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Lee S, Motegi M, Koike T. Effectiveness of active middle ear implant placement methods in pathological conditions: basilar membrane vibration simulation. Front Neurol 2024; 15:1417711. [PMID: 39175763 PMCID: PMC11339716 DOI: 10.3389/fneur.2024.1417711] [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: 05/22/2024] [Accepted: 07/24/2024] [Indexed: 08/24/2024] Open
Abstract
Active middle ear implants (AMEI) amplify mechanical vibrations in the middle ear and transmit them to the cochlea. The AMEI includes a floating mass transducer (FMT) that can be placed using two different surgical approaches: "oval window (OW) vibroplasty" and "round window (RW) vibroplasty." The OW and RW are windows located on the cochlea. Normally, sound stimulus is transmitted from the middle ear to cochlea via the OW. RW vibroplasty has been suggested as an alternative method due to the difficulty of applying OW vibroplasty in patients with ossicle dysfunction. Several reports compare the advantages of each approach through pre and postoperative hearing tests. However, quantitatively assessing the treatment effect is challenging due to individual differences in pathologies. This study investigates the vibration transmission efficiency of each surgical approach using a finite-element model of the human cochlea. Vibration of the basilar membrane (BM) of the cochlea is simulated by applying the stimulus through the OW or RW. Pathological conditions, such as impaired stapes mobility, are simulated by increasing the stiffness of the stapedial annular ligament. RW closure due to chronic middle ear diseases is a common clinical occurrence and is simulated by increasing the stiffness of the RW membrane in the model. The results show that the vibration amplitude of the BM is larger when the stimulus is applied to the RW compared to the OW, except for cases of RW membrane ossification. The difference in these amplitudes is particularly significant when stapedial mobility is limited. These results suggest that RW vibroplasty would be advantageous, especially in cases of accompanying stapedial mobility impairment. Additionally, it is suggested that transitioning to OW vibroplasty could still ensure a sufficient level of vibratory transmission efficiency when placing the FMT on the RW membrane is difficult due to anatomical problems in the tympanic cavity or confirmed severe pathological conditions around the RW.
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Affiliation(s)
- Sinyoung Lee
- Department of Mechanical Engineering, Faculty of Engineering, Graduate Faculty of Interdisciplinary Research, University of Yamanashi, Yamanashi, Japan
| | - Masaomi Motegi
- Department of Otolaryngology-Head and Neck Surgery, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Takuji Koike
- Department of Mechanical and Intelligent Systems Engineering, Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo, Japan
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2
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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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3
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Vaden KI, Neely ST, Harris SE, Dubno JR. Metabolic and Sensory Components of Age-Related Hearing Loss: Associations With Distortion- and Reflection-Based Otoacoustic Emissions. Trends Hear 2023; 27:23312165231213776. [PMID: 37969007 PMCID: PMC10655661 DOI: 10.1177/23312165231213776] [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: 05/18/2023] [Revised: 10/25/2023] [Accepted: 10/26/2023] [Indexed: 11/17/2023] Open
Abstract
Age-related hearing loss is difficult to study in humans because multiple genetic and environmental risk factors may contribute to pathology and cochlear function declines in older adults. These pathologies, including degeneration of the stria vascularis, are hypothesized to affect outer hair cells responsible for active cochlear amplification of low-level sounds. Otoacoustic emission (OAE) measures are used to quantify the energy added to the traveling wave in cochlear amplification, which typically weakens with increased pure-tone thresholds and for older individuals. Thus, the current study evaluated two OAE measures for individuals with different components of age-related hearing loss. We examined two retrospective adult lifespan datasets (18 to 89+ years of age) from independent sites (Medical University of South Carolina and Boys Town National Research Hospital), which included demographics, noise history questionnaires, distortion-product otoacoustic emissions (DPOAE), and cochlear reflectance (CR). Metabolic and sensory estimates of age-related hearing loss were derived from the audiograms in each dataset, and then tested for associations with DPOAE and CR. The results showed that metabolic estimates increased for older participants and were associated with lower overall DPOAE and CR magnitudes across frequency (i.e., lower fitted intercepts). Sensory estimates were significantly higher for males, who reported more positive noise histories compared to females and were associated with steeper negative across-frequency slopes for DPOAEs. Although significant associations were observed between OAE configurations, DPOAEs appeared uniquely sensitive to metabolic estimates. The current findings suggest that distortion-based measures may provide greater sensitivity than reflection-based measures to the components of age-related hearing loss.
