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Altoè A, Charaziak KK. Intracochlear overdrive: Characterizing nonlinear wave amplification in the mouse apex. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 154:3414-3428. [PMID: 38015028 PMCID: PMC10686682 DOI: 10.1121/10.0022446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 10/02/2023] [Accepted: 11/01/2023] [Indexed: 11/29/2023]
Abstract
In this study, we explore nonlinear cochlear amplification by analyzing basilar membrane (BM) motion in the mouse apex. Through in vivo, postmortem, and mechanical suppression recordings, we estimate how the cochlear amplifier nonlinearly shapes the wavenumber of the BM traveling wave, specifically within a frequency range where the short-wave approximation holds. Our findings demonstrate that a straightforward mathematical model, depicting the cochlear amplifier as a wavenumber modifier with strength diminishing monotonically as BM displacement increases, effectively accounts for the various experimental observations. This empirically derived model is subsequently incorporated into a physics-based "overturned" framework of cochlear amplification [see Altoè, Dewey, Charaziak, Oghalai, and Shera (2022), J. Acoust. Soc. Am. 152, 2227-2239] and tested against additional experimental data. Our results demonstrate that the relationships established within the short-wave region remain valid over a much broader frequency range. Furthermore, the model, now exclusively calibrated to BM data, predicts the behavior of the opposing side of the cochlear partition, aligning well with recent experimental observations. The success in reproducing key features of the experimental data and the mathematical simplicity of the resulting model provide strong support for the "overturned" theory of cochlear amplification.
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Affiliation(s)
- Alessandro Altoè
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90007, USA
| | - Karolina K Charaziak
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90007, USA
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2
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Boothalingam S, Peterson A, Powell L, Easwar V. Auditory brainstem mechanisms likely compensate for self-imposed peripheral inhibition. Sci Rep 2023; 13:12693. [PMID: 37542191 PMCID: PMC10403563 DOI: 10.1038/s41598-023-39850-8] [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] [Received: 01/11/2023] [Accepted: 08/01/2023] [Indexed: 08/06/2023] Open
Abstract
Feedback networks in the brain regulate downstream auditory function as peripheral as the cochlea. However, the upstream neural consequences of this peripheral regulation are less understood. For instance, the medial olivocochlear reflex (MOCR) in the brainstem causes putative attenuation of responses generated in the cochlea and cortex, but those generated in the brainstem are perplexingly unaffected. Based on known neural circuitry, we hypothesized that the inhibition of peripheral input is compensated for by positive feedback in the brainstem over time. We predicted that the inhibition could be captured at the brainstem with shorter (1.5 s) than previously employed long duration (240 s) stimuli where this inhibition is likely compensated for. Results from 16 normal-hearing human listeners support our hypothesis in that when the MOCR is activated, there is a robust reduction of responses generated at the periphery, brainstem, and cortex for short-duration stimuli. Such inhibition at the brainstem, however, diminishes for long-duration stimuli suggesting some compensatory mechanisms at play. Our findings provide a novel non-invasive window into potential gain compensation mechanisms in the brainstem that may have implications for auditory disorders such as tinnitus. Our methodology will be useful in the evaluation of efferent function in individuals with hearing loss.
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Affiliation(s)
- Sriram Boothalingam
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA.
- Macquarie University, Sydney, NSW, 2109, Australia.
- National Acoustic Laboratories, Sydney, NSW, 2109, Australia.
