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Search Results: 1 - 10 of 454435 matches for " Jérémie Mattout "
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Canonical Source Reconstruction for MEG
Jérémie Mattout,Richard N. Henson,Karl J. Friston
Computational Intelligence and Neuroscience , 2007, DOI: 10.1155/2007/67613
Abstract: We describe a simple and efficient solution to the problem of reconstructing electromagnetic sources into a canonical or standard anatomical space. Its simplicity rests upon incorporating subject-specific anatomy into the forward model in a way that eschews the need for cortical surface extraction. The forward model starts with a canonical cortical mesh, defined in a standard stereotactic space. The mesh is warped, in a nonlinear fashion, to match the subject's anatomy. This warping is the inverse of the transformation derived from spatial normalization of the subject's structural MRI image, using fully automated procedures that have been established for other imaging modalities. Electromagnetic lead fields are computed using the warped mesh, in conjunction with a spherical head model (which does not rely on individual anatomy). The ensuing forward model is inverted using an empirical Bayesian scheme that we have described previously in several publications. Critically, because anatomical information enters the forward model, there is no need to spatially normalize the reconstructed source activity. In other words, each source, comprising the mesh, has a predetermined and unique anatomical attribution within standard stereotactic space. This enables the pooling of data from multiple subjects and the reporting of results in stereotactic coordinates. Furthermore, it allows the graceful fusion of fMRI and MEG data within the same anatomical framework.
BCI Could Make Old Two-Player Games Even More Fun: A Proof of Concept with “Connect Four”
Emmanuel Maby,Margaux Perrin,Olivier Bertrand,Ga?tan Sanchez,Jérémie Mattout
Advances in Human-Computer Interaction , 2012, DOI: 10.1155/2012/124728
Abstract: We present a brain-computer interface (BCI) version of the famous “Connect Four”. Target selection is based on brain event-related responses measured with nine EEG sensors. Two players compete against each other using their brain activity only. Importantly, we turned the general difficulty of producing a reliable BCI command into an advantage, by extending the game play and rules, in a way that adds fun to the game and might well prove to trigger up motivation in future studies. The principle of this new BCI is directly inspired from our own implementation of the classical P300 Speller (Maby et al. 2010, Perrin et al. 2011). We here establish a proof of principle that the same electrophysiological markers can be used to design an efficient two-player game. Experimental evaluation on two competing healthy subjects yielded an average accuracy of 82%, which is in line with our previous results on many participants and demonstrates that the BCI “Connect Four” can effectively be controlled. Interestingly, the duration of the game is not significantly affected by the usual slowness of BCI commands. This suggests that this kind of BCI games could be of interest to healthy players as well as to disabled people who cannot play with classical games. 1. Introduction Driven by the needs of people with physical disabilities, researchers have begun to work on direct brain-computer interfaces (BCIs), in the aim of enabling them to communicate and move without resorting to the usual peripheral nervous and muscular pathways. In BCIs, users have to manipulate their brain activity to produce signals that control computers or machines directly. This is challenging for both users and researchers. The users often need to learn how to control the device, which is cumbersome if not impossible, while researchers have to deal with the difficulty of processing highly variable and noisy signals online. However, this research could have a profound impact in various pathologies, including those for which patients suffer from cognitive impairments and could possibly benefit from brain or neurofeedback training. Indeed, the latter also rests upon our ability to extract online the neurophysiological markers that should be fed back to the patients, so that they could learn how to control it and yield a cognitive or behavioral improvement [1]. The most practical and widely applicable BCI solutions are based on noninvasive electrophysiological recordings, namely, electroencephalography (EEG). As command signals, those BCI use event-related potentials (ERPs) like the P300 [2] or
Objective and Subjective Evaluation of Online Error Correction during P300-Based Spelling
Perrin Margaux,Maby Emmanuel,Daligault Sébastien,Bertrand Olivier,Mattout Jérémie
Advances in Human-Computer Interaction , 2012, DOI: 10.1155/2012/578295