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Affiliation(s)
- Kenneth I. Vaden
- Department of Otolaryngology – Head & Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
| | - Stephen T. Neely
- Center for Hearing Research, Boys Town National Research Hospital, Omaha, NE, USA
| | - Sara E. Harris
- Center for Hearing Research, Boys Town National Research Hospital, Omaha, NE, USA
| | - Judy R. Dubno
- Department of Otolaryngology – Head & Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
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4
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Vaden KI, Eckert MA, Matthews LJ, Schmiedt RA, Dubno JR. Metabolic and Sensory Components of Age-Related Hearing Loss. J Assoc Res Otolaryngol 2022; 23:253-272. [PMID: 35064426 PMCID: PMC8964894 DOI: 10.1007/s10162-021-00826-y] [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: 02/23/2021] [Accepted: 11/23/2021] [Indexed: 12/01/2022] Open
Abstract
Age-related hearing loss is a multifactorial condition with effects of aging and environmental exposures that contribute to cochlear pathologies. Metabolic hearing loss involves declines in the endocochlear potential, which broadly reduce cochlear amplification of low-level sounds. Sensory hearing loss involves damage to outer hair cells that may eliminate amplification, especially for high-frequency sounds. A novel approach was developed to estimate the extent of metabolic and sensory components (in dB) for an individual, by combining hearing loss profiles to optimally approximate their hearing thresholds (audiogram). This approach was validated using estimates of metabolic and sensory hearing loss from retrospective datasets including gerbils, cross-sectional and longitudinal audiograms from older adults, a measure of speech recognition in noise, and histopathology case reports. Simulation results showed that well-approximated audiograms can produce accurate metabolic and sensory estimates. Estimates of metabolic and sensory components of age-related hearing loss differentiated gerbils with known strial and/or sensory pathologies based on age and exposures. For older adults, metabolic estimates consistently increased with age and were associated with poorer speech recognition in noise, while sensory estimates were related to sex and noise exposure differences. Histopathology case reports (with audiograms) that described strial and outer hair cell pathology in temporal bones from older donors showed significant differences in metabolic and sensory estimates, respectively. The results support the view that audiograms include information that can be used to estimate the metabolic and sensory components of age-related hearing loss.
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Affiliation(s)
- Kenneth I. Vaden
- Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, SC 29425-5500 USA
| | - Mark A. Eckert
- Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, SC 29425-5500 USA
| | - Lois J. Matthews
- Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, SC 29425-5500 USA
| | - Richard A. Schmiedt
- Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, SC 29425-5500 USA
| | - Judy R. Dubno
- Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, SC 29425-5500 USA
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5
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Heinrich UR, Schmidtmann I, Meuser R, Ernst BP, Wünsch D, Siemer S, Gribko A, Stauber RH, Strieth S. Early Alterations of Endothelial Nitric Oxide Synthase Expression Patterns in the Guinea Pig Cochlea After Noise Exposure. J Histochem Cytochem 2019; 67:845-855. [PMID: 31510846 DOI: 10.1369/0022155419876644] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Constitutively expressed endothelial nitric oxide synthase (eNOS) is supposed to play a role in noise-induced nitric oxide (NO)-production. It is commonly known that intense noise exposure results in inducible NOS (iNOS) expression and increased NO-production, but knowledge about a contribution of the eNOS isoform is still lacking. Effects of noise exposure on eNOS immunolabeling were determined in male guinea pigs (n=24). For light microscopic analysis, 11 animals were exposed to 90 dB for 1 hr and 6 animals were used as controls. After exposure, eNOS immunostaining was performed on paraffin sections, and the staining intensities were quantified for 4 cochlear regions. For electron microscopic analysis, 2 animals were exposed for 2 hr to 90 dB and 5 animals were used as controls. The intensity of eNOS immunolabeling was found to be already comprehensively increased 1 hr after noise exposure to 90 dB. At the ultrastructural level, a clear increase in eNOS immunolabeling was found in microtubules-rich areas of cochlear cuticular structures. Hence, our findings indicate that the reticular lamina forming the endolymph-perilymph barrier at the apical side of the organ of Corti is involved in a fast intrinsic otoprotective mechanism of the cochlea.
