Les patients atteints d'épilepsie du lobe temporal (TLE) ainsi que les rats injectés à l'acide kaïnique (KA) exhibent des patrons pathophysiologiques similaires de crises, de sclérose de l'hippocampe et de perte de certains types neuronaux. Parmi les cellules atteintes dans le modèle KA du TLE on retrouve certains interneurones inhibiteurs du CA1. En effet, certains interneurones des couches oriens et alveus (O/A-IN) meurent suite à une injection de KA chez le rat, contrairement aux interneurones à la bordure des couches radiatum et lacunosum/moleculare (R/LM-IN) de la même région. Bien que cette perte soit empêchée par des antagonistes des récepteurs glutamatergiques métabotropes de groupe I (mGluR1/5), la cause de cette perte sélective des O/A-INs reste à être précisée. Au cours des travaux de cette thèse, nous avons effectué des enregistrements de patch-clamp en configuration cellule-entière en modes courant- et voltage-imposé couplés à l'imagerie calcique pour étudier les causes de la vulnérabilité sélective des O/A-INs dans ce modèle. Dans un premier temps, nous avons évalué les effets d'une application aiguë de KA sur les propriétés membranaires et calciques pour voir s'il y avait des différences entre les O/A-INs et R/LM-INs qui pourraient expliquer la vulnérabilité. Nos résultats montrent que les dépolarisations et variations de résistance d'entrée ainsi que les augmentations de calcium intracellulaire, dépendantes principalement des récepteurs -amino-3-hydroxy-5-methyl-4-isoxasole propionic acid (AMPA), sont similaires entre les deux types d'interneurones suite à des applications aigües de KA. Ceci indique que l'effet aigu du KA sur les interneurones ne serait pas la cause de la vulnérabilité des O/A-INs. Dans un second temps nous avons comparé l'implication des sous-types de récepteurs mGluR1 et 5 dans l'activité épileptiforme des deux types d'interneurones évoquée dans un modèle de tranche désinhibée. Dans ce cas, nos données montrent un rôle important des mGluR1 et 5 activés synaptiquement lors des décharges épileptiformes et ce, de manière spécifique aux O/A-INs. Les courants synaptiques sous-tendant ces décharges impliquent des récepteurs ionotropes et métabotropes du glutamate. En présence d'antagonistes des récepteurs ionotropes glutamatergiques, les courants synaptiques sont biphasiques et formés de composantes rapide et lente. Les récepteurs mGluR1 et 5 sont différemment impliqués dans ces composantes: les mGluR5 étant impliqués dans les composantes rapide et lente, et les mGluR1 que dans la composante lente. Ces résultats indiquent que les mGluR1 et 5 contribuent différemment à l'activité épileptiforme, et spécifiquement dans les O/A-INs, et pourraient donc être impliqués dans la vulnérabilité sélective de ces interneurones dans le modèle KA. / Temporal lobe epilepsy (TLE) patients, as well as kainic acid (KA)-treated rodents, display similar pathophysiological patterns of behavioural seizures, hippocampal sclerosis and loss of certain neuronal types in the hippocampus. Among the cell types selectively vulnerable in the experimental KA model of TLE are certain inhibitory interneurons of the CA1 hippocampal region. Specifically, interneurons located in the oriens and alveus layers (O/A-IN) are lost following KA injections, whereas interneurons found in the radiatum/lacunosum-moleculare layers (R/LM-IN) are resistant. Although it has been shown that the group I metabotropic glutamate receptor (mGluR1/5) inhibitors can block this cell loss seen in the KA model, the precise cause of the selective O/A-IN vulnerability remains to be clarified. In this thesis, we have performed whole-cell patch-clamp recordings with simultaneous calcium imaging in an effort to elucidate the cause of the selective vulnerability of O/A-INs. We first determined the effects of acute KA applications on membrane properties and intracellular calcium rises in hippocampal slices to see if they might be different between O/A-INs and R/LM-INs. Our results reveal similar -amino-3-hydroxy-5-methyl-4-isoxasole propionic acid (AMPA) receptor dependent membrane depolarizations, input resistance variations and calcium reponses in these cells following KA applications, suggesting that acute KA actions may not cause the selective vulnerability of O/A-INs. Furthermore, we evaluated the contribution of mGluR1/5 to epileptiform discharges evoked in a disinhibited slice model, comparing responses between O/A-INs and R/LM-INs. Our data show an important role of synaptically activated mGluR1/5 during epileptiform discharges specifically in O/A-INs. In addition we show that the synaptic currents underlying these discharges involve ionotropic and metabotropic glutamate receptors. In the presence of antagonists of ionotropic glutamate receptors, synaptic currents are biphasic and composed of fast and slow components. mGluR1 and mGluR5 are involved differently in these components with mGluR5 implicated in fast and slow components and mGluR1 in the slow component only. Our findings therefore suggest that mGluR1 and 5 contribute differently to epileptiform discharges, and do so specifically in O/A-INs, suggesting that their activation may contribute to the selective vulnerability of these interneurons in the KA model of TLE.

