Non linear time varying model identification in ill-posed problems corresponding to neural activity estimation from EEG signals
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Esta tesis trata el problema inverso dinámico para la reconstrucción de fuentes a partir de señales EEG usando dos métodos: solución del Problema Inverso Dinámico considerando Restricciones Variantes e Invariantes con el Tiempo, y solución del Problema Inverso Dinámico Ponderado. Los métodos discutidos comprenden principalmente dos contribuciones: En primer lugar, la introducción de un modelo discreto no lineal basado en consideraciones fisiológicas que describa adecuadamente la dinámica de la actividad neuronal. En segundo lugar, la estimación de parámetros variantes en el tiempo que permitan mejorar el modelo no lineal, haciéndolo apropiado para la localización de fuentes electroencefalográficas durante actividad normal y patológica, tal como ataques epilépticos. La estimación realizada usando los modelos no lineales propuestos, presenta mejores resultados en términos del error de reconstrucción, comparado con métodos lineales o invariantes con el tiempo
Abstract : This thesis addresses the dynamical inverse problem of EEG source reconstruction by using two main approaches: Dynamic Inverse Problem solution considering Time Varying and Time invariant Constraints, and Weighted Dynamic Inverse Problem solution. Discussed approach of representation comprises two main contributions: Firstly, the introduction of a discrete–time nonlinear model grounded on physiological considerations that explains better the dynamics of the brain neural activity. Secondly, the inclusion of estimation of time varying parameters that allows the enhancement of the nonlinear model, making it suitable for electroencephalographic source localization of such abnormal neuronal activity as epileptic seizures. The estimation that is performed using proposed nonlinear dynamic models with time varying parameters provides an improvement in terms of reconstruction error, if comparing with similar referred linear approximations
Abstract : This thesis addresses the dynamical inverse problem of EEG source reconstruction by using two main approaches: Dynamic Inverse Problem solution considering Time Varying and Time invariant Constraints, and Weighted Dynamic Inverse Problem solution. Discussed approach of representation comprises two main contributions: Firstly, the introduction of a discrete–time nonlinear model grounded on physiological considerations that explains better the dynamics of the brain neural activity. Secondly, the inclusion of estimation of time varying parameters that allows the enhancement of the nonlinear model, making it suitable for electroencephalographic source localization of such abnormal neuronal activity as epileptic seizures. The estimation that is performed using proposed nonlinear dynamic models with time varying parameters provides an improvement in terms of reconstruction error, if comparing with similar referred linear approximations