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Haider HF, Ribeiro D, Ribeiro SF, Trigueiros N, Caria H, Borrego L, Pinto I, Papoila AL, Hoare DJ, Paço J. Audiological biomarkers of tinnitus in an older Portuguese population. Front Aging Neurosci 2022; 14:933117. [PMID: 36092804 PMCID: PMC9449802 DOI: 10.3389/fnagi.2022.933117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 07/28/2022] [Indexed: 11/13/2022] Open
Abstract
Tinnitus is a phantom sound perceived in the absence of external acoustic stimulation. It is described in a variety of ways (e.g., buzzing, ringing, and roaring) and can be a single sound or a combination of different sounds. Our study evaluated associations between audiological parameters and the presence or severity of tinnitus, to improve tinnitus diagnosis, treatment, and prognosis. Our sample included 122 older participants (63 women and 59 men), aged 55–75 years from the Portuguese population, with or without sensory presbycusis and with or without tinnitus. All participants underwent a clinical evaluation through a structured interview, Ear, Nose, and Throat observation, and audiological evaluation (standard and extended audiometry, psychoacoustic tinnitus evaluation, auditory brainstem responses, and distortion product otoacoustic emissions). The Tinnitus Handicap Inventory was used to measure tinnitus symptom severity. Our data confirmed that the odds of developing tinnitus were significantly higher in the presence of noise exposure and hearing loss. Also, participants who had abrupt tinnitus onset and moderate or severe hyperacusis featured higher odds of at least moderate tinnitus. However, it was in the ABR that we obtained the most exciting and promising results, namely, in wave I, which was the common denominator in all findings. The increase in wave I amplitude is a protective factor to the odds of having tinnitus. Concerning the severity of tinnitus, the logistic regression model showed that for each unit of increase in the mean ratio V/I of ABR, the likelihood of having at least moderate tinnitus was 10% higher. Advancing knowledge concerning potential tinnitus audiological biomarkers can be crucial for the adequate diagnosis and treatment of tinnitus.
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Affiliation(s)
- Haúla F. Haider
- ENT Department, CUF Tejo Hospital – NOVA Medical School, Faculty of Medical Sciences, NOVA University Lisbon, Lisbon, Portugal
- Comprehensive Health Research Centre, NOVA Medical School, Faculty of Medical Sciences, Lisbon, Portugal
| | - Diogo Ribeiro
- Comprehensive Health Research Centre, NOVA Medical School, Faculty of Medical Sciences, Lisbon, Portugal
- NOVA Medical School, Faculty of Medical Sciences, NOVA University Lisbon, Lisbon, Portugal
- *Correspondence: Diogo Ribeiro,
| | - Sara F. Ribeiro
- ENT Department, CUF Tejo Hospital – NOVA Medical School, Faculty of Medical Sciences, NOVA University Lisbon, Lisbon, Portugal
| | - Nuno Trigueiros
- ENT Department, Hospital Pedro Híspano, Matosinhos, Portugal
| | - Helena Caria
- BTR Unit, Deafness Research Group, BioISI, Faculty of Sciences, University of Lisbon (FCUL), Lisbon, Portugal
- ESS/IPS – Biomedical Sciences Department, School of Health, Polytechnic Institute of Setubal, Setúbal, Portugal
| | - Luís Borrego
- NOVA Medical School, Faculty of Medical Sciences, NOVA University Lisbon, Lisbon, Portugal
- Department of Immunoallergy, CUF Descobertas Hospital, Lisbon, Portugal
| | - Iola Pinto
- Instituto Superior de Engenharia de Lisboa, Lisbon, Portugal
- Centro de Matemática e Aplicações, NOVA School of Science and Technology, FCT NOVA, Costa da Caparica, Portugal
| | - Ana L. Papoila
- NOVA Medical School, Faculty of Medical Sciences, NOVA University Lisbon, Lisbon, Portugal
| | - Derek J. Hoare
- School of Medicine, NIHR Nottingham Biomedical Research Centre, Hearing Sciences, Mental Health and Clinical Neurosciences, University of Nottingham, Nottingham, United Kingdom
| | - João Paço
- ENT Department, CUF Tejo Hospital – NOVA Medical School, Faculty of Medical Sciences, NOVA University Lisbon, Lisbon, Portugal
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Le Prell CG, Hughes LF, Dolan DF, Bledsoe SC. Effects of Calcitonin-Gene-Related-Peptide on Auditory Nerve Activity. Front Cell Dev Biol 2021; 9:752963. [PMID: 34869340 PMCID: PMC8633412 DOI: 10.3389/fcell.2021.752963] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 10/20/2021] [Indexed: 11/13/2022] Open
Abstract
Calcitonin-gene-related peptide (CGRP) is a lateral olivocochlear (LOC) efferent neurotransmitter. Depression of sound-driven auditory brainstem response amplitude in CGRP-null mice suggests the potential for endogenous CGRP release to upregulate spontaneous and/or sound-driven auditory nerve (AN) activity. We chronically infused CGRP into the guinea pig cochlea and evaluated changes in AN activity as well as outer hair cell (OHC) function. The amplitude of both round window noise (a measure of ensemble spontaneous activity) and the synchronous whole-nerve response to sound (compound action potential, CAP) were enhanced. Lack of change in both onset adaptation and steady state amplitude of sound-evoked distortion product otoacoustic emission (DPOAE) responses indicated CGRP had no effect on OHCs, suggesting the origin of the observed changes was neural. Combined with results from the CGRP-null mice, these results appear to confirm that endogenous CGRP enhances auditory nerve activity when released by the LOC neurons. However, infusion of the CGRP receptor antagonist CGRP (8–37) did not reliably influence spontaneous or sound-driven AN activity, or OHC function, results that contrast with the decreased ABR amplitude measured in CGRP-null mice.
