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Lukashkin AN, Russell IJ, Rybdylova O. Local cochlear mechanical responses revealed through outer hair cell receptor potential measurements. Biophys J 2024:S0006-3495(24)00474-0. [PMID: 39014895 DOI: 10.1016/j.bpj.2024.07.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 03/26/2024] [Accepted: 07/12/2024] [Indexed: 07/18/2024] Open
Abstract
Sensory hair cells, including the sensorimotor outer hair cells, which enable the sensitive, sharply tuned responses of the mammalian cochlea, are excited by radial shear between the organ of Corti and the overlying tectorial membrane. It is not currently possible to measure directly in vivo mechanical responses in the narrow cleft between the tectorial membrane and organ of Corti over a wide range of stimulus frequencies and intensities. The mechanical responses can, however, be derived by measuring hair cell receptor potentials. We demonstrate that the seemingly complex frequency- and intensity-dependent behavior of outer hair cell receptor potentials could be qualitatively explained by a two degrees of freedom system with local cochlear partition and tectorial membrane resonances strongly coupled by the outer hair cell stereocilia. A local minimum in the receptor potential below the characteristic frequency should always be observed at a frequency where the tectorial membrane mechanical impedance is minimal, i.e., at the presumed tectorial membrane resonance frequency. The tectorial membrane resonance frequency might, however, shift with stimulus intensity in accordance with a shift in the maximum of the tectorial membrane radial mechanical responses to lower frequencies, as observed in experiments.
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Affiliation(s)
- Andrei N Lukashkin
- Sensory Neuroscience Research Group, School of Applied Science, University of Brighton, Brighton, United Kingdom.
| | - Ian J Russell
- Sensory Neuroscience Research Group, School of Applied Science, University of Brighton, Brighton, United Kingdom
| | - Oyuna Rybdylova
- Advanced Engineering Centre, School of Architecture, Technology and Engineering, University of Brighton, Brighton, United Kingdom.
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2
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Lin WC, Macić A, Becker J, Nam JH. Asymmetric vibrations in the organ of Corti by outer hair cells measured from excised gerbil cochlea. Commun Biol 2024; 7:600. [PMID: 38762693 PMCID: PMC11102476 DOI: 10.1038/s42003-024-06293-4] [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: 09/18/2023] [Accepted: 05/06/2024] [Indexed: 05/20/2024] Open
Abstract
Pending questions regarding cochlear amplification and tuning are hinged upon the organ of Corti (OoC) active mechanics: how outer hair cells modulate OoC vibrations. Our knowledge regarding OoC mechanics has advanced over the past decade thanks to the application of tomographic vibrometry. However, recent data from live cochlea experiments often led to diverging interpretations due to complicated interaction between passive and active responses, lack of image resolution in vibrometry, and ambiguous measurement angles. We present motion measurements and analyses of the OoC sub-components at the close-to-true cross-section, measured from acutely excised gerbil cochleae. Specifically, we focused on the vibrating patterns of the reticular lamina, the outer pillar cell, and the basilar membrane because they form a structural frame encasing active outer hair cells. For passive transmission, the OoC frame serves as a rigid truss. In contrast, motile outer hair cells exploit their frame structures to deflect the upper compartment of the OoC while minimally disturbing its bottom side (basilar membrane). Such asymmetric OoC vibrations due to outer hair cell motility explain how recent observations deviate from the classical cochlear amplification theory.
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Affiliation(s)
- Wei-Ching Lin
- Department of Mechanical Engineering, University of Rochester, Rochester, NY, USA
| | - Anes Macić
- Department of Mechanical Engineering, University of Rochester, Rochester, NY, USA
| | - Jonathan Becker
- Department of Mechanical Engineering, University of Rochester, Rochester, NY, USA
| | - Jong-Hoon Nam
- Department of Mechanical Engineering, University of Rochester, Rochester, NY, USA.
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, USA.
- Department of Neuroscience, University of Rochester, Rochester, NY, USA.
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3
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Lao H, Zhu Y, Yang M, Wang L, Tang J, Xiong H. Characteristics of spatial protein expression in the mouse cochlear sensory epithelia: Implications for age-related hearing loss. Hear Res 2024; 446:109006. [PMID: 38583350 DOI: 10.1016/j.heares.2024.109006] [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: 10/23/2023] [Revised: 03/27/2024] [Accepted: 04/01/2024] [Indexed: 04/09/2024]
Abstract
Hair cells in the cochlear sensory epithelia serve as mechanosensory receptors, converting sound into neuronal signals. The basal sensory epithelia are responsible for transducing high-frequency sounds, while the apex handles low-frequency sounds. Age-related hearing loss predominantly affects hearing at high frequencies and is indicative of damage to the basal sensory epithelia. However, the precise mechanism underlying this site-selective injury remains unclear. In this study, we employed a microscale proteomics approach to examine and compare protein expression in different regions of the cochlear sensory epithelia (upper half and lower half) in 1.5-month-old (normal hearing) and 6-month-old (severe high-frequency hearing loss without hair cell loss) C57BL/6J mice. A total of 2,386 proteins were detected, and no significant differences in protein expression were detected in the upper half of the cochlear sensory epithelia between the two age groups. The expression of 20 proteins in the lower half of the cochlear sensory epithelia significantly differed between the two age groups (e.g., MATN1, MATN4, and AQP1). Moreover, there were 311 and 226 differentially expressed proteins between the upper and lower halves of the cochlear sensory epithelia in 1.5-month-old and 6-month-old mice, respectively. The expression levels of selected proteins were validated by Western blotting. These findings suggest that the spatial differences in protein expression within the cochlear sensory epithelia may play a role in determining the susceptibility of cells at different sites of the cochlea to age-related damage.
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Affiliation(s)
- Huilin Lao
- Department of Otolaryngology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China; Institute of Hearing and Speech-Language Science, Sun Yat-sen University, Guangzhou, China
| | - Yafeng Zhu
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Mei Yang
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Lingshuo Wang
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Jie Tang
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China; Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, China.
| | - Hao Xiong
- Department of Otolaryngology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China; Institute of Hearing and Speech-Language Science, Sun Yat-sen University, Guangzhou, China.
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4
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Wang M, Wang J, Liang J, Yao W. Vibration modes of three-dimensional spiral cochlea covering the organ of Corti. Comput Methods Biomech Biomed Engin 2024:1-10. [PMID: 38317606 DOI: 10.1080/10255842.2024.2313065] [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: 09/16/2023] [Accepted: 01/23/2024] [Indexed: 02/07/2024]
Abstract
So far, explaining the mechanism on active phonosensitive amplification in the cochlea is a major and difficult medical question. Among them, one of the key problems is that the motion pattern of the organ of Corti (OC) is still unknown. To this end, a multi-scale cochlear model including a three-dimensional spiral OC was established based on CT data and light source imaging experimental data, which complete combined the macroscopic and microscopic structure. On the basis of verifying the reliability of the model, acoustic-solid coupling calculation and modal analysis were performed on the model, and the vibration modes of basilar membrane (BM) and structures of the OC at different characteristic frequencies were discussed. The results show that tectorial membrane (TM) exhibits completely different vibration modes from BM at low frequencies, while the two movements gradually synchronize as the frequency increases. The amplitude position of OC's motion moves laterally with increasing frequency from Deiters' cells to Hensen's cells and then back to Deiters' cells. The OC exhibits longitudinal vibrations following BM when BM's displacement is large, while it manifests more as lateral movement of Deiters' cells when BM's displacement is small. This model can well simulate the motion process of BM and OC in the lymphatic fluid, which provides theoretical support and a numerical simulation computational platform to explore the interaction between macroscopic and microscopic tissue structures of the overall cochlea.
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Affiliation(s)
- Mianzhi Wang
- Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China
- School of Mechanics and Engineering Science, Shanghai University, Shanghai, China
| | - Jiakun Wang
- Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China
- School of Mechanics and Engineering Science, Shanghai University, Shanghai, China
| | - Junyi Liang
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Wenjuan Yao
- Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China
- School of Mechanics and Engineering Science, Shanghai University, Shanghai, China
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Frost BL, Janjušević NP, Strimbu CE, Hendon CP. Compressed sensing on displacement signals measured with optical coherence tomography. BIOMEDICAL OPTICS EXPRESS 2023; 14:5539-5554. [PMID: 38021133 PMCID: PMC10659783 DOI: 10.1364/boe.503168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 09/21/2023] [Accepted: 09/22/2023] [Indexed: 12/01/2023]
Abstract
Optical coherence tomography (OCT) is capable of angstrom-scale vibrometry of particular interest to researchers of auditory mechanics. We develop a method for compressed sensing vibrometry using OCT that significantly reduces acquisition time for dense motion maps. Our method, based on total generalized variation with uniform subsampling, can reduce the number of samples needed to measure motion maps by a factor of ten with less than 5% normalized mean square error when tested on a diverse set of in vivo measurements from the gerbil cochlea. This opens up the possibility for more complex in vivo experiments for cochlear mechanics.
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Affiliation(s)
- Brian L. Frost
- Department of Electrical Engineering, Columbia University, 500 W. 120th St., Mudd 1310, New York, NY 10027,
USA
| | - Nikola P. Janjušević
- New York University, Tandon School of
Engineering, Electrical and Computer
Engineering, 370 Jay St, Brooklyn, NY 11201, USA
| | - C. Elliott Strimbu
- Columbia
University, Department of Otolaryngology, 630 West 168th
Street, New York, NY 10032, USA
| | - Christine P. Hendon
- Department of Electrical Engineering, Columbia University, 500 W. 120th St., Mudd 1310, New York, NY 10027,
USA
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Strimbu CE, Chiriboga LA, Frost BL, Olson ES. A frame and a hotspot in cochlear mechanics. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.29.547111. [PMID: 37873430 PMCID: PMC10592637 DOI: 10.1101/2023.06.29.547111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Auditory sensation is based in nanoscale vibration of the sensory tissue of the cochlea, the organ of Corti complex (OCC). Motion within the OCC is now observable due to optical coherence tomography. In the cochlear base, in response to sound stimulation, the region that includes the electro-motile outer hair cells (OHC) was observed to move with larger amplitude than the basilar membrane (BM) and surrounding regions. The intense motion is based in active cell mechanics, and the region was termed the "hotspot" (Cooper et al., 2018, Nature comm). In addition to this quantitative distinction, the hotspot moved qualitatively differently than the BM, in that its motion scaled nonlinearly with stimulus level at all frequencies, evincing sub-BF activity. Sub-BF activity enhances non-BF motion; thus the frequency tuning of the hotspot was reduced relative to the BM. Regions that did not exhibit sub-BF activity are here defined as the OCC "frame". By this definition the frame includes the BM, the medial and lateral OCC, and most significantly, the reticular lamina (RL). The frame concept groups the majority OCC as a structure that is largely shielded from sub-BF activity. This shielding, and how it is achieved, are key to the active frequency tuning of the cochlea. The observation that the RL does not move actively sub-BF indicates that hair cell stereocilia are not exposed to sub-BF activity. A complex difference analysis reveals the motion of the hotspot relative to the frame.
