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Panah N, Brazin A, Ebrahimi Shahmabadi H. Electrophysiological Characteristics in Pediatric Cochlear Implantation. Indian J Otolaryngol Head Neck Surg 2024; 76:4962-4973. [PMID: 39376381 PMCID: PMC11456142 DOI: 10.1007/s12070-024-04806-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Accepted: 06/07/2024] [Indexed: 10/09/2024] Open
Abstract
AIMS Cochlear implantation is a potential intervention for individuals with severe to profound hearing loss, in particular in the pediatric population. This literature review aims to comprehensively evaluate the applications of electrophysiological tests in enhancing cochlear implant (CI) outcomes for children. METHODS A literature review searched Medline and PubMed databases for articles on electrophysiological tests in CI children, using the terms "electrophysiological tests," "children," and "cochlear implant." The systematic search leads to 72 eligible texts. RESULTS Electrophysiological tests can be used to test CI children without the need for their active participation. These tests can be helpful in identifying and improving the health of deaf children in various ways, such as determining the CI functional status, the semantic integration effects in CI children, the effect of central auditory structures in speech stimulus processing, the development of lexical-semantic in CI children, and tracking the maturation of the central auditory system. CI enhances central auditory nervous system (CANS) maturation and auditory/language skills. CONCLUSION The quality of electrophysiological tests can be improved to enhance hearing outcome prediction, postoperative physiology understanding, and hearing loss mechanisms. Electrophysiological tests study CANS maturation, identify lesions, aid CI programming, determine prognosis, and treatment outcomes.
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Affiliation(s)
- Naomi Panah
- School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia
| | - Ali Brazin
- Department of Otolaryngology, Faculty of Medicine, Rafsanjan University of Medical Sciences, Rafsanjan, Iran
- Clinical Research Development Unit (CRDU), Moradi Hospital, Rafsanjan University of Medical Sciences, Rafsanjan, Iran
| | - Hasan Ebrahimi Shahmabadi
- Immunology of Infectious Diseases Research Center, Research Institute of Basic Medical Sciences, Rafsanjan University of Medical Sciences, Rafsanjan, Iran
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Fabrizio-Stover EM, Oliver DL, Burghard AL. Tinnitus mechanisms and the need for an objective electrophysiological tinnitus test. Hear Res 2024; 449:109046. [PMID: 38810373 DOI: 10.1016/j.heares.2024.109046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 05/16/2024] [Accepted: 05/22/2024] [Indexed: 05/31/2024]
Abstract
Tinnitus, the perception of sound with no external auditory stimulus, is a complex, multifaceted, and potentially devastating disorder. Despite recent advances in our understanding of tinnitus, there are limited options for effective treatment. Tinnitus treatments are made more complicated by the lack of a test for tinnitus based on objectively measured physiological characteristics. Such an objective test would enable a greater understanding of tinnitus mechanisms and may lead to faster treatment development in both animal and human research. This review makes the argument that an objective tinnitus test, such as a non-invasive electrophysiological measure, is desperately needed. We review the current tinnitus assessment methods, the underlying neural correlates of tinnitus, the multiple tinnitus generation theories, and the previously investigated electrophysiological measurements of tinnitus. Finally, we propose an alternate objective test for tinnitus that may be valid in both animal and human subjects.
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Affiliation(s)
- Emily M Fabrizio-Stover
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA; Department of Otolaryngology-Head and Neck Surgery, Medical University South Carolina, Charleston, SC, USA
| | - Douglas L Oliver
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Alice L Burghard
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA.
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Mo C, Ma TF, McPherson B. ABO blood group and cochlear function: evidence from a large sample size study. Int J Audiol 2024; 63:106-116. [PMID: 36576100 DOI: 10.1080/14992027.2022.2158379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 12/05/2022] [Indexed: 12/29/2022]
Abstract
OBJECTIVE The present study investigated the effect of blood group on cochlear function in a large participant sample across different age groups. The study hypothesis was that participants with blood group O would show relatively reduced cochlear function as reflected in otoacoustic emission (OAE) measures. DESIGN Data were collected from transient evoked otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE), DPOAE input/output (I/O) function, and spontaneous otoacoustic emission (SOAE) recordings. STUDY SAMPLE Four hundred and sixty-three normal hearing adults aged 20-59 years among the four ABO blood groups participated in the study. RESULTS TEOAE and DPOAE amplitudes did not reveal significant differences for participants with blood group O compared with participants with non-O blood groups. No significant differences in I/O function categories were found among participants with different blood groups. SOAE prevalence was also not significantly different across blood groups. However, previously reported age and gender differences for OAE variables were confirmed. CONCLUSIONS Participants with blood group O were not found to have significantly reduced cochlear function, based on OAE measures. Results from the current study do not support the hypothesis that normal hearing individuals with different ABO blood groups differ in level of cochlear function.
