Ce travail précise le rôle du cervelet dans la physiopathologie de la dystonie. Nous étudions comment le cervelet contrôle le développement et l’étendue de la plasticité sensorimotrice, celle-ci étant anormale dans la dystonie. Nous démontrons l’implication du cervelet dans la dystonie en constatant des performances anormales à une tâche d’adaptation sensorimotrice dépendant du cervelet. (Hubsch et al., 2011) Puis chez des sujets sains, en utilisant des techniques d’induction de plasticité cérébrale nous démontrons que le cervelet module la plasticité corticale reposant sur des afférences sensorielles. Ainsi, une inhibition du cortex cérébelleux amplifie la réponse du cortex à un protocole d’induction de plasticité sensorimotrice, une excitation du cortex cérébelleux bloque la réponse du cortex à ce protocole. (Popa et al., 2013) Avec les mêmes méthodes, nous étudions le rôle du cervelet dans la modulation de la plasticité du cortex sensori-moteur chez des sujets atteints de dystonie focale. Dans la crampe de l’écrivain, le cervelet n’exerce plus ce rôle modulateur de la plasticité sensorimotrice: il n’y a ni inhibition ni renforcement du phénomène de plasticité induit par une modulation des sorties cérébelleuses. (Hubsch et al., 2013)Dans la dystonie cervicale, il persiste une modulation de la plasticité sensorimotrice par le cervelet mais cette modulation a une direction opposée par rapport aux sujets sains contrôles. Par des expériences complémentaires, nous démontrons que le contrôle cérébelleux sur la plasticité corticale sensorimotrice est adaptatif aux afférences proprioceptives de la nuque possiblement en rapport avec la construction de l’espace égocentré. / This study specifies the role of the cerebellum in the physiopathology of dystonia. We study how the cerebellum controls the development and the extent of sensorimotor plasticity, this one being abnormal in dystonia. We show the implication of the cerebellum in dystonia by noting abnormal performances with a task of sensorimotor adaptation depending on cerebellum. (Hubsch and al., 2011) Then with healthy subjects, by using techniques of cerebral plasticity’s induction we show that the cerebellum modulates cortical plasticity depending on sensory afferents. Thus, an inhibition of the cerebellar cortex amplifies the response of the cortex to a protocol of induction of sensorimotor plasticity, an excitation of the cerebellar cortex blocks the response of the cortex to this protocol. (Popa and al., 2013) With the same methods, we study the role of the cerebellum in the modulation of the plasticity of the sensorimotor cortex with dystonic subjects. In writer's cramp, the cerebellum does not exert any more this modulating role of sensorimotor plasticity: there is neither inhibition nor reinforcement of the phenomenon of plasticity induced by a modulation of the cerebellar outputs. (Hubsch and al., 2013) In the cervical dystonia, it persists a modulation of sensorimotor plasticity by the cerebellum but this modulation has a direction opposed compared to the healthy subjects. By complementary experiments, we show that cerebellar control on cortical sensorimotor plasticity is adaptive with the proprioceptive afferents of the neck possibly in keeping with the construction of egocentric space.

Thesis advisor: Daniel Kirschner / Thesis advisor: Caroly Shumway / Species-specific differences in visual acuity have been demonstrated across species of cichlids differing in social and habitat complexity. What is the role of plasticity? A visual acuity assay on two species of fish reared in different habitat and social complexity was used to study brain plasticity in Xenotilapia flavipinnis and Asprotilapia leptura juveniles. The X. flavipinnis lives in sandy habitats and schools as juveniles. These fry were raised in an impoverished social environment in one case and an enriched habitat environment in another. The A. leptura lives in rocky habitats naturally. These fry were raised in an impoverished habitat environment. All conditions were compared to control groups with natural social and habitat conditions. I found that a change in social complexity had a plastic effect on visual acuity but a change in habitat complexity in both cases did not. / Thesis (BS) — Boston College, 2006. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Biology. / Discipline: College Honors Program.

Dans le cortex cérébelleux, au premier chef impliqué dans l’apprentissage moteur, chaque neurone de Purkinje reçoit des centaines de milliers d'entrées provenant de cellules granulaires. Etonnement, il a été suggéré qu'une grande majorité de ces connexions (synapses) sont silencieuses, c’est-à-dire qu’elles ne transmettent pas d’information détectable. Les propriétés et le rôle de ces synapses silencieuses restent mystérieux. Jouent-elles le rôle d’une réserve ou sont-elles le produit de l’apprentissage cérébelleux ? En combinant l’enregistrement électrique de la transmission synaptique et la cartographie des entrées synaptiques dans des tranches aigües de cervelet de souris, nous avons étudié l'évolution du pourcentage des synapses qui sont silencieuses entre deux âges : avant le sevrage et une fois que l’agilité d’adulte est acquise. Nous avons observé que le pourcentage de synapses qui sont silencieuses reste remarquablement stable malgré l’augmentation du nombre total de synapses. / In the cerebellar cortex, primarily involved in motor learning, any Purkinje neuron receives hundreds of thousands of inputs from granule cells. Disturbingly, it has been suggested that the vast majority of these connections (synapses) are silent, that is to say they do not transmit any detectable information. The properties and the role of these silent synapses remains mysterious. Do they serve as a reserve pool for additional information storage or are they a byproduct of cerebellar learning? Combining the electrical recording of synaptic transmission and the mapping of synaptic inputs in acute cerebellar slices from mice, we have studied how the percentage of synapses which are silent changes between two postnatal ages: before weaning and once adult agility is acquired. Our main finding is that the percentage of synapses which are silent remains remarkably stable despite the increase in the total number of synapses.