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Oghalai JS. Linear mixed-effect modeling of organ of Corti vibratory tuning curves. Hear Res 2023; 435:108820. [PMID: 37276685 PMCID: PMC10330841 DOI: 10.1016/j.heares.2023.108820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 05/09/2023] [Accepted: 05/30/2023] [Indexed: 06/07/2023]
Abstract
Optical coherence tomography has become the most popular approach to experimental measures of sound-induced vibrations within the mammalian cochlea. Because it is relatively easy to use and works in the unopened cochlea, the measurement of vibratory tuning curves has become highly reliable, and averaging data from multiple animals in different experimental cohorts is now possible. Here I tested a modern statistical approach to compare cohorts for differences in the magnitude and phase of vibration. A linear mixed-effect approach with first, second, third, and fourth-order models to fit the data was tested. The third-order model best fit both the magnitude and phase data without having terms that did not contribute substantively to improving the R2 or the p-value for the independent variables. It identified a difference between cohorts of mice that were different and no difference between cohorts that should not be different. Thus, this approach provides a way to simply compare a full set of tuning curves between cohorts. While further analyses by the investigator will always be needed to study specific details related to the study hypothesis, this statistical technique provides a simple way for the cochlear physiologist to perform an initial assessment of whether the cohorts are same or different.
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Affiliation(s)
- John S Oghalai
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California.
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Recio-Spinoso A, Dong W, Oghalai JS. On the Tonotopy of the Low-Frequency Region of the Cochlea. J Neurosci 2023; 43:5172-5179. [PMID: 37225436 PMCID: PMC10342220 DOI: 10.1523/jneurosci.0249-23.2023] [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: 02/13/2023] [Revised: 04/11/2023] [Accepted: 04/29/2023] [Indexed: 05/26/2023] Open
Abstract
It is generally assumed that frequency selectivity varies along the cochlea. For example, at the base of the cochlea, which is a region sensitive to high-frequency sounds, the best frequency of a cochlear location increases toward the most basal end, that is, near the stapes. Response phases also vary along cochlear locations. At any given frequency, there is a decrease in phase lag toward the stapes. This tonotopic arrangement in the cochlea was originally described by Georg von Békésy in a seminal series of experiments on human cadavers and has been confirmed in more recent works on live laboratory animals. Nonetheless, our knowledge of tonotopy at the apex of the cochlea remains incomplete in animals with low-frequency hearing, which is relevant to human speech. The results of our experiments on guinea pig, gerbil, and chinchilla cochleas, regardless of the sex of the animal, show that responses to sound differ at locations across the apex in a pattern consistent with previous studies of the base of the cochlea.SIGNIFICANCE STATEMENT Tonotopy is an important property of the auditory system that has been shown to exist in many auditory centers. In fact, most auditory implants work on the assumption of its existence by assigning different frequencies to different stimulating electrodes based on their location. At the level of the basilar membrane in the cochlea, a tonotopic arrangement implies that high-frequency stimuli evoke largest displacements at the base, near the ossicles, and low-frequency sounds have their greatest effects at the apex. Although tonotopy has been confirmed at the base of the cochlea on live animals at the apex of the cochlea, however, it has been less studied. Here, we show that a tonotopic arrangement does exist at the apex of the cochlea.
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Affiliation(s)
- Alberto Recio-Spinoso
- Instituto de Investigación en Discapacidades Neurológicas, Universidad de Castilla-La Mancha, 02006 Albacete, Spain
| | - Wei Dong
- Veterans Affairs Loma Linda Healthcare System, Department of Otolaryngology-Head & Neck Surgery, Loma Linda University Health, Loma Linda, California 92374
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles, Los Angeles, California 90033
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9
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Dewey JB, Shera CA. Bandpass Shape of Distortion-Product Otoacoustic Emission Ratio Functions Reflects Cochlear Frequency Tuning in Normal-Hearing Mice. J Assoc Res Otolaryngol 2023:10.1007/s10162-023-00892-4. [PMID: 37072566 DOI: 10.1007/s10162-023-00892-4] [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: 09/19/2022] [Accepted: 02/02/2023] [Indexed: 04/20/2023] Open
Abstract
The frequency selectivity of the mammalian auditory system is critical for discriminating complex sounds like speech. This selectivity derives from the sharp tuning of the cochlea's mechanical response to sound, which is largely attributed to the amplification of cochlear vibrations by outer hair cells (OHCs). Due to its nonlinearity, the amplification process also leads to the generation of distortion products (DPs), some of which propagate out to the ear canal as DP otoacoustic emissions (DPOAEs). However, the insight that these signals provide about the tuned micro- and macro-mechanics underlying their generation remains unclear. Using optical coherence tomography to measure cochlear vibrations in mice, we show that the cochlea's frequency tuning is reflected in the bandpass shape that is observed in DPOAE amplitudes when the ratio of the two evoking stimulus frequencies is varied (here termed DPOAE "ratio functions"). The tuning sharpness of DPOAE ratio functions and cochlear vibrations co-varied with stimulus level, with a similar quantitative agreement in tuning sharpness observed for both apical and mid-cochlear locations. Measurement of intracochlear DPs revealed that the tuning of the DPOAE ratio functions was not caused by mechanisms that shape DPs locally near where they are generated. Instead, simple model simulations indicate that the bandpass shape is due to a more global wave interference phenomenon. It appears that the filtering of DPOAEs by wave interactions over an extended spatial region allows them to provide a window onto the frequency tuning of single cochlear locations.
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Affiliation(s)
- James B Dewey
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, 90033, CA, USA.
| | - Christopher A Shera
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, 90033, CA, USA
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, 90089, USA
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Samaras G, Wen H, Meaud J. Broad nonlinearity in reticular lamina vibrations requires compliant organ of Corti structures. Biophys J 2023; 122:880-891. [PMID: 36709411 PMCID: PMC10027437 DOI: 10.1016/j.bpj.2023.01.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 01/29/2023] Open
Abstract
In the mammalian cochlea, each longitudinal position of the basilar membrane (BM) has a nonlinear vibratory response in a limited frequency range around the location-dependent frequency of maximum response, known as the best frequency (BF). This nonlinear response arises from the electromechanical feedback from outer hair cells (OHCs). However, recent in vivo measurements have demonstrated that the mechanical response of other organ of Corti (OoC) structures, such as the reticular lamina (RL), and the electrical response of OHCs (measured in the local cochlear microphonic [LCM]) are nonlinear even at frequencies significantly below BF. In this work, a physiologically motivated model of the gerbil cochlea is used to demonstrate that the source of this discrepancy between the frequency range of the BM, RL, and LCM nonlinearities is greater compliance in the structures at the top of the OHCs. The predicted responses of the BM, RL, and LCM to pure tone and two-tone stimuli are shown to be in line with experimental evidence. Simulations then demonstrate that the sub-BF nonlinearity in the RL requires the structures at the top of the OHCs to be significantly more compliant than the BM. This same condition is also necessary for "optimal" gain near BF, i.e., high amplification that is in line with the experiment. This demonstrates that the conditions for OHCs to operate optimally at BF inevitably yield nonlinearity of the RL response over a broad frequency range.
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Affiliation(s)
- George Samaras
- G.W.W. School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
| | - Haiqi Wen
- G.W.W. School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
| | - Julien Meaud
- G.W.W. School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia; Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia.
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11
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Frost BL, Strimbu CE, Olson ES. Reconstruction of transverse-longitudinal vibrations in the organ of Corti complex via optical coherence tomography. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 153:1347. [PMID: 36859114 PMCID: PMC9957605 DOI: 10.1121/10.0017345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 01/27/2023] [Accepted: 02/03/2023] [Indexed: 05/06/2023]
Abstract
Optical coherence tomography (OCT) is a common modality for measuring vibrations within the organ of Corti complex (OCC) in vivo. OCT's uniaxial nature leads to limitations that complicate the interpretation of data from cochlear mechanics experiments. The relationship between the optical axis (axis of motion measurement) and anatomically relevant axes in the cochlea varies across experiments, and generally is not known. This leads to characteristically different motion measurements taken from the same structure at different orientations. We present a method that can reconstruct two-dimensional (2-D) motion of intra-OCC structures in the cochlea's longitudinal-transverse plane. The method requires only a single, unmodified OCT system, and does not require any prior knowledge of precise structural locations or measurement angles. It uses the cochlea's traveling wave to register points between measurements taken at multiple viewing angles. We use this method to reconstruct 2-D motion at the outer hair cell/Deiters cell junction in the gerbil base, and show that reconstructed transverse motion resembles directly measured transverse motion, thus validating the method. The technique clarifies the interpretation of OCT measurements, enhancing their utility in probing the micromechanics of the cochlea.
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Affiliation(s)
- Brian L Frost
- Department of Electrical Engineering, Columbia University, 500 West 120th Street, Mudd 1310, New York, New York 10027, USA
| | - Clark Elliott Strimbu
- Department of Otolaryngology Head and Neck Surgery, Vagelos College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, New York 10032, USA
| | - Elizabeth S Olson
- Department of Otolaryngology Head and Neck Surgery, Vagelos College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, New York 10032, USA
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12
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Yin D, Wang X, Ren L, Xie Y, Zhang T, Dai P. The role of medial olivocochlear activity in contralateral suppression of auditory steady-state responses. Auris Nasus Larynx 2023; 50:57-61. [PMID: 35649956 DOI: 10.1016/j.anl.2022.05.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/02/2022] [Accepted: 05/09/2022] [Indexed: 01/28/2023]
Abstract
OBJECTIVE The auditory steady-state response (ASSR) amplitudes fall in the presence of contralateral noise. However, whether and to what extent medial olivocochlear (MOC) activity involves in contralateral suppression of ASSR remain unclear. Therefore, we assess the role of MOC activity in contralateral suppression of ASSR. METHODS Mice were treated with strychnine to completely eliminate MOC activity and then measured ASSR amplitudes in the presence of contralateral noise. RESULTS The contralateral noise reduces ASSR amplitudes at some stimulus intensity. After treating with the strychnine to eliminate MOC activity, ASSR amplitudes recovered again. CONCLUSIONS MOC activity participated in contralateral suppression of ASSR.
