1
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van den Berg MM, Wong AB, Houtak G, Williamson RS, Borst JGG. Sodium salicylate improves detection of amplitude-modulated sound in mice. iScience 2024; 27:109691. [PMID: 38736549 PMCID: PMC11088340 DOI: 10.1016/j.isci.2024.109691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 01/14/2024] [Accepted: 04/05/2024] [Indexed: 05/14/2024] Open
Abstract
Salicylate is commonly used to induce tinnitus in animals, but its underlying mechanism of action is still debated. We therefore tested its effects on the firing properties of neurons in the mouse inferior colliculus (IC). Salicylate induced a large decrease in the spontaneous activity and an increase of ∼20 dB SPL in the minimum threshold of single units. In response to sinusoidally modulated noise (SAM noise) single units showed both an increase in phase locking and improved rate coding. Mice also became better at detecting amplitude modulations, and a simple threshold model based on the IC population response could reproduce this improvement. The responses to dynamic random chords (DRCs) suggested that the improved AM encoding was due to a linearization of the cochlear output, resulting in larger contrasts during SAM noise. These effects of salicylate are not consistent with the presence of tinnitus, but should be taken into account when studying hyperacusis.
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Affiliation(s)
- Maurits M. van den Berg
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, NL-3015 GD Rotterdam, the Netherlands
| | - Aaron B. Wong
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, NL-3015 GD Rotterdam, the Netherlands
| | - Ghais Houtak
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, NL-3015 GD Rotterdam, the Netherlands
| | - Ross S. Williamson
- Pittsburgh Hearing Research Center, Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - J. Gerard G. Borst
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, NL-3015 GD Rotterdam, the Netherlands
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2
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Dai Q, Qu T, Shen G, Wang H. Characterization of the neural circuitry of the auditory thalamic reticular nucleus and its potential role in salicylate-induced tinnitus. Front Neurosci 2024; 18:1368816. [PMID: 38629053 PMCID: PMC11019010 DOI: 10.3389/fnins.2024.1368816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 03/19/2024] [Indexed: 04/19/2024] Open
Abstract
Introduction Subjective tinnitus, the perception of sound without an external acoustic source, is often subsequent to noise-induced hearing loss or ototoxic medications. The condition is believed to result from neuroplastic alterations in the auditory centers, characterized by heightened spontaneous neural activities and increased synchrony due to an imbalance between excitation and inhibition. However, the role of the thalamic reticular nucleus (TRN), a structure composed exclusively of GABAergic neurons involved in thalamocortical oscillations, in the pathogenesis of tinnitus remains largely unexplored. Methods We induced tinnitus in mice using sodium salicylate and assessed tinnitus-like behaviors using the Gap Pre-Pulse Inhibition of the Acoustic Startle (GPIAS) paradigm. We utilized combined viral tracing techniques to identify the neural circuitry involved and employed immunofluorescence and confocal imaging to determine cell types and activated neurons. Results Salicylate-treated mice exhibited tinnitus-like behaviors. Our tracing clearly delineated the inputs and outputs of the auditory-specific TRN. We discovered that chemogenetic activation of the auditory TRN significantly reduced the salicylate-evoked rise in c-Fos expression in the auditory cortex. Discussion This finding posits the TRN as a potential modulatory target for tinnitus treatment. Furthermore, the mapped sensory inputs to the auditory TRN suggest possibilities for employing optogenetic or sensory stimulations to manipulate thalamocortical activities. The precise mapping of the auditory TRN-mediated neural pathways offers a promising avenue for designing targeted interventions to alleviate tinnitus symptoms.
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Affiliation(s)
| | | | - Guoming Shen
- School of Integrated Chinese and Western Medicine, Anhui University of Chinese Medicine, Hefei, China
| | - Haitao Wang
- School of Integrated Chinese and Western Medicine, Anhui University of Chinese Medicine, Hefei, China
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3
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Naghdabadi Z, Jahed M. Heterogeneous correlate and potential diagnostic biomarker of tinnitus based on nonlinear dynamics of resting-state EEG recordings. PLoS One 2024; 19:e0290563. [PMID: 38166014 PMCID: PMC10760901 DOI: 10.1371/journal.pone.0290563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 08/09/2023] [Indexed: 01/04/2024] Open
Abstract
Tinnitus is a heterogeneous condition of hearing a rattling sound when there is no auditory stimulus. This rattling sound is associated with abnormal synchronous oscillations in auditory and non-auditory cortical areas. Since tinnitus is a highly heterogeneous condition with no objective detection criteria, it is necessary to search for indicators that can be compared between and within participants for diagnostic purposes. This study introduces heterogeneous though comparable indicators of tinnitus through investigation of spontaneous fluctuations in resting-state brain dynamics. The proposed approach uses nonlinear measures of chaos theory, to detect tinnitus and cross correlation patterns to reflect many of the previously reported neural correlates of tinnitus. These indicators may serve as effective measures of tinnitus risk even at early ages before any symptom is reported. The approach quantifies differences in oscillatory brain dynamics of tinnitus and normal subjects. It demonstrates that the left temporal areas of subjects with tinnitus exhibit larger lyapunov exponent indicating irregularity of brain dynamics in these regions. More complex dynamics is further recognized in tinnitus cases through entropy. We use this evidence to distinguish tinnitus patients from normal participants. Besides, we illustrate that certain anticorrelation patterns appear in these nonlinear measures across temporal and frontal areas in the brain perhaps corresponding to increased/decreased connectivity in certain brain networks and a shift in the balance of excitation and inhibition in tinnitus. Additionally, the main correlations are lost in tinnitus participants compared to control group suggesting involvement of distinct neural mechanisms in generation and persistence of tinnitus.
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Affiliation(s)
- Zahra Naghdabadi
- Department of Electrical Engineering, Sharif University of Technology, Tehran, Iran
| | - Mehran Jahed
- Department of Electrical Engineering, Sharif University of Technology, Tehran, Iran
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4
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Ma X, Chen N, Wang F, Zhang C, Dai J, Ding H, Yan C, Shen W, Yang S. Surface-based functional metrics and auditory cortex characteristics in chronic tinnitus. Heliyon 2022; 8:e10989. [PMID: 36276740 PMCID: PMC9582700 DOI: 10.1016/j.heliyon.2022.e10989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 06/11/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
Abstract
Abnormal auditory cortex (AC) neuronal activity is thought to be a primary cause of the auditory disturbances perceived by individuals suffering from tinnitus. The present study was designed to test that possibility by evaluating auditory cortical characteristics (volume, curvature, surface area, thickness) and surface-based functional metrics in chronic tinnitus patients. In total, 63 chronic tinnitus patients and 36 age-, sex- and education level-matched healthy control (HC) patients were enrolled in this study. Hearing levels in these two groups were comparable, and following magnetic resonance imaging (MRI) of these individuals, the DPABISurf software was used to compute cerebral cortex curvature, thickness, and surface area as well as surface-based functional metrics. The Tinnitus Handicap Inventory (THI), Tinnitus Handicap Questionary (THQ), and Visual Analogue Scales (VAS) were used to gauge participant tinnitus severity, while correlation analyses were conducted to evaluate associations between these different analyzed parameters. A significant increase in the regional homogeneity (ReHo) of the right secondary AC was detected in the tinnitus group relative to the HC group. There were also significant reductions in the cortical volume and surface area of the right secondary AC in the tinnitus group relative to the HC group (all P < 0.05). In addition, significant negative correlations between tinnitus pitch and the cortical area and volume of the right secondary AC were observed in the tinnitus group.
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Affiliation(s)
- Xiaoyan Ma
- The First Affiliated Hospital of Xi'an, Jiaotong University, Shanxi, China,Medical School of Chinese PLA, Beijing, China,Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China,National Clinical Research Center for Otolaryngologic Diseases, Beijing, China,Key Lab of Hearing Science, Ministry of Education, Beijing, China,Beijing Key Lab of Hearing Impairment Prevention and Treatment, Beijing, China
| | - Ningxuan Chen
- CAS Key Laboratory of Behavioral Science, Institute of Psychology, Beijing, China,Magnetic Resonance Imaging Research Center, Institute of Psychology, Chinese Academy of Sciences, Beijing, China,International Big-Data Center for Depression Research, Chinese Academy of Sciences, Beijing, China,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China,Center for Cognitive Science of Language, Beijing Language and Culture University, Beijing, China
| | - Fangyuan Wang
- Medical School of Chinese PLA, Beijing, China,Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China,National Clinical Research Center for Otolaryngologic Diseases, Beijing, China,Key Lab of Hearing Science, Ministry of Education, Beijing, China,Beijing Key Lab of Hearing Impairment Prevention and Treatment, Beijing, China
| | - Chi Zhang
- Medical School of Chinese PLA, Beijing, China,Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China,National Clinical Research Center for Otolaryngologic Diseases, Beijing, China,Key Lab of Hearing Science, Ministry of Education, Beijing, China,Beijing Key Lab of Hearing Impairment Prevention and Treatment, Beijing, China
| | - Jing Dai
- Medical School of Chinese PLA, Beijing, China,Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China,National Clinical Research Center for Otolaryngologic Diseases, Beijing, China,Key Lab of Hearing Science, Ministry of Education, Beijing, China,Beijing Key Lab of Hearing Impairment Prevention and Treatment, Beijing, China
| | - Haina Ding
- Medical School of Chinese PLA, Beijing, China,Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China,National Clinical Research Center for Otolaryngologic Diseases, Beijing, China,Key Lab of Hearing Science, Ministry of Education, Beijing, China,Beijing Key Lab of Hearing Impairment Prevention and Treatment, Beijing, China
| | - Chaogan Yan
- CAS Key Laboratory of Behavioral Science, Institute of Psychology, Beijing, China,Magnetic Resonance Imaging Research Center, Institute of Psychology, Chinese Academy of Sciences, Beijing, China,International Big-Data Center for Depression Research, Chinese Academy of Sciences, Beijing, China,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China,Center for Cognitive Science of Language, Beijing Language and Culture University, Beijing, China,Department of Child and Adolescent Psychiatry, Hassenfeld Children's Hospital at NYU Langone, New York, NY, USA,Corresponding author.
| | - Weidong Shen
- Medical School of Chinese PLA, Beijing, China,Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China,National Clinical Research Center for Otolaryngologic Diseases, Beijing, China,Key Lab of Hearing Science, Ministry of Education, Beijing, China,Beijing Key Lab of Hearing Impairment Prevention and Treatment, Beijing, China,Corresponding author.
| | - Shiming Yang
- Medical School of Chinese PLA, Beijing, China,Department of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China,National Clinical Research Center for Otolaryngologic Diseases, Beijing, China,Key Lab of Hearing Science, Ministry of Education, Beijing, China,Beijing Key Lab of Hearing Impairment Prevention and Treatment, Beijing, China,Corresponding author.