| | - Abigayle Peterson
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA
- Macquarie University, Sydney, NSW, 2109, Australia
| | - Lindsey Powell
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA
| | - Vijayalakshmi Easwar
- Waisman Center and Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, 53705, USA
- Macquarie University, Sydney, NSW, 2109, Australia
- National Acoustic Laboratories, Sydney, NSW, 2109, Australia
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3
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Charaziak KK, Altoè A. Estimating cochlear impulse responses using frequency sweeps. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 153:2251. [PMID: 37092917 PMCID: PMC10104686 DOI: 10.1121/10.0017547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 02/10/2023] [Accepted: 02/23/2023] [Indexed: 05/03/2023]
Abstract
Cochlear mechanics tends to be studied using single-location measurements of intracochlear vibrations in response to acoustical stimuli. Such measurements, due to their invasiveness and often the instability of the animal preparation, are difficult to accomplish and, thus, ideally require stimulus paradigms that are time efficient, flexible, and result in high resolution transfer functions. Here, a swept-sine method is adapted for recordings of basilar membrane impulse responses in mice. The frequency of the stimulus was exponentially swept from low to high (upward) or high to low (downward) at varying rates (from slow to fast) and intensities. The cochlear response to the swept-sine was then convolved with the time-reversed stimulus waveform to obtain first and higher order impulse responses. Slow sweeps of either direction produce cochlear first to third order transfer functions equivalent to those measured with pure tones. Fast upward sweeps, on the other hand, generate impulse responses that typically ring longer, as observed in responses obtained using clicks. The ringing of impulse response in mice was of relatively small amplitude and did not affect the magnitude spectra. It is concluded that swept-sine methods offer flexible and time-efficient alternatives to other approaches for recording cochlear impulse responses.
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Affiliation(s)
- Karolina K Charaziak
- Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA
| | - Alessandro Altoè
- Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA
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Boothalingam S, Goodman SS, MacCrae H, Dhar S. A Time-Course-Based Estimation of the Human Medial Olivocochlear Reflex Function Using Clicks. Front Neurosci 2021; 15:746821. [PMID: 34776849 PMCID: PMC8581223 DOI: 10.3389/fnins.2021.746821] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 09/28/2021] [Indexed: 11/22/2022] Open
Abstract
The auditory efferent system, especially the medial olivocochlear reflex (MOCR), is implicated in both typical auditory processing and in auditory disorders in animal models. Despite the significant strides in both basic and translational research on the MOCR, its clinical applicability remains under-utilized in humans due to the lack of a recommended clinical method. Conventional tests employ broadband noise in one ear while monitoring change in otoacoustic emissions (OAEs) in the other ear to index efferent activity. These methods, (1) can only assay the contralateral MOCR pathway and (2) are unable to extract the kinetics of the reflexes. We have developed a method that re-purposes the same OAE-evoking click-train to also concurrently elicit bilateral MOCR activity. Data from click-train presentations at 80 dB peSPL at 62.5 Hz in 13 young normal-hearing adults demonstrate the feasibility of our method. Mean MOCR magnitude (1.7 dB) and activation time-constant (0.2 s) are consistent with prior MOCR reports. The data also suggest several advantages of this method including, (1) the ability to monitor MEMR, (2) obtain both magnitude and kinetics (time constants) of the MOCR, (3) visual and statistical confirmation of MOCR activation.
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Affiliation(s)
- Sriram Boothalingam
- Department of Communication Sciences and Disorders, University of Wisconsin-Madison, Madison, WI, United States.,Waisman Center, University of Wisconsin-Madison, Madison, WI, United States
| | - Shawn S Goodman
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, United States
| | - Hilary MacCrae
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States
| | - Sumitrajit Dhar
- Roxelyn and Richard Pepper Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States.,Knowles Center, Northwestern University, Evanston, IL, United States
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Altoè A, Charaziak KK, Dewey JB, Moleti A, Sisto R, Oghalai JS, Shera CA. The Elusive Cochlear Filter: Wave Origin of Cochlear Cross-Frequency Masking. J Assoc Res Otolaryngol 2021; 22:623-640. [PMID: 34677710 DOI: 10.1007/s10162-021-00814-2] [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: 11/23/2020] [Accepted: 08/23/2021] [Indexed: 11/28/2022] Open
Abstract
The mammalian cochlea achieves its remarkable sensitivity, frequency selectivity, and dynamic range by spatially segregating the different frequency components of sound via nonlinear processes that remain only partially understood. As a consequence of the wave-based nature of cochlear processing, the different frequency components of complex sounds interact spatially and nonlinearly, mutually suppressing one another as they propagate. Because understanding nonlinear wave interactions and their effects on hearing appears to require mathematically complex or computationally intensive models, theories of hearing that do not deal specifically with cochlear mechanics have often neglected the spatial nature of suppression phenomena. Here we describe a simple framework consisting of a nonlinear traveling-wave model whose spatial response properties can be estimated from basilar-membrane (BM) transfer functions. Without invoking jazzy details of organ-of-Corti mechanics, the model accounts well for the peculiar frequency-dependence of suppression found in two-tone suppression experiments. In particular, our analysis shows that near the peak of the traveling wave, the amplitude of the BM response depends primarily on the nonlinear properties of the traveling wave in more basal (high-frequency) regions. The proposed framework provides perhaps the simplest representation of cochlear signal processing that accounts for the spatially distributed effects of nonlinear wave propagation. Shifting the perspective from local filters to non-local, spatially distributed processes not only elucidates the character of cochlear signal processing, but also has important consequences for interpreting psychophysical experiments.