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Affiliation(s)
- Dongming Yin
- Department of Otolaryngology, Zhongshan Hospital Fudan University, Shanghai, PR China; ENT Institute, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China; NHC Hearing Medicine Key Laboratory (Fudan University), Shanghai, PR China
| | - Xiaolei Wang
- Department of Cardiology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, PR China
| | - Liujie Ren
- ENT Institute, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China; NHC Hearing Medicine Key Laboratory (Fudan University), Shanghai, PR China; Department of Facial Plastic and Reconstructive Surgery, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China
| | - Youzhou Xie
- ENT Institute, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China; NHC Hearing Medicine Key Laboratory (Fudan University), Shanghai, PR China; Department of Facial Plastic and Reconstructive Surgery, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China
| | - Tianyu Zhang
- ENT Institute, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China; NHC Hearing Medicine Key Laboratory (Fudan University), Shanghai, PR China; Department of Facial Plastic and Reconstructive Surgery, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China
| | - Peidong Dai
- ENT Institute, Eye & ENT Hospital of Fudan University, Fenyang Road 83, Shanghai 200031, PR China; NHC Hearing Medicine Key Laboratory (Fudan University), Shanghai, PR China.
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13
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Kim J, Ricci AJ. A chemo-mechanical cochleostomy preserves hearing for the in vivo functional imaging of cochlear cells. Nat Protoc 2023; 18:1137-1154. [PMID: 36599963 DOI: 10.1038/s41596-022-00786-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 10/07/2022] [Indexed: 01/05/2023]
Abstract
In vivo and real-time multicellular imaging enables the decoding of sensory circuits and the tracking of systemic drug uptake. However, in vivo imaging of the auditory periphery remains technically challenging owing to the deep location, mechanosensitivity and fluid-filled, bone-encased nature of the cochlear structure. Existing methods that expose the cochlea invariably cause irreversible damage to auditory function, severely limiting the experimental measurements possible in living animals. Here we present an in vivo surgical protocol that permits the imaging of cochlear cells in hearing mice. Our protocol describes a ventro-lateral approach for preserving external and middle ear structures while performing surgery, the correct mouse positioning for imaging cochlear cells with effective sound transmission into the ear, the chemo-mechanical cochleostomy for creating the imaging window in the otic capsule bone that prevents intracochlear fluid leakage by maintaining an intact endosteum, and the release of intracochlear pressure that separates the endosteum from the otic capsule bone while creating an imaging window. The procedure thus preserves hearing thresholds. Individual inner and outer hair cells, supporting cells and nerve fibers can be visualized in vivo while hearing function is preserved. This approach may enable future original investigations, such as the real-time tracking of ototoxic drug transport into the cochleae. The technique may be applied to the monitoring of sound-evoked functional activity in multiple cochlear cells, in combination with optogenetic tools, and may help to improve cochlear implantation in humans. The cochleostomy takes ~1 h and requires experience in surgery.
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Affiliation(s)
- Jinkyung Kim
- Department of Otolaryngology, Stanford University School of Medicine, Stanford, CA, USA
| | - Anthony J Ricci
- Department of Otolaryngology, Stanford University School of Medicine, Stanford, CA, USA. .,Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA.
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14
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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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15
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Organ of Corti vibrations are dominated by longitudinal motion in vivo. Commun Biol 2022; 5:1285. [PMID: 36424445 PMCID: PMC9691626 DOI: 10.1038/s42003-022-04234-7] [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: 02/28/2022] [Accepted: 11/08/2022] [Indexed: 11/27/2022] Open
Abstract
Recent observations of sound-evoked vibrations of the cochlea's sensory organ of Corti (ooC) using optical coherence tomography (OCT) have revealed unanticipated and complex motions. Interpreting these results in terms of the micromechanical inner-ear processes that precede hair-cell transduction is not trivial since OCT only measures a projection of the true motion, which may include transverse and longitudinal displacements. We measure ooC motions at multiple OCT beam angles relative to the longitudinal axis of the basilar membrane (BM) by using the cochlea's natural curvature and find that the relative phase between outer hair cells (OHC) and BM varies with this angle. This includes a relatively abrupt phase reversal where OHC lead (lag) the BM by ~0.25 cycles for negative (positive) beam angles, respectively. We interpret these results as evidence for significant longitudinal motion within the ooC, which should be considered when interpreting (relative) ooC vibrations in terms of inner-ear sound processing.
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16
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The reticular lamina and basilar membrane vibrations in the transverse direction in the basal turn of the living gerbil cochlea. Sci Rep 2022; 12:19810. [PMID: 36396720 PMCID: PMC9671912 DOI: 10.1038/s41598-022-24394-0] [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: 07/11/2022] [Accepted: 11/15/2022] [Indexed: 11/18/2022] Open
Abstract
The prevailing theory of cochlear function states that outer hair cells amplify sound-induced vibration to improve hearing sensitivity and frequency specificity. Recent micromechanical measurements in the basal turn of gerbil cochleae through the round window have demonstrated that the reticular lamina vibration lags the basilar membrane vibration, and it is physiologically vulnerable not only at the best frequency but also at the low frequencies. These results suggest that outer hair cells from a broad cochlear region enhance hearing sensitivity through a global hydromechanical mechanism. However, the time difference between the reticular lamina and basilar membrane vibration has been thought to result from a systematic measurement error caused by the optical axis non-perpendicular to the cochlear partition. To address this concern, we measured the reticular lamina and basilar membrane vibrations in the transverse direction through an opening in the cochlear lateral wall in this study. Present results show that the phase difference between the reticular lamina and basilar membrane vibration decreases with frequency by ~ 180 degrees from low frequencies to the best frequency, consistent with those measured through the round window. Together with the round-window measurement, the low-coherence interferometry through the cochlear lateral wall demonstrates that the time difference between the reticular lamina and basilar membrane vibration results from the cochlear active processing rather than a measurement error.
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17
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Cho NH, Puria S. Cochlear motion across the reticular lamina implies that it is not a stiff plate. Sci Rep 2022; 12:18715. [PMID: 36333415 PMCID: PMC9636238 DOI: 10.1038/s41598-022-23525-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
Within the cochlea, the basilar membrane (BM) is coupled to the reticular lamina (RL) through three rows of piezo-like outer hair cells (OHCs) and supporting cells that endow mammals with sensitive hearing. Anatomical differences across OHC rows suggest differences in their motion. Using optical coherence tomography, we measured in vivo and postmortem displacements through the gerbil round-window membrane from approximately the 40-47 kHz best-frequency (BF) regions. Our high spatial resolution allowed measurements across the RL surface at the tops of the three rows of individual OHCs and their bottoms, and across the BM. RL motion varied radially; the third-row gain was more than 3 times greater than that of the first row near BF, whereas the OHC-bottom motions remained similar. This implies that the RL mosaic, comprised of OHC and phalangeal-process tops joined together by adhesion molecules, is much more flexible than the Deiters' cells connected to the OHCs at their bottom surfaces. Postmortem, the measured points moved together approximately in phase. These imply that in vivo, the RL does not move as a stiff plate hinging around the pillar-cell heads near the first row as has been assumed, but that its mosaic-like structure may instead bend and/or stretch.
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Affiliation(s)
- Nam Hyun Cho
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02114, USA
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114, USA
| | - Sunil Puria
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02114, USA.
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114, USA.
- Speech and Hearing Bioscience and Technology Program, Harvard University, Cambridge, MA, 02138, USA.
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18
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Zhou W, Jabeen T, Sabha S, Becker J, Nam JH. Deiters Cells Act as Mechanical Equalizers for Outer Hair Cells. J Neurosci 2022; 42:8361-8372. [PMID: 36123119 PMCID: PMC9653280 DOI: 10.1523/jneurosci.2417-21.2022] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 09/06/2022] [Accepted: 09/11/2022] [Indexed: 11/21/2022] Open
Abstract
The outer hair cells in the mammalian cochlea are cellular actuators essential for sensitive hearing. The geometry and stiffness of the structural scaffold surrounding the outer hair cells will determine how the active cells shape mammalian hearing by modulating the organ of Corti (OoC) vibrations. Specifically, the tectorial membrane and the Deiters cell are mechanically in series with the hair bundle and soma, respectively, of the outer hair cell. Their mechanical properties and anatomic arrangement must determine the relative motion among different OoC structures. We measured the OoC mechanics in the cochleas acutely excised from young gerbils of both sexes at a resolution fine enough to distinguish the displacement of individual cells. A three-dimensional finite element model of fully deformable OoC was exploited to analyze the measured data in detail. As a means to verify the computer model, the basilar membrane deformations because of static and dynamic stimulations were measured and simulated. Two stiffness ratios have been identified that are critical to understand cochlear physics, which are the stiffness of the tectorial membrane with respect to the hair bundle and the stiffness of the Deiters cell with respect to the outer hair cell body. Our measurements suggest that the Deiters cells act like a mechanical equalizer so that the outer hair cells are constrained neither too rigidly nor too weakly.SIGNIFICANCE STATEMENT Mammals can detect faint sounds thanks to the action of mammalian-specific receptor cells called the outer hair cells. It is getting clearer that understanding the interactions between the outer hair cells and their surrounding structures such as the tectorial membrane and the Deiters cell is critical to resolve standing debates. Depending on theories, the stiffness of those two structures ranges from negligible to rigid. Because of their perceived importance, their properties have been measured in previous studies. However, nearly all existing data were obtained ex situ (after they were detached from the outer hair cells), which obscures their interaction with the outer hair cells. We quantified the mechanical properties of the tectorial membrane and the Deiters cell in situ.
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Affiliation(s)
| | - Talat Jabeen
- Biomedical Engineering, University of Rochester, Rochester, New York 14627
| | | | | | - Jong-Hoon Nam
- Departments of Mechanical Engineering
- Biomedical Engineering, University of Rochester, Rochester, New York 14627
- Neuroscience Program, University of Rochester Medical Center, Rochester, New York 14627
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19
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Motallebzadeh H, Puria S. Stimulus-frequency otoacoustic emissions and middle-ear pressure gains in a finite-element mouse model. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 152:2769. [PMID: 36456266 PMCID: PMC9643045 DOI: 10.1121/10.0014901] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 09/29/2022] [Accepted: 09/29/2022] [Indexed: 06/17/2023]
Abstract
For evoked otoacoustic emissions (OAEs), the stimulus and emission signals traverse the middle ear (ME) in forward and reverse directions, respectively. In this study, a fully coupled three-dimensional finite-element model of the mouse ear canal (EC), ME, and cochlea was used to calculate ME pressure gains, impedances, and reflectances at the EC-entrance and stapes-footplate-cochlear-fluid interfaces. The cochlear model incorporates a series of interdigitated Y-shaped structures sandwiched between the basilar membrane and reticular lamina, each comprised of a Deiters' cell, its phalangeal-process extension, and an outer hair cell (OHC). By introducing random perturbations to the OHC gains, stimulation-frequency otoacoustic emissions (SFOAEs) were generated. Raising the perturbation magnitude from 10% to 80% increased the SFOAE magnitude by up to 24 dB in the 10-30 kHz frequency range. Increasing or decreasing the stiffness of the stapes annular ligament and eardrum by a factor of 8 changed the SFOAEs by up to 30 dB, but the round-trip ME gain as measured could not account for this. A modified round-trip ME gain, with reflections removed at the EC-entrance and stapes-cochlea boundaries, eliminated a ±10 dB discrepancy and allowed ME changes to be quantitatively associated with changes in measured OAEs.