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5
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Olthof BMJ, Lyzwa D, Gartside SE, Rees A. Nitric oxide signalling underlies salicylate-induced increases in neuronal firing in the inferior colliculus: A central mechanism of tinnitus? Hear Res 2022; 424:108585. [DOI: 10.1016/j.heares.2022.108585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 06/17/2022] [Accepted: 07/21/2022] [Indexed: 11/16/2022]
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6
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Behavioral and Immunohistochemical Evidence for Suppressive Effects of Goshajinkigan on Salicylate-Induced Tinnitus in Rats. Brain Sci 2022; 12:brainsci12050587. [PMID: 35624974 PMCID: PMC9139011 DOI: 10.3390/brainsci12050587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 04/25/2022] [Accepted: 04/28/2022] [Indexed: 02/04/2023] Open
Abstract
Many people are affected by tinnitus, a sensation of ringing in the ear despite the absence of external sound. Goshajinkigan (GJG) is one of the formulations of Japanese traditional herbal medicine and is prescribed for the palliative treatment of patients with tinnitus. Although GJG is clinically effective in these patients, its behavioral effects and the underlying neuroanatomical substrate have not been modeled in animals. We modeled tinnitus using salicylate-treated rats, demonstrated the effectiveness of GJG on tinnitus, and examined the underlying neuronal substrate with c-Fos expression. Intraperitoneal injection of sodium salicylate (400 mg/kg) into rats for three consecutive days significantly increased false positive scores, which were used to assess tinnitus behavior. When GJG was orally administered one hour after each salicylate injection, the increase in tinnitus behavior was suppressed. The analysis of c-Fos expression in auditory-related brain areas revealed that GJG significantly reduced the salicylate-induced increase in the number of c-Fos-expressing cells in the auditory cortices, inferior colliculus, and dorsal cochlear nucleus. These results suggest a suppressive effect of GJG on salicylate-induced tinnitus in animal models.
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7
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Kenmochi M, Ochi K, Kinoshita H, Miyamoto Y, Koizuka I. The effect of systemic administration of salicylate on the auditory cortex of guinea pigs. PLoS One 2021; 16:e0259055. [PMID: 34762664 PMCID: PMC8584678 DOI: 10.1371/journal.pone.0259055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 10/11/2021] [Indexed: 11/19/2022] Open
Abstract
Objective To investigate the effect of systemic administration of salicylate as a tinnitus inducing drug in the auditory cortex of guinea pigs. Methods Extracellular recording of spikes of the primary auditory cortex and dorsocaudal areas in healthy male albino Hartley guinea pigs was continuously performed (pre- and post-salicylate). Results We recorded 160 single units in the primary auditory cortex from five guinea pigs and 156 single units in the dorsocaudal area from another five guinea pigs. The threshold was significantly elevated after the administration of salicylate in both the primary auditory cortex and dorsocaudal areas. The Q10dB value was significantly increased in the primary auditory cortex, whereas it has significantly decreased in the dorsocaudal area. Spontaneous firing activity was significantly decreased in the primary auditory cortex, whereas it has significantly increased in the dorsocaudal area. Conclusion Salicylate induces significant changes in single units of both stimulated and spontaneous activity in the auditory cortex of guinea pigs. The spontaneous activity changed differently depending on its cortical areas, which may be due to the neural elements that generate tinnitus.
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Affiliation(s)
- Mutsumi Kenmochi
- Department of Otolaryngology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Kentaro Ochi
- Department of Otolaryngology, St. Marianna University School of Medicine, Kawasaki, Japan
- * E-mail:
| | - Hirotsugu Kinoshita
- Department of Otolaryngology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Yasuhiro Miyamoto
- Department of Otolaryngology, St. Marianna University School of Medicine, Kawasaki, Japan
| | - Izumi Koizuka
- Department of Otolaryngology, St. Marianna University School of Medicine, Kawasaki, Japan
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8
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Jozefowicz-Korczynska M, Pajor A, Lucas Grzelczyk W. The Ototoxicity of Antimalarial Drugs-A State of the Art Review. Front Neurol 2021; 12:661740. [PMID: 33959089 PMCID: PMC8093564 DOI: 10.3389/fneur.2021.661740] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 03/04/2021] [Indexed: 11/19/2022] Open
Abstract
This review summarizes current knowledge about the occurrence of hearing and balance disorders after antimalarial drugs treatment. It also examines the clinical applications of antimalarials, their mechanisms behind this ototoxicity and how it can be monitored. It includes studies with larger numbers of patients and those in which auditory function was assessed using audiological tests. Some antimalarials have been repurposed for other conditions like autoimmune disorders, rheumatic diseases, some viral diseases and cancers. While old antimalarial drugs, such as quinoline derivatives, are known to demonstrate ototoxicity, a number of new synthetic antimalarial agents particularly artemisinin derivatives, demonstrate unknown ototoxicity. Adverse audiovestibular effects vary depending on the medication itself, its dose and route of administration, as well as the drug combination, treated disease and individual predispositions of the patient. Dizziness was commonly reported, while vestibular symptoms, hearing loss and tinnitus were observed much less frequently, and most of these symptoms were reversible. As early identification of ototoxic hearing loss is critical to introducing possible alternative treatments with less ototoxic medications, therefore monitoring systems of those drugs ototoxic side effects are much needed.
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Affiliation(s)
- Magdalena Jozefowicz-Korczynska
- Balance Disorders Unit, Otolaryngology Department, The Norbert Barlicki Memorial Teaching Hospital, Medical University of Lodz, Lodz, Poland
| | - Anna Pajor
- Department of Otolaryngology, Head and Neck Oncology, The Norbert Barlicki Memorial Teaching Hospital, Medical University of Lodz, Lodz, Poland
| | - Weronika Lucas Grzelczyk
- Balance Disorders Unit, Otolaryngology Department, The Norbert Barlicki Memorial Teaching Hospital, Medical University of Lodz, Lodz, Poland
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9
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Cai WW, Li ZC, Yang QT, Zhang T. Abnormal Spontaneous Neural Activity of the Central Auditory System Changes the Functional Connectivity in the Tinnitus Brain: A Resting-State Functional MRI Study. Front Neurosci 2019; 13:1314. [PMID: 31920484 PMCID: PMC6932986 DOI: 10.3389/fnins.2019.01314] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 11/25/2019] [Indexed: 01/20/2023] Open
Abstract
Objective An abnormal state of the central auditory system (CAS) likely plays a large role in the occurrence of phantom sound of tinnitus. Various tinnitus studies using resting-state functional MRI (RS-fMRI) have reported aberrant spontaneous brain activity in the non-auditory system and altered functional connectivity between the CAS and non-auditory system. This study aimed to investigate abnormal functional connections between the aberrant spontaneous activity in the CAS and the whole brain in tinnitus patients, compared to healthy controls (HC) using RS-fMRI. Materials and Methods RS-fMRI from 16 right-ear tinnitus patients with normal hearing (TNHs) and 15 HC individuals was collected, and the time series were extracted from different clusters of a CAS template, supplied by the Anatomy Toolbox of the Statistical Parametric Mapping software. These data were used to derive the smoothed mean amplitude of low-frequency fluctuation (smALFF) values and calculate the relationship between such values and the corresponding clinical data. In addition, clusters in the CAS identified by the smALFF maps were set as seed regions for calculating and comparing the brain-wide connectivity between TNH and HC. Results We identified the different clusters located in the left higher auditory cortex (HAC) and the right inferior colliculus (IC) from the smALFF maps that contained increased (HAC) and decreased (IC) activity when the TNH group was compared to the HC group, respectively. The value of increased smALFF cluster in the HAC was positively correlated with the tinnitus score, but the decreased smALFF cluster in the IC was not correlated with any clinical characters of tinnitus. The TNH group displayed increased connectivity, compared to the HC group, in brain regions that encompassed the left IC, bilateral Heschl gyrus, bilateral supplementary motor area, right insula, bilateral superior temporal gyrus, right middle temporal gyrus, left hippocampus, left amygdala, and right supramarginal gyrus. Conclusion Tinnitus may be linked to abnormal spontaneous activity in the HAC, which can arise from the neural plasticity induced from the increased functional connectivity between the auditory network, cerebellum, and limbic system.
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Affiliation(s)
- Wei-Wei Cai
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of Jinan University, Guangzhou, China.,Department of Otolaryngology-Head and Neck Surgery, Panyu Central Hospital, Guangzhou, China
| | - Zhi-Cheng Li
- Department of Otolaryngology-Head and Neck Surgery, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Qin-Tai Yang
- Department of Otolaryngology-Head and Neck Surgery, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Tao Zhang
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of Jinan University, Guangzhou, China
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10
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Sheppard A, Stocking C, Ralli M, Salvi R. A review of auditory gain, low-level noise and sound therapy for tinnitus and hyperacusis. Int J Audiol 2019; 59:5-15. [DOI: 10.1080/14992027.2019.1660812] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Adam Sheppard
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY, USA
- Department of Communicative Disorders and Sciences, University at Buffalo, Buffalo, NY, USA
| | - Christina Stocking
- Department of Communicative Disorders and Sciences, University at Buffalo, Buffalo, NY, USA
| | - Massimo Ralli
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY, USA
- Department of Communicative Disorders and Sciences, University at Buffalo, Buffalo, NY, USA
- Department of Oral and Maxillofacial Sciences, Sapienza University of Rome, Rome, Italy
| | - Richard Salvi
- Center for Hearing and Deafness, University at Buffalo, Buffalo, NY, USA
- Department of Communicative Disorders and Sciences, University at Buffalo, Buffalo, NY, USA
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11
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Borland MS, Vrana WA, Moreno NA, Fogarty EA, Buell EP, Vanneste S, Kilgard MP, Engineer CT. Pairing vagus nerve stimulation with tones drives plasticity across the auditory pathway. J Neurophysiol 2019; 122:659-671. [PMID: 31215351 DOI: 10.1152/jn.00832.2018] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Previous studies have demonstrated that pairing vagus nerve stimulation (VNS) with sounds can enhance the primary auditory cortex (A1) response to the paired sound. The neural response to sounds following VNS-sound pairing in other subcortical and cortical auditory fields has not been documented. We predicted that VNS-tone pairing would increase neural responses to the paired tone frequency across the auditory pathway. In this study, we paired VNS with the presentation of a 9-kHz tone 300 times a day for 20 days. We recorded neural responses to tones from 2,950 sites in the inferior colliculus (IC), A1, anterior auditory field (AAF), and posterior auditory field (PAF) 24 h after the last pairing session in anesthetized rats. We found that VNS-tone pairing increased the percentage of IC, A1, AAF, and PAF that responds to the paired tone frequency. Across all tested auditory fields, the response strength to tones was strengthened in VNS-tone paired rats compared with control rats. VNS-tone pairing reduced spontaneous activity, frequency selectivity, and response threshold across the auditory pathway. This is the first study to document both cortical and subcortical plasticity following VNS-sound pairing. Our findings suggest that VNS paired with sound presentation is an effective method to enhance auditory processing.NEW & NOTEWORTHY Previous studies have reported primary auditory cortex plasticity following vagus nerve stimulation (VNS) paired with a sound. This study extends previous findings by documenting that fields across the auditory pathway are altered by VNS-tone pairing. VNS-tone pairing increases the percentage of each field that responds to the paired tone frequency. This is the first study to document both cortical and subcortical plasticity following VNS-sound pairing.