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Affiliation(s)
- Ulf R Heinrich
- Department of Otorhinolaryngology, University Medical Center Mainz, Mainz, Germany
| | - Irene Schmidtmann
- Institute for Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Center Mainz, Mainz, Germany
| | - Regina Meuser
- Institute for Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Center Mainz, Mainz, Germany
| | - Benjamin P Ernst
- Department of Otorhinolaryngology, University Medical Center Mainz, Mainz, Germany
| | - Desiree Wünsch
- Department of Otorhinolaryngology, University Medical Center Mainz, Mainz, Germany
| | - Svenja Siemer
- Department of Otorhinolaryngology, University Medical Center Mainz, Mainz, Germany
| | - Alena Gribko
- Department of Otorhinolaryngology, University Medical Center Mainz, Mainz, Germany
| | - Roland H Stauber
- Department of Otorhinolaryngology, University Medical Center Mainz, Mainz, Germany
| | - Sebastian Strieth
- Department of Otorhinolaryngology, University Medical Center Mainz, Mainz, Germany
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6
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Vaden KI, Matthews LJ, Dubno JR. Transient-Evoked Otoacoustic Emissions Reflect Audiometric Patterns of Age-Related Hearing Loss. Trends Hear 2019; 22:2331216518797848. [PMID: 30198420 PMCID: PMC6131303 DOI: 10.1177/2331216518797848] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Distinct forms of age-related hearing loss are hypothesized based on evidence
from animal models of aging, which are identifiable in human audiograms. The
Sensory phenotype results from damage (e.g., excessive noise or ototoxic drugs)
to outer hair cells and sometimes inner hair cells, producing large threshold
increases predominately at high frequencies. The Metabolic phenotype results
from a decline in endocochlear potential that can reduce outer hair cell
motility throughout the cochlea, producing gradually sloping thresholds from
lower to higher frequencies. Finally, the combined Metabolic + Sensory phenotype
results in low-frequency losses similar to the Metabolic phenotype and
high-frequency losses similar to the Sensory phenotype. Because outer hair cell
function appears to be affected differently in each phenotype, this study used
audiograms from 618 adults aged 50 to 93 years (n = 1,208 ears)
to classify phenotypes and characterize differences in transient-evoked
otoacoustic emission (TEOAE) data. Significant phenotype differences were
observed in frequency-band TEOAEs and configuration (intercept and slope),
including large and broadly distributed TEOAE reductions for Metabolic and
Metabolic + Sensory ears and more focused high-frequency TEOAE reductions for
Sensory ears. These findings are consistent with metabolic declines that reduce
cochlear amplification across a broad range of frequencies and more basally
situated, high-frequency declines in sensory hearing loss. The results provide
further validation for the classification of age-related hearing loss phenotypes
based on audiograms and show human TEOAE declines that are highly consistent
with animal models.
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Affiliation(s)
- Kenneth I Vaden
- 1 Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
| | - Lois J Matthews
- 1 Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
| | - Judy R Dubno
- 1 Hearing Research Program, Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, USA
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7
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Abstract
Low-frequency hearing is critically important for speech and music perception, but no mechanical measurements have previously been available from inner ears with intact low-frequency parts. These regions of the cochlea may function in ways different from the extensively studied high-frequency regions, where the sensory outer hair cells produce force that greatly increases the sound-evoked vibrations of the basilar membrane. We used laser interferometry in vitro and optical coherence tomography in vivo to study the low-frequency part of the guinea pig cochlea, and found that sound stimulation caused motion of a minimal portion of the basilar membrane. Outside the region of peak movement, an exponential decline in motion amplitude occurred across the basilar membrane. The moving region had different dependence on stimulus frequency than the vibrations measured near the mechanosensitive stereocilia. This behavior differs substantially from the behavior found in the extensively studied high-frequency regions of the cochlea.