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Affiliation(s)
- Colleen G Le Prell
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, United States.,Department of Speech, Language, and Hearing, University of Texas at Dallas, Richardson, TX, United States
| | - Larry F Hughes
- Department of Surgery, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - David F Dolan
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, United States
| | - Sanford C Bledsoe
- Department of Otolaryngology, University of Michigan, Ann Arbor, MI, United States
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3
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De Groote E, Bockstael A, Botteldooren D, Santens P, De Letter M. The Effect of Parkinson's Disease on Otoacoustic Emissions and Efferent Suppression of Transient Evoked Otoacoustic Emissions. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2021; 64:1354-1368. [PMID: 33769843 DOI: 10.1044/2020_jslhr-20-00594] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Purpose Several studies have demonstrated increased auditory thresholds in patients with Parkinson's disease (PD) based on subjective tonal audiometry. However, the pathophysiological mechanisms underlying auditory dysfunction in PD remain elusive. The primary aim of this study was to investigate cochlear and olivocochlear function in PD using objective measurements and to assess the effect of dopaminergic medication on auditory function. Method Eighteen patients with PD and 18 gender- and age-matched healthy controls (HCs) were included. Patients with PD participated in medication on and off conditions. Linear mixed models were used to determine the effect of PD on tonal audiometry, transient evoked and distortion product otoacoustic emissions (OAEs), and efferent suppression (ES). Results Tonal audiometry revealed normal auditory thresholds in patients with PD for their age across all frequencies. OAE signal amplitudes demonstrated a significant interaction effect between group (PD vs. HC) and frequency, indicating decreased OAEs at low frequencies and increased OAEs at high frequencies in patients with PD. No significant differences were found between patients with PD and HCs regarding ES. In addition, no significant effect of medication status was found on auditory measurements in patients with PD. Conclusions Altered OAEs support the hypothesis of cochlear alterations in PD. No evidence was found for the involvement of the medial olivocochlear system. Altogether, OAEs may provide an objective early indicator of auditory alterations in PD and should complement subjective tonal audiometry when assessing and monitoring auditory function in PD.
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Affiliation(s)
| | - Annelies Bockstael
- Acoustics Research Group, Department of Information Technology, Ghent University, Belgium
| | - Dick Botteldooren
- Acoustics Research Group, Department of Information Technology, Ghent University, Belgium
| | | | - Miet De Letter
- Department of Rehabilitation Sciences, Ghent University, Belgium
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4
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Wu JS, Yi E, Manca M, Javaid H, Lauer AM, Glowatzki E. Sound exposure dynamically induces dopamine synthesis in cholinergic LOC efferents for feedback to auditory nerve fibers. eLife 2020; 9:52419. [PMID: 31975688 PMCID: PMC7043886 DOI: 10.7554/elife.52419] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 01/23/2020] [Indexed: 11/13/2022] Open
Abstract
Lateral olivocochlear (LOC) efferent neurons modulate auditory nerve fiber (ANF) activity using a large repertoire of neurotransmitters, including dopamine (DA) and acetylcholine (ACh). Little is known about how individual neurotransmitter systems are differentially utilized in response to the ever-changing acoustic environment. Here we present quantitative evidence in rodents that the dopaminergic LOC input to ANFs is dynamically regulated according to the animal's recent acoustic experience. Sound exposure upregulates tyrosine hydroxylase, an enzyme responsible for dopamine synthesis, in cholinergic LOC intrinsic neurons, suggesting that individual LOC neurons might at times co-release ACh and DA. We further demonstrate that dopamine down-regulates ANF firing rates by reducing both the hair cell release rate and the size of synaptic events. Collectively, our results suggest that LOC intrinsic neurons can undergo on-demand neurotransmitter re-specification to re-calibrate ANF activity, adjust the gain at hair cell/ANF synapses, and possibly to protect these synapses from noise damage.
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Affiliation(s)
- Jingjing Sherry Wu
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan-gun, Republic of Korea
| | - Marco Manca
- The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Hamad Javaid
- The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Amanda M Lauer
- The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
| | - Elisabeth Glowatzki
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, United States.,The Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, United States.,Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, United States
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5
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Naert G, Pasdelou MP, Le Prell CG. Use of the guinea pig in studies on the development and prevention of acquired sensorineural hearing loss, with an emphasis on noise. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:3743. [PMID: 31795705 PMCID: PMC7195866 DOI: 10.1121/1.5132711] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 07/30/2019] [Accepted: 08/12/2019] [Indexed: 05/10/2023]
Abstract
Guinea pigs have been used in diverse studies to better understand acquired hearing loss induced by noise and ototoxic drugs. The guinea pig has its best hearing at slightly higher frequencies relative to humans, but its hearing is more similar to humans than the rat or mouse. Like other rodents, it is more vulnerable to noise injury than the human or nonhuman primate models. There is a wealth of information on auditory function and vulnerability of the inner ear to diverse insults in the guinea pig. With respect to the assessment of potential otoprotective agents, guinea pigs are also docile animals that are relatively easy to dose via systemic injections or gavage. Of interest, the cochlea and the round window are easily accessible, notably for direct cochlear therapy, as in the chinchilla, making the guinea pig a most relevant and suitable model for hearing. This article reviews the use of the guinea pig in basic auditory research, provides detailed discussion of its use in studies on noise injury and other injuries leading to acquired sensorineural hearing loss, and lists some therapeutics assessed in these laboratory animal models to prevent acquired sensorineural hearing loss.
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Affiliation(s)
| | | | - Colleen G Le Prell
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas 75080, USA
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6
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Richardson KC, Sussman JE. Intensity Resolution in Individuals With Parkinson's Disease: Sensory and Auditory Memory Limitations. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2019; 62:3564-3581. [PMID: 31513750 DOI: 10.1044/2019_jslhr-h-18-0424] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Purpose The purpose of the current study was to examine sensory and auditory memory limitations on intensity resolution in individuals with Parkinson's disease as compared to healthy older and younger adults. Method Nineteen individuals with Parkinson's disease, 10 healthy age- and hearing-matched adults, and 10 healthy young adults were studied. The listeners participated in 2 intensity discrimination tasks: a lower memory load 4IAX task (sensory limitations) and a higher memory load ABX task (auditory memory limitations). Intensity resolution was examined across groups and tasks using a bias-free measurement of signal detectability known as d' (d-prime). Listeners also participated in a loudness scaling task where they were instructed to rate the loudness level of each signal intensity along the experimental continuum using a computerized 150-mm visual analog scale. Results Intensity discrimination sensitivity (d') was significantly poorer in the 4IAX and ABX conditions for the individuals with Parkinson's disease, as compared to the older and younger controls. Furthermore, a significant age-related difference was identified for the loudness scaling condition. The younger controls rated most stimuli along the experimental continuum significantly louder as compared to the older controls and the individuals with Parkinson's disease. Conclusions The present discrimination data suggest sensory and auditory memory limitations may contribute to the intensity resolution issues associated with Parkinson's disease. Age-related differences in loudness scaling will be reviewed.