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Affiliation(s)
- Alessandro Altoè
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA.
| | - Karolina K Charaziak
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA
| | - James B Dewey
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA
| | - Arturo Moleti
- Department of Physics, University of Roma Tor Vergata, Rome, Italy
| | - Renata Sisto
- DIMEILA, INAIL, Monte Porzio Catone, Rome, Italy
| | - John S Oghalai
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA
| | - Christopher A Shera
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA.,Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, USA
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Charaziak KK, Shera CA. Reflection-Source Emissions Evoked with Clicks and Frequency Sweeps: Comparisons Across Levels. J Assoc Res Otolaryngol 2021; 22:641-658. [PMID: 34606020 DOI: 10.1007/s10162-021-00813-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 08/22/2021] [Indexed: 02/07/2023] Open
Abstract
According to coherent reflection theory, otoacoustic emissions (OAE) evoked with clicks (clicked-evoked, CE) or tones (stimulus frequency, SF) originate via the same mechanism. We test this hypothesis in gerbils by investigating the similarity of CE- and SFOAEs across a wide range of stimulus levels. The results show that OAE transfer functions measured in response to clicks and sweeps have nearly equivalent time-frequency characteristics, particularly at low stimulus levels. At high stimulus levels, the two OAE types are more dissimilar, reflecting the different dynamic properties of the evoking stimulus. At mid to high stimulus levels, time-frequency analysis reveals contributions from at least two OAE source components of varying latencies. Interference between these components explains the emergence of strong spectral microstructure. Time-frequency filtering based on mean basilar-membrane (BM) group delays (τBM) shows that late-latency OAE components (latency ~ 1.6τBM) dominate at low stimulus intensities and exhibit highly compressive growth with increasing stimulus intensity. In contrast, early-latency OAE components (~ 0.7τBM) are small at low stimulus levels but can come to dominate the overall response at higher intensities. Although the properties of long-latency OAEs are consistent with an origin via coherent reflection near the peak of the traveling wave, the generation place and/or mechanisms responsible for the early-latency OAE components warrant further investigation. Because their delay remains in constant proportion to τBM across sound intensity, long-latency OAEs, whether evoked with tones or clicks, can be used to predict characteristics of cochlear processing, such as the sharpness of frequency tuning, even at high stimulus levels.
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Affiliation(s)
- Karolina K Charaziak
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA, USA.