La recherche dans le domaine de la mémoire sémantique a permis de documenter l’effet de concrétude (avantage pour les mots concrets relativement aux mots abstraits), et plus récemment, l’effet de concrétude inverse (avantage pour les mots abstraits relativement aux mots concrets). Ces effets, observés chez le sujet sain et dans différentes populations cliniques en neurologie, ont suscité de nombreuses interprétations théoriques, autant sur le plan cognitif que neuroanatomique. En effet, cette double dissociation entre les deux types de concepts suggère que leur traitement doit reposer au moins en partie sur des processus mentaux et neuroanatomiques distincts. Néanmoins, les origines de ces différences restent largement débattues et sont caractérisées par une absence notable de consensus. L’objectif principal de la présente thèse est d’explorer les substrats cérébraux sous-tendant la compréhension des concepts concrets et abstraits. Dans un premier temps, un article de revue de la littérature dresse un état des lieux des connaissances actuelles portant sur le traitement sémantique des mots concrets et abstraits ainsi que sur leurs fondements cérébraux. Cet article met une emphase particulière sur les différences inter-hémisphériques dans le traitement des mots concrets et abstraits (Article 1). Dans un deuxième temps, une étude expérimentale de la compréhension des mots concrets et abstraits a été réalisée auprès de populations cliniques rares, des patients ayant subi soit i) une résection unilatérale de la partie antérieure du lobe temporal (temporo-polaire), soit ii) une résection unilatérale de la région hippocampique (temporale interne) (Article 2). Le premier article fait ressortir la grande hétérogénéité des résultats dans le domaine, et suggère que les différences observées dans le traitement des mots concrets et abstraits peuvent difficilement être interprétées seulement en termes de différences inter-hémisphériques. Les résultats du second article indiquent qu’une lésion de la région temporale antérieure gauche ou droite entraîne une atteinte plus marquée des concepts concrets comparativement aux abstraits, alors qu’une lésion unilatérale des régions temporales internes affecte de manière équivalente le traitement sémantique des deux types de concepts. Les implications théoriques et cliniques de ces résultats sont discutées, ainsi que les limites et perspectives futures. / Research in the field of semantic memory has allowed to document the concreteness effect (advantage for concrete words relative to abstract words), and more recently, the reversal of the concreteness effect (advantage for abstract words relative to concrete words). These effects, observed in healthy subjects and in different clinical neurological populations, have yielded numerous theoretical interpretations, both on cognitive and on neuroanatomical levels. Indeed, this double dissociation between the two kinds of concepts suggests that their processing relies at least partly on distinct mental and neuroanatomical bases. Nevertheless, the origins of those differences remain largely debated and are marked by a notable lack of consensus. The principal goal of the present thesis is to explore the cerebral substrates underlying the comprehension of concrete and abstract concepts. First, a literature review summarizes current knowledge about the processing of concrete and abstract concepts as well as their neural bases. This article emphasizes in particular the inter-hemispheric differences in the processing of those concepts (Article 1). Secondly, an experimental study of the comprehension of concrete and abstract concepts was conducted with a rare clinical population, patients who have undergone either i) a unilateral resection of the anterior part of the temporal lobe (temporal pole), either ii) a unilateral resection of the hippocampal region (internal temporal structures) (Article 2). The first article highlights the important heterogeneity of the results in the field, and suggests that the observed differences in the processing of concrete and abstract concepts can hardly be explained solely in terms of inter-hemispheric differences. Results of the second article indicate that damage to anterior temporal regions, either left or right, can cause a more pronounced deficit of concrete concepts, as compared to abstract concepts, while damage to internal temporal regions affects the semantic processing of both kinds of concepts in an equivalent way. The theoretical and clinical implications of these results are discussed, and the limits and future research perspectives are also addressed.

No description available.

INTRODUÇÃO: Epilepsia do lobo temporal mesial (ELTM) por esclerose hipocampal (EH) é a forma de epilepsia focal mais comum na idade adulta e a causa mais frequente de refratariedade ao tratamento clínico. Apesar de se tratar de uma patologia da substância cinzenta, alguns estudos, por meio da imagem por tensor de difusão (diffusion tensor imaging-DTI), têm demonstrado alteração da substância branca temporal e extratemporal nestes pacientes. O corpo caloso (CC) é a maior comissura cerebral conectando áreas corticais homólogas de ambos os hemisférios cerebrais e tem sido implicado na propagação da atividade epiléptica. O objetivo principal do presente estudo foi avaliar possíveis alterações no CC de pacientes com ELTM-EH pela técnica de DTI e verificar se essas dependem da lateralidade da EH e da concordância entre os exames de ressonância magnética (RM) e os exames de vídeo-eletroencefalograma (EEG). Como objetivo secundário, também avaliou-se se estas alterações se correlacionavam com alguma variável clínica ou com as medidas volumétricas do CC. MÉTODOS: 42 pacientes com ELTM-EH (idades: 20-54 anos) e 30 voluntários saudáveis como grupo controle (idades: 18-53 anos) realizaram exame de RM de crânio, sendo obtidas sequências