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Affiliation(s)
- Hamid Motallebzadeh
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114, USA
| | - Sunil Puria
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114, USA
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20
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Xia A, Udagawa T, Quiñones PM, Atkinson PJ, Applegate BE, Cheng AG, Oghalai JS. The impact of targeted ablation of one row of outer hair cells and Deiters' cells on cochlear amplification. J Neurophysiol 2022; 128:1365-1373. [PMID: 36259670 PMCID: PMC9678430 DOI: 10.1152/jn.00501.2021] [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: 11/15/2021] [Revised: 10/13/2022] [Accepted: 10/17/2022] [Indexed: 11/22/2022] Open
Abstract
The mammalian cochlea contains three rows of outer hair cells (OHCs) that amplify the basilar membrane traveling wave with high gain and exquisite tuning. The pattern of OHC loss caused by typical methods of producing hearing loss in animal models (noise, ototoxic exposure, or aging) is variable and not consistent along the length of the cochlea. Thus, it is difficult to use these approaches to understand how forces from multiple OHCs summate to create normal cochlear amplification. Here, we selectively removed the third row of OHCs and Deiters' cells in adult mice and measured cochlear amplification. In the mature cochlear epithelia, expression of the Wnt target gene Lgr5 is restricted to the third row of Deiters' cells, the supporting cells directly underneath the OHCs. Diphtheria toxin administration to Lgr5DTR-EGFP/+ mice selectively ablated the third row of Deiters' cells and the third row of OHCs. Basilar membrane vibration in vivo demonstrated disproportionately lower reduction in cochlear amplification by about 13.5 dB. On a linear scale, this means that the 33% reduction in OHC number led to a 79% reduction in gain. Thus, these experimental data describe the impact of reducing the force of cochlear amplification by a specific amount. Furthermore, these data argue that because OHC forces progressively and sequentially amplify the traveling wave as it travels to its peak, the loss of even a relatively small number of OHCs, when evenly distributed longitudinally, will cause a substantial reduction in cochlear amplification.NEW & NOTEWORTHY Normal cochlear physiology involves force production from three rows of outer hair cells to amplify and tune the traveling wave. Here, we used a genetic approach to target and ablate the third row of outer hair cells in the mouse cochlea and found it reduced cochlear amplification by 79%. This means that the loss of even a relatively small number of OHCs, when evenly distributed, causes a substantial reduction in cochlear amplification.
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Affiliation(s)
- Anping Xia
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - Tomokatsu Udagawa
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
- Department of Otorhinolaryngology, The Jikei University School of Medicine, Tokyo, Japan
| | - Patricia M Quiñones
- Caruso Department of Otolaryngology-Head & Neck Surgery, University of Southern California, Los Angeles, California
| | - Patrick J Atkinson
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - Brian E Applegate
- Caruso Department of Otolaryngology-Head & Neck Surgery, University of Southern California, Los Angeles, California
- Department of Biomedical Engineering, Denney Research Center (DRB) 140, University of Southern California, Los Angeles, California
| | - Alan G Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head & Neck Surgery, University of Southern California, Los Angeles, California
- Department of Biomedical Engineering, Denney Research Center (DRB) 140, University of Southern California, Los Angeles, California
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21
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Altoè A, Dewey JB, Charaziak KK, Oghalai JS, Shera CA. Overturning the mechanisms of cochlear amplification via area deformations of the organ of Corti. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 152:2227. [PMID: 36319240 PMCID: PMC9578757 DOI: 10.1121/10.0014794] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 08/17/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
The mammalian ear embeds a cellular amplifier that boosts sound-induced hydromechanical waves as they propagate along the cochlea. The operation of this amplifier is not fully understood and is difficult to disentangle experimentally. In the prevailing view, cochlear waves are amplified by the piezo-electric action of the outer hair cells (OHCs), whose cycle-by-cycle elongations and contractions inject power into the local motion of the basilar membrane (BM). Concomitant deformations of the opposing (or "top") side of the organ of Corti are assumed to play a minor role and are generally neglected. However, analysis of intracochlear motions obtained using optical coherence tomography calls this prevailing view into question. In particular, the analysis suggests that (i) the net local power transfer from the OHCs to the BM is either negative or highly inefficient; and (ii) vibration of the top side of the organ of Corti plays a primary role in traveling-wave amplification. A phenomenological model derived from these observations manifests realistic cochlear responses and suggests that amplification arises almost entirely from OHC-induced deformations of the top side of the organ of Corti. In effect, the model turns classic assumptions about spatial impedance relations and power-flow direction within the sensory epithelium upside down.
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Affiliation(s)
- Alessandro Altoè
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
| | - James B Dewey
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
| | - Karolina K Charaziak
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
| | - John S Oghalai
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
| | - Christopher A Shera
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
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22
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Meenderink SWF, Lin X, Park BH, Dong W. Sound Induced Vibrations Deform the Organ of Corti Complex in the Low-Frequency Apical Region of the Gerbil Cochlea for Normal Hearing : Sound Induced Vibrations Deform the Organ of Corti Complex. J Assoc Res Otolaryngol 2022; 23:579-591. [PMID: 35798901 PMCID: PMC9613840 DOI: 10.1007/s10162-022-00856-0] [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: 03/31/2022] [Accepted: 06/16/2022] [Indexed: 10/17/2022] Open
Abstract
Human speech primarily contains low frequencies. It is well established that such frequencies maximally excite the cochlea near its apex. But, the micromechanics that precede and are involved in this transduction are not well understood. We measured vibrations from the low-frequency, second turn in intact gerbil cochleae using optical coherence tomography (OCT). The data were used to create spatial maps that detail the sound-evoked motions across the sensory organ of Corti complex (OCC). These maps were remarkably similar across animals and showed little variation with frequency or level. We identify four, anatomically distinct, response regions within the OCC: the basilar membrane (BM), the outer hair cells (OHC), the lateral compartment (lc), and the tectorial membrane (TM). Results provide evidence that active processes in the OHC play an important role in the mechanical interplay between different OCC structures which increases the amplitude and tuning sharpness of the traveling wave. The angle between the OCT beam and the OCC makes that we captured radial motions thought to be the effective stimulus to the mechano-sensitive hair bundles. We found that TM responses were relatively weak, arguing against a role in enhancing mechanical hair bundle deflection. Rather, BM responses were found to closely resemble the frequency selectivity and sensitivity found in auditory nerve fibers (ANF) that innervate the low-frequency cochlea.
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Affiliation(s)
| | - Xiaohui Lin
- VA Loma Linda Healthcare System, Loma Linda, CA, 92374, USA
| | - B Hyle Park
- Department of Bioengineering, University of California, Riverside, Riverside, CA, 92521, USA
| | - Wei Dong
- VA Loma Linda Healthcare System, Loma Linda, CA, 92374, USA.
- Loma Linda University Health, Loma Linda, CA, 92350, USA.
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23
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Strimbu CE, Olson ES. Salicylate-induced changes in organ of Corti vibrations. Hear Res 2022; 423:108389. [PMID: 34774368 PMCID: PMC9058039 DOI: 10.1016/j.heares.2021.108389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 10/19/2021] [Accepted: 10/26/2021] [Indexed: 11/04/2022]
Abstract
Intra organ of Corti (OC) vibrations differ from those measured at the basilar membrane (BM), with higher amplitudes and a wide-band nonlinearity extending well below a region's best frequency. The vibrations are boosted by the cochlear amplifier, the active processes within the mammalian hearing organ, and are thus sensitive to metabolic or pharmacological manipulation. We introduced salicylate, a known blocker of outer hair cell (OHC) based electromotility, into the perilymphatic space by applying sodium salicylate onto the round window membrane. Vibration patterns of an area of the OC were mapped with phase sensitive optical coherence tomography before and after treatment; distortion product otoacoustic emissions (DPOAEs) were measured at similar times to assess the cochlear condition. Following treatment, all regions showed a loss of vibration amplitude and tuning while OHC-region vibrations retained their wide-band nonlinearity. OC vibrations, which had been relatively confined in a region including OHCs and extending to the BM at the outer pillar foot, became less confined with structures lateral to the OHCs sometimes exhibiting the highest amplitudes. Vibrations and DPOAEs could recover to baseline levels over approximately three hours post treatment. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam.
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Affiliation(s)
- C. Elliott Strimbu
- Columbia University, Department of Otolaryngology, 630 West 168th Street, New York, NY 10032, USA
| | - Elizabeth S. Olson
- Columbia University, Department of Otolaryngology, 630 West 168th Street, New York, NY 10032, USA
- Columbia University, Department of Biomedical Engineering, 1210 Amsterdam Avenue, New York, NY 10027 USA
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24
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He W, Burwood G, Fridberger A, Nuttall AL, Ren T. An outer hair cell-powered global hydromechanical mechanism for cochlear amplification. Hear Res 2022; 423:108407. [PMID: 34922772 PMCID: PMC9156726 DOI: 10.1016/j.heares.2021.108407] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 11/23/2021] [Accepted: 11/30/2021] [Indexed: 11/04/2022]
Abstract
It is a common belief that the mammalian cochlea achieves its exquisite sensitivity, frequency selectivity, and dynamic range through an outer hair cell-based active process, or cochlear amplification. As a sound-induced traveling wave propagates from the cochlear base toward the apex, outer hair cells at a narrow region amplify the low level sound-induced vibration through a local feedback mechanism. This widely accepted theory has been tested by measuring sound-induced sub-nanometer vibrations within the organ of Corti in the sensitive living cochleae using heterodyne low-coherence interferometry and optical coherence tomography. The aim of this short review is to summarize experimental findings on the cochlear active process by the authors' group. Our data show that outer hair cells are able to generate substantial forces for driving the cochlear partition at all audible frequencies in vivo. The acoustically induced reticular lamina vibration is larger and more broadly tuned than the basilar membrane vibration. The reticular lamina and basilar membrane vibrate approximately in opposite directions at low frequencies and in the same direction at the best frequency. The group delay of the reticular lamina is larger than that of the basilar membrane. The magnitude and phase differences between the reticular lamina and basilar membrane vibration are physiologically vulnerable. These results contradict predictions based on the local feedback mechanism but suggest a global hydromechanical mechanism for cochlear amplification. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam.
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Affiliation(s)
- Wenxuan He
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States
| | - George Burwood
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States
| | - Anders Fridberger
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Alfred L Nuttall
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States
| | - Tianying Ren
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States.
