The Experts below are selected from a list of 498 Experts worldwide ranked by ideXlab platform
Daniel Bennequin - One of the best experts on this subject based on the ideXlab platform.
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Assessing morphology and function of the Semicircular Duct system: introducing new in-situ visualization and software toolbox.
Scientific Reports, 2016Co-Authors: Romain David, Alexander Stoessel, Alain Berthoz, Fred Spoor, Daniel BennequinAbstract:The Semicircular Duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual Semicircular Duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the Semicircular Duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized Duct system. We demonstrate the potential of these methods by presenting results for the Duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies.
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Assessing morphology and function of the Semicircular Duct system: introducing new in-situ visualization and software toolbox
Scientific Reports, 2016Co-Authors: Romain David, Alexander Stoessel, Alain Berthoz, Fred Spoor, Daniel BennequinAbstract:The Semicircular Duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual Semicircular Duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the Semicircular Duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized Duct system. We demonstrate the potential of these methods by presenting results for the Duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies. Ariadne is freely available at http://www.earbank.org .
M. Muller - One of the best experts on this subject based on the ideXlab platform.
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Optimization of the mechanical performance of a two-Duct Semicircular Duct system--part 3: the positioning of the Ducts in the head.
Journal of Theoretical Biology, 2002Co-Authors: M. Muller, Jan VerhagenAbstract:Abstract In the majority of vertebrates, the horizontal Duct of the vestibular system lies approximately in the yawing plane of the head. The positioning of the vertical Ducts, however, is not in the pitch- and roll planes but the vertical Ducts generally lie under an angle of about 30–45° relative to the medial plane. Using the equations for a hydrodynamically interconnected two-Duct system, optimal positions of the vertical and horizontal Ducts in different vertebrate groups can be derived. It was stated that the mean response of the vertical Ducts should be optimized. This leads to a symmetrical positioning of the vertical Ducts with respect to the medial plane. In all observed vertebrate groups, a solution of μ =( π − α /2 is found ( μ is the angle of the vertical Ducts relative to the medial plane, α is the angle between the vertical Duct planes). For α =90°, this provides an equal sensitivity for pitch- and roll- movements. For α >90°, a larger sensitivity for pitch movements is obtained, at the expense of a lower sensitivity for roll movements. It is argued that the angle α between the vertical Ducts may vary from 90 to 120°. In most vertebrates, the centre of mass is stabilized by e.g. fins, tri- or quadrupedal stability, a crawling body or upside-down resting positions (e.g. bats). Birds are generally biped, so in walking they are also rather sensitive to roll. These features are related to labyrinth positioning in the head.
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Optimization of the mechanical performance of a two-Duct Semicircular Duct system--part 1: dynamics and Duct dimensions.
Journal of Theoretical Biology, 2002Co-Authors: M. Muller, Jan VerhagenAbstract:Abstract The classical representation of the Semicircular Duct system consists of three separate Duct circuits. The Ducts are, however, in reality, hydrodynamically interconnected. Muller & Verhagen (1988a,b) derived equations for the mechanical behaviour of an interconnected system with three Ducts (anterior, posterior and horizontal). An analytical solution of these equations would, however, be too complex to provide surveyable formulae. A system of two interconnected Ducts avoids this complexity whilst keeping the essentials of the coupling of Ducts intact. The solution of the equation of motion leads to expressions for time constants and maximal endolymph excursions which are functions of morphological parameters, viz . the ratios of radii ( γ ) and lengths ( λ ) of the common vestibular part (crus commune or utriculus) and the Ducts. The system possesses two short time constants which are shown to have similar values. The maximum endolymph displacements in the two Ducts after a steplike stimulus are the proDucts of the respective initial velocities and combinations of time constants. The initial velocities depend strongly on the position of the labyrinth with respect to the excitating rotation vector. Measured data of γ and λ are compared with the theoretical results. For γ , excellent agreement was found. λ is treated elsewhere.
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Optimization of the mechanical performance of a two-Duct Semicircular Duct system--part 2: excitation of endolymph movements.
Journal of theoretical biology, 2002Co-Authors: M. Muller, Jan VerhagenAbstract:Abstract The endolymph flow inside the Semicircular Ducts is analytically investigated by considering a system of two hydrodynamically interconnected Ducts. Rotation of this system adds an amount of motion (momentum) to parts of it. This results in an endolymph flow in generally all vestibular parts. The “external impulses” are the impulses which emerge by rotation of exclusively a particular vestibular part. The real impulses can be calculated from a set of equations which contain the external impulses. Analytical expressions are derived for the initial velocities in the Ducts and for the maximum endolymph displacements. These formulae contain the external impulses and the ratios of: (1) the radii of crus commune and Ducts (γ), (2) the lengths of crus commune and Ducts (λ). It was proven that an interconnected system composed of two Ducts, and also a system composed of two such Semicircular Duct systems, behaves as a pure rotation transducer (like a single Duct does), also when it is rotated excentrically. Duct systems with polygonal and circular geometries were used to evaluate whether an optimal value of λ would exist (γ was already considered elsewhere). Optimum values of λ in a range of about 0.10–0.52 were found. This rather wide range of values agrees with values from measurements. Optimization of an interconnected Duct system appeared to be equal to optimization of a system composed of separate Ducts.