de DTI com 32 direções de gradiente e imagens volumétricas ponderadas em T1. Os pacientes foram também divididos em subgrupos: EH à direita e EH à esquerda, e em pacientes concordantes e discordantes. Os valores de anisotropia fracionada (AF), difusividade média (DM), difusividade axial (DA), difusividade radial (DR) e os dados volumétricos foram extraídos a partir de cinco segmentos obtidos automaticamente na secção sagital do CC. Foram realizadas comparações dos parâmetros de DTI no CC entre os grupos de pacientes e controles, e entre os subgrupos de pacientes. Foram investigadas correlações entre os parâmetros do tensor de difusão e as variáveis clínicas. As alterações volumétricas no CC dos pacientes com ELTM-EH bem como a correlação dessas alterações com as anormalidades de difusão também foram avaliadas. Considerou-se um valor de p < 0,05 como estatisticamente significativo. RESULTADOS: Nas regiões anterior, médio-posterior e posterior do CC dos pacientes, observaram-se redução da AF e aumento da DM e da DR, em relação aos controles. A DA manteve-se inalterada. Não foram demonstradas diferenças nos padrões de alteração de difusão entre os pacientes com EH à direita e com EH à esquerda, nem entre pacientes concordantes e discordantes. Não foram observadas correlações significativas entre os parâmetros do tensor de difusão com a idade ao evento inicial, idade de início da epilepsia, tempo de doença, tempo de epilepsia, período de latência e frequência de crises. No entanto, pacientes que apresentaram crise febril como evento precipitante inicial exibiram maior intensidade e extensão das alterações de difusão. Observou-se redução volumétrica difusa do CC, sendo demonstrada correlação negativa significativa entre DM e DR, e o volume nos segmentos central, médio-posterior e posterior, e, ainda, entre DA e volume do segmento posterior. Nós observamos, ainda, correlação negativa significativa entre o volume e o tempo de epilepsia, e o tempo de doença. CONCLUSÕES: Houve alteração dos parâmetros de DTI em áreas específicas do CC e redução volumétrica difusa desta estrutura. Tais anormalidades parecem ser secundárias à propagação das crises epilépticas ao longo de vias específicas anatômica ou funcionalmente relacionadas aos lobos temporais promovendo alterações secundárias na substância branca cerebral. O histórico de crise febril está relacionado a maior intensidade e extensão de acometimento do CC / INTRODUCTION: Mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS) is the most common form of focal epilepsy in adults and it is frequently associated with refractoriness to medical treatment. Although epilepsy is considered a grey-matter disease, abnormalities in the temporal and extra-temporal white matter have been identified in these patients with diffusion tensor imaging (DTI). The corpus callosum (CC) is the major white matter tract connecting both cerebral hemispheres and has been implicated as an important route of spread of epileptic activity. The first goal of this study was to detect DTI abnormalities in specific areas of the CC in patients with MTLE-HS and to verify if these abnormalities depend on the laterality of the HS and on the concordance between the magnetic resonance imaging (MRI) and video-electroencephalogram (EEG). As a second goal we assessed if DTI results were correlated with any clinical variable or volumetric changes of the CC. METHODS: 42 patients (age: 20-54 years) and 30 healthy controls (age:18-53 years) were submitted to brain MRI. DTI sequences with 32 gradient encoding directions and volumetric T1-weighted images were obtained. Additionally, we grouped the patients in left sided and right sided HS and in concordant and discordant HS. Mean values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and volumetric results were extracted from five segments at the midsagittal section of the CC obtained through automatic segmentation. Comparisons of DTI parameters of the CC were performed between patients and controls and between subgroups of patients. Correlations between DTI parameters and clinical findings were calculated. We also evaluated volume abnormalities of the CC in MTLE-HS patients and the correlations between these abnormalities and DTI changes. We considered a value of p <0.05 statistically significant. RESULTS: Our study showed that, when HS patients was compared to controls, the FA was lowest in the anterior, mid-posterior and posterior subregions of the CC. MD and RD were higher in these same segments. No changes were observed in AD. No differences in the CC DTI parameters were detected between right-sided HS and left-sided HS or between concordant and discordant HS patients. Age at initial event, age at epilepsy onset, duration of disease, duration of epilepsy, latency period and seizure frequency were not significantly correlated with the DTI parameters. However, patients who had febrile seizures as initial event exhibited greater intensity and extent of DTI changes. All segments demonstrated volume reduction compared to controls. Significant negative correlation was demonstrated between MD and RD and the volume in the central, midposterior and posterior segments of the CC, and between AD and volume of the posterior segment. We also demonstrated negative correlation between volume and duration of disease and duration of epilepsy. CONCLUSIONS: This study showed diffusion abnormalities in specific areas of the CC and diffuse atrophy in patients with unilateral HS, which may be secondary to seizures propagation along specific pathways leading to secondary changes in brain white matter. The history of febrile seizure is related to greater involvement of the CC

