7,352 research outputs found
An analytical model for surface EMG generation in volume conductors with smooth conductivity variations
No full textUdgivelsesdato: MA
Simulation of surface EMG signals generated by muscle tissues with in-homogeneity due to fiber pinnation
No full textSurface electromyographic (EMG) signal modeling has important applications in the interpretation of experimental EMG data. Most models of surface EMG generation considered volume conductors homogeneous in the direction of propagation of the action potentials. However, this may not be the case in practice due to local tissue inhomogeneities or to the fact that there may be groups of muscle fibers with different orientations. This study addresses the issue of analytically describing surface EMG signals generated by bi-pinnate muscles, i.e., muscles which have two groups of fibers with two orientations. The approach will also be adapted to the case of a muscle with fibers inclined in the depth direction. Such muscle anatomies are inhomogeneous in the direction of propagation of the action potentials with the consequence that the system can not be described as space invariant in the direction of source propagation. In these conditions, the potentials detected at the skin surface do not travel without shape changes. This determines numerical issues in the implementation of the model which are addressed in this work. The study provides the solution of the nonhomogenous, anisotropic problem, proposes an implementation of the results in complete surface EMG generation models (including finite-length fibers), and shows representative results of the application of the models proposed
Advances in surface EMG signal simulation with analytical and numerical descriptions of the volume conductor
No full textSurface electromyographic (EMG) signal modeling is important for signal interpretation, testing of processing algorithms, detection system design, and didactic purposes. Various surface EMG signal models have been proposed in the literature. In this study we focus on 1) the proposal of a method for modeling surface EMG signals by either analytical or numerical descriptions of the volume conductor for space-invariant systems, and 2) the development of advanced models of the volume conductor by numerical approaches, accurately describing not only the volume conductor geometry, as mainly done in the past, but also the conductivity tensor of the muscle tissue. For volume conductors that are space-invariant in the direction of source propagation, the surface potentials generated by any source can be computed by one-dimensional convolutions, once the volume conductor transfer function is derived (analytically or numerically). Conversely, more complex volume conductors require a complete numerical approach. In a numerical approach, the conductivity tensor of the muscle tissue should be matched with the fiber orientation. In some cases (e.g., multi-pinnate muscles) accurate description of the conductivity tensor may be very complex. A method for relating the conductivity tensor of the muscle tissue, to be used in a numerical approach, to the curve describing the muscle fibers is presented and applied to representatively investigate a bi-pinnate muscle with rectilinear and curvilinear fibers. The study thus propose an approach for surface EMG signal simulation in space invariant systems as well as new models of the volume conductor using numerical methods
Introduction
No full textCe volume est un hommage à la carrière de Claude Poirier et se situe dans le sillage de ses travaux. Partisan d’une vision mosaïque de la langue française nourrie des apports de la multitude de lieux où elle est parlée et des cultures dont elle se fait le vecteur, Claude Poirier peut être considéré comme un précurseur dans la diffusion de la connaissance de la variation linguistique francophone, nécessaire à sa reconnaissance, premier pas vers une définition rénovée d’une norme de référence qui restituerait au français son statut de grande langue de civilisation.
La plupart des contributions décrivent des faits linguistiques particuliers à des variétés de français d’autres lieux ou temps que la variété «parisienne » et d’aujourd’hui mais ne se penchent pas pour autant seulement sur des questions lexicales ou lexicographiques, abordant aussi la variation sous d’autres angles : stylistique, pragmatique, sémantique, terminologique et de la linguistique de corpus. Ce volume a pour but de mettre en lumière différents aspects de la variation lexicale. Il démontre la richesse qu’elle peut apporter, et combien la diversité linguistique du français mérite d’être mieux connue et entérinée dans un français de référence qui ne soit plus monochrome mais repensé sous le signe du partage, partant d’une observation scientifique «des français » qu’on ne peut ignorer désormais.
Contributions de G. Acerenza, D. Aquino-Weber, C. Brancaglion, S. Cotelli, A. Farina, K. Gauvin, A. Giaufret, C. Molinari, C. Nissille, J.-F. Plamondon, C. Poirier, J. Pruvost, N. Raschi, R. Raus, P. Rézeau, G. Saint-Yves, H. Sheeren, A. Thibault, R. Vézina, V. Zotti
In campagna elettorale senza genere né parità. Un’analisi della propaganda politica per le elezioni del 4 marzo 2018
No full text
Estimation of Muscle Fiber Conduction Velocity from Surface EMG Recordings by Optimal Spatial Filtering
No full textUdgivelsesdato: OC
Estimation of Muscle Fiber Conduction Velocity from Simulated Surface EMG in Pinnate Muscles
No full textUdgivelsesdato: MAR 1
The extraction of neural strategies from the surface EMG: an update
No full textA surface EMG signal represents the linear transformation of motor neuron discharge times by the compound action potentials of the innervated muscle fibers and is often used as a source of information about neural activation of muscle. However, retrieving the embedded neural code from a surface EMG signal is extremely challenging. Most studies use indirect approaches in which selected features of the signal are interpreted as indicating certain characteristics of the neural code. These indirect associations are constrained by limitations that have been detailed previously (Farina D, Merletti R, Enoka RM. J Appl Physiol 96: 1486 -1495, 2004) and are generally difficult to overcome. In an update on these issues, the current review extends the discussion to EMG-based coherence methods for assessing neural connectivity. We focus first on EMG amplitude cancellation, which intrinsically limits the association between EMG amplitude and the intensity of the neural activation and then discuss the limitations of coherence methods (EEG-EMG, EMG-EMG) as a way to assess the strength of the transmission of synaptic inputs into trains of motor unit action potentials. The debated influence of rectification on EMG spectral analysis and coherence measures is also discussed. Alternatively, there have been a number of attempts to identify the neural information directly by decomposing surface EMG signals into the discharge times of motor unit action potentials. The application of this approach is extremely powerful, but validation remains a central issu
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