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8
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Measurement of basilar membrane motion during round window stimulation in guinea pigs. J Assoc Res Otolaryngol 2014; 15:933-43. [PMID: 25080894 DOI: 10.1007/s10162-014-0477-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 07/01/2014] [Indexed: 10/25/2022] Open
Abstract
Driving the cochlea in reverse via the round window membrane (RWM) is an alternative treatment option for the hearing rehabilitation of a nonfunctional or malformed middle ear. However, cochlear stimulation from the RWM side is not a normal sound transmission pathway. The basilar membrane (BM) motion elicited by mechanical stimulation of the RWM is unknown. In this study, the BM movement at the basal turn was investigated in both reverse via RWM drive and acoustic stimulation in the ear canal or forward drive in postmortem isolated temporal bone preparations of guinea pigs. During reverse drive, a magnet-coil was coupled on RWM, and the BM vibration at the basal turn and the movement of the incus tip were measured with laser Doppler vibrometry. During forward drive, the vibration of the incus tip induced by sound pressure in the ear canal resulted in BM vibration and the BM movement at the same location as that in the reverse stimulation was measured. The displacement ratio of the BM to RWM in reverse drive and the ratio of the BM to incus in forward drive were compared. The results demonstrated that the BM response measured in both situations was similar in nature between forward and reverse drives. This study provides new knowledge for an understanding of BM movement induced by reverse drive via the RWM stimulation.
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9
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Nowotny M, Gummer AW. Vibration responses of the organ of Corti and the tectorial membrane to electrical stimulation. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2011; 130:3852-3872. [PMID: 22225042 DOI: 10.1121/1.3651822] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Coupling of somatic electromechanical force from the outer hair cells (OHCs) into the organ of Corti is investigated by measuring transverse vibration patterns of the organ of Cori and tectorial membrane (TM) in response to intracochlear electrical stimulation. Measurement places at the organ of Corti extend from the inner sulcus cells to Hensen's cells and at the lower (and upper) surface of the TM from the inner sulcus to the OHC region. These locations are in the neighborhood of where electromechanical force is coupled into (1) the mechanoelectrical transducers of the stereocilia and (2) fluids of the organ of Corti. Experiments are conducted in the first, second, and third cochlear turns of an in vitro preparation of the adult guinea pig cochlea. Vibration measurements are made at functionally relevant stimulus frequencies (0.48-68 kHz) and response amplitudes (<15 nm). The experiments provide phase relations between the different structures, which, dependent on frequency range and longitudinal cochlear position, include in-phase transverse motions of the TM, counterphasic transverse motions between the inner hair cell and OHCs, as well as traveling-wave motion of Hensen's cells in the radial direction. Mechanics of sound processing in the cochlea are discussed based on these phase relationships.
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Affiliation(s)
- Manuela Nowotny
- Faculty of Medicine, Section of Physiological Acoustics and Communication, Eberhard Karls University Tübingen, Elfriede-Aulhorn-Strasse 5, 72076 Tübingen, Germany
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10
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Dai C, Gan RZ. Change in cochlear response in an animal model of otitis media with effusion. Audiol Neurootol 2009; 15:155-67. [PMID: 19776565 PMCID: PMC2853584 DOI: 10.1159/000241096] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Accepted: 06/12/2009] [Indexed: 11/19/2022] Open
Abstract
Our previous studies confirm that middle ear mobility is reduced in the presence of otitis media with effusion (OME). Variations in middle ear function may result in changes in cochlear response in OME ears. With the long-term goal of evaluating cochlear function in OME ears, the aim of this study was to measure the displacement of the basilar membrane (BM) in guinea pig ears with OME. Vibrations of the BM at the apex and basal turn were measured in an in vitro preparation extracted 3 and 14 days after injection of lipopolysaccharide in the middle ear of guinea pigs. The results show that the displacement sensitivity of the BM at the apex and the basal turn to sound pressure in the ear canal was reduced up to 25 dB at their characteristic frequencies, respectively. Cochlear gain with respect to umbo movement was also changed in ears with OME in both groups. This study provides data for analysis of the change of BM vibration in a guinea pig OME model.
