Evaluation de la réorganisation cérébrale du langage chez les patients épileptiques. Apport de la psychologie cognitive

National audienceL'objectif de cet article est de rappeler les exigences spécifiques nécessaires à la mise en place d'un paradigme d'activation en IRMf dans le cadre de l'évaluation fonctionnelle du langage lors du bilan pré- et post-chirurgical de l'épilepsie

Dynamic causal modeling of spatiotemporal integration of phonological and semantic processes: an electroencephalographic study.: DCM of phonology and semantics

International audienceIntegration of phonological and lexicosemantic processes is essential for visual word recognition. Here we used dynamic causal modeling of event-related potentials, combined with group source reconstruction, to estimate how those processes translate into context-dependent modulation of effective connectivity within the temporal-frontal language network. Fifteen healthy human subjects performed a phoneme detection task in pseudo-words and a semantic categorization task in words. Cortical current densities revealed the sequential activation of temporal regions, from the occipital-temporal junction toward the anterior temporal lobe, before reaching the inferior frontal gyrus. A difference of activation between phonology and semantics was identified in the anterior temporal lobe within the 240-300 ms peristimulus time window. Dynamic causal modeling indicated this increase of activation of the anterior temporal lobe in the semantic condition as a consequence of an increase of forward connectivity from the posterior inferior temporal lobe to the anterior temporal lobe. In addition, fast activation of the inferior frontal region, which allowed a feedback control of frontal regions on the superior temporal and posterior inferior temporal cortices, was found to be likely. Our results precisely describe spatiotemporal network mechanisms occurring during integration of phonological and semantic processes. In particular, they support the hypothesis of multiple pathways within the temporal lobe for language processing, where frontal regions would exert a top-down control on temporal regions in the recruitment of the anterior temporal lobe for semantic processing

Hemispheric specialization and mapping of language in healthy subjects and epileptic patients : effect of inter-and intra-individual variable. Behavioral neuropsychological and neurophysiological (fMRI) assessment.

Le but de ce travail est d'identifier l'effet de certaines caractéristiques liée aux individus et aux paradigmes expérimentaux sur l'organisation inter-hémisphérique (spécialisation hémisphérique) et intra-hémisphérique (cartographie fonctionnelle) du langage, (a) en condition physiologique chez les sujets sains et (b) en condition pathologique chez des patients présentant une épilepsie focale et pharmaco-résistante. Pour aborder cette question, une approche méthodologique expérimentale pluridisciplinaire a été utilisée. Plus spécifiquement nous avons évalué l'effet des variables inter-individuelles (sexe, préférence manuelle, et caractéristiques pathologiques) et intra-individuelles (opération linguistique, tâche, type de stimuli) sur l'organisation cérébrale du langage. L'un des objectifs de ce travail est de corroborer les données issues de différentes méthodes pour mettre en place un modèle de représentation et de réorganisation langagière, en fonction des facteurs considérés. Un second objectif de ce travail est de proposer aux cliniciens des outils permettant de quantifier la spécialisation hémisphérique chez les patients épileptiques. Nos résultats chez les sujets sains mettent en évidence une interaction entre les variables inter- et intra-individuelles sur le degré de spécialisation hémisphérique et sur la cartographie fonctionnelle du langage. Chez les patients épileptiques, nos résultats préliminaires permettent de mettre en relation les patterns de réorganisation cérébrale et les variables évaluées. L'ensemble de nos résultats montre que la neuropsychologie cognitive et la neuroimagerie fonctionnelle apportent des informations complémentaires nous permettant une meilleure compréhension des mécanismes d'organisation et réorganisation cérébrale. Mots clés : langage, spécialisation, hémisphère, champ visuel divisé, IRMf, phonologie, sémantique, prosodie, sexe, sain, épileptique, plasticité, réorganisation.The purpose of this PhD research was to identify the effect of several individual and experimental variables on hemispheric specialization and cortical mapping of language in healthy subjects and epileptic patients. The question was addressed by means of a multidisciplinary approach including behavioral, neuropsychological and neurophysiological (fMRI) testing. The main goal of this work was to corroborate data provided from all these methods and to build a model of the representation and reorganization (plasticity) of language according to the considered factors. Moreover, we aimed to provide several practical tools to clinicians for presurgical evaluation of hemispheric specialization in patients with drug-resistant epilepsy. Overall, our results reflect the necessity to use a multidimensional approach composed of complementary techniques and methods, in order to assess cerebral representations in normal and pathological conditions. Key words: language, specialization, hemisphere, divided visual field, fMRI, phonology, semantics, prosody, gender, healthy, epilepsy, plasticity, reorganization

Spécialisation hémisphérique et cartographie du langage chez le sujet sain et les patients épileptiques : effet des variables inter- et intra-individuelles. Evaluation comportementale, neuropsychologique et neurophysiologique (IRM fonctionnelle)

