The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Dennis M. Freeman - One of the best experts on this subject based on the ideXlab platform.
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The Tectorial Membrane: Mechanical properties and functions
Cold Spring Harbor perspectives in medicine, 2019Co-Authors: Jonathan B. Sellon, Roozbeh Ghaffari, Dennis M. FreemanAbstract:The Tectorial Membrane (TM) is widely believed to play a critical role in determining the remarkable sensitivity and frequency selectivity that are hallmarks of mammalian hearing. Recently developed mouse models of human hearing disorders have provided new insights into the molecular, nanomechanical mechanisms that underlie resonance and traveling wave properties of the TM. Herein we review recent experimental and theoretical results detailing TM morphology, local poroelastic and electromechanical interactions, and global spread of excitation via TM traveling waves, with direct implications for cochlear mechanisms.
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Tectorial Membrane Traveling Waves Underlie Sharp Auditory Tuning in Humans
Biophysical journal, 2016Co-Authors: Shirin Farrahi, Roozbeh Ghaffari, Jonathan B. Sellon, Hideko Heidi Nakajima, Dennis M. FreemanAbstract:Our ability to understand speech requires neural tuning with high frequency resolution, but the peripheral mechanisms underlying sharp tuning in humans remain unclear. Sharp tuning in genetically modified mice has been attributed to decreases in spread of excitation of Tectorial Membrane traveling waves. Here we show that the spread of excitation of Tectorial Membrane waves is similar in humans and mice, although the mechanical excitation spans fewer frequencies in humans-suggesting a possible mechanism for sharper tuning.
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Electrokinetic properties of the mammalian Tectorial Membrane.
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Roozbeh Ghaffari, Shirin Farrahi, Jonathan B. Sellon, Scott Page, Dennis M. FreemanAbstract:The Tectorial Membrane (TM) clearly plays a mechanical role in stimulating cochlear sensory receptors, but the presence of fixed charge in TM constituents suggests that electromechanical properties also may be important. Here, we measure the fixed charge density of the TM and show that this density of fixed charge is sufficient to affect mechanical properties and to generate electrokinetic motions. In particular, alternating currents applied to the middle and marginal zones of isolated TM segments evoke motions at audio frequencies (1-1,000 Hz). Electrically evoked motions are nanometer scaled (∼5-900 nm), decrease with increasing stimulus frequency, and scale linearly over a broad range of electric field amplitudes (0.05-20 kV/m). These findings show that the mammalian TM is highly charged and suggest the importance of a unique TM electrokinetic mechanism.
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Tectorial Membrane traveling waves underlie impaired hearing in tectb mutant mice
WHAT FIRE IS IN MINE EARS: PROGRESS IN AUDITORY BIOMECHANICS: Proceedings of the 11th International Mechanics of Hearing Workshop, 2011Co-Authors: Roozbeh Ghaffari, Guy P. Richardson, Shirin Farrahi, Alexander J Aranyosi, Dennis M. FreemanAbstract:We show that the Tectb mutation reduces the spatial extent and propagation velocity of Tectorial Membrane (TM) traveling waves. These results can account for all of the hearing abnormalities associated with the Tectb mutation, as follows. By reducing the spatial extent of TM waves, the Tectb mutation decreases spread of excitation and thereby increases frequency selectivity at mid‐ to high frequencies. Furthermore, the decrease in Tectb TM wave velocity at low frequencies reduces the number of hair cells that effectively couple energy to the basilar Membrane, which thereby reduces sensitivity.
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The osmotic response of the isolated Tectorial Membrane of the chick to isosmotic solutions: effect of Na+, K+, and Ca2+ concentration.
Hearing research, 1994Co-Authors: Dennis M. Freeman, Douglas A. Cotanche, Farzad Ehsani, Thomas F. WeissAbstract:Changes in the size, shape, and structure of the isolated Tectorial Membrane of the chick were measured in response to isosmotic changes in the ionic composition of the perfusion solution. Substitution of artificial perilymph (AP) for artificial endolymph (AE) caused a small (~ 15%), slow (time constants τ ~ 12 min) shrinkage of the thickness of the Tectorial Membrane that was largely reversed on return to AE. Substitution of AP for AE alters not only the predominate cation (from K+ to Na t) but also the Ca2+ concentration (from < 7 μmol/1 to 2 mmol/1). Additional experiments were performed to separate effects of each of these changes. When a high-Na +, low-Ca2+ solution was substituted for a high-Kt, low-Ca2+ solution (AE), the Tectorial Membrane swelled significantly, often to more than twice its original thickness (the largest swelling was 337%), with a slow time course (τ ~ 23 min). Addition of Ca2+ to either high-K+ or high-Na + solutions caused rapid shrinkage of the Tectorial Membrane (τ ~ 2–3 min). Addition of the Ca2+ chelator EGTA caused rapid swelling (τ ~ 4 min). Large osmotic responses were only partially reversible and caused long-lasting changes. For example, long-duration solution changes that produced large, rapid osmotic responses early in an experiment tended to produce smaller and slower responses later in the experiment. In contrast, the small osmotic responses to short-duration solution changes were repcatable for tens of hours. Changes in ionic composition of the bath affected not only the thickness of the Tectorial Membrane but also its other dimensions. Responses were not generally isotropic; both the size and shape of the Tectorial Membrane generally changed. Consistent changes in microstructure accompanied the osmotic changes.