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25
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Quiñones PM, Meenderink SWF, Applegate BE, Oghalai JS. Unloading outer hair cell bundles in vivo does not yield evidence of spontaneous oscillations in the mouse cochlea. Hear Res 2022; 423:108473. [PMID: 35287989 PMCID: PMC9339463 DOI: 10.1016/j.heares.2022.108473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 02/11/2022] [Accepted: 02/28/2022] [Indexed: 12/21/2022]
Abstract
Along with outer hair cell (OHC) somatic electromotility as the actuator of cochlear amplification, active hair bundle motility may be a complementary mechanism in the mammalian auditory system. Here, we searched the mouse cochlea for the presence of spontaneous bundle oscillations that have been observed in non-mammalian ears. In those systems, removal of the overlying membrane is necessary for spontaneous bundle oscillations to manifest. Thus, we used a genetic mouse model with a C1509G (cysteine-to-glycine) point mutation in the Tecta gene where the tectorial (TM) is lifted away from the OHC bundles, allowing us to explore whether unloaded bundles spontaneously oscillate. We used VOCTV in vivo to detect OHC length changes due to electromotility as a proxy for the spontaneous opening and closing of the mechanoelectrical transduction (MET) channels associated with bundle oscillation. In wild type mice with the TM attached to OHC bundles, we did find peaks in vibratory magnitude spectra. Such peaks were not observed in the mutants where the TM is detached from the OHC bundles. Statistical analysis of the time signals indicates that these peaks do not signify active oscillations. Rather, they are filtered responses of the sensitive wild type cochlea to weak background noise. We therefore conclude that, to the limits of our system (∼30 pm), there is no spontaneous mechanical activity that manifests as oscillations in OHC electromotility within the mouse cochlea, arguing that unloaded OHC bundles do not oscillate in vivo. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam.
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Affiliation(s)
- Patricia M Quiñones
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA, USA
| | | | - Brian E Applegate
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA, USA; Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - John S Oghalai
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA, USA.
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26
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Nankali A, Shera CA, Applegate BE, Oghalai JS. Interplay between traveling wave propagation and amplification at the apex of the mouse cochlea. Biophys J 2022; 121:2940-2951. [PMID: 35778839 PMCID: PMC9388393 DOI: 10.1016/j.bpj.2022.06.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 03/08/2022] [Accepted: 06/27/2022] [Indexed: 11/18/2022] Open
Abstract
Sounds entering the mammalian ear produce waves that travel from the base to the apex of the cochlea. An electromechanical active process amplifies traveling wave motions and enables sound processing over a broad range of frequencies and intensities. The cochlear amplifier requires combining the global traveling wave with the local cellular processes that change along the length of the cochlea given the gradual changes in hair cell and supporting cell anatomy and physiology. Thus, we measured basilar membrane (BM) traveling waves in vivo along the apical turn of the mouse cochlea using volumetric optical coherence tomography and vibrometry. We found that there was a gradual reduction in key features of the active process toward the apex. For example, the gain decreased from 23 to 19 dB and tuning sharpness decreased from 2.5 to 1.4. Furthermore, we measured the frequency and intensity dependence of traveling wave properties. The phase velocity was larger than the group velocity, and both quantities gradually decrease from the base to the apex denoting a strong dispersion characteristic near the helicotrema. Moreover, we found that the spatial wavelength along the BM was highly level dependent in vivo, such that increasing the sound intensity from 30 to 90 dB sound pressure level increased the wavelength from 504 to 874 μm, a factor of 1.73. We hypothesize that this wavelength variation with sound intensity gives rise to an increase of the fluid-loaded mass on the BM and tunes its local resonance frequency. Together, these data demonstrate a strong interplay between the traveling wave propagation and amplification along the length of the cochlea.
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Affiliation(s)
- Amir Nankali
- Caruso Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles, California
| | - Christopher A Shera
- Caruso Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles, California; Department of Physics and Astronomy, University of Southern California, Los Angeles, California
| | - Brian E Applegate
- Caruso Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles, California
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head and Neck Surgery, University of Southern California, Los Angeles, California.
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27
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Unbalanced bidirectional radial stiffness gradients within the organ of Corti promoted by TRIOBP. Proc Natl Acad Sci U S A 2022; 119:e2115190119. [PMID: 35737845 PMCID: PMC9245700 DOI: 10.1073/pnas.2115190119] [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] [Indexed: 11/18/2022] Open
Abstract
Current understanding of cochlear mechanics assumes that stiffness of the cochlear partition varies only longitudinally along the cochlea. This work examines the stiffness of inner ear epithelium in individual cell types at the nanoscale level. We revealed unrecognized radial stiffness gradients of different magnitudes and opposite orientations within the epithelium. Remarkably, the observed bidirectional stiffness gradients are unbalanced between supporting and sensory cells. Deficiencies in deafness-associated Trio and F-actin binding protein (TRIOBP) caused diverse cytoskeletal ultrastructural remodeling in supporting and sensory cells and significantly diminishes the bidirectional radial stiffness gradients. These results demonstrate the complexity of the mechanical properties within the sensory epithelium and point to a hitherto unrecognized role of these gradients in sensitivity and frequency selectivity of hearing. Hearing depends on intricate morphologies and mechanical properties of diverse inner ear cell types. The individual contributions of various inner ear cell types into mechanical properties of the organ of Corti and the mechanisms of their integration are yet largely unknown. Using sub-100-nm spatial resolution atomic force microscopy (AFM), we mapped the Young’s modulus (stiffness) of the apical surface of the different cells of the freshly dissected P5–P6 cochlear epithelium from wild-type and mice lacking either Trio and F-actin binding protein (TRIOBP) isoforms 4 and 5 or isoform 5 only. Variants of TRIOBP are associated with deafness in human and in Triobp mutant mouse models. Remarkably, nanoscale AFM mapping revealed unrecognized bidirectional radial stiffness gradients of different magnitudes and opposite orientations between rows of wild-type supporting cells and sensory hair cells. Moreover, the observed bidirectional radial stiffness gradients are unbalanced, with sensory cells being stiffer overall compared to neighboring supporting cells. Deafness-associated TRIOBP deficiencies significantly disrupted the magnitude and orientation of these bidirectional radial stiffness gradients. In addition, serial sectioning with focused ion beam and backscatter scanning electron microscopy shows that a TRIOBP deficiency results in ultrastructural changes of supporting cell apical phalangeal microfilaments and bundled cortical F-actin of hair cell cuticular plates, correlating with messenger RNA and protein expression levels and AFM stiffness measurements that exposed a softening of the apical surface of the sensory epithelium in mutant mice. Altogether, this additional complexity in the mechanical properties of the sensory epithelium is hypothesized to be an essential contributor to frequency selectivity and sensitivity of mammalian hearing.
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28
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Monroy GL, Won J, Shi J, Hill MC, Porter RG, Novak MA, Hong W, Khampang P, Kerschner JE, Spillman DR, Boppart SA. Automated classification of otitis media with OCT: augmenting pediatric image datasets with gold-standard animal model data. BIOMEDICAL OPTICS EXPRESS 2022; 13:3601-3614. [PMID: 35781950 PMCID: PMC9208614 DOI: 10.1364/boe.453536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 03/28/2022] [Accepted: 05/12/2022] [Indexed: 06/15/2023]
Abstract
Otitis media (OM) is an extremely common disease that affects children worldwide. Optical coherence tomography (OCT) has emerged as a noninvasive diagnostic tool for OM, which can detect the presence and quantify the properties of middle ear fluid and biofilms. Here, the use of OCT data from the chinchilla, the gold-standard OM model for the human disease, is used to supplement a human image database to produce diagnostically relevant conclusions in a machine learning model. Statistical analysis shows the datatypes are compatible, with a blended-species model reaching ∼95% accuracy and F1 score, maintaining performance while additional human data is collected.
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Affiliation(s)
- Guillermo L. Monroy
- Beckman Institute for Advanced
Science and Technology, 405 N Mathews Ave, Urbana, IL
61801, USA
| | - Jungeun Won
- Beckman Institute for Advanced
Science and Technology, 405 N Mathews Ave, Urbana, IL
61801, USA
- Department of Bioengineering,
University of Illinois at Urbana-Champaign,
1406 W Green St, Urbana, IL 61801, USA
| | - Jindou Shi
- Beckman Institute for Advanced
Science and Technology, 405 N Mathews Ave, Urbana, IL
61801, USA
- Department of Electrical and Computer
Engineering, University of Illinois at
Urbana-Champaign, 306 N Wright St, Urbana, IL 61801,
USA
| | - Malcolm C. Hill
- Carle Foundation
Hospital, 611 W Park St., Urbana, IL 61801, USA
| | - Ryan G. Porter
- Carle Foundation
Hospital, 611 W Park St., Urbana, IL 61801, USA
- Carle Illinois College of Medicine,
University of Illinois at Urbana-Champaign,
506 S. Mathews Ave., Urbana, IL 61801, USA
| | - Michael A. Novak
- Carle Foundation
Hospital, 611 W Park St., Urbana, IL 61801, USA
- Carle Illinois College of Medicine,
University of Illinois at Urbana-Champaign,
506 S. Mathews Ave., Urbana, IL 61801, USA
| | - Wenzhou Hong
- Department of Otolaryngology and
Communication Sciences, Medical College of
Wisconsin, Milwaukee, WI 53226, USA
| | - Pawjai Khampang
- Department of Otolaryngology and
Communication Sciences, Medical College of
Wisconsin, Milwaukee, WI 53226, USA
| | - Joseph E. Kerschner
- Department of Otolaryngology and
Communication Sciences, Medical College of
Wisconsin, Milwaukee, WI 53226, USA
- Division of Otolaryngology and Pediatric
Otolaryngology, Medical College of
Wisconsin, Milwaukee, WI 53226, USA
| | - Darold R. Spillman
- Beckman Institute for Advanced
Science and Technology, 405 N Mathews Ave, Urbana, IL
61801, USA
| | - Stephen A. Boppart
- Beckman Institute for Advanced
Science and Technology, 405 N Mathews Ave, Urbana, IL
61801, USA
- Department of Bioengineering,
University of Illinois at Urbana-Champaign,
1406 W Green St, Urbana, IL 61801, USA
- Department of Electrical and Computer
Engineering, University of Illinois at
Urbana-Champaign, 306 N Wright St, Urbana, IL 61801,
USA
- Carle Illinois College of Medicine,
University of Illinois at Urbana-Champaign,
506 S. Mathews Ave., Urbana, IL 61801, USA
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29
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Cho NH, Wang H, Puria S. Cochlear Fluid Spaces and Structures of the Gerbil High-Frequency Region Measured Using Optical Coherence Tomography (OCT). J Assoc Res Otolaryngol 2022; 23:195-211. [PMID: 35194695 PMCID: PMC8964889 DOI: 10.1007/s10162-022-00836-4] [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: 05/19/2021] [Accepted: 01/04/2022] [Indexed: 10/19/2022] Open
Abstract
Since it has been difficult to directly observe the morphology of the living cochlea, our ability to infer the mechanical functioning of the living ear has been limited. Nearly all our knowledge about cochlear morphology comes from postmortem tissue that was fixed and processed using procedures that possibly distort the structures and fluid spaces of the organ of Corti. In this study, optical coherence tomography was employed to obtain volumetric images of the high-frequency hook region of the gerbil cochlea, as viewed through the round window, with far better resolution capability than had been possible before. The anatomical structures and fluid spaces of the organ of Corti were segmented and quantified in vivo and over a 90-min postmortem period. We find that the arcuate-zone and pectinate-zone widths change very little postmortem. The volume of the scala tympani between the round-window membrane and basilar membrane and the volume of the inner spiral sulcus decrease in the first 60-min postmortem. While textbook drawings of the mammalian organ of Corti and cortilymph prominently depict the tunnel of Corti, the outer tunnel is typically missing. This is likely because textbook drawings are typically made from images obtained by histological methods. Here, we show that the outer tunnel is nearly twice as big as the tunnel of Corti or the space of Nuel. This larger outer tunnel fluid space could have a substantial, little-appreciated effect on cochlear micromechanics. We speculate that the outer tunnel forms a resonant structure that may affect reticular-lamina motion.