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Affiliation(s)
- Michael S Borland
- The University of Texas at Dallas, Texas Biomedical Device Center, Richardson, Texas.,The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
| | - Will A Vrana
- The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
| | - Nicole A Moreno
- The University of Texas at Dallas, Texas Biomedical Device Center, Richardson, Texas.,The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
| | - Elizabeth A Fogarty
- The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
| | - Elizabeth P Buell
- The University of Texas at Dallas, Texas Biomedical Device Center, Richardson, Texas.,The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
| | - Sven Vanneste
- The University of Texas at Dallas, Texas Biomedical Device Center, Richardson, Texas.,The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
| | - Michael P Kilgard
- The University of Texas at Dallas, Texas Biomedical Device Center, Richardson, Texas.,The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
| | - Crystal T Engineer
- The University of Texas at Dallas, Texas Biomedical Device Center, Richardson, Texas.,The University of Texas at Dallas, School of Behavioral and Brain Sciences, Richardson, Texas
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12
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Sedley W. Tinnitus: Does Gain Explain? Neuroscience 2019; 407:213-228. [DOI: 10.1016/j.neuroscience.2019.01.027] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/15/2019] [Accepted: 01/17/2019] [Indexed: 02/01/2023]
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13
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Galazyuk A, Longenecker R, Voytenko S, Kristaponyte I, Nelson G. Residual inhibition: From the putative mechanisms to potential tinnitus treatment. Hear Res 2019; 375:1-13. [DOI: 10.1016/j.heares.2019.01.022] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 01/23/2019] [Accepted: 01/30/2019] [Indexed: 01/04/2023]
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14
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Pienkowski M. Prolonged Exposure of CBA/Ca Mice to Moderately Loud Noise Can Cause Cochlear Synaptopathy but Not Tinnitus or Hyperacusis as Assessed With the Acoustic Startle Reflex. Trends Hear 2019. [PMID: 29532738 PMCID: PMC5858683 DOI: 10.1177/2331216518758109] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Hearing loss changes the auditory brain, sometimes maladaptively. When deprived of cochlear input, central auditory neurons become more active spontaneously and begin to respond more strongly and synchronously to better preserved sound frequencies. This spontaneous and sound-evoked central hyperactivity has been postulated to trigger tinnitus and hyperacusis, respectively. Localized hyperactivity has also been observed after long-term exposure to noise levels that do not damage the cochlea. Adult animals exposed to bands of nondamaging noise exhibited suppressed spontaneous and sound-evoked activity in the area of primary auditory cortex (A1) stimulated by the exposure band but had increased spontaneous and evoked activity in neighboring A1 areas. We hypothesized that the cortically suppressed frequencies should for some time after exposure be perceived as less loud than before (hypoacusis), whereas the hyperactivity outside of the exposure band might lead to frequency-specific hyperacusis or tinnitus. To investigate this, adult CBA/Ca mice were exposed for >2 months to 8 to 16 kHz noise at 70 or 75 dB sound pressure level and tested for hypo-/hyperacusis and tinnitus using tone and gap prepulse inhibition of the acoustic startle reflex. Auditory brainstem responses and distortion product otoacoustic emissions showed evidence of cochlear synaptopathy after exposure at 75 but not 70 dB, putting a lower bound on damaging noise levels for CBA/Ca mice. Contrary to hypothesis, neither exposure significantly shifted startle results from baseline. These negative findings nevertheless have implications for startle test methodology and for the putative role of central hyperactivity in hyperacusis and tinnitus.
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Affiliation(s)
- Martin Pienkowski
- 1 Osborne College of Audiology, Salus University, Elkins Park, PA, USA
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15
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Abstract
Tinnitus is the sensation of hearing a sound with no external auditory stimulus present. It is a public health issue correlated with multiple comorbidities and precipitating factors such as noise exposure, military service, and traumatic brain injury, migraine, insomnia, small vessel disease, smoking history, stress exposure, anxiety, depression, and socioeconomic status. Clinical experience and a recent literature review point at tinnitus as a neuropsychiatric condition involving both auditory and nonauditory cortical areas of the brain and affecting brain-auditory circuitry. In fact, brain-ear connections have been highlighted in different models. Forward management of this disorder should take this body of research into consideration as tinnitus remains a challenging condition to evaluate and treat with current management protocols still symptomatic at best. With a better understanding of the etiologic factors and comorbidities of tinnitus, additional research trials and new therapeutic approaches could see the light to tackle this public health disability bringing hope to patients and doctors.
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Affiliation(s)
- Zeina Chemali
- Departments of Neurology and Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States.
| | - R Nehmé
- Cambridge Health Alliance, Harvard Medical School, Cambridge, MA, United States
| | - Gregory Fricchione
- Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
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16
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Ding YJ, Song Y, Liu JX, Du YL, Zhu L, Ma FR. Effect of Neuronal Excitability in Hippocampal CA1 Area on Auditory Pathway in a Rat Model of Tinnitus. Chin Med J (Engl) 2018; 131:1969-1974. [PMID: 30082529 PMCID: PMC6085865 DOI: 10.4103/0366-6999.238148] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Background: Tinnitus is a common disorder that causes significant morbidity; however, the neurophysiological mechanism is not yet fully understood. A relationship between tinnitus and limbic system has been reported. As a significant component of the limbic system, the hippocampus plays an important role in various pathological processes, such as emotional disturbance, decreased learning ability, and deterioration of memory. This study was aimed to explore the role of the hippocampus in the generation of tinnitus by electrophysiological technology. Methods: A tinnitus model was established in rats through intraperitoneal injection of salicylate (SA). Subsequently, the spontaneous firing rate (SFR) of neurons in the hippocampal CA1 area was recorded with in vivo multichannel recording technology to assess changes in excitability induced by SA. To investigate the effect of excitability changes of hippocampus on the auditory pathway, the hippocampus was electrically stimulated and neural excitability in the auditory cortex (AC) was monitored. Results: Totally 65 neurons in the hippocampal CA1 area were recorded, 45 from the SA group (n = 5), and 20 from the saline group (n = 5). Two hours after treatment, mean SFR of neurons in the hippocampal CA1 area had significantly increased from 3.06 ± 0.36 Hz to 9.18 ± 1.30 Hz in the SA group (t = −4.521, P < 0.05), while no significant difference was observed in the saline group (2.66 ± 0.36 Hz vs. 2.16 ± 0.36 Hz, t = 0.902, P > 0.05). In the AC, 79.3% (157/198) of recorded neurons showed responses to electrical stimulation of the hippocampal CA1 area. Presumed pyramidal neurons were excited, while intermediate neurons were inhibited after electrical stimulation of the hippocampus. Conclusions: The study shows that the hippocampus is excited in SA-induced tinnitus, and stimulation of hippocampus could modulate neuronal excitability of the AC. The hippocampus is involved in tinnitus and may also have a regulatory effect on the neural center.
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Affiliation(s)
- Yu-Jing Ding
- Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100191, China
| | - Yu Song
- Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100191, China
| | - Jun-Xiu Liu
- Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100191, China
| | - Ya-Li Du
- Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100191, China
| | - Li Zhu
- Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100191, China
| | - Fu-Rong Ma
- Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100191, China
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18
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Du Y, Liu J, Jiang Q, Duan Q, Mao L, Ma F. Paraflocculus plays a role in salicylate-induced tinnitus. Hear Res 2017; 353:176-184. [PMID: 28687184 DOI: 10.1016/j.heares.2017.06.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 06/23/2017] [Accepted: 06/28/2017] [Indexed: 12/17/2022]
Abstract
Tinnitus impairs quality of life of about 1-2% of the whole population. In most severe situation, tinnitus may cause social isolation, depression and suicide. Drug treatments for tinnitus are generally ineffective, and the mechanisms of tinnitus are still undetermined. Accumulating evidence suggests that tinnitus is related to changes of widespread brain networks. Recent studies propose that paraflocculus (PFL), which is indirectly connected to various cortical regions, may be a gating zone of tinnitus. So we examined the electrophysiological changes and neurotransmitter alterations of the PFL in a rat model of sodium salicylate (SS)-induced tinnitus. We found that spontaneous firing rate (SFR) of the putative excitatory interneurons of the PFL was significantly increased. The level of glutamic acid, which is the main excitatory neurotransmitter in the nervous system, was also dramatically increased in the PFL after SS treatment. These results confirmed the hyperactivity of PFL in the rats with SS-treatment, which might be due to the increased glutamic acid. Then we examined the SFR of the auditory cortex (AC), the center for auditory perception, before and after electrical stimulation of the PFL. 71.4% (105/147) of the recorded neurons showed a response to the stimulation of the PFL. The result demonstrated that stimulation of the PFL could modulate the activity of the AC. Our study suggests a role of PFL in SS-induced tinnitus and AC as a potential target of PFL in the process of tinnitus.
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Affiliation(s)
- Yali Du
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, 100191, PR China
| | - Junxiu Liu
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, 100191, PR China
| | - Qin Jiang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, 100190, PR China
| | - Qingchuan Duan
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, 100191, PR China
| | - Lanqun Mao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, 100190, PR China.
| | - Furong Ma
- Department of Otolaryngology Head and Neck Surgery, Peking University Third Hospital, Beijing, 100191, PR China.
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Brecht EJ, Barsz K, Gross B, Walton JP. Increasing GABA reverses age-related alterations in excitatory receptive fields and intensity coding of auditory midbrain neurons in aged mice. Neurobiol Aging 2017; 56:87-99. [PMID: 28532644 DOI: 10.1016/j.neurobiolaging.2017.04.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 03/18/2017] [Accepted: 04/04/2017] [Indexed: 11/25/2022]
Abstract
A key feature of age-related hearing loss is a reduction in the expression of inhibitory neurotransmitters in the central auditory system. This loss is partially responsible for changes in central auditory processing, as inhibitory receptive fields play a critical role in shaping neural responses to sound stimuli. Vigabatrin (VGB), an antiepileptic agent that irreversibly inhibits γ-amino butyric acid (GABA) transaminase, leads to increased availability of GABA throughout the brain. This study used multi-channel electrophysiology measurements to assess the excitatory frequency response areas in old CBA mice to which VGB had been administered. We found a significant post-VGB reduction in the proportion of V-type shapes, and an increase in primary-like excitatory frequency response areas. There was also a significant increase in the mean maximum driven spike rates across the tonotopic frequency range of all treated animals, consistent with observations that GABA buildup within the central auditory system increases spike counts of neural receptive fields. This increased spiking is also seen in the rate-level functions and seems to explain the improved low-frequency thresholds.