Guy P. Richardson - One of the best experts on this subject based on the ideXlab platform.
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accelerated age related degradation of the Tectorial Membrane in the ceacam16βgal βgal null mutant mouse a model for late onset human hereditary deafness dfnb113
Frontiers in Molecular Neuroscience, 2019Co-Authors: Richard J. Goodyear, Mary Ann Cheatham, Souvik Naskar, Yingjie Zhou, Richard T Osgood, Jing Zheng, Guy P. RichardsonAbstract:CEACAM16 is a non-collagenous protein of the Tectorial Membrane, an extracellular structure of the cochlea essential for normal hearing. Dominant and recessive mutations in CEACAM16 have been reported to cause postlingual and progressive forms of deafness in humans. In a previous study of young Ceacam16 βgal/βgal null mutant mice on a C57Bl/6J background, the incidence of spontaneous otoacoustic emissions (SOAEs) was greatly increased relative to Ceacam16+/+ and Ceacam16+/βgal mice, but auditory brain-stem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) were near normal, indicating auditory thresholds were not significantly affected. To determine if the loss of CEACAM16 leads to hearing loss at later ages in this mouse line, cochlear structure and auditory function were examined in Ceacam16+/+, Ceacam16+/βgal and Ceacam16βgal/βgal mice at 6 and 12 months of age and compared to that previously described at 1 month. Analysis of older Ceacam16βgal/βgal mice reveals a progressive loss of matrix from the core of the Tectorial Membrane that is more extensive in the apical, low-frequency regions of the cochlea. In Ceacam16βgal/βgal mice at 6-7 months, the DPOAE magnitude at 2f1-f2 and the incidence of SOAEs both decrease relative to young animals. By ~12 months, SOAEs and DPOAEs are not detected in Ceacam16βgal/βgal mice and ABR thresholds are increased by up to ~40 dB across frequency, despite a complement of hair cells similar to that present in Ceacam16+/+ mice. Although SOAE incidence decreases with age in Ceacam16βgal/βgal mice, it increases in ageing heterozygous Ceacam16+/βgal mice and is accompanied by a reduction in the accumulation of CEACAM16 in the Tectorial Membrane relative to controls. An apically-biased loss of matrix from the core of the Tectorial Membrane, similar to that observed in young Ceacam16βgal/βgal mice, is also seen in Ceacam16+/+ and Ceacam16+/βgal mice, and other strains of wild-type mice, but at much later ages. The loss of Ceacam16 therefore accelerates age-related degeneration of the Tectorial Membrane leading, as in humans with mutations in CEACAM16, to a late-onset progressive form of hearing loss.
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Structure, Function, and Development of the Tectorial Membrane: An Extracellular Matrix Essential for Hearing.
Current topics in developmental biology, 2018Co-Authors: Richard J. Goodyear, Guy P. RichardsonAbstract:The Tectorial Membrane is an extracellular matrix that lies over the apical surface of the auditory epithelia in the inner ears of reptiles, birds, and mammals. Recent studies have shown it is composed of a small set of proteins, some of which are only produced at high levels in the ear and many of which are the products of genes that, when mutated, cause nonsyndromic forms of human hereditary deafness. Quite how the proteins of the Tectorial Membrane are assembled within the lumen of the inner ear to form a structure that is precisely regulated in its size and physical properties along the length of a tonotopically organized hearing organ is a question that remains to be fully answered. In this brief review we will summarize what is known thus far about the structure, protein composition, and function of the Tectorial Membrane in birds and mammals, describe how the Tectorial Membrane develops, and discuss major events that have occurred during the evolution of this extracellular matrix.