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11
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Abstract
Normal hearing depends on sound amplification within the mammalian cochlea. The amplification, without which the auditory system is effectively deaf, can be traced to the correct functioning of a group of motile sensory hair cells, the outer hair cells of the cochlea. Acting like motor cells, outer hair cells produce forces that are driven by graded changes in membrane potential. The forces depend on the presence of a motor protein in the lateral membrane of the cells. This protein, known as prestin, is a member of a transporter superfamily SLC26. The functional and structural properties of prestin are described in this review. Whether outer hair cell motility might account for sound amplification at all frequencies is also a critical question and is reviewed here.
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Affiliation(s)
- Jonathan Ashmore
- Department of Physiology and UCL Ear Institute, University College London, London, United Kingdom.
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12
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Xia A, Visosky AMB, Cho JH, Tsai MJ, Pereira FA, Oghalai JS. Altered traveling wave propagation and reduced endocochlear potential associated with cochlear dysplasia in the BETA2/NeuroD1 null mouse. J Assoc Res Otolaryngol 2007; 8:447-63. [PMID: 17701252 PMCID: PMC2538339 DOI: 10.1007/s10162-007-0092-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Accepted: 07/20/2007] [Indexed: 11/28/2022] Open
Abstract
The BETA2/NeuroD1 null mouse has cochlear dysplasia. Its cochlear duct is shorter than normal, there is a lack of spiral ganglion neurons, and there is hair cell disorganization. We measured vertical movements of the tectorial membrane at acoustic frequencies in excised cochleae in response to mechanical stimulation of the stapes using laser doppler vibrometry. While tuning curve sharpness was similar between wild-type, heterozygotes, and null mice in the base, null mutants had broader tuning in the apex. At both the base and the apex, null mice had less phase lag accumulation with increasing stimulus frequency than wild-type or heterozygote mice. In vivo studies demonstrated that the null mouse lacked distortion product otoacoustic emissions, and the cochlear microphonic and endocochlear potential were found to be severely reduced. Electrically evoked otoacoustic emissions could be elicited, although the amplitudes were lower than those of wild-type mice. Cochlear cross-sections revealed an incomplete partition malformation, with fenestrations within the modiolus that connected the cochlear turns. Outer hair cells from null mice demonstrated the normal pattern of prestin expression within their lateral walls and normal FM 1-43 dye entry. Overall, these data demonstrate that while tonotopicity can exist with cochlear dysplasia, traveling wave propagation is abnormally fast. Additionally, the presence of electrically evoked otoacoustic emissions suggests that outer hair cell reverse transduction is present, although the acoustic response is shaped by the alterations in cochlear mechanics.