Made available in DSpace on 2014-12-17T15:28:52Z (GMT). No. of bitstreams: 1 KellySF_DISSERT.pdf: 3939064 bytes, checksum: 5be69492fa857ba043776a01195d92b4 (MD5) Previous issue date: 2012-09-21 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Crises epil?pticas s?o eventos parox?sticos do sistema nervoso central (SNC) caracterizadas por uma descarga el?trica neuronal anormal, com ou sem perda de consci?ncia e com sintomas cl?nicos variados. Nas epilepsias do lobo temporal as crises tem in?cio focal, em estruturas do sistema l?mbico. Dados cl?nicos e experimentais mostram que essas regi?es apresentam morte neuronal (esclerose hipocampal), reorganiza??o sin?ptica (brotamento aberrante das fibras musgosas) e gliose reativa, sendo esses marcadores biol?gicos da zona epileptog?nica. Registros extracelulares mostram que al?m das altera??es anat?micas mencionadas acima, a zona epileptog?nica tamb?m apresenta oscila??es de alta frequ?ncia patol?gicas (pOAF). As pOAF s?o oscila??es transientes (50 100 ms de dura??o), de baixa amplitude (200 &#956;V - 1.5 mV) e de frequ?ncias vari?veis (80 800 Hz). A rela??o entre essas oscila??es e a g?nese das crises espont?neas ainda ? desconhecida. O objetivo do presente trabalho foi avaliar os efeitos da estimula??o el?trica intracerebral (EIC) nas pOAF e frequ?ncia de crises espont?neas de animais cronicamente epil?pticos (modelo da epilepsia do lobo temporal). Atualmente, a EIC ? utilizada no tratamento de dist?rbios do movimento (e.g., doen?a de Parkinson) e em alguns casos de dor cr?nica, e experimentalmente, no tratamento das epilepsias de dif?cil controle. A hip?tese de trabalho dessa disserta??o ? de que a indu??o de depress?o de longa dura??o por EIC, ao reduzir a excitabilidade neuronal local, modular? as pOAF, bem como a frequ?ncia de crises espont?neas. Para isso, comparamos as caracter?sticas espectrais das pOAF e a frequ?ncia de crises espont?neas antes e depois de um protocolo de 12 horas de estimula??o el?trica de baixa frequ?ncia (0,2 Hz) aplicado na via perforante. De fato, esse protocolo reduziu a amplitude do potencial de a??o coletivo registrado no giro denteado (GD) do hipocampo dorsal em 45% (amplitude m?dia da primeira e da ?ltima hora de estimula??o: 7,3 ? 3,0 mV e 4,1 ? 1,5 mV, respectivamente; p<0,05; teste t). O monitoramento cont?nuo do potencial de campo local, realizado no GD e em CA3 simultaneamente, mostrou que o protocolo de estimula??o empregado foi eficaz em (i) aumentar a dura??o (64,6 ? 9,3 ms vs. 70,5 ? 11,5 ms) e reduzir (ii) a entropia (3,72 ? 0,28 vs. 3,58 ? 0,30), (iii) o ?ndice pOAF (0,20 ? 0,08 vs. 0,15 ? 0,07) e (iv) o modo espectral (237,5 ? 15,8 Hz vs. 228,7 ? 15,2 Hz) das pOAF (valores do GD, expressos como m?dia ? desvio-padr?o, para os per?odos pr? e p?s estimula??o respectivamente; p<0,05; teste t). Ainda, este protocolo reduziu significativamente a frequ?ncia de crises espont?neas (1,8 ? 0,4 vs. 1,0 ? 0,3 crises/hora; pr? e p?s estimula??o, respectivamente; p<0,05; teste t). Curiosamente, observamos um aumento na dura??o m?dia das crises espont?neas ap?s o t?rmino do protocolo (39,7 ? 6,0 vs. 51,6 ? 12,5 s; pr? e p?s estimula??o respectivamente; p<0,05; teste t). Estes resultados sugerem que a redu??o da excitabilidade neuronal, por meio de protocolos de estimula??o el?trica, altera o perfil espectral das pOAF. Esse efeito foi acompanhado de redu??o na frequ?ncia de crises espont?neas. Apesar de preliminar, o presente trabalho contribui para o refinamento de terapias baseadas em EIC para indiv?duos com epilepsia

La métabolomique a pour objet l’identification et la quantification de métabolites dans un échantillon biologique. Cette discipline s’inscrit dans une approche du vivant connue sous le terme de « biologie des systèmes ». La spectroscopie par résonance magnétique nucléaire haute résolution à l’angle magique (RMN HRMAS) est une méthode de choix pour l’obtention de ce type de profilage métabolique. L’épilepsie du lobe temporal (ELT) est une épilepsie focale fréquente associée le plus souvent à des pertes neuronales sélectives, une gliose réactionnelle et une plasticité cellulaire spécifique. Bien que restant débattue, une origine neurométabolique reste un axe de recherche majeur. A ce jour une caractérisation métabolomique des tissus épileptogènes par RMN HRMAS reste à effectuer. Notre travail a consisté dans un premier temps à caractériser, chez le rat, les effets des méthodes de prélèvement et de fixation sur le métabolome cérébral dans le cadre des acquisitions RMN HRMAS. Dans un second temps, nous avons travaillé sur le modèle animal lithium-pilocarpine d’ELT. Nous avons pu décrire le métabolome issu des données RMN 1H HRMAS de différentes structures cérébrales impliquéesdans l’épileptogénèse. Des analyses multivariées de type PLS-DA ont pu mettre en évidence des profils métaboliques pathologiques au sein du cortex entorhinal et de l’hippocampe. A l’aide de substrats marqués au carbone 13 ([1-13C]glucose et de [1,2-13C]acétate) nous avons étudié les voies métaboliques neuronales et gliales. Nos résultats suggèrent l’absence d’anomalies métaboliques au sein des astrocytes. Enfin dans un dernier temps, nous avons effectué des analyses RMN 1H HRMAS sur près de 200 échantillons cérébraux de patients atteints d’ELT. Une analyse multivariée a permis de distinguer les profils métaboliques des hippocampes sclérosés et non sclérosés. En revanche la construction de modèles sur la base d’hypothèses clinico métaboliques (durée de la maladie, fréquence de crises, antécédents de convulsions fébriles) n’a pas permis d’identifier de profils métaboliques spécifiques. L’ensemble de ces données suggère l’existence de profils métabolomiques distincts en fonction des caractéristiques neuropathologiques des patients atteints d’ELT. Notre travail confirme la nécessité d’une approche intégrée de type « biologie des systèmes » pour l’étude de l’ELT aussi bien chez l’homme que dans des modèles animaux. / Metabolomics relates to the identification and quantification of metabolites in biological samples. This discipline is part of an approach