The purpose of this PhD research was to identify the effect of several individual and experimental variables on hemispheric specialization and cortical mapping of language in healthy subjects and epileptic patients. The question was addressed by means of a multidisciplinary approach including behavioral, neuropsychological and neurophysiological (fMRI) testing. The main goal of this work was to corroborate data provided from all these methods and to build a model of the representation and reorganization (plasticity) of language according to the considered factors. Moreover, we aimed to provide several practical tools to clinicians for presurgical evaluation of hemispheric specialization in patients with drug-resistant epilepsy. Overall, our results reflect the necessity to use a multidimensional approach composed of complementary techniques and methods, in order to assess cerebral representations in normal and pathological conditions. Key words: language, specialization, hemisphere, divided visual field, fMRI, phonology, semantics, prosody, gender, healthy, epilepsy, plasticity, reorganization.Le but de ce travail est d'identifier l'effet de certaines caractéristiques liée aux individus et aux paradigmes expérimentaux sur l'organisation inter-hémisphérique (spécialisation hémisphérique) et intra-hémisphérique (cartographie fonctionnelle) du langage, (a) en condition physiologique chez les sujets sains et (b) en condition pathologique chez des patients présentant une épilepsie focale et pharmaco-résistante. Pour aborder cette question, une approche méthodologique expérimentale pluridisciplinaire a été utilisée. Plus spécifiquement nous avons évalué l'effet des variables inter-individuelles (sexe, préférence manuelle, et caractéristiques pathologiques) et intra-individuelles (opération linguistique, tâche, type de stimuli) sur l'organisation cérébrale du langage. L'un des objectifs de ce travail est de corroborer les données issues de différentes méthodes pour mettre en place un modèle de représentation et de réorganisation langagière, en fonction des facteurs considérés. Un second objectif de ce travail est de proposer aux cliniciens des outils permettant de quantifier la spécialisation hémisphérique chez les patients épileptiques. Nos résultats chez les sujets sains mettent en évidence une interaction entre les variables inter- et intra-individuelles sur le degré de spécialisation hémisphérique et sur la cartographie fonctionnelle du langage. Chez les patients épileptiques, nos résultats préliminaires permettent de mettre en relation les patterns de réorganisation cérébrale et les variables évaluées. L'ensemble de nos résultats montre que la neuropsychologie cognitive et la neuroimagerie fonctionnelle apportent des informations complémentaires nous permettant une meilleure compréhension des mécanismes d'organisation et réorganisation cérébrale. Mots clés : langage, spécialisation, hémisphère, champ visuel divisé, IRMf, phonologie, sémantique, prosodie, sexe, sain, épileptique, plasticité, réorganisation

Spécialisation hémisphérique et cartographie du langage chez le sujet sain et les patients épileptiques (effet des variables inter- et intra-individuelles. Evaluation comportementale, neuropsychologique et neurophysiologique (IRM fonctionnelle))

Le but de ce travail est d'identifier l'effet de certaines caractéristiques liée aux individus et aux paradigmes expérimentaux sur l'organisation inter-hémisphérique (spécialisation hémisphérique) et intra-hémisphérique (cartographie fonctionnelle) du langage, (a) en condition physiologique chez les sujets sains et (b) en condition pathologique chez des patients présentant une épilepsie focale et pharmaco-résistante. Pour aborder cette question, une approche méthodologique expérimentale pluridisciplinaire a été utilisée. Plus spécifiquement nous avons évalué l'effet des variables inter-individuelles (sexe, préférence manuelle, et caractéristiques pathologiques) et intra-individuelles (opération linguistique, tâche, type de stimuli) sur l'organisation cérébrale du langage. L'un des objectifs de ce travail est de corroborer les données issues de différentes méthodes pour mettre en place un modèle de représentation et de réorganisation langagière, en fonction des facteurs considérés. Un second objectif de ce travail est de proposer aux cliniciens des outils permettant de quantifier la spécialisation hémisphérique chez les patients épileptiques. Nos résultats chez les sujets sains mettent en évidence une interaction entre les variables inter- et intra-individuelles sur le degré de spécialisation hémisphérique et sur la cartographie fonctionnelle du langage. Chez les patients épileptiques, nos résultats préliminaires permettent de mettre en relation les patterns de réorganisation cérébrale et les variables évaluées. L'ensemble de nos résultats montre que la neuropsychologie cognitive et la neuroimagerie fonctionnelle apportent des informations complémentaires nous permettant une meilleure compréhension des mécanismes d'organisation et réorganisation cérébrale. Mots clés : langage, spécialisation, hémisphère, champ visuel divisé, IRMf, phonologie, sémantique, prosodie, sexe, sain, épileptique, plasticité, réorganisation.The purpose of this PhD research was to identify the effect of several individual and experimental variables on hemispheric specialization and cortical mapping of language in healthy subjects and epileptic patients. The question was addressed by means of a multidisciplinary approach including behavioral, neuropsychological and neurophysiological (fMRI) testing. The main goal of this work was to corroborate data provided from all these methods and to build a model of the representation and reorganization (plasticity) of language according to the considered factors. Moreover, we aimed to provide several practical tools to clinicians for presurgical evaluation of hemispheric specialization in patients with drug-resistant epilepsy. Overall, our results reflect the necessity to use a multidimensional approach composed of complementary techniques and methods, in order to assess cerebral representations in normal and pathological conditions. Key words: language, specialization, hemisphere, divided visual field, fMRI, phonology, semantics, prosody, gender, healthy, epilepsy, plasticity, reorganization.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