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Affiliation(s)
- Nam Hyun Cho
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02114, USA
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114, USA
| | - Haobing Wang
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02114, USA
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114, USA
| | - Sunil Puria
- Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, 02114, USA.
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, MA, 02114, USA.
- Speech and Hearing Bioscience and Technology Program, Harvard University, Cambridge, MA, 02138, USA.
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30
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Kim W, Liu D, Kim S, Ratnayake K, Macias-Escriva F, Mattison S, Oghalai JS, Applegate BE. Vector of motion measurements in the living cochlea using a 3D OCT vibrometry system. BIOMEDICAL OPTICS EXPRESS 2022; 13:2542-2553. [PMID: 35519276 PMCID: PMC9045890 DOI: 10.1364/boe.451537] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 03/11/2022] [Accepted: 03/11/2022] [Indexed: 05/22/2023]
Abstract
Optical coherence tomography (OCT) has become an important tool for measuring the vibratory response of the living cochlea. It stands alone in its capacity to measure the intricate motion of the hearing organ through the surrounding otic capsule bone. Nevertheless, as an extension of phase-sensitive OCT, it is only capable of measuring motion along the optical axis. Hence, measurements are 1-D. To overcome this limitation and provide a measure of the 3-D vector of motion in the cochlea, we developed an OCT system with three sample arms in a single interferometer. Taking advantage of the long coherence length of our swept laser, we depth (frequency) encode the three channels. An algorithm to depth decode and coregister the three channels is followed by a coordinate transformation that takes the vibrational data from the experimental coordinate system to Cartesian or spherical polar coordinates. The system was validated using a piezo as a known vibrating element that could be positioned at various angles. The angular measurement on the piezo was shown to have an RMSE of ≤ 0.30° (5.2 mrad) with a standard deviation of the amplitude of ≤ 120 pm. Finally, we demonstrate the system for in vivo imaging by measuring the vector of motion over a volume image in the apex of the mouse cochlea.
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Affiliation(s)
- Wihan Kim
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033, USA
- Contributed equally
| | - Derek Liu
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033, USA
- Contributed equally
| | - Sangmin Kim
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Kumara Ratnayake
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033, USA
| | - Frank Macias-Escriva
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033, USA
| | - Scott Mattison
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA
- Current address: Department of Engineering and Physics, University of Central Oklahoma, Edmond, OK 73034, USA
| | - John S. Oghalai
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033, USA
| | - Brian E. Applegate
- Caruso Department of Otolaryngology - Head and Neck Surgery, University of Southern California, Los Angeles, CA 90033, USA
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA. 90089, USA
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31
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Perez-Flores MC, Verschooten E, Lee JH, Kim HJ, Joris PX, Yamoah EN. Intrinsic mechanical sensitivity of mammalian auditory neurons as a contributor to sound-driven neural activity. eLife 2022; 11:74948. [PMID: 35266451 PMCID: PMC8942473 DOI: 10.7554/elife.74948] [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: 10/22/2021] [Accepted: 03/09/2022] [Indexed: 11/18/2022] Open
Abstract
Mechanosensation – by which mechanical stimuli are converted into a neuronal signal – is the basis for the sensory systems of hearing, balance, and touch. Mechanosensation is unmatched in speed and its diverse range of sensitivities, reaching its highest temporal limits with the sense of hearing; however, hair cells (HCs) and the auditory nerve (AN) serve as obligatory bottlenecks for sounds to engage the brain. Like other sensory neurons, auditory neurons use the canonical pathway for neurotransmission and millisecond-duration action potentials (APs). How the auditory system utilizes the relatively slow transmission mechanisms to achieve ultrafast speed, and high audio-frequency hearing remains an enigma. Here, we address this paradox and report that the mouse, and chinchilla, AN are mechanically sensitive, and minute mechanical displacement profoundly affects its response properties. Sound-mimicking sinusoidal mechanical and electrical current stimuli affect phase-locked responses. In a phase-dependent manner, the two stimuli can also evoke suppressive responses. We propose that mechanical sensitivity interacts with synaptic responses to shape responses in the AN, including frequency tuning and temporal phase locking. Combining neurotransmission and mechanical sensation to control spike patterns gives the mammalian AN a secondary receptor role, an emerging theme in primary neuronal functions.
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Affiliation(s)
| | - Eric Verschooten
- Laboratory of Auditory Neurophysiology, University of Leuven, Leuven, Belgium
| | | | | | - Philip X Joris
- Laboratory of Auditory Neurophysiology, University of Leuven, Leuven, Belgium
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32
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In vivo real-time imaging reveals megalin as the aminoglycoside gentamicin transporter into cochlea whose inhibition is otoprotective. Proc Natl Acad Sci U S A 2022; 119:2117946119. [PMID: 35197290 PMCID: PMC8892513 DOI: 10.1073/pnas.2117946119] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2022] [Indexed: 01/01/2023] Open
Abstract
Aminoglycosides (AGs) are commonly used antibiotics that cause deafness through the irreversible loss of cochlear sensory hair cells (HCs). How AGs enter the cochlea and then target HCs remains unresolved. Here, we performed time-lapse multicellular imaging of cochlea in live adult hearing mice via a chemo-mechanical cochleostomy. The in vivo tracking revealed that systemically administered Texas Red-labeled gentamicin (GTTR) enters the cochlea via the stria vascularis and then HCs selectively. GTTR uptake into HCs was completely abolished in transmembrane channel-like protein 1 (TMC1) knockout mice, indicating mechanotransducer channel-dependent AG uptake. Blockage of megalin, the candidate AG transporter in the stria vascularis, by binding competitor cilastatin prevented GTTR accumulation in HCs. Furthermore, cilastatin treatment markedly reduced AG-induced HC degeneration and hearing loss in vivo. Together, our in vivo real-time tracking of megalin-dependent AG transport across the blood-labyrinth barrier identifies new therapeutic targets for preventing AG-induced ototoxicity.
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33
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Frost BL, Strimbu CE, Olson ES. Using volumetric optical coherence tomography to achieve spatially resolved organ of Corti vibration measurements. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 151:1115. [PMID: 35232061 PMCID: PMC8853734 DOI: 10.1121/10.0009576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 01/03/2022] [Accepted: 01/26/2022] [Indexed: 05/22/2023]
Abstract
Optical coherence tomography (OCT) has become a powerful tool for measuring vibrations within the organ of Corti complex (OCC) in cochlear mechanics experiments. However, the one-dimensional nature of OCT measurements, combined with experimental and anatomical constraints, make these data ambiguous: Both the relative positions of measured structures and their orientation relative to the direction of measured vibrations are not known a priori. We present a method by which these measurement features can be determined via the use of a volumetric OCT scan to determine the relationship between the imaging/measurement axes and the canonical anatomical axes. We provide evidence that the method is functional by replicating previously measured radial vibration patterns of the basilar membrane (BM). We used the method to compare outer hair cell and BM vibration phase in the same anatomical cross section (but different optical cross sections), and found that outer hair cell region vibrations lead those of the BM across the entire measured frequency range. In contrast, a phase lead is only present at low frequencies in measurements taken within a single optical cross section. Relative phase is critical to the workings of the cochlea, and these results emphasize the importance of anatomically oriented measurement and analysis.
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Affiliation(s)
- Brian L Frost
- Department of Electrical Engineering, Columbia University, 500 W. 120th St., Mudd 1310, New York, New York 1002, USA
| | - Clark Elliott Strimbu
- Department of Otolaryngology Head and Neck Surgery, Vagelos College of Physicians and Surgeons, Columbia University, 630 W. 168th St., New York, New York 10032, USA
| | - Elizabeth S Olson
- Department of Otolaryngology Head and Neck Surgery, Vagelos College of Physicians and Surgeons, Columbia University, 630 W. 168th St., New York, New York 10032, USA
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34
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Ashmore JF. On Bottlenecks, Helmholtz and Hearing. FUNCTION (OXFORD, ENGLAND) 2021; 3:zqab068. [PMID: 35402920 PMCID: PMC8991014 DOI: 10.1093/function/zqab068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 12/17/2021] [Accepted: 12/20/2021] [Indexed: 01/07/2023]
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35
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Burwood G, He WX, Fridberger A, Ren TY, Nuttall AL. Outer hair cell driven reticular lamina mechanical distortion in living cochleae. Hear Res 2021; 423:108405. [PMID: 34916081 DOI: 10.1016/j.heares.2021.108405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 10/25/2021] [Accepted: 11/25/2021] [Indexed: 11/17/2022]
Abstract
Cochlear distortions afford researchers and clinicians a glimpse into the conditions and properties of inner ear signal processing mechanisms. Until recently, our examination of these distortions has been limited to measuring the vibration of the basilar membrane or recording acoustic distortion output in the ear canal. Despite its importance, the generation mechanism of cochlear distortion remains a substantial task to understand. The ability to measure the vibration of the reticular lamina in rodent models is a recent experimental advance. Surprising mechanical properties have been revealed. These properties merit both discussion in context with our current understanding of distortion, and appraisal of the significance of new interpretations of cochlear mechanics. This review focusses on some of the recent data from our research groups and discusses the implications of these data on our understanding of vocalization processing in the periphery, and their influence upon future experimental directions. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam.
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Affiliation(s)
- G Burwood
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States
| | - W X He
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States
| | - A Fridberger
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - T Y Ren
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States
| | - A L Nuttall
- Department of Otolaryngology, Head and Neck Surgery, Oregon Health & Science University, Portland OR, United States.