known under the term of "systems biology". High Resolution Nuclear Magnetic Resonance Spectroscopy at Magic Angle Spinning (HRMAS NMR) is a method for obtaining metabolic profiling in such sample. Temporal Lobe Epilepsy (TLE ) is a common focal epilepsy often associated with selective neuronal loss, reactive gliosis and specific cellular plasticity. A neurometabolic origin of this epilepsy is a major area of research. To date no characterization of human cerebral biopsy from TLE patients has been conducted using HRMAS NMR. In the present work we aimed first at characterizing, in rats, the effects of sampling methods and fixation on brain metabolome under HRMAS NMR acquisitions. In a second step, we studied the lithium-pilocarpine model of TLE. In this model, we could describe the metabolome from HRMAS 1H NMR data of different brain structures involved in epileptogenesis. Multivariate analysis could highlight pathological metabolic profiles in the entorhinal cortex and hippocampus. Using substrates labeled with carbon 13 ( [1 -13C ]-glucose and [1,2-13C ]-acetate) we studied neuronal and glial metabolic pathways. Our results suggest the absence of metabolic abnormalities in astrocytes metabolism as previously reported. Finally, we conducted HRMAS 1H NMR analysis in nearly 200 brain samples from TLEpatients. Multivariate analysis was able to distinguish metabolic profiles between sclerotic and non sclerotic hippocampi. However mutlivariate models based on clinico- metabolic assumptions (disease duration, frequency of seizures, history of febrile seizures ) did not identify specific metabolic profile. All these data suggest the existence of distinct metabolomic profile based on neuropathological features of patients with TLE. Our work confirm the need of an integrated approach such as " systems biology" for the study of TLE in humans as long as in animal models.

Introdução: A esclerose mesial temporal (EMT) é a principal causa de epilepsia resistente ao tratamento medicamentoso. Pacientes com EMT apresentam dificuldades no processamento semântico e fonológico de linguagem e maior incidência de reorganização cerebral da linguagem (bilateral ou à direita) em relação à população geral. A ressonância magnética funcional (RMf) permite avaliar a reorganização cerebral das redes de linguagem, comparando padrões de ativação cerebral entre diversas regiões cerebrais. Objetivo: Investigar o desempenho linguístico de pacientes com EMT unilateral esquerda e direita e a ocorrência de reorganização das redes de linguagem com RMf para avaliar se a reorganização foi benéfica para a linguagem nestes pacientes. Métodos: Utilizamos provas clínicas de linguagem e paradigmas de nomeação visual e responsiva para RMf, desenvolvidos para este estudo. Foram avaliados 24 pacientes com EMTe, 22 pacientes com EMTd e 24 controles saudáveis, submetidos a provas de linguagem (fluência semântica e fonológica, nomeação de objetos, verbos, nomes próprios e responsiva, e compreensão de palavras) e a três paradigmas de linguagem por RMf [nomeação por confrontação visual (NCV), nomeação responsiva à leitura (NRL) e geração de palavras (GP)]. Seis regiões cerebrais de interesse (ROI) foram selecionadas (giro frontal inferior, giro frontal médio, giro frontal superior, giro temporal inferior, giro temporal médio e giro temporal superior). Índices de Lateralidade (ILs) foram calculados com dois métodos: bootstrap, do programa LI-Toolbox, independe de limiar, e PSC, que indica a intensidade da ativação cerebral de cada voxel. Cada grupo de pacientes (EMTe e EMTd) foi dividido em dois subgrupos, de acordo com o desempenho em relação aos controles na avaliação clinica de linguagem. O <= -1,5 foi utilizado como nota de corte para dividir os grupos em pacientes com bom e com mau desempenho de linguagem. Em seguida, comparou-se o desempenho linguístico dos subgrupos ao índices IL-boot. Resultados: Pacientes com EMT esquerda e direita mostraram pior desempenho que controles nas provas clínicas de nomeação de verbos, nomeação de nomes próprios, nomeação responsiva e fluência verbal. Os mapas de ativação cerebral por RMf mostraram efeito BOLD em regiões frontais e temporoparietais de linguagem. Os mapas de comparação de ativação cerebral entre os grupos revelaram que pacientes com EMT esquerda e direita apresentam maior ativação em regiões homólogas do hemisfério direito em relação aos controles. Os ILs corroboraram estes resultados, mostrando valores médios menores para os pacientes em relação aos controles e, portanto, maior simetria na representação da linguagem. A comparação entre o IL-boot e o desempenho nas provas clínicas de linguagem indicou que, no paradigma de nomeação responsiva à leitura, a reorganização funcional no giro temporal médio, e possivelmente, nos giros temporal inferior e superior associou-se a desempenho preservado em provas de nomeação. Conclusão: Pacientes com EMT direita e esquerda apresentam comprometimento de nomeação e fluência verbal e reorganização da rede cerebral de linguagem. A reorganização funcional de linguagem em regiões temporais, especialmente o giro temporal médio associou-se a desempenho preservado em provas de nomeação em pacientes com EMT esquerda no paradigma de RMf de nomeação responsiva à leitura / Introduction: Mesial temporal sclerosis (MTS) is the commonest cause of drug resistant epilepsy. MTS patients experience phonological and semantic processing difficulties, and increased prevalence of atypical (bilateral or right hemisphere) language dominance compared to the general population. Language reorganization can be studied with functional magnetic resonance imaging (fMRI), which allows comparison of brain activation patterns in different brain regions. Objective: To investigate performance on language tasks in patients with unilateral left and right MTS, and occurrence of atypical language dominance