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Tectorial Membrane traveling waves underlie impaired hearing in tectb mutant mice
WHAT FIRE IS IN MINE EARS: PROGRESS IN AUDITORY BIOMECHANICS: Proceedings of the 11th International Mechanics of Hearing Workshop, 2011Co-Authors: Roozbeh Ghaffari, Guy P. Richardson, Shirin Farrahi, Alexander J Aranyosi, Dennis M. FreemanAbstract:We show that the Tectb mutation reduces the spatial extent and propagation velocity of Tectorial Membrane (TM) traveling waves. These results can account for all of the hearing abnormalities associated with the Tectb mutation, as follows. By reducing the spatial extent of TM waves, the Tectb mutation decreases spread of excitation and thereby increases frequency selectivity at mid‐ to high frequencies. Furthermore, the decrease in Tectb TM wave velocity at low frequencies reduces the number of hair cells that effectively couple energy to the basilar Membrane, which thereby reduces sensitivity.
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Exploiting Transgenic Mice to Explore the Role of the Tectorial Membrane in Cochlear Sensory Processing
The Neurophysiological Bases of Auditory Perception, 2010Co-Authors: Guy P. Richardson, Andrei N. Lukashkin, Victoria A. Lukashkina, Ian J. RussellAbstract:Recent observations have changed our understanding of Tectorial Membrane function. Transgenic mice have shown that the Tectorial Membrane is a structure that can influence the sensitivity and tuning properties of the cochlea in several ways. It ensures that the gain and timing of cochlear feedback are optimal; that the hair bundles of the inner hair cells are driven efficiently by the outer hair cells, and it may influence the extent to which different elements are coupled along the length of the cochlea.
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Multiple roles for the Tectorial Membrane in the active cochlea.
Hearing research, 2009Co-Authors: Andrei N. Lukashkin, Guy P. Richardson, Ian J. RussellAbstract:This review is concerned with experimental results that reveal multiple roles for the Tectorial Membrane in active signal processing in the mammalian cochlea. We discuss the dynamic mechanical properties of the Tectorial Membrane as a mechanical system with several degrees of freedom and how its different modes of movement can lead to hair-cell excitation. The role of the Tectorial Membrane in distributing energy along the cochlear partition and how it channels this energy to the inner hair cells is described.
Jonathan B. Sellon - One of the best experts on this subject based on the ideXlab platform.
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The Tectorial Membrane: Mechanical properties and functions
Cold Spring Harbor perspectives in medicine, 2019Co-Authors: Jonathan B. Sellon, Roozbeh Ghaffari, Dennis M. FreemanAbstract:The Tectorial Membrane (TM) is widely believed to play a critical role in determining the remarkable sensitivity and frequency selectivity that are hallmarks of mammalian hearing. Recently developed mouse models of human hearing disorders have provided new insights into the molecular, nanomechanical mechanisms that underlie resonance and traveling wave properties of the TM. Herein we review recent experimental and theoretical results detailing TM morphology, local poroelastic and electromechanical interactions, and global spread of excitation via TM traveling waves, with direct implications for cochlear mechanisms.
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Tectorial Membrane Traveling Waves Underlie Sharp Auditory Tuning in Humans
Biophysical journal, 2016Co-Authors: Shirin Farrahi, Roozbeh Ghaffari, Jonathan B. Sellon, Hideko Heidi Nakajima, Dennis M. FreemanAbstract:Our ability to understand speech requires neural tuning with high frequency resolution, but the peripheral mechanisms underlying sharp tuning in humans remain unclear. Sharp tuning in genetically modified mice has been attributed to decreases in spread of excitation of Tectorial Membrane traveling waves. Here we show that the spread of excitation of Tectorial Membrane waves is similar in humans and mice, although the mechanical excitation spans fewer frequencies in humans-suggesting a possible mechanism for sharper tuning.
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Electrokinetic properties of the mammalian Tectorial Membrane.
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Roozbeh Ghaffari, Shirin Farrahi, Jonathan B. Sellon, Scott Page, Dennis M. FreemanAbstract:The Tectorial Membrane (TM) clearly plays a mechanical role in stimulating cochlear sensory receptors, but the presence of fixed charge in TM constituents suggests that electromechanical properties also may be important. Here, we measure the fixed charge density of the TM and show that this density of fixed charge is sufficient to affect mechanical properties and to generate electrokinetic motions. In particular, alternating currents applied to the middle and marginal zones of isolated TM segments evoke motions at audio frequencies (1-1,000 Hz). Electrically evoked motions are nanometer scaled (∼5-900 nm), decrease with increasing stimulus frequency, and scale linearly over a broad range of electric field amplitudes (0.05-20 kV/m). These findings show that the mammalian TM is highly charged and suggest the importance of a unique TM electrokinetic mechanism.