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Affiliation(s)
- Elliott J Brecht
- Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL, USA; Global Center of Speech and Hearing Research, University of South Florida, Tampa, FL, USA
| | - Kathy Barsz
- School of Nursing, University of Rochester, Rochester, NY, USA
| | - Benjamin Gross
- Global Center of Speech and Hearing Research, University of South Florida, Tampa, FL, USA; Department of Physics, University of South Florida, Tampa, FL, USA
| | - Joseph P Walton
- Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL, USA; Global Center of Speech and Hearing Research, University of South Florida, Tampa, FL, USA; Department of Communication Sciences and Disorders, University of South Florida, Tampa, FL, USA.
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20
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Emmert K, Kopel R, Koush Y, Maire R, Senn P, Van De Ville D, Haller S. Continuous vs. intermittent neurofeedback to regulate auditory cortex activity of tinnitus patients using real-time fMRI - A pilot study. NEUROIMAGE-CLINICAL 2017; 14:97-104. [PMID: 28154796 PMCID: PMC5278116 DOI: 10.1016/j.nicl.2016.12.023] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 12/18/2016] [Accepted: 12/19/2016] [Indexed: 11/20/2022]
Abstract
The emerging technique of real-time fMRI neurofeedback trains individuals to regulate their own brain activity via feedback from an fMRI measure of neural activity. Optimum feedback presentation has yet to be determined, particularly when working with clinical populations. To this end, we compared continuous against intermittent feedback in subjects with tinnitus. Fourteen participants with tinnitus completed the whole experiment consisting of nine runs (3 runs × 3 days). Prior to the neurofeedback, the target region was localized within the auditory cortex using auditory stimulation (1 kHz tone pulsating at 6 Hz) in an ON-OFF block design. During neurofeedback runs, participants received either continuous (n = 7, age 46.84 ± 12.01, Tinnitus Functional Index (TFI) 49.43 ± 15.70) or intermittent feedback (only after the regulation block) (n = 7, age 47.42 ± 12.39, TFI 49.82 ± 20.28). Participants were asked to decrease auditory cortex activity that was presented to them by a moving bar. In the first and the last session, participants also underwent arterial spin labeling (ASL) and resting-state fMRI imaging. We assessed tinnitus severity using the TFI questionnaire before all sessions, directly after all sessions and six weeks after all sessions. We then compared neuroimaging results from neurofeedback using a general linear model (GLM) and region-of-interest analysis as well as behavior measures employing a repeated-measures ANOVA. In addition, we looked at the seed-based connectivity of the auditory cortex using resting-state data and the cerebral blood flow using ASL data. GLM group analysis revealed that a considerable part of the target region within the auditory cortex was significantly deactivated during neurofeedback. When comparing continuous and intermittent feedback groups, the continuous group showed a stronger deactivation of parts of the target region, specifically the secondary auditory cortex. This result was confirmed in the region-of-interest analysis that showed a significant down-regulation effect for the continuous but not the intermittent group. Additionally, continuous feedback led to a slightly stronger effect over time while intermittent feedback showed best results in the first session. Behaviorally, there was no significant effect on the total TFI score, though on a descriptive level TFI scores tended to decrease after all sessions and in the six weeks follow up in the continuous group. Seed-based connectivity with a fixed-effects analysis revealed that functional connectivity increased over sessions in the posterior cingulate cortex, premotor area and part of the insula when looking at all patients while cerebral blood flow did not change significantly over time. Overall, these results show that continuous feedback is suitable for long-term neurofeedback experiments while intermittent feedback presentation promises good results for single session experiments when using the auditory cortex as a target region. In particular, the down-regulation effect is more pronounced in the secondary auditory cortex, which might be more susceptible to voluntary modulation in comparison to a primary sensory region. Comparison of continuous and intermittent fMRI neurofeedback in tinnitus patients Both groups attempted down-regulation of the auditory cortex. The continuous feedback group seemed to improve after multiple sessions. Intermittent feedback worked best for a single session. Down-regulation effect seems more pronounced in the secondary auditory cortex.
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Affiliation(s)
- Kirsten Emmert
- Department of Radiology and Medical Informatics, University Hospitals of Geneva, Rue Gabrielle-Perret-Gentil 4, 1205 Geneva, Switzerland
- Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Campus Biotech, Chemin des Mines 9, Case postale 60, 1211 Geneva 20, Switzerland
| | - Rotem Kopel
- Department of Radiology and Medical Informatics, University Hospitals of Geneva, Rue Gabrielle-Perret-Gentil 4, 1205 Geneva, Switzerland
- Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Campus Biotech, Chemin des Mines 9, Case postale 60, 1211 Geneva 20, Switzerland
| | - Yury Koush
- Department of Radiology and Medical Informatics, University Hospitals of Geneva, Rue Gabrielle-Perret-Gentil 4, 1205 Geneva, Switzerland
- Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Campus Biotech, Chemin des Mines 9, Case postale 60, 1211 Geneva 20, Switzerland
- Department of Radiology and Biomedical Imaging, Yale University, 300 Cedar Street, New Haven, CT 06519, USA
| | - Raphael Maire
- Department of ENT, Head & Neck Surgery, Neurotology and Audiology Unit, University Hospital of Lausanne, Rue du Bugnon 21, 1011 Lausanne, Switzerland
| | - Pascal Senn
- Department of Clinical Neurosciences, Service of ORL and HNS, University Hospitals of Geneva, Rue Gabrielle-Perret-Gentil 4, 1205 Geneva, Switzerland
| | - Dimitri Van De Ville
- Department of Radiology and Medical Informatics, University Hospitals of Geneva, Rue Gabrielle-Perret-Gentil 4, 1205 Geneva, Switzerland
- Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Campus Biotech, Chemin des Mines 9, Case postale 60, 1211 Geneva 20, Switzerland
| | - Sven Haller
- Affidea CDRC - Centre Diagnostique Radiologique de Carouge, Clos de la Fonderie 1, 1227 Carouge, Switzerland
- Department of Surgical Sciences, Radiology, Uppsala University, Uppsala, Sweden
- Department of Neuroradiology, University Hospital Freiburg, Germany
- Faculty of Medicine of the University of Geneva, Switzerland
- Corresponding author at: Affidea CDRC - Centre Diagnostique Radiologique de Carouge, Clos de la Fonderie 1, 1227 Carouge, Switzerland.Affidea CDRC - Centre Diagnostique Radiologique de CarougeClos de la Fonderie 1Carouge1227Switzerland
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21
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Eggermont JJ. Can Animal Models Contribute to Understanding Tinnitus Heterogeneity in Humans? Front Aging Neurosci 2016; 8:265. [PMID: 27895575 PMCID: PMC5107573 DOI: 10.3389/fnagi.2016.00265] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/24/2016] [Indexed: 12/30/2022] Open
Abstract
The brain activity of humans with tinnitus of various etiologies is typically studied with electro- and magneto-encephalography and functional magnetic resonance imaging-based imaging techniques. Consequently, they measure population responses and mostly from the neocortex. The latter also underlies changes in neural networks that may be attributed to tinnitus. However, factors not strictly related to tinnitus such as hearing loss and hyperacusis, as well as other co-occurring disorders play a prominent role in these changes. Different types of tinnitus can often not be resolved with these brain-imaging techniques. In animal models of putative behavioral signs of tinnitus, neural activity ranging from auditory nerve to auditory cortex, is studied largely by single unit recordings, augmented by local field potentials (LFPs), and the neural correlates of tinnitus are mainly based on spontaneous neural activity, such as spontaneous firing rates and pair-wise spontaneous spike-firing correlations. Neural correlates of hyperacusis rely on measurement of stimulus-evoked activity and are measured as increased driven firing rates and LFP amplitudes. Connectivity studies would rely on correlated neural activity between pairs of neurons or LFP amplitudes, but are only recently explored. In animal models of tinnitus, only two etiologies are extensively studied; tinnitus evoked by salicylate application and by noise exposure. It appears that they have quite different neural biomarkers. The unanswered question then is: does this different etiology also result in different tinnitus?
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Affiliation(s)
- Jos J Eggermont
- Department of Physiology and Pharmacology, University of Calgary, CalgaryAB, Canada; Department of Psychology, University of Calgary, CalgaryAB, Canada
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22
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Alvan G, Berninger E, Gustafsson LL, Karlsson KK, Paintaud G, Wakelkamp M. Concentration-Response Relationship of Hearing Impairment Caused by Quinine and Salicylate: Pharmacological Similarities but Different Molecular Mechanisms. Basic Clin Pharmacol Toxicol 2016; 120:5-13. [PMID: 27398982 DOI: 10.1111/bcpt.12640] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2016] [Accepted: 07/04/2016] [Indexed: 01/01/2023]
Abstract
This review has the purpose to summarize concentration-effect studies made with quinine and to compare the effects on hearing between quinine and salicylate. Quinine and salicylate have roles in experimental hearing research and may induce pronounced and reversible hearing impairment when administered in sizeable doses. The quinine-induced increase in hearing threshold and its recovery can be analysed according to 'the psychophysical power function'. The power function is a special case of the Hill equation when the stimulus (e.g. a drug concentration) is exceedingly small compared with the concentration that would elicit a half-maximum response. Quinine and salicylate induce sensorineural hearing impairment and tinnitus when given in higher dose ranges in man. The drugs influence the presence, magnitude, and quality of audiological responses, such as spontaneous and evoked otoacoustic emissions. Quinine reversibly reduces frequency selectivity and hearing sensitivity, whereas the self-attained most comfortable speech level and the acoustic stapedius reflex are not affected, that is the dynamic range of hearing is reversibly reduced. This observation supports the view that quinine acts on the outer hair cell of the cochlea. Both drugs share a protective effect against the permanent hearing damages caused by gentamicin. This action is interpreted as a request for functioning mechanoelectric transducer (MET) channels to elicit the ill effect of aminoglycosides. Both drugs may interfere with the cochlear amplifier through blocking MET channels and the motor protein prestin. This review finds considerable overlap between type and extent of pharmacological actions of quinine and salicylate, supposedly caused by partly shared mechanisms of action but performed with different molecular mechanisms.