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Affiliation(s)
- Anping Xia
- The Bobby R. Alford Department of Otolaryngology – Head and Neck Surgery, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030 USA
| | - Ann Marie B. Visosky
- The Bobby R. Alford Department of Otolaryngology – Head and Neck Surgery, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030 USA
| | - Jang-Hyeon Cho
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030 USA
| | - Ming-Jer Tsai
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030 USA
| | - Fred A. Pereira
- The Bobby R. Alford Department of Otolaryngology – Head and Neck Surgery, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030 USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030 USA
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030 USA
- Department of Bioengineering, Rice University, Houston, TX 77251 USA
| | - John S. Oghalai
- The Bobby R. Alford Department of Otolaryngology – Head and Neck Surgery, Baylor College of Medicine, One Baylor Plaza, NA102, Houston, TX 77030 USA
- Department of Bioengineering, Rice University, Houston, TX 77251 USA
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13
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Dong W, Cooper NP. An experimental study into the acousto-mechanical effects of invading the cochlea. J R Soc Interface 2006; 3:561-71. [PMID: 16849252 PMCID: PMC1664639 DOI: 10.1098/rsif.2006.0117] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The active and nonlinear mechanical processing of sound that takes place in the mammalian cochlea is fundamental to our sense of hearing. We have investigated the effects of opening the cochlea in order to make experimental observations of this processing. Using an optically transparent window that permits laser interferometric access to the apical turn of the guinea-pig cochlea, we show that the acousto-mechanical transfer functions of the sealed (i.e. near intact) cochlea are considerably simpler than those of the unsealed cochlea. Comparison of our results with those of others suggests that most previous investigations of apical cochlear mechanics have been made under unsealed conditions, and are therefore likely to have misrepresented the filtering of low-frequency sounds in the cochlea. The mechanical filtering that is apparent in the apical turns of sealed cochleae also differs from the filtering seen in individual auditory nerve fibres with similar characteristic frequencies. As previous studies have shown the neural and mechanical tuning of the basal cochlea to be almost identical, we conclude that the strategies used to process low frequency sounds in the apical turns of the cochlea might differ fundamentally from those used to process high frequency sounds in the basal turns.
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Affiliation(s)
- Wei Dong
- Physiology Department, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
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14
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Summers V, de Boer E, Nuttall AL. Basilar-membrane responses to multicomponent (Schroeder-phase) signals: understanding intensity effects. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2003; 114:294-306. [PMID: 12880042 DOI: 10.1121/1.1580813] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Harmonic complexes comprised of the same spectral components in either positive-Schroeder (+Schr) or negative-Schroeder (-Schr) phase [see Schroeder, IEEE Trans. Inf. Theory 16, 85-89 (1970)] have identical long-term spectra and similar waveform envelopes. However, localized patterns of basilar-membrane (BM) excitation can be quite different in response to these two stimuli. Measurements in chinchillas showed more modulated (peakier) BM excitation for +Schr than -Schr complexes [Recio and Rhode, J. Acoust. Soc. Am. 108, 2281-2298 (2000)]. In the current study, laser velocimetry was used to examine BM responses at a location tuned to approximately 17 kHz in the basal turn of the guinea-pig cochlea, for +Schr and -Schr complexes with a 203-Hz fundamental frequency and including 101 equal-amplitude components from 2031 to 22,344 Hz. At 35-dB SPL, +Schr response waveforms showed greater amplitude modulation than -Schr responses. With increasing stimulation level, internal modulation decreased for both complexes. To understand the observed phenomena quantitatively, responses were predicted on the basis of a linearized model of the cochlea. Prediction was based on an "indirect impulse response" measured in the same animal. Response waveforms for Schroeder-phase signals were accurately predicted, provided that the level of the indirect impulse used in prediction closely matched the level of the Schroeder-phase stimulus. This result confirms that the underlying model, which originally was developed for noise stimuli, is valid for stimuli that produce completely different response waveforms. Moreover, it justifies explanation of cochlear filtering (i.e., differential treatment of different frequencies) in terms of a linear system.
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Affiliation(s)
- Van Summers
- Army Audiology & Speech Center, Walter Reed Army Medical Center, Washington, DC 20307-5001, USA
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15
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Spector AA, Brownell WE, Popel AS. Effect of outer hair cell piezoelectricity on high-frequency receptor potentials. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2003; 113:453-461. [PMID: 12558282 DOI: 10.1121/1.1526493] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The low-pass voltage response of outer hair cells predicted by conventional equivalent circuit analysis would preclude the active force production at high frequencies. We have found that the band pass characteristics can be improved by introducing the piezoelectric properties of the cell wall. In contrast to the conventional analysis, the receptor potential does not tend to zero and at any frequency is greater than a limiting value. In addition, the phase shift between the transduction current and receptor potential tends to zero. The piezoelectric properties cause an additional, strain-dependent, displacement current in the cell wall. The wall strain is estimated on the basis of a model of the cell deformation in the organ of Corti. The limiting value of the receptor potential depends on the ratio of a parameter determined by the piezoelectric coefficients and the strain to the membrane capacitance. In short cells, we have found that for the low-frequency value of about 2-3 mV and the strain level of 0.1% the receptor potential can reach 0.4 mV throughout the whole frequency range. In long cells, we have found that the effect of the piezoelectric properties is much weaker. These results are consistent with major features of the cochlear amplifier.
