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Goodman SS, Haysley S, Jennings SG. Human Olivocochlear Effects: A Statistical Detection Approach Applied to the Cochlear Microphonic Evoked by Swept Tones. J Assoc Res Otolaryngol 2024:10.1007/s10162-024-00956-z. [PMID: 38954166 DOI: 10.1007/s10162-024-00956-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 06/12/2024] [Indexed: 07/04/2024] Open
Abstract
The human medial olivocochlear (MOC) reflex was assessed by observing the effects of contralateral acoustic stimulation (CAS) on the cochlear microphonic (CM) across a range of probe frequencies. A frequency-swept probe tone (125-4757 Hz, 90 dB SPL) was presented in two directions (up sweep and down sweep) to normal-hearing young adults. This study assessed MOC effects on the CM in individual participants using a statistical approach that calculated minimum detectable changes in magnitude and phase based on CM signal-to-noise ratio (SNR). Significant increases in CM magnitude, typically 1-2 dB in size, were observed for most participants from 354 to 1414 Hz, where the size and consistency of these effects depended on participant, probe frequency, sweep direction, and SNR. CAS-related phase lags were also observed, consistent with CM-based MOC studies in laboratory animals. Observed effects on CM magnitude and phase were in the opposite directions of reported effects on otoacoustic emissions (OAEs). OAEs are sensitive to changes in the motility of outer hair cells located near the peak region of the traveling wave, while the effects of CAS on the CM likely originate from MOC-related changes in the conductance of outer hair cells located in the basal tail of the traveling wave. Thus, MOC effects on the CM are complementary to those observed for OAEs.
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Affiliation(s)
- Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA
| | - Sarah Haysley
- Department of Communication Sciences and Disorders, University of Utah, Salt Lake City, UT, USA
| | - Skyler G Jennings
- Department of Communication Sciences and Disorders, University of Utah, Salt Lake City, UT, USA.
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Goodman SS, Lefler SM, Lee C, Guinan JJ, Lichtenhan JT. The Origin Along the Cochlea of Otoacoustic Emissions Evoked by Mid-Frequency Tone Pips. J Assoc Res Otolaryngol 2024:10.1007/s10162-024-00955-0. [PMID: 38937327 DOI: 10.1007/s10162-024-00955-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 06/12/2024] [Indexed: 06/29/2024] Open
Abstract
PURPOSE Tone-pip-evoked otoacoustic emissions (PEOAEs) are transient-evoked otoacoustic emissions (OAEs) that are hypothesized to originate from reflection of energy near the best-frequency (BF) cochlear place of the stimulus frequency. However, individual PEOAEs have energy with a wide range of delays. We sought to determine whether some PEOAE energy is consistent with having been generated far from BF. METHODS PEOAEs from 35 and 47 dB SPL tone pips were obtained by removing pip-stimulus energy by subtracting the ear-canal sound pressure from scaled-down 59 dB SPL tone pips (which evoke relatively small OAEs). PEOAE delays were measured at each peak in the PEOAE absolute-value waveforms. While measuring PEOAEs and auditory-nerve compound action potentials (CAPs), amplification was blocked sequentially from apex to base by cochlear salicylate perfusion. The perfusion time when a CAP was reduced identified when the perfusion reached the tone-pip BF place. The perfusion times when each PEOAE peak was reduced identified where along the cochlea it received cochlear amplification. PEOAEs and CAPs were measured simultaneously using one pip frequency in each ear (1.4 to 4 kHz across 16 ears). RESULTS Most PEOAE peaks received amplification primarily between the BF place and 1-2 octaves basal of the BF place. PEOAE peaks with short delays received amplification basal of BF place. PEOAE peaks with longer delays sometimes received amplification apical of BF place, consistent with previous stimulus-frequency-OAE results. CONCLUSION PEOAEs provide information about cochlear amplification primarily within ~ 1.5 octave of the tone-pip BF place, not about regions > 3 octaves basal of BF.
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Affiliation(s)
- Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, Iowa, USA
| | - Shannon M Lefler
- Department of Otolaryngology, Washington University School of Medicine in St. Louis, Saint Louis, MO, USA
| | - Choongheon Lee
- Department of Otolaryngology, University of Rochester, Rochester, NY, USA
| | - John J Guinan
- Massachusetts Eye and Ear, Eaton-Peabody Laboratories, Boston, MA, USA
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA
| | - Jeffery T Lichtenhan
- Department of Otolaryngology, University of South Florida Morsani College of Medicine, Tampa, FL, USA.