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Affiliation(s)
- Gunnar Alvan
- Division of Clinical Pharmacology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Erik Berninger
- Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.,Department of Audiology, Karolinska University Hospital, Stockholm, Sweden
| | - Lars L Gustafsson
- Division of Clinical Pharmacology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Kjell K Karlsson
- Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.,Department of Audiology, Karolinska University Hospital, Stockholm, Sweden
| | - Gilles Paintaud
- Division of Clinical Pharmacology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden.,Laboratory of Pharmacology-Toxicology, Tours University Hospital, Tours, France
| | - Monique Wakelkamp
- Division of Clinical Pharmacology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
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23
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Gröschel M, Götze R, Müller S, Ernst A, Basta D. Central Nervous Activity upon Systemic Salicylate Application in Animals with Kanamycin-Induced Hearing Loss--A Manganese-Enhanced MRI (MEMRI) Study. PLoS One 2016; 11:e0153386. [PMID: 27078034 PMCID: PMC4831817 DOI: 10.1371/journal.pone.0153386] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 03/29/2016] [Indexed: 11/18/2022] Open
Abstract
This study investigated the effect of systemic salicylate on central auditory and non-auditory structures in mice. Since cochlear hair cells are known to be one major target of salicylate, cochlear effects were reduced by using kanamycin to remove or impair hair cells. Neuronal brain activity was measured using the non-invasive manganese-enhanced magnetic resonance imaging technique. For all brain structures investigated, calcium-related neuronal activity was increased following systemic application of a sodium salicylate solution: probably due to neuronal hyperactivity. In addition, it was shown that the central effect of salicylate was not limited to the auditory system. A general alteration of calcium-related activity was indicated by an increase in manganese accumulation in the preoptic area of the anterior hypothalamus, as well as in the amygdala. The present data suggest that salicylate-induced activity changes in the auditory system differ from those shown in studies of noise trauma. Since salicylate action is reversible, central pharmacological effects of salicylate compared to those of (permanent) noise-induced hearing impairment and tinnitus might induce different pathophysiologies. These should therefore, be treated as different causes with the same symptoms.
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Affiliation(s)
- Moritz Gröschel
- Department of Otolaryngology, Unfallkrankenhaus Berlin, Charité Medical School, Berlin, Germany
| | - Romy Götze
- Department of Otolaryngology, Unfallkrankenhaus Berlin, Charité Medical School, Berlin, Germany
| | - Susanne Müller
- Neuroscience Research Center (NWFZ), Charité Medical School, Berlin, Germany
| | - Arne Ernst
- Department of Otolaryngology, Unfallkrankenhaus Berlin, Charité Medical School, Berlin, Germany
| | - Dietmar Basta
- Department of Otolaryngology, Unfallkrankenhaus Berlin, Charité Medical School, Berlin, Germany
- * E-mail:
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24
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Sodium salicylate potentiates the GABAB-GIRK pathway to suppress rebound depolarization in neurons of the rat's medial geniculate body. Hear Res 2015; 332:104-112. [PMID: 26688177 DOI: 10.1016/j.heares.2015.11.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 11/16/2015] [Accepted: 11/23/2015] [Indexed: 12/15/2022]
Abstract
Rebound depolarization (RD) is a voltage response to the offset from pre-hyperpolarization of neuronal membrane potential, which manifests a particular form of the postsynaptic membrane potential response to inhibitory presynaptic inputs. We previously demonstrated that sodium salicylate (NaSal), a tinnitus inducer, can drastically suppress the RD in neurons of rat medial geniculate body (MGB) (Su et al, 2012; PLoS ONE 7, e46969). The purpose of the present study was to investigate the underlying cellular mechanism by using whole-cell patch-clamp recordings in rat MGB slices. NaSal (1.4 mM) had no effects on the current mediated by T-type Ca(2+) channels, indicating that it does not target these channels to suppress the RD. Instead, NaSal was shown to hyperpolarize the resting membrane potential to suppress the RD. NaSal had no effects on the current mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, indicating that it does not target these channels to hyperpolarize the resting membrane potential. NaSal induced an outward leak current that could be abolished by CGP55845, a GABAB receptor blocker, or respectively by Ba(2+) and Tertiapin-Q, blockers for G-protein-gated inwardly rectifying potassium (GIRK) channels, indicating that NaSal potentiates the GABAB-GIRK pathway to hyperpolarize the resting membrane potential. Our study demonstrates that NaSal targets GABAB receptors to alter functional behaviors of MGB neurons, which may be implicated in NaSal-induced tinnitus.
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25
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Jiang Q, Guo Z, Zhao Y, Wang F, Mao L. In vivo fluorescence sensing of the salicylate-induced change of zinc ion concentration in the auditory cortex of rat brain. Analyst 2015; 140:197-203. [PMID: 25298977 DOI: 10.1039/c4an01443j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This study demonstrates a fluorescence method for in vivo sensing of the dynamic change of Zn(2+) concentration in auditory cortex microdialysates induced by salicylate with N'-(7-nitro-2,1,3-benzoxadiazole-4-yl)-N,N,N'-tris(pyridine-2-ylmethyl) ethane-1,2-diamine (NBD-TPEA) as a probe. The excellent properties of the NBD-TPEA probe make it possible to achieve a high selectivity for Zn(2+) sensing with the co-existence of amino acids and other metal ions as well as the species commonly existing in the cerebral system. To validate the method for in vivo fluorescence sensing of Zn(2+) in the rat brain, we pre-mix the microdialysates in vivo sampled from the auditory cortex with the NBD-TPEA probe and then perfuse the mixtures into a fluorescent cuvette for continuous-flow fluorescence detection. The method demonstrated here shows a linear relationship between the signal output and Zn(2+) concentration within the concentration range from 0.5 μM to 4 μM, with a detection limit of 156 nM (S/N = 3). The basal level of extracellular Zn(2+) in auditory cortex microdialysates is determined to be 0.52 ± 0.082 μM (n = 4). This value is increased by the injection of 100 mg mL(-1) of salicylate (1 μL min(-1), 5 min, i.p.), reaches a peak at the time point of 90 min, and levels off with time. Such an increase is attenuated by the injection of MK-801, a potent and specific NMDA receptor antagonist, after the pre-injection of 100 mg mL(-1) salicylate for 5 min. This study offers a fluorescence method for in vivo sensing of Zn(2+) in the rat brain that could be useful for the investigations of chemical processes involved in brain functions.
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Affiliation(s)
- Qin Jiang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190, P. R. China.
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26
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Eggermont JJ, Roberts LE. Tinnitus: animal models and findings in humans. Cell Tissue Res 2015; 361:311-36. [PMID: 25266340 PMCID: PMC4487353 DOI: 10.1007/s00441-014-1992-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 08/14/2014] [Indexed: 12/19/2022]
Abstract
Chronic tinnitus (ringing of the ears) is a medically untreatable condition that reduces quality of life for millions of individuals worldwide. Most cases are associated with hearing loss that may be detected by the audiogram or by more sensitive measures. Converging evidence from animal models and studies of human tinnitus sufferers indicates that, while cochlear damage is a trigger, most cases of tinnitus are not generated by irritative processes persisting in the cochlea but by changes that take place in central auditory pathways when auditory neurons lose their input from the ear. Forms of neural plasticity underlie these neural changes, which include increased spontaneous activity and neural gain in deafferented central auditory structures, increased synchronous activity in these structures, alterations in the tonotopic organization of auditory cortex, and changes in network behavior in nonauditory brain regions detected by functional imaging of individuals with tinnitus and corroborated by animal investigations. Research on the molecular mechanisms that underlie neural changes in tinnitus is in its infancy and represents a frontier for investigation.
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Affiliation(s)
- Jos J Eggermont
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, and Department of Psychology, University of Calgary, 2500 University Drive N.W, Calgary, AB, Canada,
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27
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Eggermont JJ. Animal models of spontaneous activity in the healthy and impaired auditory system. Front Neural Circuits 2015; 9:19. [PMID: 25983679 PMCID: PMC4415415 DOI: 10.3389/fncir.2015.00019] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 04/10/2015] [Indexed: 11/30/2022] Open
Abstract
Spontaneous neural activity in the auditory nerve fibers and in auditory cortex in healthy animals is discussed with respect to the question: Is spontaneous activity noise or information carrier? The studies reviewed suggest strongly that spontaneous activity is a carrier of information. Subsequently, I review the numerous findings in the impaired auditory system, particularly with reference to noise trauma and tinnitus. Here the common assumption is that tinnitus reflects increased noise in the auditory system that among others affects temporal processing and interferes with the gap-startle reflex, which is frequently used as a behavioral assay for tinnitus. It is, however, more likely that the increased spontaneous activity in tinnitus, firing rate as well as neural synchrony, carries information that shapes the activity of downstream structures, including non-auditory ones, and leading to the tinnitus percept. The main drivers of that process are bursting and synchronous firing, which facilitates transfer of activity across synapses, and allows formation of auditory objects, such as tinnitus.
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Affiliation(s)
- Jos J Eggermont
- Department of Physiology and Pharmacology, Department of Psychology, University of Calgary Calgary, AB, Canada
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28
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Berger JI, Coomber B. Tinnitus-related changes in the inferior colliculus. Front Neurol 2015; 6:61. [PMID: 25870582 PMCID: PMC4378364 DOI: 10.3389/fneur.2015.00061] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 03/09/2015] [Indexed: 12/21/2022] Open
Abstract
Tinnitus is highly complex, diverse, and difficult to treat, in part due to the fact that the underlying causes and mechanisms remain elusive. Tinnitus is generated within the auditory brain; however, consolidating our understanding of tinnitus pathophysiology is difficult due to the diversity of reported effects and the variety of implicated brain nuclei. Here, we focus on the inferior colliculus (IC), a midbrain structure that integrates the vast majority of ascending auditory information and projects via the thalamus to the auditory cortex. The IC is also a point of convergence for corticofugal input and input originating outside the auditory pathway. We review the evidence, from both studies with human subjects and from animal models, for the contribution the IC makes to tinnitus. Changes in the IC, caused by either noise exposure or drug administration, involve fundamental, heterogeneous alterations in the balance of excitation and inhibition. However, differences between hearing loss-induced pathology and tinnitus-related pathology are not well understood. Moreover, variability in tinnitus induction methodology has a significant impact on subsequent neural and behavioral changes, which could explain some of the seemingly contradictory data. Nonetheless, the IC is likely involved in the generation and persistence of tinnitus perception.