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Affiliation(s)
- Changgeng Mo
- Human Communication, Development and Information Sciences, Faculty of Education, University of Hong Kong, Hong Kong SAR, China
| | - Ting Fung Ma
- Department of Statistics, University of South Carolina, Columbia, South Carolina, USA
| | - Bradley McPherson
- Human Communication, Development and Information Sciences, Faculty of Education, University of Hong Kong, Hong Kong SAR, China
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Cogen T, Cetin Kara H, Kara E, Telci F, Yener HM. Investigation of the relationship between hyperacusis and auditory processing difficulties in individuals with normal hearing. Eur Arch Otorhinolaryngol 2024; 281:469-477. [PMID: 37819548 DOI: 10.1007/s00405-023-08269-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 09/26/2023] [Indexed: 10/13/2023]
Abstract
PURPOSE This study aimed to investigate the prevalence of hyperacusis and auditory processing (listening) difficulties (APDiff) in normal-hearing young adults and to explore the relationship between these two conditions. METHODS A total of 333 participants aged 18-24 underwent pure-tone audiometry tests and completed the Khalfa Hyperacusis Questionnaire (KHQ) and the University of Cincinnati Auditory Processing Inventory (UCAPI) online. RESULTS Hyperacusis was identified in 26.43% of participants, and APDiff in 36.04%. A strong, positive correlation was found between KHQ and UCAPI scores (r = 0.603, p < 0.001). Logistic regression models indicated that hyperacusis significantly increased the likelihood of having APDiff (OR 7.688, p < 0.001). CONCLUSION Despite the high prevalence of hyperacusis and APDiff in young adults, few seek help from audiology clinics. Our findings highlight a significant link between hyperacusis and APDiff, emphasizing the need for screening protocols for auditory processing skills in young adults due to these conditions' potential social and academic impacts.
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Affiliation(s)
- Talha Cogen
- Department of Audiology, Faculty of Health Sciences, Istanbul University-Cerrahpaşa, Istanbul, Turkey.
| | - Halide Cetin Kara
- Department of Otorhinolaryngology, Cerrahpasa Faculty of Medicine, Istanbul University-Cerrahpaşa, Istanbul, Turkey
| | - Eyyup Kara
- Department of Audiology, Faculty of Health Sciences, Istanbul University-Cerrahpaşa, Istanbul, Turkey
| | - Fatma Telci
- Department of Audiology, Institute of Graduate Studies, Istanbul University-Cerrahpaşa, Istanbul, Turkey
| | - Haydar Murat Yener
- Department of Otorhinolaryngology, Cerrahpasa Faculty of Medicine, Istanbul University-Cerrahpaşa, Istanbul, Turkey
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Robot-Assisted Electrode Insertion in Cochlear Implantation Controlled by Intraoperative Electrocochleography-A Pilot Study. J Clin Med 2022; 11:jcm11237045. [PMID: 36498620 PMCID: PMC9737018 DOI: 10.3390/jcm11237045] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 11/21/2022] [Indexed: 12/03/2022] Open
Abstract
Robotics in otology has been developing in many directions for more than two decades. Current clinical trials focus on more accurate stapes surgery, minimally invasive access to the cochlea and less traumatic insertion of cochlear implant (CI) electrode arrays. In this study we evaluated the use of the RobOtol® (Collin, Bagneux, France) otologic robot to insert CI electrodes into the inner ear with intraoperative ECochG analysis. This prospective, pilot study included two adult patients implanted with Advanced Bionics (Westinghouse PI, CA, USA) cochlear implant, with HiFocus™ Mid-Scala electrode array. The standard surgical approach was used. For both subjects, who had residual hearing in the implanted ear, intraoperative and postoperative ECochG was performed with the AIMTM system. The surgeries were uneventful. A credible ECochG response was obtained after complete electrode insertion in both cases. Preoperative BC thresholds compared to intraoperative estimated ECochG thresholds and 2-day postoperative BC thresholds had similar values at frequencies where all thresholds were measurable. The results of the ECochG performed one month after the surgery showed that in both patients the hearing residues were preserved for the selected frequencies. The RobOtol® surgical robot allows for the correct, safe and gentle insertion of the cochlear implant electrode inside the cochlea. The use of electrocochleography measurements during robotic cochlear implantation offers an additional opportunity to evaluate and modify the electrode array insertion on an ongoing basis, which may contribute to the preservation of residual hearing.
