Blind Source Separation Methods Applied to Muscle Artefacts Removing from Epileptic Eeg Recording: A Comparative Study.

International audienceElectroencephalogram (EEG) recordings are often contaminated with muscle artifacts. These artifacts obscure the EEG and complicate its interpretation or even make the interpretation unfeasible. In this paper, realistic spike EEG signals are simulated from the activation of a 5 cm2 epileptic patch in the left superior temporal gyrus. Background activities and real muscle artifacts are then added to the simulated data. We compare the efficiency of Empirical Mode Decomposition (EMD), Independent Component Analysis (ICA) and Blind Source Separation based on Canonical Correlation Analysis (BSS-CCA) to remove muscle artifacts from the EEG signals. The quantitative comparison indicates that the EMD approach exhibits a better performance than ICA and BSS-CCA, especially in the case of very low Signal to Noise Ratio (SNR)

Identification of the period of stability in a balance test after stepping up using a simplified cumulative sum

Falls are a major cause of death in older people. One method used to predict falls is analysis of Centre of Pressure (CoP) displacement, which provides a measure of balance quality. The Balance Quality Tester (BQT) is a device based on a commercial bathroom scale that calculates instantaneous values of vertical ground reaction force (Fz) as well as the CoP in both anteroposterior (AP) and mediolateral (ML) directions. The entire testing process needs to take no longer than 12 s to ensure subject compliance, making it vital that calculations related to balance are only calculated for the period when the subject is static. In the present study, a method is presented to detect the stabilization period after a subject has stepped onto the BQT. Four different phases of the test are identified (stepping-on, stabilization, balancing, stepping-off), ensuring that subjects are static when parameters from the balancing phase are calculated. The method, based on a simplified cumulative sum (CUSUM) algorithm, could detect the change between unstable and stable stance. The time taken to stabilize significantly affected the static balance variables of surface area and trajectory velocity, and was also related to Timed-up-and-Go performance. Such a finding suggests that the time to stabilize could be a worthwhile parameter to explore as a potential indicator of balance problems and fall risk in older people

ARPEGE: Anticipation et Répérage: Pack d’évaluation Gérontologique Embarqué

International audienc

ICA versus CCA pour le débruitage de signaux épileptiques intercritiques : une étude comparative de performances basée sur la localisation de la zone épileptogène. [ICA vs CCA for the denoising of interictal epileptic signals: A study of performance based on source localization.]

International audienceWe propose in this study to compare the performances of two stochastic approaches (independent component analysis [ICA] and canonical correlation analysis [CCA]) to remove the muscular artefacts (EMG) from surface EEG signals in the context of epilepsy. The goal is to choose the method that better enhance the signals of interest (transient events called interictal spikes occur between seizures and background activity). In this paper, realistic EEG epileptic spikes are simulated from the activation of an epileptic patch. Real muscle artefacts and EEG background are then added to the simulated surface EEG. Such data allow us to quantify the performance of denoising methods since we have the "ground truth"

Performances des approches déterministes et stochastiques pour le débruitage des signaux épileptiques intercritiques

National audienceOn propose dans cette étude de comparer les performances d'une approche déterministe (Décomposition Modale Empirique, EMD), et deux approches stochastiques (l'Analyse en Composantes Indépendantes, ICA et l'Analyse de Corrélation Canonique, CCA) pour l'élimination des artéfacts musculaires (EMG) affectant les signaux ElectroEncéphaloGraphiques (EEG, électrodes de scalp) des patients épileptiques. L'objectif final est de choisir la méthode qui réhausse au mieux les signaux d'intérêt (transitoires de type pointes épileptiques et activité de fond) afin d'améliorer leur analyse qualitative et quantitative. La démarche entreprise pour la comparaison de ces trois méthodes est originale puisqu'elle exploite des signaux EEG de surface simulés, qui reproduisent de façon très réaliste les pointes épileptiques ainsi que l'activité EEG de fond; on ajoute à ces simulations des activités musculaires provenant de tracés EEG réels. Ces simulations nous apportent la "vérité terrain" concernant les sources d'intérêt et permettent donc de quantifier les performances de chacune des trois méthodes étudiées. Les résultats quantitatifs montrent que l'EMD offre des performances plus intéressantes que celles de l'ICA et de la CCA dans le contexte étudié lorsque le rapport signal sur bruit est très faible

Muscle artifact removal in ictal scalp-EEG based on blind source separation

International audienceElectroencephalogram (EEG) recordings are often contaminated with muscle artifacts. These artifacts obscure the EEG and complicate its interpretation or even make the interpretation unfeasible. This paper focuses on the particular context of extraction of low-voltage rapid ictal discharges from ictal scalp-EEG activity cantaminated by muscle artifact. In this context our aim was to evaluate the ability of Independent Component Analysis (ICA) and Canonical Correlation Analysis (CCA), to remove muscle artefacts from surface EEG sig- nals. The efficiency of ICA and CCA to correct the muscular artifact was evaluated both on simulated data and on real data recorded in an epileptic patient. The obtained results show that some ICA methods and CCA removed successfully the muscle artifact without altering the recorded underlying ictal activity

Balance quality assessment as an early indicator of physical frailty in older people

Frailty is an increasingly common geriatric condition that results in an increased risk of adverse health outcomes such as falls. The most widely-used means of detecting frailty is the Fried phenotype, which includes several objective measures such as grip strength and gait velocity. One method of screening for falls is to measure balance, which can be done by a range of techniques including the assessment of the Centre of Pressure (CoP) during a balance assessment. The Balance Quality Tester (BQT) is a device based on a commercial bathroom scale that can evaluate balance quality. The BQT provides instantaneously the position of the CoP (stabilogram) in both anteroposterior (AP) and mediolateral (ML) directions and can estimate the vertical ground reaction force. The purpose of this study was to examine the relationship between balance quality assessment and physical frailty. Balance quality was compared to physical frailty in 186 older subjects. Rising rate (RR) was slower and trajectory velocity (TV) was higher in subjects classified as frail for both grip strength and gait velocity (p<;0.05). Balance assessment could be used in conjunction with functional tests of grip strength and gait velocity as a means of screening for frailty

Is there a relationship between frailty indices and balance assessment in older people?

Grip-strength, walking speed and weight-loss are key measurements in the evaluation of frailty. According to L. Fried, these quantities are compared with thresholds, leading to associated frailty indices that would afterwards be combined to establish an overall decision. One of the consequences of frailty is an increasing risk of falls, which are a major cause of death of older people. The purpose of this study is to examine the possible relationships that could exist between grip-strength, walking speed, weight-loss and other parameters extracted from balance quality assessment for older subjects. The study shows that a relationship does exist between the balance quality parameters and the frailty indices

Projet Innovant pour le Changement d’Ampleur de la Domomédecine (PiCADo)

International audienc

Projet Innovant pour le Changement d’Ampleur de la Domomédecine (PiCADo)

International audienc