What do patients with epilepsy tell us about language dynamics? A review of fMRI studies

International audienceThe objective of this review is to resume major neuroimaging findings on language organization and plasticity in patients with focal and refractory epilepsy, to discuss the effect of modulatory variables that should be considered alongside patterns of reorganization, and to propose possible models of language reorganization. The focal and refractory epilepsy provides a real opportunity to investigate various types of language reorganization in different conditions. The ‘chronic’ condition (induced by the epileptogenic zone or EZ) is associated with either recruitment of homologous regions of the opposite hemisphere or recruitment of intrahemispheric, nonlinguistic regions. In the ‘acute’ condition (neurosurgery and EZ resection), the initial interhemispheric shift (induced by the chronic EZ) could follow a reverse direction, back to the initial hemisphere. These different patterns depend on several modulatory factors and are associated with various levels of language performance. As a neuroimaging tool, functional magnetic resonance imaging enables the detailed investigation of both hemispheres simultaneously and allows for comparison with healthy controls, potentially creating a more comprehensive and more realistic picture of brain-language relations. Importantly, functional neuroimaging approaches demonstrate a good degree of concordance on a theoretical level, but also a considerable degree of individual variability, attesting to the clinical importance with these methods to establish, empirically, language localization in individual patients. Overall, the unique features of epilepsy, combined with ongoing advances in technology, promise further improvement in understanding of language substrate

Short case Report: Ictal inner speech jargon

International audienceWe report on the case of a woman with jargon aphasic seizures who provided a careful written report of inner speech jargon occurring during her seizures. This inner speech jargon description is an unusual finding since in most aphasic disorders, patients also suffer from anosognosia. This case report may suggest that jargon could also involve inner speech and could be innerly detected as such. It provides an argument supporting the idea that common mechanisms may underlie both "overt" and "covert" production of jargon during aphasia

Behavioral evidence for inter-hemispheric cooperation during a lexical decision task: a divided visual field experiment.

International audienceHIGHLIGHTSThe redundant bilateral visual presentation of verbal stimuli decreases asymmetry and increases the cooperation between the two hemispheres.The increased cooperation between the hemispheres is related to semantic information during lexical processing.The inter-hemispheric interaction is represented by both inhibition and cooperation. This study explores inter-hemispheric interaction (IHI) during a lexical decision task by using a behavioral approach, the bilateral presentation of stimuli within a divided visual field experiment. Previous studies have shown that compared to unilateral presentation, the bilateral redundant (BR) presentation decreases the inter-hemispheric asymmetry and facilitates the cooperation between hemispheres. However, it is still poorly understood which type of information facilitates this cooperation. In the present study, verbal stimuli were presented unilaterally (left or right visual hemi-field successively) and bilaterally (left and right visual hemi-field simultaneously). Moreover, during the bilateral presentation of stimuli, we manipulated the relationship between target and distractors in order to specify the type of information which modulates the IHI. Thus, three types of information were manipulated: perceptual, semantic, and decisional, respectively named pre-lexical, lexical and post-lexical processing. Our results revealed left hemisphere (LH) lateralization during the lexical decision task. In terms of inter-hemisphere interaction, the perceptual and decision-making information increased the inter-hemispheric asymmetry, suggesting the inhibition of one hemisphere upon the other. In contrast, semantic information decreased the inter-hemispheric asymmetry, suggesting cooperation between the hemispheres. We discussed our results according to current models of IHI and concluded that cerebral hemispheres interact and communicate according to various excitatory and inhibitory mechanisms, all which depend on specific processes and various levels of word processing

Hemispheric specialization for language according to grapho-phonemic transformation and gender. A divided visual field experiment.

International audienceThis behavioral study aimed at assessing the effect of two variables on the degree of hemispheric specialization for language. One of them was the grapho-phonemic translation (transformation) (letter-sound mapping) and the other was the participants'gender. The experiment was conducted with healthy volunteers. A divided visual field procedure has been used to perform a phoneme detection task implying either regular (transparent) grapho-phonemic translation (letter-sound mapping consistency) or irregular (non-transparent) grapho-phonemic translation (letter-sound mapping inconsistency). Our results reveal a significant effect of grapho-phonemic translation on the degree of hemispheric dominance for language. The phoneme detection on items with transparent translation (TT) was performed faster than phoneme detection on items with non-transparent translation (NTT). This effect seems to be due to faster identification of TT than NTT when the items were presented in the left visual field (LVF)-right hemisphere (RH). There was no difference between TT and NTT for stimuli presented in the right visual field (RVF)-left hemisphere (LH). This result suggests that grapho-phonemic translation or the degree of transparency can affect the degree of hemispheric specialization, by modulating the right hemisphere activity. With respect to gender, male participants were significantly more lateralized than female participants but no interaction was observed between gender and degree of transparency