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Intraoperative Electrocochleography in Subjects Affected by Vestibular Schwannoma and Ménière's Disease: Comparison of Results. Ear Hear 2021; 43:874-882. [PMID: 34582395 DOI: 10.1097/aud.0000000000001133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES Histologic reports of temporal bones of ears with vestibular schwannomas (VSs) have indicated findings of endolymphatic hydrops (ELH) in some cases. The main goal of this investigation was to test ears with VSs to determine if they exhibit electrophysiological characteristics similar to those of ears expected to experience ELH. DESIGN Fifty-three subjects with surgically confirmed VS aged ≥18 and with normal middle ear status were included in this study. In addition, a second group of adult subjects (n = 24) undergoing labyrinthectomy (n = 6) or endolymphatic sac decompression and shunt (ELS) placement (n = 18) for poorly controlled vestibular symptoms associated with Meniere's disease (MD) participated in this research. Intraoperative electrocochleography (ECochG) from the round window was performed using tone burst stimuli. Audiometric testing and word recognition scores (WRS) were performed preoperatively. ECochG amplitudes, cochlear microphonic/auditory nerve neurophonic (ANN) in the form of the "ongoing" response and summation potential, were analyzed and compared between the two groups of subjects. In addition, to evaluate any effect of auditory nerve function, the auditory nerve score was calculated for each subject. Pure-tone averages were obtained using the average air conduction thresholds at 0.5, 1, and 2 kHz while WRS was assessed using Northwestern University Auditory Test No. 6 word lists. RESULTS In the VS group the average pure-tone averages and WRS were 59.6 dB HL and 44.8%, respectively, while in the MD group they were 52.3 dB HL and 73.8%. ECochG findings in both groups revealed a reduced trend in amplitude of the ongoing response with increased stimulus frequency. The summation potential amplitudes of subjects with VS were found to be less negative than the MD subjects for nearly all test frequencies. Finally, the VS group exhibited poorer amounts of auditory nerve function compared to the MD group. CONCLUSIONS The current findings suggest cochlear pathology (e.g., hair cell loss) in both groups but do not support the hypothesis that VSs cause ELH.
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Valenzuela CV, Lichtenhan JT, Lefler SM, Koka K, Buchman CA, Ortmann AJ. Intracochlear Electrocochleography and Speech Perception Scores in Cochlear Implant Recipients. Laryngoscope 2021; 131:E2681-E2688. [PMID: 34019310 DOI: 10.1002/lary.29629] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Revised: 05/05/2021] [Accepted: 05/11/2021] [Indexed: 11/07/2022]
Abstract
OBJECTIVES/HYPOTHESIS Previous studies have demonstrated that electrocochleography (ECochG) measurements made at the round window prior to cochlear implant (CI) electrode insertion can account for 47% of the variability in 6-month speech perception scores. Recent advances have made it possible to use the apical CI electrode to record intracochlear responses to acoustic stimuli. Study objectives were to determine 1) the relationship between intracochlear ECochG response amplitudes and 6-month speech perception scores and 2) to determine the relationship between behavioral auditory thresholds and ECochG threshold estimates. The hypothesis was that intracochlear ECochG response amplitudes made immediately after electrode insertion would be larger than historical controls (at the extracochlear site) and explain more variability in speech perception scores. STUDY DESIGN Prospective case series. METHODS Twenty-two adult CI recipients with varying degrees of low-frequency hearing had intracochlear ECochG measurements made immediately after CI electrode insertion using 110 dB SPL tone bursts. Tone bursts were centered at five octave-spaced frequencies between 125 and 2,000 Hz. RESULTS There was no association between intracochlear ECochG response amplitudes and speech perception scores. But, the data suggest a mild to moderate relationship between preoperative behavioral audiometric testing and intraoperative ECochG threshold estimates. CONCLUSION Performing intracochlear ECochG is highly feasible and results in larger response amplitudes, but performing ECochG before, rather than after, CI insertion may provide a more accurate assessment of a patient's speech perception potential. LEVEL OF EVIDENCE 4 Laryngoscope, 2021.