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Stiepan S, Shera CA, Abdala C. Characterizing a Joint Reflection-Distortion OAE Profile in Humans With Endolymphatic Hydrops. Ear Hear 2023; 44:1437-1450. [PMID: 37450653 PMCID: PMC10593104 DOI: 10.1097/aud.0000000000001387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
OBJECTIVES Endolymphatic hydrops (EH), a hallmark of Meniere disease, is an inner-ear disorder where the membranes bounding the scala media are distended outward due to an abnormally increased volume of endolymph. In this study, we characterize the joint-otoacoustic emission (OAE) profile, a results profile including both distortion- and reflection-class emissions from the same ear, in individuals with EH and speculate on its potential utility in clinical assessment and monitoring. DESIGN Subjects were 16 adults with diagnosed EH and 18 adults with normal hearing (N) matched for age. Both the cubic distortion product (DP) OAE, a distortion-type emission, and the stimulus-frequency (SF) OAE, a reflection-type emission, were measured and analyzed as a joint OAE profile. OAE level, level growth (input/output functions), and phase-gradient delays were measured at frequencies corresponding to the apical half of the human cochlea and compared between groups. RESULTS Normal hearers and individuals with EH shared some common OAE patterns, such as the reflection emissions being generally higher in level than distortion emissions and showing more linear growth than the more strongly compressed distortion emissions. However, significant differences were noted between the EH and N groups as well. OAE source strength (a metric based on OAE amplitude re: stimulus level) was significantly reduced, as was OAE level, at low frequencies in the EH group. These reductions were more marked for distortion than reflection emissions. Furthermore, two significant changes in the configuration of OAE input/output functions were observed in ears with EH: a steepened growth slope for reflection emissions and an elevated compression knee for distortion emissions. SFOAE phase-gradient delays at 40 dB forward-pressure level were slightly shorter in the group with EH compared with the normal group. CONCLUSIONS The underlying pathology associated with EH impacts the generation of both emission types, reflection and distortion, as shown by significant group differences in OAE level, growth, and delay. However, hydrops impacts reflection and distortion emissions differently. Most notably, DPOAEs were more reduced by EH than were SFOAEs, suggesting that pathologies associated with the hydropic state do not act identically on the generation of nonlinear distortion at the hair bundle and intracochlear reflection emissions near the peak of the traveling wave. This differential effect underscores the value of applying a joint OAE approach to access both intracochlear generation processes concurrently.
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Affiliation(s)
- Samantha Stiepan
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA 90033, USA
| | - Christopher A Shera
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA 90033, USA
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089, USA
| | - Carolina Abdala
- Auditory Research Center, Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA 90033, USA
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Guinan JJ. Cochlear amplification in the short-wave region by outer hair cells changing organ-of-Corti area to amplify the fluid traveling wave. Hear Res 2022. [DOI: 10.1016/j.heares.2022.108641] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Pacheco D, Rajagopal N, Prieve BA, Nangia S. Joint Profile Characteristics of Long-Latency Transient Evoked and Distortion Otoacoustic Emissions. Am J Audiol 2022; 31:684-697. [PMID: 35862753 DOI: 10.1044/2022_aja-21-00182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE In clinical practice, otoacoustic emissions (OAEs) are interpreted as either "present" or "absent." However, OAEs have the potential to inform about etiology and severity of hearing loss if analyzed in other dimensions. A proposed method uses the nonlinear component of the distortion product OAEs together with stimulus frequency OAEs to construct a joint reflection-distortion profile. The objective of the current study is to determine if joint reflection-distortion profiles can be created using long-latency (LL) components of transient evoked OAEs (TEOAEs) as the reflection-type emission. METHOD LL TEOAEs and the nonlinear distortion OAEs were measured from adult ears. Individual input-output (I/O) functions were created, and OAE level was normalized by dividing by the stimulus level yielding individual gain functions. Peak strength, compression threshold, and OAE level at compression threshold were derived from individual gain functions to create joint reflection-distortion profiles. RESULTS TEOAEs with a poststimulus window starting at 6 ms had I/O functions with compression characteristics similar to LL TEOAE components. The model fit the LL gain functions, which had R 2 > .93, significantly better than the nonlinear distortion OAE gain functions, which had R 2 = .596-.99. Interquartile ranges for joint reflection-distortion profiles were larger for compression threshold and OAE level at compression threshold but smaller for peak strength than those previously published. CONCLUSIONS The gain function fits LL TEOAEs well. Joint reflection-distortion profiles are a promising method that could enhance diagnosis of hearing loss, and use of the LL TEOAE in the profile for peak strength may be important because of narrow interquartile ranges. SUPPLEMENTAL MATERIAL https://doi.org/10.23641/asha.20323593.