to determine if reorganization of language networks is beneficial to \' f . : W w y-four left MTS, 22 right MTS patients and 24 healthy controls. Subjects underwent language tasks (semantic and phonological fluency, object, verb, proper noun, and responsive naming, and word comprehension), and fMRI language paradigms [visual confrontation naming (VCN), reading responsive reading (RRN) and word generation (WG)]. Six regions of interest (ROI) (inferior frontal, middle frontal, superior frontal, inferior temporal, middle temporal and superior temporal gyri) were defined. Two language lateralization indexes (LI) were obtained for each ROI, one with a threshold-independent method using a bootstrap algorithm (LI-boot), and one that measures brain activation intensity in each voxel (Percentage Signal Change - PSC). Each patient group (left MTS and right MTS) was divided into two subgroups according to performance relative to controls in the language tasks. Z- <= -1.5 was used as a cut-off to divide patients in good and poor language performance groups. LI-boot indexes were compared between language performance subgroups. Left and right MTS patients showed worse performance than controls in verb, proper noun, and responsive naming, and verbal fluency language tasks. fMRI activation maps showed increased BOLD signal in frontal and temporoparietal language regions. Group comparison activation maps revealed that left and right MTS patients showed increased activation in homologous right hemisphere regions compared to controls. These results were corroborated by lower LI mean values for patients compared to controls, indicating greater hemispheric language representation symmetry. Comparison between LI-boot indexes and performance in language tasks showed that functional reorganization in the middle temporal, and, possibly, inferior and superior temporal gyri was associated with preserved naming performance. Conclusion: Left and right MTS patients display impaired naming and verbal fluency, as well as reorganization of the language network. Language network reorganization in the temporal regions, specially middle temporal gyrus, was associated with preserved naming in left MTS patients, in the responsive reading naming fMRI paradigm

Racional: A epilepsia do lobo temporal está comumente associada à farmacorresistência e tem a esclerose hipocampal como achado neuropatológico em mais da metade dos casos. Histologicamente, a esclerose hipocampal está associada à perda neuronal diferencial e gliose, além de alterações nos níveis de moléculas associadas à homeostase da água tecidual, como a aquaporina 4 e a molécula de matriz sulfato de condroitina. Em imagens de ressonância nuclear magnética, a esclerose é caracterizada por redução de volume em sequências ponderadas em T1, aumento de sinal e tempo de relaxamento em sequências ponderadas em T2 e redução na transferência de magnetização. Justificativa e Objetivos: Uma vez que tanto o sinal T2 quando a transferência de magnetização são dependentes da água tecidual, nosso objetivo é avaliar, na formação hipocampal de pacientes com epilepsia do lobo temporal, as correlações entre populações celulares e moléculas ligadas à homeostase da água e as imagens ponderadas em T2 e transferência de magnetização. Visamos ainda definir, na formação hipocampal de indivíduos sem alterações neuropatológicas, o volume de cada um dos subcampos hipocampais. Metodologia: Pacientes com epilepsia do lobo temporal farmacorresistente (ELT, n = 43), bem como voluntários sadios (controle radiológico, CH, n = 20), foram submetidos a exames de ressonância magnética em máquina de 3T para mensuração da volumetria hipocampal, tempo de relaxamento T2 e transferência de magnetização hipocampal (exames in vivo). Após o tratamento cirúrgico para o controle das crises, os hipocampos dos pacientes com ELT foram fixados por 8 dias e submetidos aos exames ex vivo em máquina de 3T para cálculo do tempo de relaxamento T2 de cada subcampo hipocampal. Hipocampos controle (Controle historadiológico, CHR, n = 14), foram obtidos de autópsias de pacientes sem histórico ante-mortem de doença neurológica ou presença de patologia no exame do encéfalo pos mortem. Ambos os grupos controle foram pareados para idade em relação ao grupo ELT. Alguns dos casos CHR (n = 6) foram também submetidos à imagem 3D T2 em máquina de 4,7T para cálculo de volumetria dos subcampos hipocampais. Após emblocamento em parafina, secções coronais hipocampais dos casos CHR e ELT foram submetidas às técnicas de histoquímica básica Hematoxilina e Eosina e Luxol Fast Blue, e às imuno-histoquímicas para avaliação das populações neuronais (NeuN), astrócitos reativos (GFAP), micróglias ativadas (HLA-DR) e para a expressão de aquaporina 4 (AQP4) e níveis de sulfato de condroitina (CS-56). Para a comparação entre os grupos, foram realizados testes t para dados paramétricos e Mann-Whitney para dados não-paramétricos. Testes de correlação foram empregados para análise da associação entre as avaliações histológicas e os exames de ressonância magnética. Resultados: Pacientes com ELT apresentaram menor volume hipocampal, maior tempo de relaxamento T2 e menor transferência de magnetização no exame in vivo, quando comparados com o CR. O exame ex vivo para a volumetria dos subcampos hipocampais em casos do grupo CHR indicou que a fascia dentata, a região CA1 e o subículo correspondem à 85 % do volume hipocampal total. Quanto ao tempo de relaxamento T2 ex vivo, foi observado aumento em todos os subcampos hipocampais do grupo ELT, à exceção da fascia dentata, quando comparados ao CHR. A avaliação da densidade neuronal indicou redução significativa em todos os subcampos dos casos ELT, à exceção do subículo, quando comparados ao CHR. Em relação aos valores do grupo CHR, foi observada astrogliose em quase todos subcampos da formação hipocampal (a exceção da zona subgranular