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Affiliation(s)
- Alexander A Spector
- Department of Biomedical Engineering and Center for Computational Medicine and Biology, Johns Hopkins University, Baltimore, Maryland 21205, USA.
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Abstract
The vibration of the hearing organ that occurs during sound stimulation is based on mechanical interactions between different cellular structures inside the organ of Corti. The exact nature of these interactions is unclear and subject to debate. In this study, dynamic structural changes were produced by stepwise alterations of scala tympani pressure in an in vitro preparation of the guinea pig temporal bone. Confocal images were acquired at each level of pressure. In this way, the motion of several structures could be observed simultaneously with high resolution in a nearly intact system. Images were analyzed using a novel wavelet-based optical flow estimation algorithm. Under these conditions, the reticular lamina moved as a stiff plate with a center of rotation in the region of the inner hair cells. Despite being enclosed in several types of supporting cells, the inner hair cells, together with the adjacent inner pillar cells, moved in a manner signifying high compliance. The outer hair cells displayed radial motion indicative of cellular bending. Together, these results show that shearing motion occurs between several parts of the organ, and that structural relationships within the organ change dynamically during displacement of the basilar membrane.
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Abstract
In mammals, environmental sounds stimulate the auditory receptor, the cochlea, via vibrations of the stapes, the innermost of the middle ear ossicles. These vibrations produce displacement waves that travel on the elongated and spirally wound basilar membrane (BM). As they travel, waves grow in amplitude, reaching a maximum and then dying out. The location of maximum BM motion is a function of stimulus frequency, with high-frequency waves being localized to the "base" of the cochlea (near the stapes) and low-frequency waves approaching the "apex" of the cochlea. Thus each cochlear site has a characteristic frequency (CF), to which it responds maximally. BM vibrations produce motion of hair cell stereocilia, which gates stereociliar transduction channels leading to the generation of hair cell receptor potentials and the excitation of afferent auditory nerve fibers. At the base of the cochlea, BM motion exhibits a CF-specific and level-dependent compressive nonlinearity such that responses to low-level, near-CF stimuli are sensitive and sharply frequency-tuned and responses to intense stimuli are insensitive and poorly tuned. The high sensitivity and sharp-frequency tuning, as well as compression and other nonlinearities (two-tone suppression and intermodulation distortion), are highly labile, indicating the presence in normal cochleae of a positive feedback from the organ of Corti, the "cochlear amplifier." This mechanism involves forces generated by the outer hair cells and controlled, directly or indirectly, by their transduction currents. At the apex of the cochlea, nonlinearities appear to be less prominent than at the base, perhaps implying that the cochlear amplifier plays a lesser role in determining apical mechanical responses to sound. Whether at the base or the apex, the properties of BM vibration adequately account for most frequency-specific properties of the responses to sound of auditory nerve fibers.
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Affiliation(s)
- L Robles
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Programa Disciplinario de Fisiología y Biofísica, Universidad de Chile, Santiago, Chile
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Abstract
The Reissner's membrane (RM) was visualised by confocal microscopy in the isolated temporal bone of the guinea pig. The function of the organ was followed by measuring its physiological response. Static pressure applied in the basal coil caused a distention of the RM in the apical coil into the scala vestibuli. The sensitivity to a test tone was reduced. When the pressure was relieved, the RM returned to its original position and the response recovered. If the increased pressure was maintained, the RM would bulge further. The RM could then be reversibly stretched and return gradually, with a delay, to its original position. Alternatively, it could be over-stretched and return with an over-shoot past its original position toward the organ of Corti. In response to repetitive tone pulses of above 80 dB, hydrops of the RM also developed. This was accompanied by a reduced sensitivity. A slow recovery to the original position, or over-shoot, and return of responsiveness could be seen. Above 106 dB sustained loss was generally seen. It is concluded that the RM can accommodate increased scala media pressure by distention. This will relieve the organ of Corti from part of the pressure and may protect the organ from trauma.