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36
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Badash I, Quiñones PM, Oghalai KJ, Wang J, Lui CG, Macias-Escriva F, Applegate BE, Oghalai JS. Endolymphatic Hydrops is a Marker of Synaptopathy Following Traumatic Noise Exposure. Front Cell Dev Biol 2021; 9:747870. [PMID: 34805158 PMCID: PMC8602199 DOI: 10.3389/fcell.2021.747870] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 10/20/2021] [Indexed: 12/28/2022] Open
Abstract
After acoustic trauma, there can be loss of synaptic connections between inner hair cells and auditory neurons in the cochlea, which may lead to hearing abnormalities including speech-in-noise difficulties, tinnitus, and hyperacusis. We have previously studied mice with blast-induced cochlear synaptopathy and found that they also developed a build-up of endolymph, termed endolymphatic hydrops. In this study, we used optical coherence tomography to measure endolymph volume in live CBA/CaJ mice exposed to various noise intensities. We quantified the number of synaptic ribbons and postsynaptic densities under the inner hair cells 1 week after noise exposure to determine if they correlated with acute changes in endolymph volume measured in the hours after the noise exposure. After 2 h of noise at an intensity of 95 dB SPL or below, both endolymph volume and synaptic counts remained normal. After exposure to 2 h of 100 dB SPL noise, mice developed endolymphatic hydrops and had reduced synaptic counts in the basal and middle regions of the cochlea. Furthermore, round-window application of hypertonic saline reduced the degree of endolymphatic hydrops that developed after 100 dB SPL noise exposure and partially prevented the reduction in synaptic counts in the cochlear base. Taken together, these results indicate that endolymphatic hydrops correlates with noise-induced cochlear synaptopathy, suggesting that these two pathologic findings have a common mechanistic basis.
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Affiliation(s)
- Ido Badash
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Patricia M Quiñones
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Kevin J Oghalai
- Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States
| | - Juemei Wang
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Christopher G Lui
- Department of Otolaryngology-Head and Neck Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Frank Macias-Escriva
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Brian E Applegate
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States.,Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States.,Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States
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37
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Cochlear outer hair cell electromotility enhances organ of Corti motion on a cycle-by-cycle basis at high frequencies in vivo. Proc Natl Acad Sci U S A 2021; 118:2025206118. [PMID: 34686590 DOI: 10.1073/pnas.2025206118] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2021] [Indexed: 11/18/2022] Open
Abstract
Mammalian hearing depends on an amplification process involving prestin, a voltage-sensitive motor protein that enables cochlear outer hair cells (OHCs) to change length and generate force. However, it has been questioned whether this prestin-based somatic electromotility can operate fast enough in vivo to amplify cochlear vibrations at the high frequencies that mammals hear. In this study, we measured sound-evoked vibrations from within the living mouse cochlea and found that the top and bottom of the OHCs move in opposite directions at frequencies exceeding 20 kHz, consistent with fast somatic length changes. These motions are physiologically vulnerable, depend on prestin, and dominate the cochlea's vibratory response to high-frequency sound. This dominance was observed despite mechanisms that clearly low-pass filter the in vivo electromotile response. Low-pass filtering therefore does not critically limit the OHC's ability to move the organ of Corti on a cycle-by-cycle basis. Our data argue that electromotility serves as the primary high-frequency amplifying mechanism within the mammalian cochlea.
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38
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Berger J, Rubinstein J. A flexible anatomical set of mechanical models for the organ of Corti. ROYAL SOCIETY OPEN SCIENCE 2021; 8:210016. [PMID: 34540242 PMCID: PMC8441134 DOI: 10.1098/rsos.210016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 08/23/2021] [Indexed: 06/13/2023]
Abstract
We build a flexible platform to study the mechanical operation of the organ of Corti (OoC) in the transduction of basilar membrane (BM) vibrations to oscillations of an inner hair cell bundle (IHB). The anatomical components that we consider are the outer hair cells (OHCs), the outer hair cell bundles, Deiters cells, Hensen cells, the IHB and various sections of the reticular lamina. In each of the components we apply Newton's equations of motion. The components are coupled to each other and are further coupled to the endolymph fluid motion in the subtectorial gap. This allows us to obtain the forces acting on the IHB, and thus study its motion as a function of the parameters of the different components. Some of the components include a nonlinear mechanical response. We find that slight bending of the apical ends of the OHCs can have a significant impact on the passage of motion from the BM to the IHB, including critical oscillator behaviour. In particular, our model implies that the components of the OoC could cooperate to enhance frequency selectivity, amplitude compression and signal to noise ratio in the passage from the BM to the IHB. Since the model is modular, it is easy to modify the assumptions and parameters for each component.
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Affiliation(s)
- Jorge Berger
- Department of Physics and Optical Engineering, Ort Braude College, Karmiel, Israel
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39
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Wang Y, Steele CR, Puria S, Ricci AJ. In situ motions of individual inner-hair-cell stereocilia from stapes stimulation in adult mice. Commun Biol 2021; 4:958. [PMID: 34381157 PMCID: PMC8357788 DOI: 10.1038/s42003-021-02459-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 07/12/2021] [Indexed: 11/09/2022] Open
Abstract
In vertebrate hearing organs, mechanical vibrations are converted to ionic currents through mechanoelectrical-transduction (MET) channels. Concerted stereocilia motion produces an ensemble MET current driving the hair-cell receptor potential. Mammalian cochleae are unique in that the tuning of sensory cells is determined by their mechanical environment and the mode of hair-bundle stimulation that their environment creates. However, little is known about the in situ intra-hair-bundle motions of stereocilia relative to one another, or to their environment. In this study, high-speed imaging allowed the stereocilium and cell-body motions of inner hair cells to be monitored in an ex vivo organ of Corti (OoC) mouse preparation. We have found that the OoC rotates about the base of the inner pillar cell, the hair bundle rotates about its base and lags behind the motion of the apical surface of the cell, and the individual stereocilia move semi-independently within a given hair bundle.
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Affiliation(s)
- Yanli Wang
- Otolaryngology-HNS, Stanford University, Stanford, CA, USA
- Mechanical Engineering, Stanford University, Stanford, CA, USA
- Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA
| | | | - Sunil Puria
- Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA
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40
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Model of cochlear microphonic explores the tuning and magnitude of hair cell transduction current. Biophys J 2021; 120:3550-3565. [PMID: 34384762 DOI: 10.1016/j.bpj.2021.08.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 06/24/2021] [Accepted: 08/04/2021] [Indexed: 11/20/2022] Open
Abstract
The mammalian cochlea relies on the active forcing of sensory outer hair cells (OHCs) to amplify traveling wave responses along the basilar membrane. These forces are the result of electromotility, wherein current through the OHCs leads to conformational changes in the cells that provide stresses on surrounding structures. OHC transducer current can be detected via the voltage in the scala tympani (the cochlear microphonic, CM), and the CM can be used as an indicator of healthy cochlear operation. The CM represents a summation of OHC currents (the inner hair cell contribution is known to be small) and to use CM to probe the properties of OHC transduction requires a model that simulates that summation. We developed a finite element model for that purpose. The pattern of current generators (the model input) was initially based on basilar membrane displacement, with the current size based on in vitro data. The model was able to reproduce the amplitude of experimental CM results reasonably well when the input tuning was enhanced slightly (peak increased by ∼6 dB), which can be regarded as additional hair bundle tuning, and with a current/input value of 200-260 pA/nm, which is ∼4 times greater than the largest in vitro measures.
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41
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Lui CG, Kim W, Dewey JB, Macías-Escrivá FD, Ratnayake K, Oghalai JS, Applegate BE. In vivo functional imaging of the human middle ear with a hand-held optical coherence tomography device. BIOMEDICAL OPTICS EXPRESS 2021; 12:5196-5213. [PMID: 34513251 PMCID: PMC8407818 DOI: 10.1364/boe.430935] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 07/02/2021] [Accepted: 07/06/2021] [Indexed: 06/13/2023]
Abstract
We describe an optical coherence tomography and vibrometry system designed for portable hand-held usage in the otology clinic on awake patients. The system provides clinically relevant point-of-care morphological imaging with 14-44 µm resolution and functional vibratory measures with sub-nanometer sensitivity. We evaluated various new approaches for extracting functional information including a multi-tone stimulus, a continuous chirp stimulus, and alternating air and bone stimulus. We also explored the vibratory response over an area of the tympanic membrane (TM) and generated TM thickness maps. Our results suggest that the system can provide real-time in vivo imaging and vibrometry of the ear and could prove useful for investigating otologic pathology in the clinic setting.
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Affiliation(s)
- Christopher G. Lui
- Department of Otolaryngology - Head and Neck Surgery, Keck School of Medicine, University of Southern California, 1450 San Pablo Street, Suite 5708, Los Angeles, CA 90033, USA
- These authors contributed equally to this work
| | - Wihan Kim
- Department of Otolaryngology - Head and Neck Surgery, Keck School of Medicine, University of Southern California, 1450 San Pablo Street, Suite 5708, Los Angeles, CA 90033, USA
- These authors contributed equally to this work
| | - James B. Dewey
- Department of Otolaryngology - Head and Neck Surgery, Keck School of Medicine, University of Southern California, 1450 San Pablo Street, Suite 5708, Los Angeles, CA 90033, USA
| | - Frank D. Macías-Escrivá
- Department of Otolaryngology - Head and Neck Surgery, Keck School of Medicine, University of Southern California, 1450 San Pablo Street, Suite 5708, Los Angeles, CA 90033, USA
| | - Kumara Ratnayake
- Department of Otolaryngology - Head and Neck Surgery, Keck School of Medicine, University of Southern California, 1450 San Pablo Street, Suite 5708, Los Angeles, CA 90033, USA
| | - John S. Oghalai
- Department of Otolaryngology - Head and Neck Surgery, Keck School of Medicine, University of Southern California, 1450 San Pablo Street, Suite 5708, Los Angeles, CA 90033, USA
| | - Brian E. Applegate
- Department of Otolaryngology - Head and Neck Surgery, Keck School of Medicine, University of Southern California, 1450 San Pablo Street, Suite 5708, Los Angeles, CA 90033, USA
- Department of Biomedical Engineering, University of Southern California, 1042 Downey Way, Denney Research Center (DRB) 140, Los Angeles, CA 90089, USA
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Sharma GK, Chen LY, Chou L, Badger C, Hong E, Rangarajan S, Chang TH, Armstrong WB, Verma SP, Chen Z, Ramalingam R, Wong BJF. Surface kinematic and depth-resolved analysis of human vocal folds in vivo during phonation using optical coherence tomography. JOURNAL OF BIOMEDICAL OPTICS 2021; 26:JBO-210125R. [PMID: 34414705 PMCID: PMC8374544 DOI: 10.1117/1.jbo.26.8.086005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 07/26/2021] [Indexed: 05/30/2023]
Abstract
SIGNIFICANCE The human vocal fold (VF) oscillates in multiple vectors and consists of distinct layers with varying viscoelastic properties that contribute to the mucosal wave. Office-based and operative laryngeal endoscopy are limited to diagnostic evaluation of the VF epithelial surface only and are restricted to axial-plane characterization of the horizontal mucosal wave. As such, understanding of the biomechanics of human VF motion remains limited. AIM Optical coherence tomography (OCT) is a micrometer-resolution, high-speed endoscopic imaging modality which acquires cross-sectional images of tissue. Our study aimed to leverage OCT technology and develop quantitative methods for analyzing the anatomy and kinematics of in vivo VF motion in the coronal plane. APPROACH A custom handheld laryngeal stage was used to capture OCT images with 800 A-lines at 250 Hz. Automated image postprocessing and analytical methods were developed. RESULTS Novel kinematic analysis of in vivo, long-range OCT imaging of the vibrating VF in awake human subjects is reported. Cross-sectional, coronal-plane panoramic videos of the larynx during phonation are presented with three-dimensional videokymographic and space-time velocity analysis of VF motion. CONCLUSIONS Long-range OCT with automated computational methods allows for cross-sectional dynamic laryngeal imaging and has the potential to broaden our understanding of human VF biomechanics and sound production.
