Search results for "EEG"
showing 10 items of 313 documents
Gradient flows in random walk spaces
2021
El món digital ha comportat l'aparició de molts tipus de dades, de mida i complexitat creixents. De fet, els dispositius moderns ens permeten obtenir fàcilment imatges de major resolució, així com recopilar dades sobre cerques a la xarxa, anàlisis sanitàries, xarxes socials, sistemes d'informació geogràfica, etc. En conseqüència, l'estudi i el tractament d'aquests grans conjunts de dades té un gran interès i valor. En aquest sentit, els grafs ponderats proporcionen un espai de treball natural i flexible on representar les dades. En aquest context, un vèrtex representa una dada concreta i a cada aresta se li assigna un pes segons alguna mesura de semblança adequadament triada entre els vèrte…
Les compléments neurophysiologiques du diagnostic
2009
Les recherches presentees mettent en evidence des relations entre anomalies comportementales et cognitives et dysfonctionnements cerebraux sous-jacents a partir de methodes d'exploration electrophysiologique non invasives (electroencephalogramme, potentiels evoques auditifs). Trois types de troubles sont etudies : les troubles du sommeil, l'intolerance au changement et l'exploration visuelle atypique des visages humains. La complementarite des approches cliniques et neurophysiologiques est cruciale aux etapes du diagnostic fonctionnel, de l'intervention therapeutique et educative.
Discrimination des expressions faciales et environnement olfactif – Corrélats cérébraux en électroencéphalographie (EEG) chez l’adulte et le très jeu…
2019
This thesis examines the mechanisms subtending the perception of emotional facial expressions and their early development using a Fast Periodic Visual Presentation (FPVS) approach coupled with electroencephalography (EEG). More specifically, we tried to characterize brain responses reflecting facial expression discrimination and to determine whether hedonic odor contexts influence these responses in adults (studies 1 and 2), and in infants at different developmental stages (studies 3 and 4).We showed specific responses to the discrimination of every facial expression in the adult brain, indicating rapid and automatic categorization of basic facial expressions (study 1). In addition, we reve…
A deep learning framework for automatic diagnosis of unipolar depression.
2019
Abstract Background and purpose In recent years, the development of machine learning (ML) frameworks for automatic diagnosis of unipolar depression has escalated to a next level of deep learning frameworks. However, this idea needs further validation. Therefore, this paper has proposed an electroencephalographic (EEG)-based deep learning framework that automatically discriminated depressed and healthy controls and provided the diagnosis. Basic procedures In this paper, two different deep learning architectures were proposed that utilized one dimensional convolutional neural network (1DCNN) and 1DCNN with long short-term memory (LSTM) architecture. The proposed deep learning architectures au…
Auditory event-related potentials over medial frontal electrodes express both negative and positive prediction errors
2015
International audience; While the neuronal activation in the medial frontal cortex is thought to reflect higher-order evaluation processes of reward prediction errors when a reward deviates from our expectation, there is increasing evidence that the medial frontal activity might express prediction errors in general. However, given that several studies examined the medial frontal event-related potentials (ERPs) by comparing signals triggered by different stimuli and different anticipations, it remains an open question whether the medial frontal signals are sensitive to the valence of prediction errors. Here we orthogonally manipulated expectation magnitude (i.e., large/small expectation) and…
Driving on the motorway: the effect of alternating speed on driver's activation level and mental effort
2002
When most of the driving tasks are performed automatically, a driver's level of alertness may decline, as has been pointed out in the study of the phenomenon called 'highway hypnosis'. One possible countermeasure is to periodically vary the speed (Wertheim 1978), but the authors have not found any studies that directly assess the effectiveness of this countermeasure. The objective of our study has been to provide empirical evidence regarding the effects of this strategy on the level of driver activation on a motorway route in real traffic. In the present study activation level as indexed by a relative measure based on slow EEG activity tended to be significantly higher when speed was modifi…
Latency of interictal epileptiform discharges in long-term EEG recordings in epilepsy patients.
2015
AbstractPurposeTo assess the latency of interictal epileptiform discharges (IED) and seizures in long-term EEG recordings of patients with epilepsy.MethodIED latency was measured in 210 consecutive patients (mean (SD) age 38.6±13.9 years) with active epilepsy and the relationship to clinical variables was analyzed retrospectively. Median duration of EEG recording was 101.5h (95% confidence interval [CI] 92 to 117h).ResultsIEDs were absent in 45 (21.4%) and present in 165 (78.6%) patients who had a longer duration (p<0.001) and early onset (p<0.01) of epilepsy and more often had IEDs in prior standard EEGs (p<0.01), a structural etiology (OR 2.4, CI: 2.1–2.7), or temporal lobe epilepsy (OR 9…
Spontaneous brain activity and EEG microstates. A novel EEG/fMRI analysis approach to explore resting-state networks.
2009
The brain is active even in the absence of explicit input or output as demonstrated from electrophysiological as well as imaging studies. Using a combined approach we measured spontaneous fluctuations in the blood oxygen level dependent (BOLD) signal along with electroencephalography (EEG) in eleven healthy subjects during relaxed wakefulness (eyes closed). In contrast to other studies which used the EEG frequency information to guide the functional MRI (fMRI) analysis, we opted for transient EEG events, which identify and quantify brain electric microstates as time epochs with quasi-stable field topography. We then used this microstate information as regressors for the BOLD fluctuations. S…
Low-frequency rTMS inhibitory effects in the primary motor cortex: Insights from TMS-evoked potentials
2014
The neuromodulatory effects of repetitive transcranial magnetic stimulation (rTMS) have been mostly investigated by peripheral motor-evoked potentials (MEPs). New TMS-compatible EEG systems allow a direct investigation of the stimulation effects through the analysis of TMS-evoked potentials (TEPs).We investigated the effects of 1-Hz rTMS over the primary motor cortex (M1) of 15 healthy volunteers on TEP evoked by single pulse TMS over the same area. A second experiment in which rTMS was delivered over the primary visual cortex (V1) of 15 healthy volunteers was conducted to examine the spatial specificity of the effects. Single-pulse TMS evoked four main components: P30, N45, P60 and N100. M…
k-Nearest neighbour local linear prediction of scalp EEG activity during intermittent photic stimulation
2011
The characterization of the EEG response to photic stimulation (PS) is an important issue with significant clinical relevance. This study aims to quantify and map the complexity of the EEG during PS, where complexity is measured as the degree of unpredictability resulting from local linear prediction. EEG activity was recorded with eyes closed (EC) and eyes open (EO) during resting and PS at 5, 10, and 15. Hz in a group of 30 healthy subjects and in a case-report of a patient suffering from cerebral ischemia. The mean squared prediction error (MSPE) resulting from k-nearest neighbour local linear prediction was calculated in each condition as an index of EEG unpredictability. The linear or …