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Affiliation(s)
- Kelly C Richardson
- Department of Communication Disorders, University of Massachusetts Amherst
| | - Joan E Sussman
- Department of Communicative Disorders & Sciences, University at Buffalo, NY
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Sheppard AM, Zhao DL, Salvi R. Isoflurane anesthesia suppresses distortion product otoacoustic emissions in rats. J Otol 2018; 13:59-64. [PMID: 30559766 PMCID: PMC6291629 DOI: 10.1016/j.joto.2018.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 03/30/2018] [Indexed: 02/01/2023] Open
Abstract
A commonly used anesthetic, isoflurane, can impair auditory function in a dose-dependent manner. However, in rats, isoflurane-induced auditory impairments have only been assessed with auditory brainstem responses; a measure which is unable to distinguish if changes originate from the central or peripheral auditory system. Studies performed in other species, such as mice and guinea-pigs, suggests auditory impairment stems from disrupted OHC amplification. Despite the wide use of the rat in auditory research, these observations have yet to be replicated in the rat animal model. This study used distortion product otoacoustic emissions to assess outer hair cell function in rats that were anesthetized with either isoflurane or a ketamine/xylazine cocktail for approximately 45 min. Results indicate that isoflurane can significantly reduce DPOAE amplitudes compared to ketamine/xylazine, and that responses were more variable with isoflurane than ketamine/xylazine over the 45-min test period. Based on these observations, isoflurane should be used with caution when assessing peripheral auditory function to avoid potentially confounding effects.
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Affiliation(s)
- Adam M Sheppard
- Center for Hearing and Deafness, State University of New York at Buffalo, 137 Cary Hall, 3435 Main Street, Buffalo, NY 14214, USA
| | - Deng-Ling Zhao
- Department of Radiology, Zhongda Hospital, School of Medicine, Southeast University, Nanjing, Jiangsu Providence, China
| | - Richard Salvi
- Center for Hearing and Deafness, State University of New York at Buffalo, 137 Cary Hall, 3435 Main Street, Buffalo, NY 14214, USA
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8
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Smith SB, Lichtenhan JT, Cone BK. Contralateral Inhibition of Click- and Chirp-Evoked Human Compound Action Potentials. Front Neurosci 2017; 11:189. [PMID: 28420960 PMCID: PMC5378791 DOI: 10.3389/fnins.2017.00189] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 03/21/2017] [Indexed: 11/13/2022] Open
Abstract
Cochlear outer hair cells (OHC) receive direct efferent feedback from the caudal auditory brainstem via the medial olivocochlear (MOC) bundle. This circuit provides the neural substrate for the MOC reflex, which inhibits cochlear amplifier gain and is believed to play a role in listening in noise and protection from acoustic overexposure. The human MOC reflex has been studied extensively using otoacoustic emissions (OAE) paradigms; however, these measurements are insensitive to subsequent "downstream" efferent effects on the neural ensembles that mediate hearing. In this experiment, click- and chirp-evoked auditory nerve compound action potential (CAP) amplitudes were measured electrocochleographically from the human eardrum without and with MOC reflex activation elicited by contralateral broadband noise. We hypothesized that the chirp would be a more optimal stimulus for measuring neural MOC effects because it synchronizes excitation along the entire length of the basilar membrane and thus evokes a more robust CAP than a click at low to moderate stimulus levels. Chirps produced larger CAPs than clicks at all stimulus intensities (50-80 dB ppeSPL). MOC reflex inhibition of CAPs was larger for chirps than clicks at low stimulus levels when quantified both in terms of amplitude reduction and effective attenuation. Effective attenuation was larger for chirp- and click-evoked CAPs than for click-evoked OAEs measured from the same subjects. Our results suggest that the chirp is an optimal stimulus for evoking CAPs at low stimulus intensities and for assessing MOC reflex effects on the auditory nerve. Further, our work supports previous findings that MOC reflex effects at the level of the auditory nerve are underestimated by measures of OAE inhibition.
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Affiliation(s)
- Spencer B. Smith
- Department of Speech, Language, and Hearing Sciences, University of ArizonaTucson, AZ, USA
| | - Jeffery T. Lichtenhan
- Department of Otolaryngology, Washington University School of MedicineSt. Louis, MO, USA
| | - Barbara K. Cone
- Department of Speech, Language, and Hearing Sciences, University of ArizonaTucson, AZ, USA
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Ablation of the auditory cortex results in changes in the expression of neurotransmission-related mRNAs in the cochlea. Hear Res 2017; 346:71-80. [PMID: 28216123 DOI: 10.1016/j.heares.2017.02.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 02/09/2017] [Accepted: 02/14/2017] [Indexed: 01/02/2023]
Abstract
The auditory cortex (AC) dynamically regulates responses of the Organ of Corti to sound through descending connections to both the medial (MOC) and lateral (LOC) olivocochlear efferent systems. We have recently provided evidence that AC has a reinforcement role in the responses to sound of the auditory brainstem nuclei. In a molecular level, we have shown that descending inputs from AC are needed to regulate the expression of molecules involved in outer hair cell (OHC) electromotility control, such as prestin and the α10 nicotinic acetylcholine receptor (nAchR). In this report, we show that descending connections from AC to olivocochlear neurons are necessary to regulate the expression of molecules involved in cochlear afferent signaling. RT-qPCR was performed in rats at 1, 7 and 15 days after unilateral ablation of the AC, and analyzed the time course changes in gene transcripts involved in neurotransmission at the first auditory synapse. This included the glutamate metabolism enzyme glutamate decarboxylase 1 (glud1) and AMPA glutamate receptor subunits GluA2-4. In addition, gene transcripts involved in efferent regulation of type I spiral ganglion neuron (SGN) excitability mediated by LOC, such as the α7 nAchR, the D2 dopamine receptor, and the α1, and γ2 GABAA receptor subunits, were also investigated. Unilateral AC ablation induced up-regulation of GluA3 receptor subunit transcripts, whereas both GluA2 and GluA4 mRNA receptors were down-regulated already at 1 day after the ablation. Unilateral removal of the AC also resulted in up-regulation of the transcripts for α7 nAchR subunit, D2 dopamine receptor, and α1 GABAA receptor subunit at 1 day after the ablation. Fifteen days after the injury, AC ablations induced an up-regulation of glud1 transcripts.
