spankovich
- University of Mississippi Medical Center, Department of Otolaryngology and Communicative Sciences, USA
| | - Colleen G Le Prell
- The University of Texas at Dallas, School of Behavioral and Brain Sciences, USA
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199
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Guest H, Munro KJ, Prendergast G, Howe S, Plack CJ. Tinnitus with a normal audiogram: Relation to noise exposure but no evidence for cochlear synaptopathy. Hear Res 2016; 344:265-274. [PMID: 27964937 PMCID: PMC5256478 DOI: 10.1016/j.heares.2016.12.002] [Citation(s) in RCA: 152] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 12/06/2016] [Accepted: 12/08/2016] [Indexed: 11/25/2022]
Abstract
In rodents, exposure to high-level noise can destroy synapses between inner hair cells and auditory nerve fibers, without causing hair cell loss or permanent threshold elevation. Such "cochlear synaptopathy" is associated with amplitude reductions in wave I of the auditory brainstem response (ABR) at moderate-to-high sound levels. Similar ABR results have been reported in humans with tinnitus and normal audiometric thresholds, leading to the suggestion that tinnitus in these cases might be a consequence of synaptopathy. However, the ABR is an indirect measure of synaptopathy and it is unclear whether the results in humans reflect the same mechanisms demonstrated in rodents. Measures of noise exposure were not obtained in the human studies, and high frequency audiometric loss may have impacted ABR amplitudes. To clarify the role of cochlear synaptopathy in tinnitus with a normal audiogram, we recorded ABRs, envelope following responses (EFRs), and noise exposure histories in young adults with tinnitus and matched controls. Tinnitus was associated with significantly greater lifetime noise exposure, despite close matching for age, sex, and audiometric thresholds up to 14 kHz. However, tinnitus was not associated with reduced ABR wave I amplitude, nor with significant effects on EFR measures of synaptopathy. These electrophysiological measures were also uncorrelated with lifetime noise exposure, providing no evidence of noise-induced synaptopathy in this cohort, despite a wide range of exposures. In young adults with normal audiograms, tinnitus may be related not to cochlear synaptopathy but to other effects of noise exposure.
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Affiliation(s)
- Hannah Guest
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK.
| | - Kevin J Munro
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK; Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
| | - Garreth Prendergast
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK
| | - Simon Howe
- Audiology Department, James Cook University Hospital, South Tees Hospitals NHS Foundation Trust, Middlesbrough, UK
| | - Christopher J Plack
- Manchester Centre for Audiology and Deafness, University of Manchester, Manchester Academic Health Science Centre, UK; Department of Psychology, Lancaster University, Lancaster, UK
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200
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Chintanpalli A, Ahlstrom JB, Dubno JR. Effects of age and hearing loss on concurrent vowel identification. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2016; 140:4142. [PMID: 28040038 PMCID: PMC5848863 DOI: 10.1121/1.4968781] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 11/09/2016] [Accepted: 11/11/2016] [Indexed: 06/06/2023]
Abstract
Differences in formant frequencies and fundamental frequencies (F0) are important cues for segregating and identifying two simultaneous vowels. This study assessed age- and hearing-loss-related changes in the use of these cues for recognition of one or both vowels in a pair and determined differences related to vowel identity and specific vowel pairings. Younger adults with normal hearing, older adults with normal hearing, and older adults with hearing loss listened to different-vowel and identical-vowel pairs that varied in F0 differences. Identification of both vowels as a function of F0 difference revealed that increased age affects the use of F0 and formant difference cues for different-vowel pairs. Hearing loss further reduced the use of these cues, which was not attributable to lower vowel sensation levels. High scores for one vowel in the pair and no effect of F0 differences suggested that F0 cues are important only for identifying both vowels. In contrast to mean scores, widely varying differences in effects of F0 cues, age, and hearing loss were observed for particular vowels and vowel pairings. These variations in identification of vowel pairs were not explained by acoustical models based on the location and level of formants within the two vowels.
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Affiliation(s)
- Ananthakrishna Chintanpalli
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, South Carolina 29425-5500, USA
| | - Jayne B Ahlstrom
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, South Carolina 29425-5500, USA
| | - Judy R Dubno
- Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, South Carolina 29425-5500, USA
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