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Affiliation(s)
- Devon Pacheco
- Department of Communication Sciences and Disorders, Syracuse University, NY
| | - Nandhini Rajagopal
- Department of Biomedical and Chemical Engineering, Syracuse University, NY
| | - Beth A Prieve
- Department of Communication Sciences and Disorders, Syracuse University, NY
| | - Shikha Nangia
- Department of Biomedical and Chemical Engineering, Syracuse University, NY
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Wen H, Meaud J. Link between stimulus otoacoustic emissions fine structure peaks and standing wave resonances in a cochlear model. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 151:1875. [PMID: 35364913 PMCID: PMC8934193 DOI: 10.1121/10.0009839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 03/03/2022] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
In response to an external stimulus, the cochlea emits sounds, called stimulus frequency otoacoustic emissions (SFOAEs), at the stimulus frequency. In this article, a three-dimensional computational model of the gerbil cochlea is used to simulate SFOAEs and clarify their generation mechanisms and characteristics. This model includes electromechanical feedback from outer hair cells (OHCs) and cochlear roughness due to spatially random inhomogeneities in the OHC properties. As in the experiments, SFOAE simulations are characterized by a quasiperiodic fine structure and a fast varying phase. Increasing the sound pressure level broadens the peaks and decreases the phase-gradient delay of SFOAEs. A state-space formulation of the model provides a theoretical framework to analyze the link between the fine structure and global modes of the cochlea, which arise as a result of standing wave resonances. The SFOAE fine structure peaks correspond to weakly damped resonant modes because they are observed at the frequencies of nearly unstable modes of the model. Variations of the model parameters that affect the reflection mechanism show that the magnitude and sharpness of the tuning of these peaks are correlated with the modal damping ratio of the nearly unstable modes. The analysis of the model predictions demonstrates that SFOAEs originate from the peak of the traveling wave.
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Affiliation(s)
- Haiqi Wen
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332, USA
| | - Julien Meaud
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332, USA
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Lefler SM, Duncan RK, Goodman SS, Guinan JJ, Lichtenhan JT. Measurements From Ears With Endolymphatic Hydrops and 2-Hydroxypropyl-Beta-Cyclodextrin Provide Evidence That Loudness Recruitment Can Have a Cochlear Origin. Front Surg 2021; 8:687490. [PMID: 34676239 PMCID: PMC8523923 DOI: 10.3389/fsurg.2021.687490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 09/02/2021] [Indexed: 11/21/2022] Open
Abstract
Background: Loudness recruitment is commonly experienced by patients with putative endolymphatic hydrops. Loudness recruitment is abnormal loudness growth with high-level sounds being perceived as having normal loudness even though hearing thresholds are elevated. The traditional interpretation of recruitment is that cochlear amplification has been reduced. Since the cochlear amplifier acts primarily at low sound levels, an ear with elevated thresholds from reduced cochlear amplification can have normal processing at high sound levels. In humans, recruitment can be studied using perceptual loudness but in animals physiological measurements are used. Recruitment in animal auditory-nerve responses has never been unequivocally demonstrated because the animals used had damage to sensory and neural cells, not solely a reduction of cochlear amplification. Investigators have thus looked for, and found, evidence of recruitment in the auditory central nervous system (CNS). While studies on CNS recruitment are informative, they cannot rule out the traditional interpretation of recruitment originating in the cochlea. Design: We used techniques that could assess hearing function throughout entire frequency- and dynamic-range of hearing. Measurements were made from two animal models: guinea-pig ears with endolymphatic-sac-ablation surgery to produce endolymphatic hydrops, and naïve guinea-pig ears with cochlear perfusions of 13 mM 2-Hydroxypropyl-Beta-Cyclodextrin (HPBCD) in artificial perilymph. Endolymphatic sac ablation caused low-frequency loss. Animals treated with HPBCD had hearing loss at all frequencies. None of these animals had loss of hair cells or synapses on auditory nerve fibers. Results: In ears with endolymphatic hydrops and those perfused with HPBCD, auditory-nerve based measurements at low frequencies showed recruitment compared to controls. Recruitment was not found at high frequencies (> 4 kHz) where hearing thresholds were normal in ears with endolymphatic hydrops and elevated in ears treated with HPBCD. Conclusions: We found compelling evidence of recruitment in auditory-nerve data. Such clear evidence has never been shown before. Our findings suggest that, in patients suspected of having endolymphatic hydrops, loudness recruitment may be a good indication that the associated low-frequency hearing loss originates from a reduction of cochlear amplification, and that measurements of recruitment could be used in differential diagnosis and treatment monitoring of Ménière's disease.