e do hilo) e microgliose em todos os subcampos (exceto pelo subículo) dos casos com ELT. Pacientes com ELT apresentaram redução na expressão de aquaporina 4 perivascular em todos os subcampos do hipocampo, comparados ao CHR. Aumento nos níveis de sulfato de condroitina foi observado em todos os subcampos da formação hipocampal, à exceção da camada granular, nos pacientes com ELT. O volume hipocampal e a transferência de magnetização in vivo dos pacientes com ELT correlacionaram-se tanto com a população neuronal como com os níveis de sulfato de condroitina, enquanto que o tempo de relaxamento in vivo correlacionou-se com a população astroglial e os níveis de sulfato de condroitina. O exame ex vivo corroborou a correlação entre a população glial e o tempo de relaxamento observado nos pacientes com ELT. A diferença entre o tempo de relaxamento in vivo e ex vivo correlacionou-se tanto com a difusibilidade da água no tecido como com os níveis de sulfato de condroitina. Conclusões: Nossos dados indicam correlação entre a patologia hipocampal e as imagens de ressonância nuclear magnética, sendo que a maior qualidade das imagens ex vivo permitiu uma avaliação mais direta entre o sinal de ressonância e a patologia, indicando importância da população celular e matriz extracelular para o volume hipocampal e a transferência de magnetização, e da astrogliose para o tempo de relaxamento T2. Finalmente, nossos dados mostraram que CA1, subículo e fascia dentata tem grande participação no volume hipocampal, sendo que alterações nestas regiões tem um papel mais relevante nas alterações observadas na ressonância magnética, como indicado por nossas correlações. / Rationale: Drug resistant temporal lobe epilepsy is often associated with hippocampal sclerosis. Histological evaluation reveals differential neuronal loss, gliosis and changes in molecules associated with water homeostasis, such as aquaporin 4 and chondroitin sulfate. Magnetic resonance imaging in these cases often reveals hippocampal atrophy, increased T2 signal and T2 relaxation and reduced magnetization transfer ratio in the hippocampus. Aims: Once both T2 signal and magnetization transfer are affected by tissue water, our goal was to evaluate, in the hippocampus of drug-resistant temporal lobe epilepsy patients who underwent surgery for seizure control, the associations between cellular populations, aquaporin 4 and chondroitin sulfate with T2 relaxation time and magnetization transfer. Additionally, we intended to measure the individual volume of each hippocampal subfield in hippocampus from patients without neurological disease. Methods: Patients with drug-resistant temporal lobe epilepsy (TLE, n = 43) and age-matched health volunteers (radiological control, RC, n = 20) were submitted to magnetic resonance in a 3T machine for hippocampal volumetry measure, T2 relaxation and magnetization transfer (in vivo examination). After surgical treatment for seizure control, hippocampi from the TLE patients were fixed in formalin for 8 days and then submitted to ex vivo imaging in 3T for relaxation time of every hippocampal subfield. Control hippocampi were obtained from autopsies of age-matched patients without ante mortem history of neurological disease or post mortem neurological pathology, and underwent the same ex vivo imaging (histo-radiological control, HRC, n = 14). Six cases from the HRC underwent 3D T2 imaging in a 4.7T machine, in order to measure the volumes of the hippocampal subfields. Paraffin embedded hippocampal sections from TLE and HRC were submitted to Hematoxilin-Eosin and Luxol Fast Blue histochemistries, and to immunohistochemistries for the evaluation of neurons (NeuN), reactive astrocytes (GFAP), activated microglia (HLA-DR), for aquaporin 4 (AQP4) and for chondroitin sulfate (CS-56). Students t-test or Mann-Whitneys test were performed for comparison between groups, and correlation tests were performed for the comparison between histological and magnetic resonance measures. Results: Patients with TLE presented reduced hippocampal volume, increased T2 relaxation time and reduced magnetization transfer, when compared to RC. The ex vivo volumetry of the hippocampal subfields revealed that fascia dentata, CA1 and subiculum together correspond to 85 % of the total hippocampal volume. Ex vivo relaxation time, as the in vivo, were increased in the subfields of TLE patients, when compared to HRC. Compared to HRC, TLE patients presented neuron loss and microgliosis in all hippocampal subfields but the subiculum, and astrogliosis in all hippocampal subfields but the subgranule zone and the hilus. Reduced perivascular aquaporin 4 was observed in all hippocampal subfields of TLE patients, and increased chondroitin sulfate was observed in all hippocampal subfields, with the exception of granule cell layer, of TLE patients, when compared to HRC. In TLE, both in vivo hippocampal volume and magnetization transfer correlated with the levels of chondroitin sulfate and the neuronal population, whereas the in vivo relaxation time correlated with the astroglial population and the levels of chondroitin sulfate. Ex vivo relaxation time also correlated with the astroglial population in TLE patients. The difference between in vivo and ex vivo relaxation values correlated with water difusibility and the levels of chondroitin sulfate. Conclusion: Our data indicate the importance of neuron population and extracellular matrix to both hippocampal volume and magnetization transfer, and of the reactive astrocytes for T2 relaxation. Ex vivo relaxation time allowed a more detailed evaluation, and indicated more robust correlations between reactive astrocytes and T2 relaxation. Finally, Our data indicated that CA1, the subiculum and fascia dentata are the major contributors to hippocampal volume, so changes in these subfields most likely will affect magnetic resonance imaging.