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Affiliation(s)
- Giriraj K. Sharma
- University of California, Irvine Medical Center, Department of Otolaryngology–Head and Neck Surgery, Irvine, California, United States
- University of California, Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Lily Y. Chen
- University of California, Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | - Lidek Chou
- OCT Medical Imaging, Inc., Irvine, California, United States
| | - Christopher Badger
- University of California, Irvine, School of Medicine, Irvine, California, United States
| | - Ellen Hong
- University of California, Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
| | | | | | - William B. Armstrong
- University of California, Irvine Medical Center, Department of Otolaryngology–Head and Neck Surgery, Irvine, California, United States
| | - Sunil P. Verma
- University of California, Irvine Medical Center, Department of Otolaryngology–Head and Neck Surgery, Irvine, California, United States
| | - Zhongping Chen
- University of California, Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
- University of California, Irvine, Department of Biomedical Engineering, Irvine, California, United States
| | - Ram Ramalingam
- OCT Medical Imaging, Inc., Irvine, California, United States
| | - Brian J.-F. Wong
- University of California, Irvine Medical Center, Department of Otolaryngology–Head and Neck Surgery, Irvine, California, United States
- University of California, Irvine, Beckman Laser Institute and Medical Clinic, Irvine, California, United States
- University of California, Irvine, Department of Biomedical Engineering, Irvine, California, 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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Motallebzadeh H, Puria S. Mouse middle-ear forward and reverse acoustics. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 149:2711. [PMID: 33940924 PMCID: PMC8060050 DOI: 10.1121/10.0004218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 05/26/2023]
Abstract
The mouse is an important animal model for hearing science. However, our knowledge of the relationship between mouse middle-ear (ME) anatomy and function is limited. The ME not only transmits sound to the cochlea in the forward direction, it also transmits otoacoustic emissions generated in the cochlea to the ear canal (EC) in the reverse direction. Due to experimental limitations, a complete characterization of the mouse ME has not been possible. A fully coupled finite-element model of the mouse EC, ME, and cochlea was developed and calibrated against experimental measurements. Impedances of the EC, ME, and cochlea were calculated, alongside pressure transfer functions for the forward, reverse, and round-trip directions. The effects on sound transmission of anatomical changes such as removing the ME cavity, pars flaccida, and mallear orbicular apophysis were also calculated. Surprisingly, below 10 kHz, the ME cavity, eardrum, and stapes annular ligament were found to significantly affect the cochlear input impedance, which is a result of acoustic coupling through the round window. The orbicular apophysis increases the delay of the transmission line formed by the flexible malleus, incus, and stapes, and improves the forward sound-transmission characteristics in the frequency region of 7-30 kHz.
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Affiliation(s)
- Hamid Motallebzadeh
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114, USA
| | - Sunil Puria
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts 02114, USA
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Cochlear development, cellular patterning and tonotopy. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.09.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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46
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Altoè A, Shera CA. The cochlear ear horn: geometric origin of tonotopic variations in auditory signal processing. Sci Rep 2020; 10:20528. [PMID: 33239701 PMCID: PMC7689495 DOI: 10.1038/s41598-020-77042-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 11/03/2020] [Indexed: 11/08/2022] Open
Abstract
While separating sounds into frequency components and subsequently converting them into patterns of neural firing, the mammalian cochlea processes signal components in ways that depend strongly on frequency. Indeed, both the temporal structure of the response to transient stimuli and the sharpness of frequency tuning differ dramatically between the apical and basal (i.e., the low- and high-frequency) regions of the cochlea. Although the mechanisms that give rise to these pronounced differences remain incompletely understood, they are generally attributed to tonotopic variations in the constituent hair cells or cytoarchitecture of the organ of Corti. As counterpoint to this view, we present a general acoustic treatment of the horn-like geometry of the cochlea, accompanied by a simple 3-D model to elucidate the theoretical predictions. We show that the main apical/basal functional differences can be accounted for by the known spatial gradients of cochlear dimensions, without the need to invoke mechanical specializations of the sensory tissue. Furthermore, our analysis demonstrates that through its functional resemblance to an ear horn (aka ear trumpet), the geometry of the cochlear duct manifests tapering symmetry, a felicitous design principle that may have evolved not only to aid the analysis of natural sounds but to enhance the sensitivity of hearing.
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Affiliation(s)
- Alessandro Altoè
- 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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Olson ES, Strimbu CE. Cochlear mechanics: new insights from vibrometry and Optical Coherence Tomography. CURRENT OPINION IN PHYSIOLOGY 2020; 18:56-62. [PMID: 33103018 DOI: 10.1016/j.cophys.2020.08.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The cochlea is a complex biological machine that transduces sound-induced mechanical vibrations to neural signals. Hair cells within the sensory tissue of the cochlea transduce vibrations into electrical signals, and exert electromechanical feedback that enhances the passive frequency separation provided by the cochlea's traveling wave mechanics; this enhancement is termed cochlear amplification. The vibration of the sensory tissue has been studied with many techniques, and the current state of the art is optical coherence tomography (OCT). The OCT technique allows for motion of intra-organ structures to be measured in vivo at many layers within the sensory tissue, at several angles and in previously under-explored species. OCT-based observations are already impacting our understanding of hair cell excitation and cochlear amplification.
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Affiliation(s)
- Elizabeth S Olson
- Department of Otolaryngolgy Head and Neck Surgery, Vagelos College of Physicians and Surgeons, Columbia University, 630 W 168th St, New York, NY 10032.,Department Biomedical Engineering, Columbia University, 351 Engineering Terrace, 1210 Amsterdam Avenue,New York, NY 10027
| | - C Elliott Strimbu
- Department of Otolaryngolgy Head and Neck Surgery, Vagelos College of Physicians and Surgeons, Columbia University, 630 W 168th St, New York, NY 10032
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48
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Strimbu CE, Wang Y, Olson ES. Manipulation of the Endocochlear Potential Reveals Two Distinct Types of Cochlear Nonlinearity. Biophys J 2020; 119:2087-2101. [PMID: 33091378 DOI: 10.1016/j.bpj.2020.10.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 09/02/2020] [Accepted: 10/07/2020] [Indexed: 11/26/2022] Open
Abstract
The mammalian hearing organ, the cochlea, contains an active amplifier to boost the vibrational response to low level sounds. Hallmarks of this active process are sharp location-dependent frequency tuning and compressive nonlinearity over a wide stimulus range. The amplifier relies on outer hair cell (OHC)-generated forces driven in part by the endocochlear potential, the ∼+80 mV potential maintained in scala media, generated by the stria vascularis. We transiently eliminated the endocochlear potential in vivo by an intravenous injection of furosemide and measured the vibrations of different layers in the cochlea's organ of Corti using optical coherence tomography. Distortion product otoacoustic emissions were also monitored. After furosemide injection, the vibrations of the basilar membrane lost the best frequency (BF) peak and showed broad tuning similar to a passive cochlea. The intra-organ of Corti vibrations measured in the region of the OHCs lost the BF peak and showed low-pass responses but retained nonlinearity. This strongly suggests that OHC electromotility was operating and being driven by nonlinear OHC current. Thus, although electromotility is presumably necessary to produce a healthy BF peak, the mere presence of electromotility is not sufficient. The BF peak recovered nearly fully within 2 h, along with the recovery of odd-order distortion product otoacoustic emissions. The recovery pattern suggests that physical shifts in operating condition are a critical step in the recovery process.
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Affiliation(s)
- C Elliott Strimbu
- Columbia University Medical Center, Department of Otolaryngology, New York, New York
| | - Yi Wang
- Columbia University, Department of Biomedical Engineering, New York, New York
| | - Elizabeth S Olson
- Columbia University Medical Center, Department of Otolaryngology, New York, New York; Columbia University, Department of Biomedical Engineering, New York, New York.
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49
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Nankali A, Wang Y, Strimbu CE, Olson ES, Grosh K. A role for tectorial membrane mechanics in activating the cochlear amplifier. Sci Rep 2020; 10:17620. [PMID: 33077807 PMCID: PMC7573614 DOI: 10.1038/s41598-020-73873-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 09/21/2020] [Indexed: 12/02/2022] Open
Abstract
The mechanical and electrical responses of the mammalian cochlea to acoustic stimuli are nonlinear and highly tuned in frequency. This is due to the electromechanical properties of cochlear outer hair cells (OHCs). At each location along the cochlear spiral, the OHCs mediate an active process in which the sensory tissue motion is enhanced at frequencies close to the most sensitive frequency (called the characteristic frequency, CF). Previous experimental results showed an approximate 0.3 cycle phase shift in the OHC-generated extracellular voltage relative the basilar membrane displacement, which was initiated at a frequency approximately one-half octave lower than the CF. Findings in the present paper reinforce that result. This shift is significant because it brings the phase of the OHC-derived electromotile force near to that of the basilar membrane velocity at frequencies above the shift, thereby enabling the transfer of electrical to mechanical power at the basilar membrane. In order to seek a candidate physical mechanism for this phenomenon, we used a comprehensive electromechanical mathematical model of the cochlear response to sound. The model predicts the phase shift in the extracellular voltage referenced to the basilar membrane at a frequency approximately one-half octave below CF, in accordance with the experimental data. In the model, this feature arises from a minimum in the radial impedance of the tectorial membrane and its limbal attachment. These experimental and theoretical results are consistent with the hypothesis that a tectorial membrane resonance introduces the correct phasing between mechanical and electrical responses for power generation, effectively turning on the cochlear amplifier.
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Affiliation(s)
- Amir Nankali
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Yi Wang
- Biomedical Engineering, Columbia University, New York, NY, USA
| | | | - Elizabeth S Olson
- Otolaryngology, Head and Neck Surgery, Columbia University, New York, NY, USA.,Biomedical Engineering, Columbia University, New York, NY, USA
| | - Karl Grosh
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA. .,Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
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50
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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 PMCID: PMC7502208 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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