Dinesh Rao - One of the best experts on this subject based on the ideXlab platform.
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Tectorial Membrane injury in adult and pediatric trauma patients: a retrospective review and proposed classification scheme
Emergency Radiology, 2019Co-Authors: Peter Fiester, Erik Soule, Patrick Natter, Dinesh RaoAbstract:Background and purpose Traumatic Tectorial Membrane injuries have different radiologic presentations in adult versus pediatric patients. The purpose of this study was to identify and classify the different types of Tectorial Membrane injuries that occur in the adult and pediatric populations. Materials and methods Patients who suffered Tectorial Membrane injury were identified retrospectively using the keywords ‘Tectorial Membrane,” “craniocervical ligament tear/injury,” and “atlanto-occipital dissociation” included in radiology reports between 2012 and 2018 using Nuance mPower software. All relevant imaging studies were reviewed by two certificates of additional qualification-certified neuroradiologists. Detailed descriptions of injuries were recorded along with any relevant additional findings, including clinical history. Results Ten adults and six pediatric patients were identified with acute traumatic injuries of the Tectorial Membrane. Ninety percent of the adult patients sustained complete disruptions inferior to the clivus, or subclival, with 22% of tears at the level of the basion and 78% at the level of the odontoid tip. In contrast, 83% of pediatric patients suffered a stripping injury of the Tectorial Membrane located posterior to the clivus, or retroclival. Stretch injuries of the Tectorial Membrane were identified in 10% of adults and 17% of pediatric patients. The juvenile-type injury, which causes retroclival epidural hematoma, was determined to preferentially occur in patients less than or equal to 14 years of age with a high level of statistical significance ( p value = 0.0014). Conclusions A classification system for Tectorial Membrane injuries is proposed based on this data: type 1—retroclival stripping injury (more common in pediatric patients); type 2a—subclival disruption at the basion and type 2b—subclival disruption at the odontoid (both more common in adult patients); and type 3—thinning of the Tectorial Membrane.
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Tectorial Membrane injury in adult and pediatric trauma patients: a retrospective review and proposed classification scheme
Emergency radiology, 2019Co-Authors: Peter Fiester, Erik Soule, Patrick Natter, Dinesh RaoAbstract:Traumatic Tectorial Membrane injuries have different radiologic presentations in adult versus pediatric patients. The purpose of this study was to identify and classify the different types of Tectorial Membrane injuries that occur in the adult and pediatric populations. Patients who suffered Tectorial Membrane injury were identified retrospectively using the keywords ‘Tectorial Membrane,” “craniocervical ligament tear/injury,” and “atlanto-occipital dissociation” included in radiology reports between 2012 and 2018 using Nuance mPower software. All relevant imaging studies were reviewed by two certificates of additional qualification-certified neuroradiologists. Detailed descriptions of injuries were recorded along with any relevant additional findings, including clinical history. Ten adults and six pediatric patients were identified with acute traumatic injuries of the Tectorial Membrane. Ninety percent of the adult patients sustained complete disruptions inferior to the clivus, or subclival, with 22% of tears at the level of the basion and 78% at the level of the odontoid tip. In contrast, 83% of pediatric patients suffered a stripping injury of the Tectorial Membrane located posterior to the clivus, or retroclival. Stretch injuries of the Tectorial Membrane were identified in 10% of adults and 17% of pediatric patients. The juvenile-type injury, which causes retroclival epidural hematoma, was determined to preferentially occur in patients less than or equal to 14 years of age with a high level of statistical significance (p value = 0.0014). A classification system for Tectorial Membrane injuries is proposed based on this data: type 1—retroclival stripping injury (more common in pediatric patients); type 2a—subclival disruption at the basion and type 2b—subclival disruption at the odontoid (both more common in adult patients); and type 3—thinning of the Tectorial Membrane.
Ian J. Russell - One of the best experts on this subject based on the ideXlab platform.
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Exploiting Transgenic Mice to Explore the Role of the Tectorial Membrane in Cochlear Sensory Processing
The Neurophysiological Bases of Auditory Perception, 2010Co-Authors: Guy P. Richardson, Andrei N. Lukashkin, Victoria A. Lukashkina, Ian J. RussellAbstract:Recent observations have changed our understanding of Tectorial Membrane function. Transgenic mice have shown that the Tectorial Membrane is a structure that can influence the sensitivity and tuning properties of the cochlea in several ways. It ensures that the gain and timing of cochlear feedback are optimal; that the hair bundles of the inner hair cells are driven efficiently by the outer hair cells, and it may influence the extent to which different elements are coupled along the length of the cochlea.