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Affiliation(s)
- Carla V Valenzuela
- Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, St. Louis, Missouri, U.S.A
| | - Jeffery T Lichtenhan
- Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, St. Louis, Missouri, U.S.A
| | - Shannon M Lefler
- Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, St. Louis, Missouri, U.S.A
| | - Kanthaiah Koka
- Department of Research and Technology, Advanced Bionics Corporation, Valencia, California, U.S.A
| | - Craig A Buchman
- Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, St. Louis, Missouri, U.S.A
| | - Amanda J Ortmann
- Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine, St. Louis, Missouri, U.S.A
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Abstract
OBJECTIVE Given the heterogeneity of papers about electrocochleography (ECochG) and cochlear implantation (CI) and the absence of a systematic review in the current literature, the aim of this work was to analyze the uses of ECochG in the different stages of CI. DATA SOURCES A search of PubMed from inception to December 8, 2019, with cross-references, was executed. Keywords were: "Cochlear Implant" OR "Cochlear Implantation" AND "Electrocochleography" OR "ECochG." The main eligibility criteria were English-language articles, investigating the use of ECochG in the different phases of CI. STUDY SELECTION Literature reviews, editorials, case reports, conference papers were excluded, as were papers in which ECochG was just sporadically executed. DATA EXTRACTION The quality of the included studies was assessed using "The Strengthening the Reporting of Observational Studies in Epidemiology" (STROBE) Statement. DATA SYNTHESIS A total of 95 articles were identified and 60 papers were included. The included articles covered a timeframe from 2003 to 2019. Of the 60 papers, 46 were human studies, 12 animal studies, and two involved more data sets. Eleven related to the diagnostic phase, 43 described intraoperative monitoring, and 10 were regarding follow-up testing. Hearing preservation was the most discussed topic with 25 included articles. CONCLUSIONS AND RELEVANCE ECochG measurements appeared to be useful in many aspects of CI, such as hearing preservation. Our review is the first that shows the evolution of the technique and how much has been achieved from the earliest experiments to the most recent signal process refinements and device implementation in CI.
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Zhan KY, Adunka OF, Eshraghi A, Riggs WJ, Prentiss SM, Yan D, Telischi FF, Liu X, He S. Electrophysiology and genetic testing in the precision medicine of congenital deafness: A review. J Otol 2021; 16:40-46. [PMID: 33505449 PMCID: PMC7814082 DOI: 10.1016/j.joto.2020.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 07/11/2020] [Accepted: 07/21/2020] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Congenital hearing loss is remarkably heterogeneous, with over 130 deafness genes and thousands of variants, making for innumerable genotype/phenotype combinations. Understanding both the pathophysiology of hearing loss and molecular site of lesion along the auditory pathway permits for significantly individualized counseling. Electrophysiologic techniques such as electrocochleography (ECochG) and electrically-evoked compound action potentials (eCAP) are being studied to localize pathology and estimate residual cochlear vs. neural health. This review describes the expanding roles of genetic and electrophysiologic evaluation in the precision medicine of congenital hearing loss.The basics of genetic mutations in hearing loss and electrophysiologic testing (ECochG and eCAP) are reviewed, and how they complement each other in the diagnostics and prognostication of hearing outcomes. Used together, these measures improve the understanding of insults to the auditory system, allowing for individualized counseling for CI candidacy/outcomes or other habilitation strategies. CONCLUSION Despite tremendous discovery in deafness genes, the effects of individual genes on neural function remain poorly understood. Bridging the understanding between molecular genotype and neural and functional phenotype is paramount to interpreting genetic results in clinical practice. The future hearing healthcare provider must consolidate an ever-increasing amount of genetic and phenotypic information in the precision medicine of hearing loss.
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Affiliation(s)
- Kevin Y. Zhan
- Department of Otolaryngology – Head & Neck Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Oliver F. Adunka
- Department of Otolaryngology – Head & Neck Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- Department of Audiology, Nationwide Children’s Hospital, Columbus, OH, USA
| | - Adrien Eshraghi
- Department of Otolaryngology – Head & Neck Surgery, University of Miami Miller School of Medicine, Miami, FL, USA
| | - William J. Riggs
- Department of Otolaryngology – Head & Neck Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- Department of Audiology, Nationwide Children’s Hospital, Columbus, OH, USA
| | - Sandra M. Prentiss
- Department of Otolaryngology – Head & Neck Surgery, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Denise Yan
- Department of Otolaryngology – Head & Neck Surgery, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Fred F. Telischi
- Department of Otolaryngology – Head & Neck Surgery, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Xuezhong Liu
- Department of Otolaryngology – Head & Neck Surgery, University of Miami Miller School of Medicine, Miami, FL, USA
- Dr. John T. MacDonald Foundation, Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Shuman He
- Department of Otolaryngology – Head & Neck Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- Department of Audiology, Nationwide Children’s Hospital, Columbus, OH, USA
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Abstract
OBJECTIVE We present a unique case of a patient with a jugular foramen tumor with serviceable hearing. This study discusses the audiometric results and intraoperative electrocochleographic (ECochG) findings recorded during tumor removal to illustrate the potential utility of this technique in skull base surgery. PATIENTS A 22-year-old female patient presented with a jugular foramen schwannoma and associated symptoms of right-sided otalgia, mild hearing loss, and blurry vision. INTERVENTIONS Intraoperative ECochG responses during an infratemporal fossa approach: click and tone burst (1, 2, 4 kHz) stimuli were used and presented at 90 dB nHL. MAIN OUTCOME MEASURES Intraoperative ECochG testing using frequency-specific tone bursts and clicks before and after tumor resection. RESULTS The compound action potential magnitudes, cochlear microphonic, and summation potential were recorded pre- and post-tumor removal. For statistical analysis, a paired t test with significance set at p < 0.05 was used. The compound action potential magnitudes increased at all test frequencies (p < 0.01) while the summation potential and cochlear microphonic remained relatively stable (p > 0.05). Audiometric testing demonstrated an improvement of the preoperative mild right-sided hearing loss after tumor resection (pure-tone average for 0.5, 1, 2, and 4 kHz of 30 dB HL preoperation and 7.5 dB HL after tumor resection). CONCLUSIONS Intraoperative ECochG may allow for real-time monitoring during complex skull base surgery.