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10
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Krauss P, Tziridis K, Metzner C, Schilling A, Hoppe U, Schulze H. Stochastic Resonance Controlled Upregulation of Internal Noise after Hearing Loss as a Putative Cause of Tinnitus-Related Neuronal Hyperactivity. Front Neurosci 2016; 10:597. [PMID: 28082861 PMCID: PMC5187388 DOI: 10.3389/fnins.2016.00597] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 12/14/2016] [Indexed: 11/25/2022] Open
Abstract
Subjective tinnitus is generally assumed to be a consequence of hearing loss. In animal studies it has been demonstrated that acoustic trauma induced cochlear damage can lead to behavioral signs of tinnitus. In addition it was shown that noise trauma may lead to deafferentation of cochlear inner hair cells (IHC) even in the absence of elevated hearing thresholds, and it seems conceivable that such hidden hearing loss may be sufficient to cause tinnitus. Numerous studies have indicated that tinnitus is correlated with pathologically increased spontaneous firing rates and hyperactivity of neurons along the auditory pathway. It has been proposed that this hyperactivity is the consequence of a mechanism aiming to compensate for reduced input to the auditory system by increasing central neuronal gain, a mechanism referred to as homeostatic plasticity (HP), thereby maintaining mean firing rates over longer timescales for stabilization of neuronal processing. Here we propose an alternative, new interpretation of tinnitus-related development of neuronal hyperactivity in terms of information theory. In particular, we suggest that stochastic resonance (SR) plays a key role in both short- and long-term plasticity within the auditory system and that SR is the primary cause of neuronal hyperactivity and tinnitus. We argue that following hearing loss, SR serves to lift signals above the increased neuronal thresholds, thereby partly compensating for the hearing loss. In our model, the increased amount of internal noise-which is crucial for SR to work-corresponds to neuronal hyperactivity which subsequently causes neuronal plasticity along the auditory pathway and finally may lead to the development of a phantom percept, i.e., subjective tinnitus. We demonstrate the plausibility of our hypothesis using a computational model and provide exemplary findings in human patients that are consistent with that model. Finally we discuss the observed asymmetry in human tinnitus pitch distribution as a consequence of asymmetry of the distribution of auditory nerve type I fibers along the cochlea in the context of our model.
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Affiliation(s)
- Patrick Krauss
- Experimental Otolaryngology, ENT-Hospital, Head and Neck Surgery, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
- Biophysics Group, Department of Physics, Center for Medical Physics and Technology, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
| | - Konstantin Tziridis
- Experimental Otolaryngology, ENT-Hospital, Head and Neck Surgery, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
| | - Claus Metzner
- Biophysics Group, Department of Physics, Center for Medical Physics and Technology, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
| | - Achim Schilling
- Experimental Otolaryngology, ENT-Hospital, Head and Neck Surgery, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
- Biophysics Group, Department of Physics, Center for Medical Physics and Technology, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
| | - Ulrich Hoppe
- Department of Audiology, ENT-Hospital, Head and Neck Surgery, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
| | - Holger Schulze
- Experimental Otolaryngology, ENT-Hospital, Head and Neck Surgery, Friedrich-Alexander University Erlangen-NürnbergErlangen, Germany
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Dlugaiczyk J, Hecker D, Neubert C, Buerbank S, Campanelli D, Becker CM, Betz H, Knipper M, Rüttiger L, Schick B. Loss of glycine receptors containing the α3 subunit compromises auditory nerve activity, but not outer hair cell function. Hear Res 2016; 337:25-34. [DOI: 10.1016/j.heares.2016.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 04/25/2016] [Accepted: 05/13/2016] [Indexed: 10/21/2022]
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12
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Reijntjes DO, Pyott SJ. The afferent signaling complex: Regulation of type I spiral ganglion neuron responses in the auditory periphery. Hear Res 2016; 336:1-16. [DOI: 10.1016/j.heares.2016.03.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 02/12/2016] [Accepted: 03/07/2016] [Indexed: 12/19/2022]
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Abstract
UNLABELLED The senses of hearing and balance are subject to modulation by efferent signaling, including the release of dopamine (DA). How DA influences the activity of the auditory and vestibular systems and its site of action are not well understood. Here we show that dopaminergic efferent fibers innervate the acousticolateralis epithelium of the zebrafish during development but do not directly form synapses with hair cells. However, a member of the D1-like receptor family, D1b, tightly localizes to ribbon synapses in inner ear and lateral-line hair cells. To assess modulation of hair-cell activity, we reversibly activated or inhibited D1-like receptors (D1Rs) in lateral-line hair cells. In extracellular recordings from hair cells, we observed that D1R agonist SKF-38393 increased microphonic potentials, whereas D1R antagonist SCH-23390 decreased microphonic potentials. Using ratiometric calcium imaging, we found that increased D1R activity resulted in larger calcium transients in hair cells. The increase of intracellular calcium requires Cav1.3a channels, as a Cav1 calcium channel antagonist, isradipine, blocked the increase in calcium transients elicited by the agonist SKF-38393. Collectively, our results suggest that DA is released in a paracrine fashion and acts at ribbon synapses, likely enhancing the activity of presynaptic Cav1.3a channels and thereby increasing neurotransmission. SIGNIFICANCE STATEMENT The neurotransmitter dopamine acts in a paracrine fashion (diffusion over a short distance) in several tissues and bodily organs, influencing and regulating their activity. The cellular target and mechanism of the action of dopamine in mechanosensory organs, such as the inner ear and lateral-line organ, is not clearly understood. Here we demonstrate that dopamine receptors are present in sensory hair cells at synaptic sites that are required for signaling to the brain. When nearby neurons release dopamine, activation of the dopamine receptors increases the activity of these mechanosensitive cells. The mechanism of dopamine activation requires voltage-gated calcium channels that are also present at hair-cell synapses.