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Affiliation(s)
- Joel I Berger
- Medical Research Council Institute of Hearing Research, University of Nottingham , Nottingham , UK
| | - Ben Coomber
- Medical Research Council Institute of Hearing Research, University of Nottingham , Nottingham , UK
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Coomber B, Kowalkowski VL, Berger JI, Palmer AR, Wallace MN. Modulating central gain in tinnitus: changes in nitric oxide synthase in the ventral cochlear nucleus. Front Neurol 2015; 6:53. [PMID: 25806021 PMCID: PMC4354362 DOI: 10.3389/fneur.2015.00053] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/25/2015] [Indexed: 01/30/2023] Open
Abstract
A significant challenge in tinnitus research lies in explaining how acoustic insult leads to tinnitus in some individuals, but not others. One possibility is genetic variability in the expression and function of neuromodulators – components of neural signaling that alter the balance of excitation and inhibition in neural circuits. An example is nitric oxide (NO) – a free radical and potent neuromodulator in the mammalian brain – that regulates plasticity via both pre-synaptic and postsynaptic mechanisms. Changes in NO have previously been implicated in tinnitus generation, specifically in the ventral cochlear nucleus (VCN). Here, we examined nitric oxide synthase (NOS) – the enzyme responsible for NO production – in the guinea pig VCN following acoustic trauma. NOS was present in most cell types – including spherical and globular bushy cells, small, medium, and large multipolar cells, and octopus cells – spanning the entire extent of the VCN. The staining pattern was symmetrical in control animals. Unilateral acoustic over-exposure (AOE) resulted in marked asymmetries between ipsilateral and contralateral sides of the VCN in terms of the distribution of NOS across the cochlear nuclei in animals with behavioral evidence of tinnitus: fewer NOS-positive cells and a reduced level of NOS staining was present across the whole extent of the contralateral VCN, relative to the ipsilateral VCN. The asymmetric pattern of NOS-containing cells was observed as early as 1 day after AOE and was also present in some animals at 3, 7, and 21 days after AOE. However, it was not until 8 weeks after AOE, when tinnitus had developed, that asymmetries were significant overall, compared with control animals. Asymmetrical NOS expression was not correlated with shifts in the threshold hearing levels. Variability in NOS expression between animals may represent one underlying difference that can be linked to whether or not tinnitus develops after noise exposure.
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Affiliation(s)
- Ben Coomber
- MRC Institute of Hearing Research , Nottingham , UK
| | - Victoria L Kowalkowski
- MRC Institute of Hearing Research , Nottingham , UK ; Otology and Hearing, Division of Clinical Neuroscience, University of Nottingham , Nottingham , UK
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Eggermont JJ. The auditory cortex and tinnitus - a review of animal and human studies. Eur J Neurosci 2015; 41:665-76. [DOI: 10.1111/ejn.12759] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 09/23/2014] [Accepted: 09/24/2014] [Indexed: 12/22/2022]
Affiliation(s)
- Jos J. Eggermont
- Department of Physiology and Pharmacology; University of Calgary; Calgary AB Canada
- Department of Psychology; University of Calgary; 2500 University Drive N.W. Calgary AB T2N 1N4 Canada
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Liu XP, Chen L. Forward acoustic masking enhances the auditory brainstem response in a diotic, but not dichotic, paradigm in salicylate-induced tinnitus. Hear Res 2015; 323:51-60. [PMID: 25668125 DOI: 10.1016/j.heares.2015.01.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 01/22/2015] [Accepted: 01/29/2015] [Indexed: 11/30/2022]
Abstract
We recently reported that forward acoustic masking can enhance the auditory brainstem response (ABR) in rats treated with a high dose of sodium salicylate (NaSal), a tinnitus inducer, when tested in open acoustic field (Liu and Chen, 2012, Brain Research 1485, 88-94). In the present study, we first replicated this experiment in closed acoustic field under two conditions: (1) the forward masker and the probe were presented to both ears (diotic paradigm); (2) the forward masker was presented to one ear and the probe to the other ear (dichotic paradigm). We found that only when the stimuli were presented by using the diotic, rather than the dichotic, paradigm could forward acoustic masking enhance the ABR in the rat treated with NaSal (300 mg/kg). The enhancement was obvious for ABR waves II and IV, but not for wave I, indicating a central origin. The enhancement occurred at the high frequencies (16, 24, 32 kHz) at which the animals demonstrated a tinnitus-like behavior as revealed by using the gap prepulse inhibition of acoustic startle paradigm. We then administered vigabatrin, a GABA transaminase inhibitor, in the animals to suppress NaSal-induced tinnitus. The vigabatrin treatment successfully prevented forward acoustic masking from enhancing the ABR. These findings demonstrate that the observed enhancement of ABRs by forward acoustic masking originates in the central auditory pathway ipsilateral to the stimulated ear. We propose that the enhancement is closely associated with NaSal-induced tinnitus.
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Affiliation(s)
- Xiao-Peng Liu
- Center for Biomedical Engineering, School of Information Science and Technology, University of Science and Technology of China, Hefei 230027, China
| | - Lin Chen
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China; Auditory Research Laboratory, University of Science and Technology of China, Hefei 230027, China.
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Eggermont JJ. Tinnitus and neural plasticity (Tonndorf lecture at XIth International Tinnitus Seminar, Berlin, 2014). Hear Res 2015; 319:1-11. [DOI: 10.1016/j.heares.2014.10.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 09/23/2014] [Accepted: 10/02/2014] [Indexed: 11/13/2022]
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Offutt SJ, Ryan KJ, Konop AE, Lim HH. Suppression and facilitation of auditory neurons through coordinated acoustic and midbrain stimulation: investigating a deep brain stimulator for tinnitus. J Neural Eng 2014; 11:066001. [PMID: 25307351 PMCID: PMC4244264 DOI: 10.1088/1741-2560/11/6/066001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE The inferior colliculus (IC) is the primary processing center of auditory information in the midbrain and is one site of tinnitus-related activity. One potential option for suppressing the tinnitus percept is through deep brain stimulation via the auditory midbrain implant (AMI), which is designed for hearing restoration and is already being implanted in deaf patients who also have tinnitus. However, to assess the feasibility of AMI stimulation for tinnitus treatment we first need to characterize the functional connectivity within the IC. Previous studies have suggested modulatory projections from the dorsal cortex of the IC (ICD) to the central nucleus of the IC (ICC), though the functional properties of these projections need to be determined. APPROACH In this study, we investigated the effects of electrical stimulation of the ICD on acoustic-driven activity within the ICC in ketamine-anesthetized guinea pigs. MAIN RESULTS We observed ICD stimulation induces both suppressive and facilitatory changes across ICC that can occur immediately during stimulation and remain after stimulation. Additionally, ICD stimulation paired with broadband noise stimulation at a specific delay can induce greater suppressive than facilitatory effects, especially when stimulating in more rostral and medial ICD locations. SIGNIFICANCE These findings demonstrate that ICD stimulation can induce specific types of plastic changes in ICC activity, which may be relevant for treating tinnitus. By using the AMI with electrode sites positioned with the ICD and the ICC, the modulatory effects of ICD stimulation can be tested directly in tinnitus patients.
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Affiliation(s)
- Sarah J. Offutt
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
| | - Kellie J. Ryan
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
| | - Alexander E. Konop
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
| | - Hubert H. Lim
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, USA
- Institute for Translational Neuroscience, University of Minnesota, Minneapolis, USA
- Department of Otolaryngology, Head and Neck Surgery, University of Minnesota, Minneapolis, USA
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Patel CR, Zhang H. Local Application of Sodium Salicylate Enhances Auditory Responses in the Rat's Dorsal Cortex of the Inferior Colliculus. Front Neurol 2014; 5:235. [PMID: 25452744 PMCID: PMC4231951 DOI: 10.3389/fneur.2014.00235] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 10/30/2014] [Indexed: 11/19/2022] Open
Abstract
Sodium salicylate (SS) is a widely used medication with side effects on hearing. In order to understand these side effects, we recorded sound-driven local-field potentials in a neural structure, the dorsal cortex of the inferior colliculus (ICd). Using a microiontophoretic technique, we applied SS at sites of recording and studied how auditory responses were affected by the drug. Furthermore, we studied how the responses were affected by combined local application of SS and an agonists/antagonist of the type-A or type-B γ-aminobutyric acid receptor (GABAA or GABAB receptor). Results revealed that SS applied alone enhanced auditory responses in the ICd, indicating that the drug had local targets in the structure. Simultaneous application of the drug and a GABAergic receptor antagonist synergistically enhanced amplitudes of responses. The synergistic interaction between SS and a GABAA receptor antagonist had a relatively early start in reference to the onset of acoustic stimulation and the duration of this interaction was independent of sound intensity. The interaction between SS and a GABAB receptor antagonist had a relatively late start, and the duration of this interaction was dependent on sound intensity. Simultaneous application of the drug and a GABAergic receptor agonist produced an effect different from the sum of effects produced by the two drugs released individually. These differences between simultaneous and individual drug applications suggest that SS modified GABAergic inhibition in the ICd. Our results indicate that SS can affect sound-driven activity in the ICd by modulating local GABAergic inhibition.
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Affiliation(s)
- Chirag R Patel
- Department of Biological Sciences, University of Windsor , Windsor, ON , Canada
| | - Huiming Zhang
- Department of Biological Sciences, University of Windsor , Windsor, ON , Canada
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Adjamian P. The application of electro- and magneto-encephalography in tinnitus research - methods and interpretations. Front Neurol 2014; 5:228. [PMID: 25431567 PMCID: PMC4230045 DOI: 10.3389/fneur.2014.00228] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 10/22/2014] [Indexed: 12/11/2022] Open
Abstract
In recent years, there has been a significant increase in the use of electroencephalography (EEG) and magnetoencephalography (MEG) to investigate changes in oscillatory brain activity associated with tinnitus with many conflicting results. Current view of the underlying mechanism of tinnitus is that it results from changes in brain activity in various structures of the brain as a consequence of sensory deprivation. This in turn gives rise to increased spontaneous activity and/or synchrony in the auditory centers but also involves modulation from non-auditory processes from structures of the limbic and paralimbic system. Some of the neural changes associated with tinnitus may be assessed non-invasively in human beings with MEG and EEG (M/EEG) in ways, which are superior to animal studies and other non-invasive imaging techniques. However, both MEG and EEG have their limitations and research results can be misinterpreted without appropriate consideration of these limitations. In this article, I intend to provide a brief review of these techniques, describe what the recorded signals reflect in terms of the underlying neural activity, and their strengths and limitations. I also discuss some pertinent methodological issues involved in tinnitus-related studies and conclude with suggestions to minimize possible discrepancies between results. The overall message is that while MEG and EEG are extremely useful techniques, the interpretation of results from tinnitus studies requires much caution given the individual variability in oscillatory activity and the limits of these techniques.