Le gyrus denté occupe une position clé au sein du lobe temporal des mammifères en constituant le point de contrôle entre le système néocortical et le système hippocampique. Considéré comme la porte de l'hippocampe, le gyrus denté filtre les activités excitatrices en provenance du cortex entorhinal grâce à la décharge éparse des cellules granulaires. Ce type de codage neuronal lui confère également un rôle déterminant dans les mécanismes de l'apprentissage et de la mémoire lors de la distinction d'évènements similaires mais différents, en permettant la décorrélation des patrons d'activité corticale. Grâce à un ensemble de propriétés structurales et fonctionnelles, les cellules granulaires du gyrus denté génèrent des évènements synaptiques extrêmement rapides restreignant leur fenêtre temporelle d'intégration et leur permettant de jouer le rôle de détecteurs de coïncidence. Au cours d'une épilepsie du lobe temporal (ELT), l'hippocampe présente d'importantes altérations de codage neuronal qui pourraient participer aux troubles cognitifs décrits chez les patients et les modèles animaux. Dans ces conditions pathologiques, les axones des cellules granulaires du gyrus denté (les fibres moussues) bourgeonnent et établissent des synapses aberrantes au niveau d'autres cellules granulaires, créant ainsi un puissant réseau excitateur récurrent. Ces fibres moussues récurrentes convertissent la nature de la transmission glutamatergique car elles opèrent via des récepteurs kaïnate générant des potentiels post-synaptiques à cinétique lente, absents en condition contrôle. / The dentate gyrus plays a major role at the gate of the hippocampus, filtering incoming information from the entorhinal cortex. A fundamental coding property of dentate granule cells (DGCs) is their sparse firing. Indeed, they behave as a coincidence detector due to the fast kinetics of excitatory synaptic events restricting integration of afferent inputs to a narrow time window. In temporal lobe epilepsy (TLE), the hippocampus displays important coding alterations that may play a role in cognitive impairments described in patients and animal models. However, the cellular mechanisms remain poorly understood. In animal models of TLE and human patients, neuronal tissue undergoes major reorganization; some neurons die whereas others, which are severed in their inputs or outputs, sprout and form novel aberrant connections. This phenomenon, called reactive plasticity, is well documented in the dentate gyrus where DGC axons (the mossy fibres) sprout and create a powerful excitatory network between DGCs. We recently showed that in addition to the axonal rewiring, recurrent mossy fibres convert the nature of glutamatergic transmission in the dentate gyrus because they operate via long-lasting kainate receptor (KAR)-mediated EPSPs (EPSPKA) not present in the naive condition.

Le but de ce travail de thèse a été de caractériser in vivo chez l’Homme, la connectivité cérébrale sur son versant fonctionnel, par le biais de deux techniques: la stéréoélectroencéphalographie (SEEG) et l’IRM fonctionnelle (IRMf) de repos. Ces travaux se sont intégrés dans le cadre du bilan préchirurgical des épilepsies du lobe temporal pharmacorésistantes, dont le but est de déterminer la zone épileptogène à réséquer pour traiter ces patients. Alors que plusieurs études en électrophysiologie ont montré que durant les crises, il existait une synchronisation anormalement élevée entre les structures impliquées dans les processus épileptogènes, aucune donnée de connectivité n’était disponible en période intercritique. Pourtant, la période intercritique est le siège d’anomalies interictales enregistrées en EEG, de profonds remaniements morphologiques, et est associée à des troubles cognitifs. Nous apportons avec ce travail, grâce au recueil et au traitement de signaux SEEG et IRMf enregistrés durant la période intercritique, de nouvelles connaissances i) sur l’organisation de la connectivité fonctionnelle basale (CFB) chez les sujets sains ; ii) sur les altérations de la CFB chez des groupes de patients mais également au niveau individuel ; iii) sur le rapport entre ces anomalies de CFB et les troubles cognitifs observés chez ces patients ; iv) enfin, sur les différences et les similitudes de la CFB évaluée par SEEG et IRMf chez les mêmes sujets, ouvrant ainsi de nouvelles perspectives dans la compréhension des relations entre le signal BOLD et le signal EEG. / The aim of this thesis was to characterize the Human brain functional connectivity in vivo based on signals recorded using stereoelectroencephalography (SEEG) and resting-state functional MRI (fMRI). This work was conducted during the presurgical assessment of drug resistant temporal lobe epilepsy, which aims at determining the epileptogenic zone to be removed to treat these patients. While several electrophysiological studies have shown high synchronization between structures involved in the epileptogenic process during seizure, no similar connectivity data was available during inter-critical period. However, the interictal period is characterized by spikes recorded on EEG, morphological alterations and cognitive impairment. By analyzing fMRI and SEEG signals recorded during the interictal period, this work provides new insights into, i) basal functional connectivity (BFC) organization in healthy subjects, ii) BFC alterations in patients groups but also at the individual level, iii) the relationship between these BFC abnormalities and cognitive impairment observed in these patients; iv) the differences and similarities of BFC evaluated by SEEG and fMRI in the same subjects, thus opening up new perspectives in better understanding of relationships between BOLD and SEEG signal coupling.