Abstract: Error potentials (ErrP) are alterations of EEG traces following the subject’s perception of erroneous feedbacks. They provide a way to recognize misinterpreted commands in brain-computer interfaces (BCI). However, this has been evaluated online in only a couple of studies and mostly with very few subjects. In this study, we implemented a P300-based BCI, including not only online error detection but also, for the first time, automatic correction. We evaluated it in 16 healthy volunteers. Whenever an error was detected, a new decision was made based on the second best guess of a probabilistic classifier. At the group level, correction did neither improve nor deteriorate spelling accuracy. However, automatic correction yielded a higher bit rate than a respelling strategy. Furthermore, the fine examination of interindividual differences in the efficiency of error correction and spelling clearly distinguished between two groups who differed according to individual specificity in ErrP detection. The high specificity group had larger evoked responses and made fewer errors which were corrected more efficiently, yielding a 4% improvement in spelling accuracy and a higher bit rate. Altogether, our results suggest that the more the subject is engaged into the task, the more useful and well accepted the automatic error correction. 1. Introduction A brain-computer interface (BCI) is a system that connects the brain to a computer directly and avoids the need for peripheral nerve and muscle activities to execute user’s actions. A major aim of BCI research is to allow patients with severe motor disabilities to regain autonomy and communication abilities [1]. This raises the crucial challenge of achieving a reliable control by measuring and interpreting brain activity on the fly. Due to the highly complex, noisy, and variable nature of brain signals, especially those obtained with noninvasive recordings using scalp EEG, the computer sometimes misinterprets the signals and makes a decision that does not match the user’s intention. In this context, it is highly relevant to look for a way to detect and correct errors. One way to tackle this issue is to appeal to the hybrid BCI approach [2], where it has been shown that BCI performance could be improved by supplementing the first-order brain signal with second-level information to aid the primary classifier and to improve the final decision or BCI output [3]. This complementary signal can be either of a cerebral origin or of a very different nature [2]. Along that line, a couple of recent studies have proposed to use
EEG and MEG Data Analysis in SPM8
Vladimir Litvak,Jérémie Mattout,Stefan Kiebel,Christophe Phillips,Richard Henson,James Kilner,Gareth Barnes,Robert Oostenveld,Jean Daunizeau,Guillaume Flandin,Will Penny,Karl Friston
Computational Intelligence and Neuroscience , 2011, DOI: 10.1155/2011/852961
Abstract: SPM is a free and open source software written in MATLAB (The MathWorks, Inc.). In addition to standard M/EEG preprocessing, we presently offer three main analysis tools: (i) statistical analysis of scalp-maps, time-frequency images, and volumetric 3D source reconstruction images based on the general linear model, with correction for multiple comparisons using random field theory; (ii) Bayesian M/EEG source reconstruction, including support for group studies, simultaneous EEG and MEG, and fMRI priors; (iii) dynamic causal modelling (DCM), an approach combining neural modelling with data analysis for which there are several variants dealing with evoked responses, steady state responses (power spectra and cross-spectra), induced responses, and phase coupling. SPM8 is integrated with the FieldTrip toolbox , making it possible for users to combine a variety of standard analysis methods with new schemes implemented in SPM and build custom analysis tools using powerful graphical user interface (GUI) and batching tools. 1. Introduction Statistical parametric mapping (SPM) is a free and open source academic software distributed under GNU General Public License. The aim of SPM is to communicate and disseminate methods for neuroimaging data analysis to the scientific community that have been developed by the SPM coauthors associated with the Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology. The origins of SPM software go back to 1990, when SPM was first formulated for the statistical analysis of positron emission tomography (PET) data [1, 2]. The software incorporated several important theoretical advances, such as the use of general linear model (GLM) to describe, in a generic way, a variety of experimental designs [3] and random field theory (RFT) to solve the problem of multiple comparisons arising from the application of mass univariate tests to images with multiple voxels [4]. As functional magnetic resonance imaging (fMRI) gained popularity later in the decade, SPM was further developed to support this new imaging modality, introducing the notion of a hemodynamic response function and associated convolution models for serially correlated time series. This formulation became an established standard in the field and most other free and commercial packages for fMRI analysis implement variants of it. In parallel, increasingly more sophisticated tools for registration, spatial normalization, and segmentation of functional and structural images were developed [5]. In addition to finessing fMRI and PET analyses, these methods made it possible to
Portraits avec visage absent: Aminadab (1942) de Maurice Blanchot
Majorel, Jérémie;
Alea : Estudos Neolatinos , 2010, DOI: 10.1590/S1517-106X2010000100007
Abstract: aminadab, the second novel published by blanchot, in 1942, reports the wander of thomas in a labyrinthine hotel. one there is observed a leitmotiv: descriptions of portraits whose faces are systematically erased or scrambled. this device puts a place a double law space and temporal of neutralization which informs the course of the character and plunges it in at the same time disappointing interpretative search and liberator: there is nothing to discover, if it is this nothing, beyond negativity.