| | - Christopher A Shera
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, CA, USA.,Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, USA
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Mepani AM, Verhulst S, Hancock KE, Garrett M, Vasilkov V, Bennett K, de Gruttola V, Liberman MC, Maison SF. Envelope following responses predict speech-in-noise performance in normal-hearing listeners. J Neurophysiol 2021; 125:1213-1222. [PMID: 33656936 DOI: 10.1152/jn.00620.2020] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Permanent threshold elevation after noise exposure or aging is caused by loss of sensory cells; however, animal studies show that hair cell loss is often preceded by degeneration of the synapses between sensory cells and auditory nerve fibers. Silencing these neurons is likely to degrade auditory processing and may contribute to difficulties understanding speech in noisy backgrounds. Reduction of suprathreshold ABR amplitudes can be used to quantify synaptopathy in inbred mice. However, ABR amplitudes are highly variable in humans, and thus more challenging to use. Since noise-induced neuropathy preferentially targets fibers with high thresholds and low spontaneous rate and because phase locking to temporal envelopes is particularly strong in these fibers, measuring envelope following responses (EFRs) might be a more robust measure of cochlear synaptopathy. A recent auditory model further suggests that modulation of carrier tones with rectangular envelopes should be less sensitive to cochlear amplifier dysfunction and, therefore, a better metric of cochlear neural damage than sinusoidal amplitude modulation. In this study, we measure performance scores on a variety of difficult word-recognition tasks among listeners with normal audiograms and assess correlations with EFR magnitudes to rectangular versus sinusoidal modulation. Higher harmonics of EFR magnitudes evoked by a rectangular-envelope stimulus were significantly correlated with word scores, whereas those evoked by sinusoidally modulated tones did not. These results support previous reports that individual differences in synaptopathy may be a source of speech recognition variability despite the presence of normal thresholds at standard audiometric frequencies.NEW & NOTEWORTHY Recent studies suggest that millions of people may be at risk of permanent impairment from cochlear synaptopathy, the age-related and noise-induced degeneration of neural connections in the inner ear. This study examines electrophysiological responses to stimuli designed to improve detection of neural damage in subjects with normal hearing sensitivity. The resultant correlations with word recognition performance are consistent with a contribution of cochlear neural damage to deficits in hearing in noise abilities.
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Affiliation(s)
- Anita M Mepani
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts
| | - Sarah Verhulst
- Department of Information Technology, Ghent University, Ghent, Belgium
| | - Kenneth E Hancock
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts
| | - Markus Garrett
- Department of Information Technology, Ghent University, Ghent, Belgium.,Department of Medical Physics and Acoustics, University of Oldenburg, Oldenburg, Germany
| | | | - Kara Bennett
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
| | - Victor de Gruttola
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
| | - M Charles Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts.,Harvard Program in Speech and Hearing Bioscience and Technology, Harvard University, Boston, Massachusetts
| | - Stéphane F Maison
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts.,Department of Otolaryngology-Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts.,Harvard Program in Speech and Hearing Bioscience and Technology, Harvard University, Boston, Massachusetts
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Vencovský V, Vetešník A, Gummer AW. Nonlinear reflection as a cause of the short-latency component in stimulus-frequency otoacoustic emissions simulated by the methods of compression and suppression. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 147:3992. [PMID: 32611132 DOI: 10.1121/10.0001394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/22/2020] [Indexed: 06/11/2023]
Abstract
Stimulus-frequency otoacoustic emissions (SFOAEs) are generated by coherent reflection of forward traveling waves by perturbations along the basilar membrane. The strongest wavelets are backscattered near the place where the traveling wave reaches its maximal amplitude (tonotopic place). Therefore, the SFOAE group delay might be expected to be twice the group delay estimated in the cochlear filters. However, experimental data have yielded steady-state SFOAE components with near-zero latency. A cochlear model is used to show that short-latency SFOAE components can be generated due to nonlinear reflection of the compressor or suppressor tones used in SFOAE measurements. The simulations indicate that suppressors produce more pronounced short-latency components than compressors. The existence of nonlinear reflection components due to suppressors can also explain why SFOAEs can still be detected when suppressors are presented more than half an octave above the probe-tone frequency. Simulations of the SFOAE suppression tuning curves showed that phase changes in the SFOAE residual as the suppressor frequency increases are mostly determined by phase changes of the nonlinear reflection component.
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Affiliation(s)
- Václav Vencovský
- Department of Radioelectronics, Czech Technical University in Prague, Technická 2, 166 27 Prague, Czech Republic
| | - Aleš Vetešník
- Department of Nuclear Chemistry, Czech Technical University in Prague, Břehová 7, 115 19 Prague, Czech Republic
| | - Anthony W Gummer
- Department of Otolaryngology, Section of Physiological Acoustics and Communication, Eberhard-Karls-University Tübingen, Elfriede-Aulhorn-Strasse 5, 72076 Tübingen, Germany
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