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Minen MT, Camprodon J, Nehme R, Chemali Z. The neuropsychiatry of tinnitus: a circuit-based approach to the causes and treatments available. J Neurol Neurosurg Psychiatry 2014; 85:1138-44. [PMID: 24744443 DOI: 10.1136/jnnp-2013-307339] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Patients presenting with tinnitus commonly have neuropsychiatric symptoms with which physicians need to be familiar. We provide an overview of tinnitus, including its types and pathophysiology. We discuss how recent methods such as transcranial magnetic stimulation, positron emission tomography, MRI, magnetoencephalography and quantitative EEG improve our understanding of the pathophysiology of tinnitus and connect tinnitus to the neuropsychiatric symptoms. We then explain why treatment of the tinnitus patient falls within the purview of neuropsychiatry. Psychiatric problems such as depression, anxiety and personality disorders are discussed. We also discuss how stress, headache, cognitive processing speed and sleep disturbance are associated with tinnitus. Finally, we provide a brief overview of treatment options and discuss the efficacy of various medications, including benzodiazepines, antidepressants, antipsychotics and mood-stabilising agents, and various non-pharmacological treatment options, such as cognitive behavioural therapy, habituation therapy and acupuncture. We also discuss how brain stimulation therapies are being developed for the treatment of tinnitus. In conclusion, a review of the literature demonstrates the varied neuropsychiatric manifestations of tinnitus. Imaging studies help to explain the mechanism of the association. However, more research is needed to elucidate the neurocircuitry underlying the association.
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Affiliation(s)
- Mia T Minen
- Department of Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA Harvard Medical School, Boston, Massachusetts, USA
| | - Joan Camprodon
- Harvard Medical School, Boston, Massachusetts, USA Departments of Neurology and Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Romy Nehme
- Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Zeina Chemali
- Harvard Medical School, Boston, Massachusetts, USA Departments of Neurology and Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA Massachusetts Eye Ear Infirmary, Boston, Massachusetts, USA
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Gold JR, Bajo VM. Insult-induced adaptive plasticity of the auditory system. Front Neurosci 2014; 8:110. [PMID: 24904256 PMCID: PMC4033160 DOI: 10.3389/fnins.2014.00110] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 04/28/2014] [Indexed: 01/10/2023] Open
Abstract
The brain displays a remarkable capacity for both widespread and region-specific modifications in response to environmental challenges, with adaptive processes bringing about the reweighing of connections in neural networks putatively required for optimizing performance and behavior. As an avenue for investigation, studies centered around changes in the mammalian auditory system, extending from the brainstem to the cortex, have revealed a plethora of mechanisms that operate in the context of sensory disruption after insult, be it lesion-, noise trauma, drug-, or age-related. Of particular interest in recent work are those aspects of auditory processing which, after sensory disruption, change at multiple—if not all—levels of the auditory hierarchy. These include changes in excitatory, inhibitory and neuromodulatory networks, consistent with theories of homeostatic plasticity; functional alterations in gene expression and in protein levels; as well as broader network processing effects with cognitive and behavioral implications. Nevertheless, there abounds substantial debate regarding which of these processes may only be sequelae of the original insult, and which may, in fact, be maladaptively compelling further degradation of the organism's competence to cope with its disrupted sensory context. In this review, we aim to examine how the mammalian auditory system responds in the wake of particular insults, and to disambiguate how the changes that develop might underlie a correlated class of phantom disorders, including tinnitus and hyperacusis, which putatively are brought about through maladaptive neuroplastic disruptions to auditory networks governing the spatial and temporal processing of acoustic sensory information.
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Affiliation(s)
- Joshua R Gold
- Department of Physiology, Anatomy and Genetics, University of Oxford Oxford, UK
| | - Victoria M Bajo
- Department of Physiology, Anatomy and Genetics, University of Oxford Oxford, UK
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Salicylate-induced auditory perceptual disorders and plastic changes in nonclassical auditory centers in rats. Neural Plast 2014; 2014:658741. [PMID: 24891959 PMCID: PMC4033555 DOI: 10.1155/2014/658741] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/26/2014] [Accepted: 04/02/2014] [Indexed: 12/05/2022] Open
Abstract
Previous studies have shown that sodium salicylate (SS) activates not only central auditory structures, but also nonauditory regions associated with emotion and memory. To identify electrophysiological changes in the nonauditory regions, we recorded sound-evoked local field potentials and multiunit discharges from the striatum, amygdala, hippocampus, and cingulate cortex after SS-treatment. The SS-treatment produced behavioral evidence of tinnitus and hyperacusis. Physiologically, the treatment significantly enhanced sound-evoked neural activity in the striatum, amygdala, and hippocampus, but not in the cingulate. The enhanced sound evoked response could be linked to the hyperacusis-like behavior. Further analysis showed that the enhancement of sound-evoked activity occurred predominantly at the midfrequencies, likely reflecting shifts of neurons towards the midfrequency range after SS-treatment as observed in our previous studies in the auditory cortex and amygdala. The increased number of midfrequency neurons would lead to a relative higher number of total spontaneous discharges in the midfrequency region, even though the mean discharge rate of each neuron may not increase. The tonotopical overactivity in the midfrequency region in quiet may potentially lead to tonal sensation of midfrequency (the tinnitus). The neural changes in the amygdala and hippocampus may also contribute to the negative effect that patients associate with their tinnitus.
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Hu SS, Mei L, Chen JY, Huang ZW, Wu H. Expression of immediate-early genes in the inferior colliculus and auditory cortex in salicylate-induced tinnitus in rat. Eur J Histochem 2014; 58:2294. [PMID: 24704997 PMCID: PMC3980210 DOI: 10.4081/ejh.2014.2294] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 01/31/2014] [Accepted: 01/31/2014] [Indexed: 11/23/2022] Open
Abstract
Tinnitus could be associated with neuronal hyperactivity in the auditory center. As a neuronal activity marker, immediate-early gene (IEG) expression is considered part of a general neuronal response to natural stimuli. Some IEGs, especially the activity-dependent cytoskeletal protein (Arc) and the early growth response gene-1 (Egr-1), appear to be highly correlated with sensory-evoked neuronal activity. We hypothesize, therefore, an increase of Arc and Egr-1 will be observed in a tinnitus model. In our study, we used the gap prepulse inhibition of acoustic startle (GPIAS) paradigm to confirm that salicylate induces tinnitus-like behavior in rats. However, expression of the Arc gene and Egr-1 gene were decreased in the inferior colliculus (IC) and auditory cortex (AC), in contradiction of our hypothesis. Expression of N-methyl d-aspartate receptor subunit 2B (NR2B) was increased and all of these changes returned to normal 14 days after treatment with salicylate ceased. These data revealed long-time administration of salicylate induced tinnitus markedly but reversibly and caused neural plasticity changes in the IC and the AC. Decreased expression of Arc and Egr-1 might be involved with instability of synaptic plasticity in tinnitus.
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Henry JA, Roberts LE, Caspary DM, Theodoroff SM, Salvi RJ. Underlying mechanisms of tinnitus: review and clinical implications. J Am Acad Audiol 2014; 25:5-22; quiz 126. [PMID: 24622858 PMCID: PMC5063499 DOI: 10.3766/jaaa.25.1.2] [Citation(s) in RCA: 151] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND The study of tinnitus mechanisms has increased tenfold in the last decade. The common denominator for all of these studies is the goal of elucidating the underlying neural mechanisms of tinnitus with the ultimate purpose of finding a cure. While these basic science findings may not be immediately applicable to the clinician who works directly with patients to assist them in managing their reactions to tinnitus, a clear understanding of these findings is needed to develop the most effective procedures for alleviating tinnitus. PURPOSE The goal of this review is to provide audiologists and other health-care professionals with a basic understanding of the neurophysiological changes in the auditory system likely to be responsible for tinnitus. RESULTS It is increasingly clear that tinnitus is a pathology involving neuroplastic changes in central auditory structures that take place when the brain is deprived of its normal input by pathology in the cochlea. Cochlear pathology is not always expressed in the audiogram but may be detected by more sensitive measures. Neural changes can occur at the level of synapses between inner hair cells and the auditory nerve and within multiple levels of the central auditory pathway. Long-term maintenance of tinnitus is likely a function of a complex network of structures involving central auditory and nonauditory systems. CONCLUSIONS Patients often have expectations that a treatment exists to cure their tinnitus. They should be made aware that research is increasing to discover such a cure and that their reactions to tinnitus can be mitigated through the use of evidence-based behavioral interventions.
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Affiliation(s)
- James A. Henry
- VA RR&D National Center for Rehabilitative Auditory Research (NCRAR), VA Medical Center, Portland, OR
- Department of Otolaryngology/Head and Neck Surgery, Oregon Health and Science University, Portland, OR
| | - Larry E. Roberts
- Department of Psychology, Neuroscience, and Behaviour, McMaster University, Hamilton, Ontario, Canada
| | - Donald M. Caspary
- Pharmacology Department, Southern Illinois University School of Medicine, Springfield, IL
| | - Sarah M. Theodoroff
- VA RR&D National Center for Rehabilitative Auditory Research (NCRAR), VA Medical Center, Portland, OR
- Department of Otolaryngology/Head and Neck Surgery, Oregon Health and Science University, Portland, OR
| | - Richard J. Salvi
- Center for Hearing and Deafness, University of Buffalo, Buffalo, NY
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Trans-canal laser irradiation reduces tinnitus perception of salicylate treated rat. Neurosci Lett 2013; 544:131-5. [DOI: 10.1016/j.neulet.2013.03.058] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 03/28/2013] [Accepted: 03/29/2013] [Indexed: 11/21/2022]
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Abstract
PURPOSE OF REVIEW Tinnitus is the sensation of hearing a sound when no external auditory stimulus is present. Most individuals experience tinnitus for brief, unobtrusive periods. However, chronic sensation of tinnitus affects approximately 17% (44 million people) of the general US population. Tinnitus, usually a benign symptom, can be constant, loud and annoying to the point that it causes significant emotional distress, poor sleep, less efficient activities of daily living, anxiety, depression and suicidal ideation/attempts. Tinnitus remains a major challenge to physicians because its pathophysiology is poorly understood and there are few management options to offer to patients. The purpose of this article is to describe the current understanding of central neural mechanisms in tinnitus and to summarize recent developments in clinical approaches to tinnitus patients. RECENT FINDINGS Recently developed animal models of tinnitus provide the possibility to determine neuronal mechanisms of tinnitus generation and to test the effects of various treatments. The latest research using animal models has identified a number of abnormal changes, in both auditory and nonauditory brain regions, that underlie tinnitus. Furthermore this research sheds light on cellular mechanisms that are responsible for development of these abnormal changes. SUMMARY Tinnitus remains a challenging disorder for patients, physicians, audiologists and scientists studying tinnitus-related brain changes. This article reviews recent findings of brain changes in animal models associated with tinnitus and a brief review of clinical approach to tinnitus patients.