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Affiliation(s)
- A Flock
- Department of Physiology and Pharmacology, Division of Physiology II, Karolinska Institutet, S-171 77, Stockholm, Sweden.
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19
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Abstract
The vibration of the organ of Corti, a three-dimensional micromechanical structure that incorporates the sensory cells of the hearing organ, was measured in three mutually orthogonal directions. This was achieved by coupling the light of a laser Doppler vibrometer into the side arm of an epifluorescence microscope to measure velocity along the optical axis of the microscope, called the transversal direction. Displacements were measured in the plane orthogonal to the transverse direction with a differential photodiode mounted on the microscope in the focal plane. Vibration responses were measured in the fourth turn of a temporal-bone preparation of the guinea-pig cochlea. Responses were corrected for a "fast" wave component caused by the presence of the hole in the cochlear wall, made to view the structures. The frequency responses of the basilar membrane and the reticular lamina were similar, with little phase differences between the vibration components. Their motion was rectilinear and vertical to the surface of their membranes. The organ of Corti rotated about a point near the edge of the inner limbus. A second vibration mode was detected in the motion of the tectorial membrane. This vibration mode was directed parallel to the reticular lamina and became apparent for frequencies above approximately 0.5 oct below the characteristic frequency. This radial vibration mode presumably controls the shearing action of the hair bundles of the outer hair cells.
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Affiliation(s)
- W Hemmert
- University of Tübingen, Department of Otolaryngology, Section for Physiological Acoustics and Communication, 72076 Tübingen, Germany.
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Zinn C, Maier H, Zenner H, Gummer AW. Evidence for active, nonlinear, negative feedback in the vibration response of the apical region of the in-vivo guinea-pig cochlea. Hear Res 2000; 142:159-83. [PMID: 10748337 DOI: 10.1016/s0378-5955(00)00012-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The transverse vibration response of the organ of Corti near the apical end of the guinea-pig cochlea was measured in vivo. For cochleae in good physiological condition, as ascertained with threshold compound action potentials and the endocochlear potential, increasing amounts of attenuation and phase lag were found as the intensity was decreased below 80 dB SPL. These nonlinear phenomena disappeared post mortem. The data suggest that an active, nonlinear damping mechanism exists at low intensities at the apex of the cochlea. The phase nonlinearity, evident at all frequencies except at the best frequency (BF), was limited to a total phase change of 0.25 cycles, implying negative feedback of electromechanical force from the outer hair cells into a compliant organ of Corti. The amplitude nonlinearity was largest above BF, possibly due to interaction with a second vibration mode. The high-frequency flank of the amplitude response curve was shifted to lower frequencies by as much as 0.6 octave (oct) for a 50-dB reduction of sound intensity; the reduction of BF was 0.3 oct, but there was no change of relative bandwidth (Q(10 dB)). Detailed frequency responses measured at 60 dB SPL were consistent with non-dispersive, travelling-wave motion: travel time to the place of BF (400 Hz at 60 dB SPL) was 2.9 ms, Q(10 dB) was 1.0; standing-wave motion occurred above 600 Hz. Based on comparison with neural and mechanical data from the base of the cochlea, amplitudes at the apex appear to be sufficient to yield behavioural thresholds. It is concluded that active negative feedback may be a hallmark of the entire cochlea at low stimulus frequencies and that, in contrast to the base, the apex does not require active amplification.
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Affiliation(s)
- C Zinn
- Section Physiological Acoustics and Communication, Department of Otolaryngology, University of Tübingen, Silcherstr. 5, D-72076, Tübingen, Germany
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