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14
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Le Prell CG, Dolan DF, Hughes LF, Altschuler RA, Shore SE, Bledsoe SC. Disruption of lateral olivocochlear neurons with a dopaminergic neurotoxin depresses spontaneous auditory nerve activity. Neurosci Lett 2014; 582:54-8. [PMID: 25175420 DOI: 10.1016/j.neulet.2014.08.040] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 08/09/2014] [Accepted: 08/22/2014] [Indexed: 11/28/2022]
Abstract
Neurons of the lateral olivocochlear (LOC) system project from the auditory brainstem to the cochlea, where they synapse on radial dendrites of auditory nerve fibers. Selective LOC disruption depresses sound-evoked auditory nerve activity in the guinea pig, but enhances it in the mouse. Here, LOC disruption depressed spontaneous auditory nerve activity in the guinea pig. Recordings from single auditory nerve fibers revealed a significantly reduced proportion of fibers with the highest spontaneous firing rates (SRs) and an increased proportion of neurons with lower SRs. Ensemble activity, estimated using round window noise, also decreased after LOC disruption. Decreased spontaneous activity after LOC disruption may be a consequence of reduced tonic release of excitatory transmitters from the LOC terminals in guinea pigs.
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Affiliation(s)
- Colleen G Le Prell
- Department of Speech, Language, and Hearing Sciences, University of Florida, Gainesville, FL 32610 USA.
| | - David F Dolan
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Larry F Hughes
- Department of Surgery, Southern Illinois University Medical School, Springfield, IL 62794 USA
| | - Richard A Altschuler
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Susan E Shore
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Sanford C Bledsoe
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109 USA
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15
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Le Prell CG, Hughes LF, Bledsoe SC. Dynorphin release by the lateral olivocochlear efferents may inhibit auditory nerve activity: a cochlear drug delivery study. Neurosci Lett 2014; 571:17-22. [PMID: 24780562 DOI: 10.1016/j.neulet.2014.04.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 04/15/2014] [Accepted: 04/18/2014] [Indexed: 11/28/2022]
Abstract
Dynorphin (dyn) is suggested to excite the auditory nerve (AN) when released by the lateral olivocochlear (LOC) efferents. However, previous studies evaluated either intravenously delivered dyn-like agents, raising the potential for systemic (central) effects, or agent concentrations unlikely to be achieved via endogenous cochlear release. This study tested the hypothesis that biologically relevant increases in dyn levels in the cochlea achieved via diffusion of the drug of (-)pentazocine across the round window membrane enhances AN firing. In general, amplitude of the cochlear whole-nerve action potential (CAP) was depressed following drug application. These results suggest that dyn released by the LOC neurons would likely act as an inhibitory transmitter substance in the LOC system; neurotransmission is one of the LOC system's vast unknowns.
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Affiliation(s)
| | - Larry F Hughes
- Department of Surgery, Southern Illinois University School of Medicine, USA
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16
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Gu JW, Herrmann BS, Levine RA, Melcher JR. Brainstem auditory evoked potentials suggest a role for the ventral cochlear nucleus in tinnitus. J Assoc Res Otolaryngol 2012; 13:819-33. [PMID: 22869301 PMCID: PMC3505586 DOI: 10.1007/s10162-012-0344-1] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 07/19/2012] [Indexed: 10/28/2022] Open
Abstract
Numerous studies have demonstrated elevated spontaneous and sound-evoked brainstem activity in animal models of tinnitus, but data on brainstem function in people with this common clinical condition are sparse. Here, auditory nerve and brainstem function in response to sound was assessed via auditory brainstem responses (ABR) in humans with tinnitus and without. Tinnitus subjects showed reduced wave I amplitude (indicating reduced auditory nerve activity) but enhanced wave V (reflecting elevated input to the inferior colliculi) compared with non-tinnitus subjects matched in age, sex, and pure-tone threshold. The transformation from reduced peripheral activity to central hyperactivity in the tinnitus group was especially apparent in the V/I and III/I amplitude ratios. Compared with a third cohort of younger, non-tinnitus subjects, both tinnitus, and matched, non-tinnitus groups showed elevated thresholds above 4 kHz and reduced wave I amplitude, indicating that the differences between tinnitus and matched non-tinnitus subjects occurred against a backdrop of shared peripheral dysfunction that, while not tinnitus specific, cannot be discounted as a factor in tinnitus development. Animal lesion and human neuroanatomical data combine to indicate that waves III and V in humans reflect activity in a pathway originating in the ventral cochlear nucleus (VCN) and with spherical bushy cells (SBC) in particular. We conclude that the elevated III/I and V/I amplitude ratios in tinnitus subjects reflect disproportionately high activity in the SBC pathway for a given amount of peripheral input. The results imply a role for the VCN in tinnitus and suggest the SBC pathway as a target for tinnitus treatment.