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Affiliation(s)
- Shannon M Lefler
- Department of Otolaryngology, Washington University School of Medicine in St. Louis, Saint Louis, MO, United States
| | - Robert K Duncan
- Department of Otolaryngology-Head and Neck Surgery, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI, United States
| | - Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, United States
| | - John J Guinan
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, United States.,Department of Otolaryngology, Harvard Medical School, Boston, MA, United States
| | - Jeffery T Lichtenhan
- Department of Otolaryngology, Washington University School of Medicine in St. Louis, Saint Louis, MO, United States
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Bowling T, Wen H, Meenderink SWF, Dong W, Meaud J. Intracochlear distortion products are broadly generated by outer hair cells but their contributions to otoacoustic emissions are spatially restricted. Sci Rep 2021; 11:13651. [PMID: 34211051 PMCID: PMC8249639 DOI: 10.1038/s41598-021-93099-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/14/2021] [Indexed: 02/06/2023] Open
Abstract
Detection of low-level sounds by the mammalian cochlea requires electromechanical feedback from outer hair cells (OHCs). This feedback arises due to the electromotile response of OHCs, which is driven by the modulation of their receptor potential caused by the stimulation of mechano-sensitive ion channels. Nonlinearity in these channels distorts impinging sounds, creating distortion-products that are detectable in the ear canal as distortion-product otoacoustic emissions (DPOAEs). Ongoing efforts aim to develop DPOAEs, which reflects the ear's health, into diagnostic tools for sensory hearing loss. These efforts are hampered by limited knowledge on the cochlear extent contributing to DPOAEs. Here, we report on intracochlear distortion products (IDPs) in OHC electrical responses and intracochlear fluid pressures. Experiments and simulations with a physiologically motivated cochlear model show that widely generated electrical IDPs lead to mechanical vibrations in a frequency-dependent manner. The local cochlear impedance restricts the region from which IDPs contribute to DPOAEs at low to moderate intensity, which suggests that DPOAEs may be used clinically to provide location-specific information about cochlear damage.
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Affiliation(s)
- Thomas Bowling
- grid.213917.f0000 0001 2097 4943GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA USA
| | - Haiqi Wen
- grid.213917.f0000 0001 2097 4943GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA USA
| | - Sebastiaan W. F. Meenderink
- grid.422066.40000 0001 2195 7301VA Loma Linda Healthcare System, Loma Linda, CA 92357 USA ,grid.429814.2Department of Otolaryngology - Head and Neck Surgery, Loma Linda University Health, Loma Linda, CA 92350 USA
| | - Wei Dong
- grid.422066.40000 0001 2195 7301VA Loma Linda Healthcare System, Loma Linda, CA 92357 USA ,grid.429814.2Department of Otolaryngology - Head and Neck Surgery, Loma Linda University Health, Loma Linda, CA 92350 USA
| | - Julien Meaud
- grid.213917.f0000 0001 2097 4943GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA USA ,grid.213917.f0000 0001 2097 4943Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, GA USA
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Guinan JJ, Lefler SM, Buchman CA, Goodman SS, Lichtenhan JT. Altered mapping of sound frequency to cochlear place in ears with endolymphatic hydrops provide insight into the pitch anomaly of diplacusis. Sci Rep 2021; 11:10380. [PMID: 34001971 PMCID: PMC8128888 DOI: 10.1038/s41598-021-89902-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 04/26/2021] [Indexed: 11/22/2022] Open
Abstract
A fundamental property of mammalian hearing is the conversion of sound pressure into a frequency-specific place of maximum vibration along the cochlear length, thereby creating a tonotopic map. The tonotopic map makes possible systematic frequency tuning across auditory-nerve fibers, which enables the brain to use pitch to separate sounds from different environmental sources and process the speech and music that connects us to people and the world. Sometimes a tone has a different pitch in the left and right ears, a perceptual anomaly known as diplacusis. Diplacusis has been attributed to a change in the cochlear frequency-place map, but the hypothesized abnormal cochlear map has never been demonstrated. Here we assess cochlear frequency-place maps in guinea-pig ears with experimentally-induced endolymphatic hydrops, a hallmark of Ménière’s disease. Our findings are consistent with the hypothesis that diplacusis is due to an altered cochlear map. Map changes can lead to altered pitch, but the size of the pitch change is also affected by neural synchrony. Our data show that the cochlear frequency-place map is not fixed but can be altered by endolymphatic hydrops. Map changes should be considered in assessing hearing pathologies and treatments.