Avita ronell: French connexion
Marjorel, Jérémie;
Alea : Estudos Neolatinos , 2011, DOI: 10.1590/S1517-106X2011000100004
Abstract: the spectacular style of philosopher american avital ronell, inspired by the performative devices of derrida, is good in the service of an authentic philosophic thought. she proceeds less by deconstruction of the fence of the western metaphysics than by secret connections and short circuit which electrify networks of unnoticed senses at fundamental authors, since plato until blanchot by way of flaubert, nietzsche and heidegger.
Putting Factions ‘Back in’ the Civil-Military Relations EquationGenesis, Maturation and Distortion of the Bangladeshi Army
Jérémie Codron
South Asia Multidisciplinary Academic Journal , 2007,
Abstract: This paper attempts to highlight two characteristics of the Bangladeshi army, namely factionalism and politicization. It shows how they hampered the institutionalization of civil-military relations in this country, and also suggests that the political power’s manoeuvres aggravated the army’s structural instability born of the Independence war. While arguing that the military’s professionalism and the institutionalization of the armed forces’ role were, in fact, encouraged during the 1980s military rule, the main thesis points to the return of civilians to power in 1991, which reintroduced partisan cleavages into the army and threatened the stability of civil-military relations. The trajectory of the Bangladeshi army indeed suggests that democratization does not necessarily lead to a higher degree of professionalism in armed forces.
Economia Política da Gest o de Resíduos Sólidos Municipais em Vitória (Espírito Santo)
Jérémie Cavé
Geografares , 2011,
Abstract: O artigo trata das intera es entre a globaliza o dos intercambios econ micos e a gest o dos resíduos sólidos municipais, através do estudo de caso de Vitória-ES. Além do servi o municipal de gest o do lixo, uma diversidade de atores participa da economia da recupera o dos resíduos sólidos secos. O lixo sendo por defini o aquilo que n o pertence a ninguém, esses diversos atores disputam sua apropria o e conflitos surgem. Ora, a recupera o dos resíduos recicláveis é um setor de interven o cujo caráter lucrativo é instável, dependente das varia es de valor das matérias primas. A quest o que se coloca, para os poderes públicos, é a de como conciliar uma cadeia de capta o de resíduos sólidos ritmada pelas flutua es do mercado com um servi o publico territorial?
Une école de la maturation ? A gestation school ? Analysis of artistic teaching between immediate gift, academic rhythm and creation process
Jérémie Vandenbunder
Temporalités , 2011,
Abstract: Cet article porte sur l'enseignement artistique tel qu'il est délivré dans les écoles des Beaux-arts fran aises. Il montre comment les acteurs investis dans ces formations, que ce soit les étudiants ou les enseignants, sont pris dans des jeux aux temporalités différentes. Posant tout d'abord comme paradoxale l'opposition entre l'innéité du don, valorisé aux beaux-arts, et la nécessité de suivre des études longues, nous tentons de montrer que le mythe de l'autodidaxie s'inscrit dans une perspective de socialisation propre au domaine des arts plastiques. Centré sur la socialisation professionnelle, dans le sillage des sociologues de l'école de Chicago, l’article présente les différentes étapes de ce processus en identifiant les stratégies et perspectives adoptées par les étudiants. Par ce biais, il met en lumière le passage progressif des élèves du monde profane au groupe professionnel. Enfin, il détaille la manière dont les formes atypiques d'organisation du travail, comme le travail par projets, sont appréhendées dans les écoles, en lien avec les contraintes du milieu scolaire. In French art schools, temporality is obviously an issue for students and teachers alike. First, while teachers and students are insisting on gift and talent, they also put the stress on the need to study and experiment in the long run. I consider this “myth of autodidaxy” as a sign of professional socialization. Art students are trying to assimilate their own path with the myths of artistic life. In addition to that, I have followed the steps of this socialization for five years, the length of an entire art school curriculum. As students, young artists have to leave behind their initial stereotypes on artists and the art world in order to enter the professional world. Eventually, I try here to analyze how specific forms of work and organization such as project-based work are taught in art schools and how students deal with them.
L'évolution de l'armature urbaine en Arabie du Sud: la vallée du Jawf du VIIIe siècle av. au VIe siècle apr. J.-C.
Jérémie Schiettecatte
M@ppemonde , 2006,
Abstract: L'approche archéogéographique du peuplement de la vallée du Jawf (Yémen) met ici en évidence les dynamiques qui affectent le réseau urbain de cette région au cours du Ier mill. av. J.-C. et au début de l'ère chrétienne. Cette approche permet de relativiser les causes jusqu'ici avancées du déclin et de la disparition des villes tout en mettant en avant l'impact de probables modifications environnementales et les conséquences d'une action anthropique sur le paysage plus en amont.
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