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Affiliation(s)
- Jianwen Wendy Gu
- />Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114 USA
- />Speech and Hearing Bioscience and Technology Program, Harvard–MIT Division of Health Sciences and Technology, Cambridge, MA USA
| | - Barbara S. Herrmann
- />Speech and Hearing Bioscience and Technology Program, Harvard–MIT Division of Health Sciences and Technology, Cambridge, MA USA
- />Audiology Department, Massachusetts Eye and Ear Infirmary, Boston, MA USA
- />Department of Otology and Laryngology, Harvard Medical School, Boston, MA USA
| | - Robert A. Levine
- />Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114 USA
- />Department of Otology and Laryngology, Harvard Medical School, Boston, MA USA
- />Neurology Service, Massachusetts General Hospital, Boston, MA USA
| | - Jennifer R. Melcher
- />Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114 USA
- />Speech and Hearing Bioscience and Technology Program, Harvard–MIT Division of Health Sciences and Technology, Cambridge, MA USA
- />Department of Otology and Laryngology, Harvard Medical School, Boston, MA USA
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17
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León A, Elgueda D, Silva MA, Hamamé CM, Delano PH. Auditory cortex basal activity modulates cochlear responses in chinchillas. PLoS One 2012; 7:e36203. [PMID: 22558383 PMCID: PMC3340362 DOI: 10.1371/journal.pone.0036203] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 04/03/2012] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND The auditory efferent system has unique neuroanatomical pathways that connect the cerebral cortex with sensory receptor cells. Pyramidal neurons located in layers V and VI of the primary auditory cortex constitute descending projections to the thalamus, inferior colliculus, and even directly to the superior olivary complex and to the cochlear nucleus. Efferent pathways are connected to the cochlear receptor by the olivocochlear system, which innervates outer hair cells and auditory nerve fibers. The functional role of the cortico-olivocochlear efferent system remains debated. We hypothesized that auditory cortex basal activity modulates cochlear and auditory-nerve afferent responses through the efferent system. METHODOLOGY/PRINCIPAL FINDINGS Cochlear microphonics (CM), auditory-nerve compound action potentials (CAP) and auditory cortex evoked potentials (ACEP) were recorded in twenty anesthetized chinchillas, before, during and after auditory cortex deactivation by two methods: lidocaine microinjections or cortical cooling with cryoloops. Auditory cortex deactivation induced a transient reduction in ACEP amplitudes in fifteen animals (deactivation experiments) and a permanent reduction in five chinchillas (lesion experiments). We found significant changes in the amplitude of CM in both types of experiments, being the most common effect a CM decrease found in fifteen animals. Concomitantly to CM amplitude changes, we found CAP increases in seven chinchillas and CAP reductions in thirteen animals. Although ACEP amplitudes were completely recovered after ninety minutes in deactivation experiments, only partial recovery was observed in the magnitudes of cochlear responses. CONCLUSIONS/SIGNIFICANCE These results show that blocking ongoing auditory cortex activity modulates CM and CAP responses, demonstrating that cortico-olivocochlear circuits regulate auditory nerve and cochlear responses through a basal efferent tone. The diversity of the obtained effects suggests that there are at least two functional pathways from the auditory cortex to the cochlea.
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Affiliation(s)
- Alex León
- Laboratorio de Neurobiología de la Audición, Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Diego Elgueda
- Laboratorio de Neurobiología de la Audición, Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Institute of Systems Research and Neuroscience and Cognitive Sciences Program, University of Maryland, College Park, Maryland, United States of America
| | - María A. Silva
- Laboratorio de Neurobiología de la Audición, Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Carlos M. Hamamé
- Laboratorio de Neurobiología de la Audición, Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Lyon Neuroscience Research Center (INSERM U1028 - CNRS UMR5292), Brain Dynamics and Cognition Team, Lyon, France
| | - Paul H. Delano
- Laboratorio de Neurobiología de la Audición, Programa de Fisiología y Biofísica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Servicio Otorrinolaringología, Hospital Clínico de la Universidad de Chile, Santiago, Chile
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18
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Lauer AM, Fuchs PA, Ryugo DK, Francis HW. Efferent synapses return to inner hair cells in the aging cochlea. Neurobiol Aging 2012; 33:2892-902. [PMID: 22405044 DOI: 10.1016/j.neurobiolaging.2012.02.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 02/09/2012] [Accepted: 02/10/2012] [Indexed: 01/04/2023]
Abstract
Efferent innervation of the cochlea undergoes extensive modification early in development, but it is unclear if efferent synapses are modified by age, hearing loss, or both. Structural alterations in the cochlea affecting information transfer from the auditory periphery to the brain may contribute to age-related hearing deficits. We investigated changes to efferent innervation in the vicinity of inner hair cells (IHCs) in young and old C57BL/6 mice using transmission electron microscopy to reveal increased efferent innervation of IHCs in older animals. Efferent contacts on IHCs contained focal presynaptic accumulations of small vesicles. Synaptic vesicle size and shape were heterogeneous. Postsynaptic cisterns were occasionally observed. Increased IHC efferent innervation was associated with a smaller number of afferent synapses per IHC, increased outer hair cell loss, and elevated auditory brainstem response thresholds. Efferent axons also formed synapses on afferent dendrites but with a reduced prevalence in older animals. Age-related reduction of afferent activity may engage signaling pathways that support the return to an immature state of efferent innervation of the cochlea.
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Affiliation(s)
- Amanda M Lauer
- The Center for Hearing and Balance, Department of Otolaryngology-HNS, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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19
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Le Prell CG, Dolan DF, Bennett DC, Boxer PA. Nutrient plasma levels achieved during treatment that reduces noise-induced hearing loss. Transl Res 2011; 158:54-70. [PMID: 21708356 PMCID: PMC3125531 DOI: 10.1016/j.trsl.2011.02.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 02/04/2011] [Accepted: 02/07/2011] [Indexed: 10/18/2022]
Abstract
Hearing loss encompasses both temporary and permanent deficits. If temporary threshold shift (TTS) and permanent threshold shift (PTS) share common pathological mechanisms, then agents that reduce PTS also should reduce TTS. Several antioxidant agents have reduced PTS in rodent models; however, reductions in TTS have been inconsistent. This study first determined whether dietary antioxidants (beta-carotene and vitamins C and E) delivered in combination with magnesium (Mg) reliably increase plasma concentrations of the active agents. Then, additional manipulations tested the hypothesis that these nutrients reduce acute TTS insult in the first 24 h after loud sound as well as longer lasting changes in hearing measured up to 7 days postnoise. Saline or nutrients were administered to guinea pigs prior to and after noise exposure. Sound-evoked electrophysiological responses were measured before noise, with tests repeated 1-h postnoise, as well as 1-day, 3-days, 5-days, and 7-days postnoise. All subjects showed significant functional recovery; subjects treated with nutrients recovered more rapidly and had better hearing outcomes at early postnoise times as well as the final test time. Thus, this combination of nutrients, which produced significant increases in plasma concentrations of vitamins C and E and Mg, effectively reduced hearing loss at multiple postnoise times. These data suggest that free radical formation contributes to TTS as well as PTS insults and suggest a potential opportunity to prevent TTS in human populations.
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Affiliation(s)
- Colleen G Le Prell
- Department of Speech, Language, and Hearing Sciences, University of Florida, Gainesville, FL 32610, USA.