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Multiple roles for the Tectorial Membrane in the active cochlea.
Hearing research, 2009Co-Authors: Andrei N. Lukashkin, Guy P. Richardson, Ian J. RussellAbstract:This review is concerned with experimental results that reveal multiple roles for the Tectorial Membrane in active signal processing in the mammalian cochlea. We discuss the dynamic mechanical properties of the Tectorial Membrane as a mechanical system with several degrees of freedom and how its different modes of movement can lead to hair-cell excitation. The role of the Tectorial Membrane in distributing energy along the cochlear partition and how it channels this energy to the inner hair cells is described.
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The Tectorial Membrane: One Slice of a Complex Cochlear Sandwich
Current opinion in otolaryngology & head and neck surgery, 2008Co-Authors: Guy P. Richardson, Andrei N. Lukashkin, Ian J. RussellAbstract:Purpose of review: The review is both timely and relevant, as recent findings have shown the Tectorial Membrane plays a more dynamic role in hearing than hitherto suspected, and that many forms of deafness can result from mutations in Tectorial Membrane proteins. Recent findings: Main themes covered are (i) the molecular composition, structural organisation and properties of the Tectorial Membrane, (ii) the role of the Tectorial Membrane as a second resonator and a structure within which there is significant longitudinal coupling, and (iii) how mutations in Tectorial Membrane proteins cause deafness in mice and men. Implications: Findings from experimental models imply that the Tectorial Membrane plays multiple, critical roles in hearing. These include coupling elements along the length of the cochlea, supporting a travelling wave and ensuring the gain and timing of cochlear feedback are optimal. The clinical findings suggest stable, moderate-to-severe forms hereditary hearing loss may be diagnostic of a mutation in TECTA, the gene encoding one of the major, non-collagenous proteins of the Tectorial Membrane.
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Sharpened cochlear tuning in a mouse with a genetically modified Tectorial Membrane.
Nature neuroscience, 2007Co-Authors: Ian J. Russell, Andrei N. Lukashkin, Richard J. Goodyear, P. Kevin Legan, Victoria A. Lukashkina, Guy P. RichardsonAbstract:Frequency tuning in the cochlea is determined by the passive mechanical properties of the basilar Membrane and active feedback from the outer hair cells, sensory-effector cells that detect and amplify sound-induced basilar Membrane motions. The sensory hair bundles of the outer hair cells are imbedded in the Tectorial Membrane, a sheet of extracellular matrix that overlies the cochlea's sensory epithelium. The Tectorial Membrane contains radially organized collagen fibrils that are imbedded in an unusual striated-sheet matrix formed by two glycoproteins, alpha-tectorin (Tecta) and beta-tectorin (Tectb). In Tectb(-/-) mice the structure of the striated-sheet matrix is disrupted. Although these mice have a low-frequency hearing loss, basilar-Membrane and neural tuning are both significantly enhanced in the high-frequency regions of the cochlea, with little loss in sensitivity. These findings can be attributed to a reduction in the acting mass of the Tectorial Membrane and reveal a new function for this structure in controlling interactions along the cochlea.
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A deafness mutation isolates a second role for the Tectorial Membrane in hearing
Nature Neuroscience, 2005Co-Authors: P. Kevin Legan, Andrei N. Lukashkin, Ian J. Russell, Richard J. Goodyear, Victoria A. Lukashkina, Kristien Verhoeven, Guy Van Camp, Guy P. RichardsonAbstract:α-tectorin (encoded by Tecta ) is a component of the Tectorial Membrane, an extracellular matrix of the cochlea. In humans, the Y1870C missense mutation in TECTA causes a 50- to 80-dB hearing loss. In transgenic mice with the Y1870C mutation in Tecta , the Tectorial Membrane's matrix structure is disrupted, and its adhesion zone is reduced in thickness. These abnormalities do not seriously influence the Tectorial Membrane's known role in ensuring that cochlear feedback is optimal, because the sensitivity and frequency tuning of the mechanical responses of the cochlea are little changed. However, neural thresholds are elevated, neural tuning is broadened, and a sharp decrease in sensitivity is seen at the tip of the neural tuning curve. Thus, using Tecta ^Y1870C/+ mice, we have genetically isolated a second major role for the Tectorial Membrane in hearing: it enables the motion of the basilar Membrane to optimally drive the inner hair cells at their best frequency.