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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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Lee C, Guinan JJ, Rutherford MA, Kaf WA, Kennedy KM, Buchman CA, Salt AN, Lichtenhan JT. Cochlear compound action potentials from high-level tone bursts originate from wide cochlear regions that are offset toward the most sensitive cochlear region. J Neurophysiol 2019; 121:1018-1033. [PMID: 30673362 DOI: 10.1152/jn.00677.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Little is known about the spatial origins of auditory nerve (AN) compound action potentials (CAPs) evoked by moderate to intense sounds. We studied the spatial origins of AN CAPs evoked by 2- to 16-kHz tone bursts at several sound levels by slowly injecting kainic acid solution into the cochlear apex of anesthetized guinea pigs. As the solution flowed from apex to base, it sequentially reduced CAP responses from low- to high-frequency cochlear regions. The times at which CAPs were reduced, combined with the cochlear location traversed by the solution at that time, showed the cochlear origin of the removed CAP component. For low-level tone bursts, the CAP origin along the cochlea was centered at the characteristic frequency (CF). As sound level increased, the CAP center shifted basally for low-frequency tone bursts but apically for high-frequency tone bursts. The apical shift was surprising because it is opposite the shift expected from AN tuning curve and basilar membrane motion asymmetries. For almost all high-level tone bursts, CAP spatial origins extended over 2 octaves along the cochlea. Surprisingly, CAPs evoked by high-level low-frequency (including 2 kHz) tone bursts showed little CAP contribution from CF regions ≤ 2 kHz. Our results can be mostly explained by spectral splatter from the tone-burst rise times, excitation in AN tuning-curve "tails," and asynchronous AN responses to high-level energy ≤ 2 kHz. This is the first time CAP origins have been identified by a spatially specific technique. Our results show the need for revising the interpretation of the cochlear origins of high-level CAPs-ABR wave 1. NEW & NOTEWORTHY Cochlear compound action potentials (CAPs) and auditory brain stem responses (ABRs) are routinely used in laboratories and clinics. They are typically interpreted as arising from the cochlear region tuned to the stimulus frequency. However, as sound level is increased, the cochlear origins of CAPs from tone bursts of all frequencies become very wide and their centers shift toward the most sensitive cochlear region. The standard interpretation of CAPs and ABRs from moderate to intense stimuli needs revision.
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Affiliation(s)
- C Lee
- Department of Otolaryngology, Washington University School of Medicine in St. Louis , St. Louis, Missouri
| | - J J Guinan
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, and Department of Otolaryngology, Harvard Medical School , Boston, Massachusetts
| | - M A Rutherford
- Department of Otolaryngology, Washington University School of Medicine in St. Louis , St. Louis, Missouri
| | - W A Kaf
- Communication Sciences and Disorders Department, Missouri State University , Springfield, Missouri
| | - K M Kennedy
- Department of Otolaryngology, Washington University School of Medicine in St. Louis , St. Louis, Missouri.,Communication Sciences and Disorders Department, Missouri State University , Springfield, Missouri
| | - C A Buchman
- Department of Otolaryngology, Washington University School of Medicine in St. Louis , St. Louis, Missouri
| | - A N Salt
- Department of Otolaryngology, Washington University School of Medicine in St. Louis , St. Louis, Missouri
| | - J T Lichtenhan
- Department of Otolaryngology, Washington University School of Medicine in St. Louis , St. Louis, Missouri
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