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20
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Abstract
PURPOSE OF REVIEW For the perception of sound, acoustic signals need to be encoded into a neuronal code. This takes place at the inner hair cells of the organ of Corti and the afferent fibres of the auditory nerve. We will review the current knowledge of the anatomy and function of these elements as well as their connection - formed by the afferent inner hair cell synapse. RECENT FINDINGS Depending on their tonotopic location, inner hair cells are innervated by 5-30 dendrites of spiral ganglion neurons. Electrophysiological recordings from single fibres demonstrate - apart from a high-frequency selectivity - a pronounced heterogeneity in their response to sound of varying intensity. The source as well as the function of this heterogeneity is not well understood, but recent publications have suggested several mechanisms, including variations in the presynaptic Ca2+ influx and subsequent transmitter release, the postsynaptic sensitivity to neurotransmitter and electrical as well as anatomical variability of single fibres. These mechanisms might act together to expand the dynamic range of sound that can be encoded. SUMMARY Classical studies as well as recent publications demonstrate that sound encoding at the inner hair cell afferent synapse involves mechanisms leading to tonotopic frequency separation and distribution of intensity coding over many neuronal channels.
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21
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Fu B, Le Prell C, Simmons D, Lei D, Schrader A, Chen AB, Bao J. Age-related synaptic loss of the medial olivocochlear efferent innervation. Mol Neurodegener 2010; 5:53. [PMID: 21110869 PMCID: PMC3000387 DOI: 10.1186/1750-1326-5-53] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 11/26/2010] [Indexed: 01/26/2023] Open
Abstract
Age-related functional decline of the nervous system is consistently observed, though cellular and molecular events responsible for this decline remain largely unknown. One of the most prevalent age-related functional declines is age-related hearing loss (presbycusis), a major cause of which is the loss of outer hair cells (OHCs) and spiral ganglion neurons. Previous studies have also identified an age-related functional decline in the medial olivocochlear (MOC) efferent system prior to age-related loss of OHCs. The present study evaluated the hypothesis that this functional decline of the MOC efferent system is due to age-related synaptic loss of the efferent innervation of the OHCs. To this end, we used a recently-identified transgenic mouse line in which the expression of yellow fluorescent protein (YFP), under the control of neuron-specific elements from the thy1 gene, permits the visualization of the synaptic connections between MOC efferent fibers and OHCs. In this model, there was a dramatic synaptic loss between the MOC efferent fibers and the OHCs in older mice. However, age-related loss of efferent synapses was independent of OHC status. These data demonstrate for the first time that age-related loss of efferent synapses may contribute to the functional decline of the MOC efferent system and that this synaptic loss is not necessary for age-related loss of OHCs.
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Affiliation(s)
- Benjamin Fu
- Department of Otolaryngology, Washington University, St, Louis, MO, 63110, USA.
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22
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23
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Halmos G, Horváth T, Polony G, Fekete Á, Kittel A, Vizi E, van der Laan B, Zelles T, Lendvai B. The role of N-methyl-d-aspartate receptors and nitric oxide in cochlear dopamine release. Neuroscience 2008; 154:796-803. [DOI: 10.1016/j.neuroscience.2008.03.071] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Revised: 03/27/2008] [Accepted: 03/27/2008] [Indexed: 11/26/2022]
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24
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Zhu X, Vasilyeva ON, Kim S, Jacobson M, Romney J, Waterman MS, Tuttle D, Frisina RD. Auditory efferent feedback system deficits precede age-related hearing loss: contralateral suppression of otoacoustic emissions in mice. J Comp Neurol 2007; 503:593-604. [PMID: 17559088 DOI: 10.1002/cne.21402] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The C57BL/6J mouse has been a useful model of presbycusis, as it displays an accelerated age-related peripheral hearing loss. The medial olivocochlear efferent feedback (MOC) system plays a role in suppressing cochlear outer hair cell (OHC) responses, particularly for background noise. Neurons of the MOC system are located in the superior olivary complex, particularly in the dorsomedial periolivary nucleus (DMPO) and in the ventral nucleus of the trapezoid body (VNTB). We previously discovered that the function of the MOC system declines with age prior to OHC degeneration, as measured by contralateral suppression (CS) of distortion product otoacoustic emissions (DPOAEs) in humans and CBA mice. The present study aimed to determine the time course of age changes in MOC function in C57s. DPOAE amplitudes and CS of DPOAEs were collected for C57s from 6 to 40 weeks of age. MOC responses were observed at 6 weeks but were gone at middle (15-30 kHz) and high (30-45 kHz) frequencies by 8 weeks. Quantitative stereological analyses of Nissl sections revealed smaller neurons in the DMPO and VNTB of young adult C57s compared with CBAs. These findings suggest that reduced neuron size may underlie part of the noteworthy rapid decline of the C57 efferent system. In conclusion, the C57 mouse has MOC function at 6 weeks, but it declines quickly, preceding the progression of peripheral age-related sensitivity deficits and hearing loss in this mouse strain.
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Affiliation(s)
- Xiaoxia Zhu
- Department of Otolaryngology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642-8629, USA
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25
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Le Prell CG. Role for the lateral olivocochlear neurons in auditory function. Focus on "Selective removal of lateral olivocochlear efferents increases vulnerability to acute acoustic injury". J Neurophysiol 2006; 97:963-5. [PMID: 17182904 DOI: 10.1152/jn.01223.2006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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26
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Le Prell CG, Kawamoto K, Raphael Y, Dolan DF. Electromotile hearing: acoustic tones mask psychophysical response to high-frequency electrical stimulation of intact guinea pig cochleae. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2006; 120:3889-900. [PMID: 17225416 PMCID: PMC3132799 DOI: 10.1121/1.2359238] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
When sinusoidal electric stimulation is applied to the intact cochlea, a frequency-specific acoustic emission can be recorded in the ear canal. Acoustic emissions are produced by basilar membrane motion, and have been used to suggest a corresponding acoustic sensation termed "electromotile hearing." Electromotile hearing has been specifically attributed to electric stimulation of outer hair cells in the intact organ of Corti. To determine the nature of the auditory perception produced by electric stimulation of a cochlea with intact outer hair cells, guinea pigs were tested in a psychophysical task. First, subjects were trained to report detection of sinusoidal acoustic stimuli and dynamic range was assessed using response latency. Subjects were then implanted with a ball electrode placed into scala tympani. Following the surgical implant procedure, subjects were transferred to a task in which acoustic signals were replaced by sinusoidal electric stimulation, and dynamic range was assessed again. Finally, the ability of acoustic pure-tone stimuli to mask the detection of the electric signals was assessed. Based on the masking effects, it is concluded that sinusoidal electric stimulation of the intact cochlea results in perception of a tonal (rather than a broadband or noisy) sound at a frequency of 8 kHz or above.