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Affiliation(s)
- J J Guinan
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, USA.,Department of Otolaryngology, Harvard Medical School, Boston, MA, USA
| | - S M Lefler
- Department of Otolaryngology, School of Medicine, Washington University St. Louis, Campus Box 8115, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - C A Buchman
- Department of Otolaryngology, School of Medicine, Washington University St. Louis, Campus Box 8115, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA
| | - S S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA
| | - J T Lichtenhan
- Department of Otolaryngology, School of Medicine, Washington University St. Louis, Campus Box 8115, 660 South Euclid Avenue, Saint Louis, MO, 63110, USA.
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Liu TC, Liu YW, Wu HT. Denoising click-evoked otoacoustic emission signals by optimal shrinkage. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 149:2659. [PMID: 33940909 DOI: 10.1121/10.0004264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/24/2021] [Indexed: 06/12/2023]
Abstract
Click-evoked otoacoustic emissions (CEOAEs) are clinically used as an objective way to infer whether cochlear functions are normal. However, because the sound pressure level of CEOAEs is typically much lower than the background noise, it usually takes hundreds, if not thousands, of repetitions to estimate the signal with sufficient accuracy. In this paper, we propose to improve the signal-to-noise ratio (SNR) of CEOAE signals within limited measurement time by optimal shrinkage (OS) in two different settings: covariance-based optimal shrinkage (cOS) and singular value decomposition-based optimal shrinkage (sOS). By simulation, the cOS consistently enhanced the SNR by 1-2 dB from a baseline method that is based on calculating the median. In real data, however, the cOS cannot enhance the SNR over 1 dB. The sOS achieved a SNR enhancement of 2-3 dB in simulation and demonstrated capability to enhance the SNR in real recordings. In addition, the level of enhancement increases as the baseline SNR decreases. An appealing property of OS is that it produces an estimate of all single trials. This property makes it possible to investigate CEOAE dynamics across a longer period of time when the cochlear conditions are not strictly stationary.
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Affiliation(s)
- Tzu-Chi Liu
- Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yi-Wen Liu
- Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Hau-Tieng Wu
- Department of Mathematics and Department of Statistical Science, Duke University, Durham, North Carolina 27708, USA
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Goodman SS, Boothalingam S, Lichtenhan JT. Medial olivocochlear reflex effects on amplitude growth functions of long- and short-latency components of click-evoked otoacoustic emissions in humans. J Neurophysiol 2021; 125:1938-1953. [PMID: 33625926 DOI: 10.1152/jn.00410.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Functional outcomes of medial olivocochlear reflex (MOCR) activation, such as improved hearing in background noise and protection from noise damage, involve moderate to high sound levels. Previous noninvasive measurements of MOCR in humans focused primarily on otoacoustic emissions (OAEs) evoked at low sound levels. Interpreting MOCR effects on OAEs at higher levels is complicated by the possibility of the middle-ear muscle reflex and by components of OAEs arising from different locations along the length of the cochlear spiral. We overcame these issues by presenting click stimuli at a very slow rate and by time-frequency windowing the resulting click-evoked (CE)OAEs into short-latency (SL) and long-latency (LL) components. We characterized the effects of MOCR on CEOAE components using multiple measures to more comprehensively assess these effects throughout much of the dynamic range of hearing. These measures included CEOAE amplitude attenuation, equivalent input attenuation, phase, and slope of growth functions. Results show that MOCR effects are smaller on SL components than LL components, consistent with SL components being generated slightly basal of the characteristic frequency region. Amplitude attenuation measures showed the largest effects at the lowest stimulus levels, but slope change and equivalent input attenuation measures did not decrease at higher stimulus levels. These latter measures are less commonly reported and may provide insight into the variability in listening performance and noise susceptibility seen across individuals.NEW & NOTEWORTHY The auditory efferent system, operating at moderate to high sound levels, may improve hearing in background noise and provide protection from noise damage. We used otoacoustic emissions to measure these efferent effects across a wide range of sound levels and identified level-dependent and independent effects. Previous reports have focused on level-dependent measures. The level-independent effects identified here may provide new insights into the functional relevance of auditory efferent activity in humans.