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Biomechanical aspects of the evolution of Semicircular Duct systems
Netherlands Journal of Zoology, 2000Co-Authors: M. MullerAbstract:The system of Semicircular Ducts of the vertebrate labyrinth shows a conservative design on which considerable variations are present in individual species. During the last century, a single circular Duct model has been used to describe the mechanics of this system. MULLER & VERHAGEN (1988a, b) have constructed a more elaborate model in which three Semicircular Ducts are mutually interconnected. Thus, endolymph may flow from one Duct to another, driven by pressure-differences between the points of confluence of the Ducts, even when the rotation takes place only in the plane of a particular Duct. The system of interconnected Ducts fundamentally differs from a system of three separate Ducts. Time constants (indicating the response speed and recovery of the system after rotation) and endolymph displacement (indicating the sensitivity) are now determined by the flow in all parts of the vestibular system. The three-Duct theory gives physical evidence for the possible evolution of the Semicircular Duct system. It is proposed that the early vertebrates already possessed a three-Duct system comparable to that of recent Tetrapoda. This three-Duct system is preserved in Holocephali, Osteichthyes and Tetrapoda. The two-Duct system of recent Agnatha can be considered as a reDuction of the original three-Duct-design, related to their semi-sessile or parasitic lifestyle. The two-plus-one Duct system of Elasmobranchii forms a unique evolution-line which can also be derived from the original design.
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Size limitations in Semicircular Duct systems
Journal of Theoretical Biology, 1999Co-Authors: M. MullerAbstract:Abstract The present article discusses mechanical requirements and limitations which are applicable to the construction of the system of Semicircular Ducts, especially to its size. The simplified case of a single, uniform Duct system has been considered which can be described by a second order equation of motion. The principal functional quantities for this rotation-sensor are: (1) response speed; (2) sensitivity; and (3) regular flow. The response speed of a single, uniform Semicircular Duct is characterized by the short time constant (T2) which is dependent on the Duct radius (r). Its estimated range is from 0.04 ms in the smallest to 140 ms in the largest known labyrinth. The sensitivity is characterized by the maximal endolymph displacement after a step stimulus (xmax). Its estimated range is from 0.0016 μm to 5.97 mm (6.56 decades!), assuming an input angular velocity of ω=1 rad s−1. The Reynolds number is a measure for an undisturbed laminar flow. Its estimated range varies from 7.38·10−4to 45.1 for ω=1 rad s−1. The above data follow from graphs in which, for a single uniform Duct, circuit radius (R) is plotted against Duct radius (r) for labyrinths of 233 species belonging to different vertebrate-groups. A relation R =38.9·r1.60was determined. The smallest labyrinth was found in a carp larva (Cyprinus), the largest in a whale shark (Rhincodon). Large whales possess labyrinths of average mammalian size. It is revealed that Semicircular Duct size is bound by requirements concerning regular flow and by a too low response speed for large labyrinths, and by a too low sensitivity for small labyrinths. Other important quantities are mechanical amplification factors which are a consequence of more complex vestibular constructions than a single uniform Duct circuit. Allometric relationships are interpreted as compromises between the quantities mentioned. A hypothesis for the relatively large Semicircular Duct sizes of fishes, especially Elasmobranchii , compared with mammals and birds is presented.
Romain David - One of the best experts on this subject based on the ideXlab platform.
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Assessing morphology and function of the Semicircular Duct system: introducing new in-situ visualization and software toolbox.
Scientific Reports, 2016Co-Authors: Romain David, Alexander Stoessel, Alain Berthoz, Fred Spoor, Daniel BennequinAbstract:The Semicircular Duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual Semicircular Duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the Semicircular Duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized Duct system. We demonstrate the potential of these methods by presenting results for the Duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies.
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Assessing morphology and function of the Semicircular Duct system: introducing new in-situ visualization and software toolbox
Scientific Reports, 2016Co-Authors: Romain David, Alexander Stoessel, Alain Berthoz, Fred Spoor, Daniel BennequinAbstract:The Semicircular Duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual Semicircular Duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the Semicircular Duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized Duct system. We demonstrate the potential of these methods by presenting results for the Duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies. Ariadne is freely available at http://www.earbank.org .
Jan Verhagen - One of the best experts on this subject based on the ideXlab platform.
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Optimization of the mechanical performance of a two-Duct Semicircular Duct system--part 3: the positioning of the Ducts in the head.