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Berger JI, Coomber B, Shackleton TM, Palmer AR, Wallace MN. A novel behavioural approach to detecting tinnitus in the guinea pig. J Neurosci Methods 2013; 213:188-95. [PMID: 23291084 PMCID: PMC3580292 DOI: 10.1016/j.jneumeth.2012.12.023] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/30/2012] [Accepted: 12/22/2012] [Indexed: 11/18/2022]
Abstract
Tinnitus, the perception of sound in the absence of an external stimulus, is a particularly challenging condition to demonstrate in animals. In any animal model, objective confirmation of tinnitus is essential before we can study the neural changes that produce it. A gap detection method, based on prepulse inhibition of the whole-body startle reflex, is often used as a behavioural test for tinnitus in rodents. However, in the guinea pig the whole-body startle reflex is subject to rapid habituation and hence is not an ideal behavioural measure. By contrast, in this species the Preyer or pinna reflex is a very reliable indicator of the startle response and is much less subject to habituation. We have developed a novel adaptation of the gap detection paradigm, which uses the Preyer reflex to measure the startle response, rather than whole-body movement. Using this method, we have demonstrated changes in gap detection, in guinea pigs where tinnitus had been induced by the administration of a high dose of salicylate. Our data indicate that the Preyer reflex gap detection method is a reliable test for tinnitus in guinea pigs.
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Affiliation(s)
- Joel I Berger
- MRC Institute of Hearing Research, University Park, Nottingham, UK.
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45
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Eggermont JJ. Hearing loss, hyperacusis, or tinnitus: What is modeled in animal research? Hear Res 2013; 295:140-9. [DOI: 10.1016/j.heares.2012.01.005] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 01/09/2012] [Accepted: 01/16/2012] [Indexed: 11/29/2022]
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Engineer ND, Møller AR, Kilgard MP. Directing neural plasticity to understand and treat tinnitus. Hear Res 2012; 295:58-66. [PMID: 23099209 DOI: 10.1016/j.heares.2012.10.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2012] [Revised: 09/28/2012] [Accepted: 10/02/2012] [Indexed: 01/01/2023]
Abstract
The functional organization of cortical and subcortical networks can be altered by sensory experience. Sensory deprivation destabilizes neural networks resulting in increased excitability, greater neural synchronization and increased spontaneous firing in cortical and subcortical neurons. This pathological activity is thought to generate the phantom percept of chronic tinnitus. While sound masking, pharmacotherapy and cortical stimulation can temporarily suppress tinnitus for some patients, these interventions do not eliminate the pathological activity that is responsible for tinnitus. A treatment that could reverse the underlying pathology would be expected to be effective in alleviating the symptoms, if not curative. Targeted neural plasticity can provide the specificity required to restore normal neural activity in dysfunctional neural circuits that are assumed to underlie many forms of tinnitus. The forebrain cholinergic system and the noradrenergic system play a significant role in modulating cortical plasticity. Stimulation of the vagus nerve is known to activate these neuromodulatory pathways. Our earlier studies have demonstrated that pairing sounds with either nucleus basalis of Meynert (NB) stimulation or vagus nerve stimulation (VNS) generates highly specific and long-lasting plasticity in auditory cortex neurons. Repeatedly pairing tones with brief pulses of VNS reversed the physiological and behavioral correlates of tinnitus in noise exposed rats. We also recently demonstrated that VNS modulates synchrony and excitability in the auditory cortex at least in part by activation of muscarinic acetylcholine receptors, suggesting that acetylcholine is involved in the mechanism of action of VNS. These results suggest that pairing sounds with VNS provides a new avenue of treatment for some forms of tinnitus. This paper discusses neuromodulation as treatment for tinnitus with a focus on the potential value of pairing VNS with sound stimulation as a treatment of chronic tinnitus.
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Affiliation(s)
- Navzer D Engineer
- MicroTransponder, Inc., 2802 Flintrock Trace, Suite 225, Austin, TX 78738, USA.
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Su YY, Luo B, Jin Y, Wu SH, Lobarinas E, Salvi RJ, Chen L. Altered neuronal intrinsic properties and reduced synaptic transmission of the rat's medial geniculate body in salicylate-induced tinnitus. PLoS One 2012; 7:e46969. [PMID: 23071681 PMCID: PMC3468622 DOI: 10.1371/journal.pone.0046969] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 09/10/2012] [Indexed: 12/31/2022] Open
Abstract
Sodium salicylate (NaSal), an aspirin metabolite, can cause tinnitus in animals and human subjects. To explore neural mechanisms underlying salicylate-induced tinnitus, we examined effects of NaSal on neural activities of the medial geniculate body (MGB), an auditory thalamic nucleus that provides the primary and immediate inputs to the auditory cortex, by using the whole-cell patch-clamp recording technique in MGB slices. Rats treated with NaSal (350 mg/kg) showed tinnitus-like behavior as revealed by the gap prepulse inhibition of acoustic startle (GPIAS) paradigm. NaSal (1.4 mM) decreased the membrane input resistance, hyperpolarized the resting membrane potential, suppressed current-evoked firing, changed the action potential, and depressed rebound depolarization in MGB neurons. NaSal also reduced the excitatory and inhibitory postsynaptic response in the MGB evoked by stimulating the brachium of the inferior colliculus. Our results demonstrate that NaSal alters neuronal intrinsic properties and reduces the synaptic transmission of the MGB, which may cause abnormal thalamic outputs to the auditory cortex and contribute to NaSal-induced tinnitus.
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Affiliation(s)
- Yan-Yan Su
- CAS Key Laboratory of Brain Function and Disease, School of Life Sciences, University of Science and Technology of China, Hefei, China
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Zhang J. Auditory cortex stimulation to suppress tinnitus: mechanisms and strategies. Hear Res 2012; 295:38-57. [PMID: 22683861 DOI: 10.1016/j.heares.2012.05.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 05/06/2012] [Accepted: 05/14/2012] [Indexed: 01/08/2023]
Abstract
Brain stimulation is an important method used to modulate neural activity and suppress tinnitus. Several auditory and non-auditory brain regions have been targeted for stimulation. This paper reviews recent progress on auditory cortex (AC) stimulation to suppress tinnitus and its underlying neural mechanisms and stimulation strategies. At the same time, the author provides his opinions and hypotheses on both animal and human models. The author also proposes a medial geniculate body (MGB)-thalamic reticular nucleus (TRN)-Gating mechanism to reflect tinnitus-related neural information coming from upstream and downstream projection structures. The upstream structures include the lower auditory brainstem and midbrain structures. The downstream structures include the AC and certain limbic centers. Both upstream and downstream information is involved in a dynamic gating mechanism in the MGB together with the TRN. When abnormal gating occurs at the thalamic level, the spilled-out information interacts with the AC to generate tinnitus. The tinnitus signals at the MGB-TRN-Gating may be modulated by different forms of stimulations including brain stimulation. Each stimulation acts as a gain modulator to control the level of tinnitus signals at the MGB-TRN-Gate. This hypothesis may explain why different types of stimulation can induce tinnitus suppression. Depending on the tinnitus etiology, MGB-TRN-Gating may be different in levels and dynamics, which cause variability in tinnitus suppression induced by different gain controllers. This may explain why the induced suppression of tinnitus by one type of stimulation varies across individual patients.
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Affiliation(s)
- Jinsheng Zhang
- Department of Otolaryngology - Head and Neck Surgery, Wayne State University, School of Medicine, 5E-UHC, 4201 Saint Antoine, Detroit, MI 48201, USA.
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Manzoor NF, Licari FG, Klapchar M, Elkin RL, Gao Y, Chen G, Kaltenbach JA. Noise-induced hyperactivity in the inferior colliculus: its relationship with hyperactivity in the dorsal cochlear nucleus. J Neurophysiol 2012; 108:976-88. [PMID: 22552192 DOI: 10.1152/jn.00833.2011] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Intense noise exposure causes hyperactivity to develop in the mammalian dorsal cochlear nucleus (DCN) and inferior colliculus (IC). It has not yet been established whether the IC hyperactivity is driven by hyperactivity from extrinsic sources that include the DCN or instead is maintained independently of this input. We have investigated the extent to which IC hyperactivity is dependent on input from the contralateral DCN by comparing recordings of spontaneous activity in the IC of noise-exposed and control hamsters before and after ablation of the contralateral DCN. One group of animals was binaurally exposed to intense sound (10 kHz, 115 dB SPL, 4 h), whereas the control group was not. Both groups were studied electrophysiologically 2-3 wk later by first mapping spontaneous activity along the tonotopic axis of the IC to confirm induction of hyperactivity. Spontaneous activity was then recorded at a hyperactive IC locus over two 30-min periods, one with DCNs intact and the other after ablation of the contralateral DCN. In a subset of animals, activity was again mapped along the tonotopic axis after the time course of the activity was recorded before and after DCN ablation. Following recordings, the brains were fixed, and histological evaluations were performed to assess the extent of DCN ablation. Ablation of the DCN resulted in major reductions of IC hyperactivity. Levels of postablation activity in exposed animals were similar to the levels of activity in the IC of control animals, indicating an almost complete loss of hyperactivity in exposed animals. The results suggest that hyperactivity in the IC is dependent on support from extrinsic sources that include and may even begin with the DCN. This finding does not rule out longer term compensatory or homeostatic adjustments that might restore hyperactivity in the IC over time.
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Affiliation(s)
- N F Manzoor
- Department of Neurosciences, Lerner Research Institute, Head and Neck Institute, The Cleveland Clinic, Cleveland, OH, USA
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Liu XP, Chen L. Auditory brainstem response as a possible objective indicator for salicylate-induced tinnitus in rats. Brain Res 2012; 1485:88-94. [PMID: 22607819 DOI: 10.1016/j.brainres.2012.04.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Revised: 04/24/2012] [Accepted: 04/24/2012] [Indexed: 11/18/2022]
Abstract
The auditory response to an acoustic stimulus will usually be suppressed, or masked, by a preceding sound. Here, we show that forward acoustic masking at a high frequency can boost the auditory brainstem response (ABR) in rats injected with a high dose of sodium salicylate (NaSal), a tinnitus inducer. The forward narrow band noise caused a decrease in the amplitude of the ABR to a probe tone burst in normal rats, but caused an unexpected increase in the amplitude at 16 kHz in rats treated with NaSal (300 mg/kg). The observed effect could be manifested in normal rats presented with a background tone added to the masker and the probe, suggesting an underlying mechanism associated with tinnitus. We hypothesize that in NaSal-treated rats, tinnitus can "internally" mask the ABR in a similar way as an external background sound does and the "unmasking" effect of forward masking can result in a rebound of the otherwise suppressed ABR. Our study raises the possibility of using the ABR as an objective indicator for NaSal-induced tinnitus in animals. This article is part of a Special Issue entitled: Tinnitus Neuroscience.
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Affiliation(s)
- Xiao-Peng Liu
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
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