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Affiliation(s)
- Colleen G Le Prell
- Kresge Hearing Research Institute, 1301 East Ann Street, Ann Arbor, Michigan 48109-0506, USA.
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27
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Darrow KN, Maison SF, Liberman MC. Selective removal of lateral olivocochlear efferents increases vulnerability to acute acoustic injury. J Neurophysiol 2006; 97:1775-85. [PMID: 17093118 PMCID: PMC1805782 DOI: 10.1152/jn.00955.2006] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cochlear sensory cells and neurons receive efferent feedback from the olivocochlear (OC) system. The myelinated medial component of the OC system and its effects on outer hair cells (OHCs) have been implicated in protection from acoustic injury. The unmyelinated lateral (L)OC fibers target ipsilateral cochlear nerve dendrites and pharmacological studies suggest the LOC's dopaminergic component may protect these dendrites from excitotoxic effects of acoustic overexposure. Here, we explore LOC function in vivo by selective stereotaxic destruction of LOC cell bodies in mouse. Lesion success in removing the LOC, and sparing the medial (M)OC, was assessed by histological analysis of brain stem sections and cochlear whole mounts. Auditory brain stem responses (ABRs), a neural-based metric, and distortion product otoacoustic emissions (DPOAEs), an OHC-based metric, were measured in control and surgical mice. In cases where the LOC was at least partially destroyed, there were increases in suprathreshold neural responses that were frequency- and level-independent and not attributable to OHC-based effects. These interaural response asymmetries were not found in controls or in cases where the lesion missed the LOC. In LOC-lesion cases, after exposure to a traumatic stimulus, temporary threshold shifts were greater in the ipsilateral ear, but only when measured in the neural response; OHC-based measurements were always bilaterally symmetric, suggesting OHC vulnerability was unaffected. Interaural asymmetries in threshold shift were not found in either unlesioned controls or in cases that missed the LOC. These findings suggest that the LOC modulates cochlear nerve excitability and protects the cochlea from neural damage in acute acoustic injury.
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Affiliation(s)
- Keith N. Darrow
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114
- Program in Speech and Hearing Bioscience and Technology, Division of Health Science and Technology, Harvard and MIT, Cambridge, MA
| | - Stéphane F. Maison
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114
| | - M. Charles Liberman
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA 02114
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114
- Program in Speech and Hearing Bioscience and Technology, Division of Health Science and Technology, Harvard and MIT, Cambridge, MA
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28
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Ruel J, Wang J, Rebillard G, Eybalin M, Lloyd R, Pujol R, Puel JL. Physiology, pharmacology and plasticity at the inner hair cell synaptic complex. Hear Res 2006; 227:19-27. [PMID: 17079104 DOI: 10.1016/j.heares.2006.08.017] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 04/14/2006] [Accepted: 08/30/2006] [Indexed: 02/07/2023]
Abstract
This report summarizes recent neuropharmacological data at the IHC afferent/efferent synaptic complex: the type of Glu receptors and transporter involved and the modulation of this fast synaptic transmission by the lateral efferents. Neuropharmacological data were obtained by coupling the recording of cochlear potentials and single unit of the auditory nerve with intra-cochlear applications of drugs (multi-barrel pipette). We also describe the IHC afferent/efferent functioning in pathological conditions. After acoustic trauma or ischemia, acute disruption of IHC-auditory dendrite synapses are seen. However, a re-growth of the nerve fibres and a re-afferentation of the IHC were completely done 5 days after injury. During this synaptic repair, multiple presynaptic bodies were commonly found, either linked to the membrane or "floating" in ectopic positions. In the meantime, the lateral efferents directly contact the IHCs. The demonstration that NMDA receptors blockade delayed the re-growth of neurites suggests a neurotrophic role of NMDA receptors in pathological conditions.
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Affiliation(s)
- Jérôme Ruel
- INSERM U583-INM, Hôpital Saint Eloi, 80 Avenue Augustin Fliche, BP 74103, 34091 Montpellier cedex 5, France
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29
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Ruel J, Wang J, Demêmes D, Gobaille S, Puel JL, Rebillard G. Dopamine transporter is essential for the maintenance of spontaneous activity of auditory nerve neurones and their responsiveness to sound stimulation. J Neurochem 2006; 97:190-200. [PMID: 16524378 DOI: 10.1111/j.1471-4159.2006.03722.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Dopamine, a neurotransmitter released by the lateral olivocochlear efferents, has been shown tonically to inhibit the spontaneous and sound-evoked activity of auditory nerve fibres. This permanent inhibition probably requires the presence of an efficient transporter to remove dopamine from the synaptic cleft. Here, we report that the dopamine transporter is located in the lateral efferent fibres both below the inner hair cells and in the inner spiral bundle. Perilymphatic perfusion of the dopamine transporter inhibitors nomifensine and N-[1-(2-benzo[b]thiophenyl)cyclohexyl]piperidine into the cochlea reduced the spontaneous neural noise and the sound-evoked compound action potential of the auditory nerve in a dose-dependent manner, leading to both neural responses being completely abolished. We observed no significant change in cochlear responses generated by sensory hair cells (cochlear microphonic, summating potential, distortion products otoacoustic emissions) or in the endocochlear potential reflecting the functional state of the stria vascularis. This is consistent with a selective action of dopamine transporter inhibitors on auditory nerve activity. Capillary electrophoresis with laser-induced fluorescence (EC-LIF) measurements showed that nomifensine-induced inhibition of auditory nerve responses was due to increased extracellular dopamine levels in the cochlea. Altogether, these results show that the dopamine transporter is essential for maintaining the spontaneous activity of auditory nerve neurones and their responsiveness to sound stimulation.
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Affiliation(s)
- Jérôme Ruel
- Institut National de la Santé et de la Recherche Médicale U583, Institut des Neurosciences de Montpellier and University of Montpellier 1, Montpellier, France.
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