Journal of Theoretical Biology, 2002Co-Authors: M. Muller, Jan VerhagenAbstract:Abstract In the majority of vertebrates, the horizontal Duct of the vestibular system lies approximately in the yawing plane of the head. The positioning of the vertical Ducts, however, is not in the pitch- and roll planes but the vertical Ducts generally lie under an angle of about 30–45° relative to the medial plane. Using the equations for a hydrodynamically interconnected two-Duct system, optimal positions of the vertical and horizontal Ducts in different vertebrate groups can be derived. It was stated that the mean response of the vertical Ducts should be optimized. This leads to a symmetrical positioning of the vertical Ducts with respect to the medial plane. In all observed vertebrate groups, a solution of μ =( π − α /2 is found ( μ is the angle of the vertical Ducts relative to the medial plane, α is the angle between the vertical Duct planes). For α =90°, this provides an equal sensitivity for pitch- and roll- movements. For α >90°, a larger sensitivity for pitch movements is obtained, at the expense of a lower sensitivity for roll movements. It is argued that the angle α between the vertical Ducts may vary from 90 to 120°. In most vertebrates, the centre of mass is stabilized by e.g. fins, tri- or quadrupedal stability, a crawling body or upside-down resting positions (e.g. bats). Birds are generally biped, so in walking they are also rather sensitive to roll. These features are related to labyrinth positioning in the head.
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Optimization of the mechanical performance of a two-Duct Semicircular Duct system--part 1: dynamics and Duct dimensions.
Journal of Theoretical Biology, 2002Co-Authors: M. Muller, Jan VerhagenAbstract:Abstract The classical representation of the Semicircular Duct system consists of three separate Duct circuits. The Ducts are, however, in reality, hydrodynamically interconnected. Muller & Verhagen (1988a,b) derived equations for the mechanical behaviour of an interconnected system with three Ducts (anterior, posterior and horizontal). An analytical solution of these equations would, however, be too complex to provide surveyable formulae. A system of two interconnected Ducts avoids this complexity whilst keeping the essentials of the coupling of Ducts intact. The solution of the equation of motion leads to expressions for time constants and maximal endolymph excursions which are functions of morphological parameters, viz . the ratios of radii ( γ ) and lengths ( λ ) of the common vestibular part (crus commune or utriculus) and the Ducts. The system possesses two short time constants which are shown to have similar values. The maximum endolymph displacements in the two Ducts after a steplike stimulus are the proDucts of the respective initial velocities and combinations of time constants. The initial velocities depend strongly on the position of the labyrinth with respect to the excitating rotation vector. Measured data of γ and λ are compared with the theoretical results. For γ , excellent agreement was found. λ is treated elsewhere.
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Optimization of the mechanical performance of a two-Duct Semicircular Duct system--part 2: excitation of endolymph movements.
Journal of theoretical biology, 2002Co-Authors: M. Muller, Jan VerhagenAbstract:Abstract The endolymph flow inside the Semicircular Ducts is analytically investigated by considering a system of two hydrodynamically interconnected Ducts. Rotation of this system adds an amount of motion (momentum) to parts of it. This results in an endolymph flow in generally all vestibular parts. The “external impulses” are the impulses which emerge by rotation of exclusively a particular vestibular part. The real impulses can be calculated from a set of equations which contain the external impulses. Analytical expressions are derived for the initial velocities in the Ducts and for the maximum endolymph displacements. These formulae contain the external impulses and the ratios of: (1) the radii of crus commune and Ducts (γ), (2) the lengths of crus commune and Ducts (λ). It was proven that an interconnected system composed of two Ducts, and also a system composed of two such Semicircular Duct systems, behaves as a pure rotation transducer (like a single Duct does), also when it is rotated excentrically. Duct systems with polygonal and circular geometries were used to evaluate whether an optimal value of λ would exist (γ was already considered elsewhere). Optimum values of λ in a range of about 0.10–0.52 were found. This rather wide range of values agrees with values from measurements. Optimization of an interconnected Duct system appeared to be equal to optimization of a system composed of separate Ducts.
Alexander Stoessel - One of the best experts on this subject based on the ideXlab platform.
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Assessing morphology and function of the Semicircular Duct system: introducing new in-situ visualization and software toolbox.
Scientific Reports, 2016Co-Authors: Romain David, Alexander Stoessel, Alain Berthoz, Fred Spoor, Daniel BennequinAbstract:The Semicircular Duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual Semicircular Duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the Semicircular Duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized Duct system. We demonstrate the potential of these methods by presenting results for the Duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies.
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Assessing morphology and function of the Semicircular Duct system: introducing new in-situ visualization and software toolbox
Scientific Reports, 2016Co-Authors: Romain David, Alexander Stoessel, Alain Berthoz, Fred Spoor, Daniel BennequinAbstract:The Semicircular Duct system is part of the sensory organ of balance and essential for navigation and spatial awareness in vertebrates. Its function in detecting head rotations has been modelled with increasing sophistication, but the biomechanics of actual Semicircular Duct systems has rarely been analyzed, foremost because the fragile membranous structures in the inner ear are hard to visualize undistorted and in full. Here we present a new, easy-to-apply and non-invasive method for three-dimensional in-situ visualization and quantification of the Semicircular Duct system, using X-ray micro tomography and tissue staining with phosphotungstic acid. Moreover, we introduce Ariadne, a software toolbox which provides comprehensive and improved morphological and functional analysis of any visualized Duct system. We demonstrate the potential of these methods by presenting results for the Duct system of humans, the squirrel monkey and the rhesus macaque, making comparisons with past results from neurophysiological, oculometric and biomechanical studies. Ariadne is freely available at http://www.earbank.org .