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Affiliation(s)
- Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, Iowa
| | - Sriram Boothalingam
- Department of Communication Sciences and Disorders, Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin
| | - Jeffery T Lichtenhan
- Department of Otolaryngology, Washington University School of Medicine in St. Louis, St. Louis, Missouri
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Cheatham MA. Comparing spontaneous and stimulus frequency otoacoustic emissions in mice with tectorial membrane defects. Hear Res 2020; 400:108143. [PMID: 33340968 DOI: 10.1016/j.heares.2020.108143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/20/2020] [Accepted: 12/02/2020] [Indexed: 01/28/2023]
Abstract
The global standing-wave model for generation of spontaneous otoacoustic emissions (SOAEs) suggests that they are amplitude-stabilized standing waves and that the spacing between SOAEs corresponds to the interval over which the phase changes by one cycle as determined from the phase-gradient delays of stimulus frequency otoacoustic emissions (SFOAEs). Because data characterizing the relationship between spontaneous and evoked emissions in nonhuman mammals are limited, we examined SOAEs and SFOAEs in tectorial membrane (TM) mutants and their controls. Computations indicate that the spacing between adjacent SOAEs is predicted by the SFOAE phase-gradient delays for TM mutants lacking Ceacam16, where SOAE frequencies are greater than ~20 kHz and the mutants retain near-normal hearing when young. Mice with a missense mutation in Tecta (TectaY1870C/+), as well as mice lacking Otoancorin (Otoa-/-), were also examined. Although these mutants exhibit hearing loss, they generate SOAEs with average frequencies of 11 kHz in TectaY1870C/+ and 6 kHz in Otoa-/-. In these animals, the spacing between adjacent SOAEs is larger than predicted by the SFOAE phase delays. It is also demonstrated that mice do not exhibit the strong frequency-dependence in signal coding that characterizes species with good low-frequency hearing. In fact, a transition occurs near the apical end of the mouse cochlea rather than at the mid-point along the cochlear partition. Hence, disagreements with the standing-wave model are not easily explained by a transition in tuning ratios between apical and basal regions of the cochlea, especially for SOAEs generated in TectaY1870C/+mice.
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Affiliation(s)
- Mary Ann Cheatham
- The Knowles Hearing Center, Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, 2-240 Frances Searle Building, 2240 Campus Drive, Evanston IL 60208, USA.
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13
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Guinan JJ. The interplay of organ-of-Corti vibrational modes, not tectorial- membrane resonance, sets outer-hair-cell stereocilia phase to produce cochlear amplification. Hear Res 2020; 395:108040. [PMID: 32784038 DOI: 10.1016/j.heares.2020.108040] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 01/27/2023]
Abstract
The mechanical motions that deflect outer-hair-cell (OHC) stereocilia and the resulting effects of OHC motility are reviewed, concentrating on high-frequency cochlear regions. It has been proposed that a tectorial-membrane (TM) resonance makes the phase of OHC stereocilia motion be appropriate to produce cochlear amplification, i.e. so that the OHC force that pushes the basilar membrane (BM) is in the same direction as BM velocity. Evidence for and against the TM-resonance hypothesis are considered, including new cochlear-motion measurements using optical coherence tomography, and it is concluded that there is no such TM resonance. The evidence points to there being an advance in the phase of reticular lamina (RL) radial motion at a frequency approximately ½ octave below the BM characteristic frequency, and that this is the main source of the phase difference between the TM and RL radial motions that produces cochlear amplification. It appears that the change in phase of RL radial motion comes about because of a transition between different organ-of-Corti (OoC) vibrational modes that changes RL motion relative to BM and TM motion. The origins and consequences of the large phase change of RL radial motion relative to BM motion are considered; differences in the reported patterns of these changes may be due to different viewing angles. Detailed motion data and new models are needed to better specify the vibrational patterns of the OoC modes and the role of the various OoC structures in producing the modes and the mode transition.
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Affiliation(s)
- John J Guinan
- Eaton-Peabody Lab, Mass. Eye and Ear, 243 Charles St, Boston, MA, 02114, USA; Harvard Medical School, Dept. of Otolaryngology, Boston, MA, USA.
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