New neuroimaging techniques have made it possible to examine imagery and found evidence for that imagery share similar neural correlates as in perception. Imagery can be used in different areas to enhance performance, and it is a popular technique in sports. Similar to physical practice (PP), motor imagery (MI) can result in brain plasticity. The aim of this thesis is to describe what imagery means and describe different theories of imagery. This is to further look into what impact MI has on performance in different sports, and then to further see if there are any changes in brain plasticity as a result of using MI. There is a lack of studies done on MI, performance and brain plasticity in sport. To answer the latter focus of this thesis, studies of healthy persons and patient studies using MI to improve performance and examining changes in the brain have been used. In order to do that this thesis aims to do a literature review. The results indicate that MI combined with PP can improve sport performance. It has also been showed that MI alone can be as good as PP. Most studies found that MI combined with PP can result in brain plasticity, and only one study did not found evidence for it. It has also showed that MI alone can result in brain plasticity. Future research should include larger samples, matching subjects, and comparing the effects of MI in several kinds of sports.

Ce travail s'inscrit dans le cadre d'un partenariat scientifique entre le Laboratoire Navier et la société STRAINS. Convaincue du besoin de renouveler les méthodes actuelles de calcul de structures, STRAINS développe un nouveau logiciel dédié à l'analyse des ouvrages d'art. Dans ce contexte, cette thèse propose de nouveaux outils pour l'analyse des structures élancées. Le modèle élastique de poutre d'ordre supérieur développé par cite{Ferradi2016} est d'abord adapté au cas des déformations imposées, permettant ainsi au modèle de représenter un grand nombre de phénomènes physiques tels que le fluage, la précontrainte ou les chargements thermiques. Différents exemples viennent souligner la précision numérique du modèle ainsi que ses performances en temps de calcul. Le modèle est également étendu au cadre de la théorie de la plasticité. Considérant les déformations plastiques comme des déformations imposées, les résultats précédemment obtenus sont utilisés pour développer une nouvelle cinématique d'ordre supérieur. Enfin, un nouvel élément de poutre élastoplastique pour le béton armé est proposé. Le béton est décrit grâce au modèle élastoplastique et les ferraillages sont modélisés par des éléments barres à une dimension. Cette méthode permet une description précise du comportement du béton et une représentation fidèle des renforcements. La validité des calculs est évaluée par des considérations de dissipation énergétique / This thesis work is presented in the framework of a scientific partnership between Laboratoire Navier and the french start-up STRAINS. Believing in the need for new methodologies in structural analysis, STRAINS is developing a new software dedicated to the structural analysis of bridges. In this context, this work suggests new tools for the analysis of slender structures.The higher-order elastic beam element developed by cite{Ferradi2016} is first extended to the case of eigenstrains, enabling the model to deal with various physical phenomena such as creep, prestress or thermal loads. An enriched kinematics is used to capture the local response of the structure. Different examples highlight the local accuracy of the model and its fast computational performances. The model is also extended to plasticity in small perturbations. Considering the plastic strains developing in the structure as eigenstrains, the previous works are used to derive a higher-order elastoplastic kinematics.Finally, a new elastoplastic beam element for reinforced concrete is suggested. The concrete material is described by using the elastoplastic beam model developed previously while steel rebars are modeled by one dimensional bar elements. This method enables a fine local description of the concrete behavior and an accurate representation of the reinforcement. The validity of computations is assessed thanks to energy considerations

Este trabalho tem o intuito de fazer uso do processamento paralelo na análise não linear de cascas pelo método dos elementos finitos. O elemento finito de casca é obtido com o acoplamento de um elemento de placa e um de chapa. O elemento de placa utiliza formulação de Kirchhof (DKT) para placas delgadas e o elemento de chapa faz uso da formulação livre (FF), introduzindo um grau de liberdade rotacional nos vértices. A análise não-linear com plasticidade utiliza o modelo de plasticidade associada com algoritmo de integração explícito, modelo de escoamento de von Mises com integração em camadas (modelo estratificado), para materiais isotrópicos. A implementação em paralelo é realizada em um sistema com memória distribuída e biblioteca de troca de mensagens PVM (Parallel Virtual Machine). O procedimento não-linear é completamente paralelizado, excetuando a impressão final de resultados. As etapas que constituem o método dos elementos finitos, matriz de rigidez da estrutura e resolução do sistema de equações lineares são paralelizadas. Para o cálculo da matriz de rigidez utiliza-se um algoritmo com decomposição de domínio explícito. Para resolução do sistema de equações lineares utiliza-se o método dos gradientes conjugados com implementação em paralelo. É apresentada uma breve revisão bibliográfica sobre o paralelismo, com comentários sobre perspectivas em análise estrutural / This work aims at using parallel processing for nonlinear analysis of shells through finite element method. The shell finite element is obtained by coupling a plate element with a membrane one. The plate element uses Kirchhoff’s formulation (DKT) for thin plates and the membrane element makes use of the free formulation (FF), introducing a rotational degree of freedom at the vertexes. Nonlinear plastic analysis uses associated plasticity model with explicit integration algorithm, von Mises yelding model with layer integration (stratified model) for isotropic materials. Parallel implementation is done on a distributed memory system and message exchange library PVM (Parallel Virtual Machine). Nonlinear procedure is completely parallelised, but final printing of results. The finite element method steps, structural stifness matrix and solution of the linear equation system are parallelised. An explicit domain decomposition algorithm is used for the stifness matrix evaluation. To solve the linear equation system, one uses conjugated gradients method, with parallel implementation. A brief bibliography about parallelism is presented, with comments on structural analysis perspectives

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.

Coral reef ecosystems worldwide are facing increasing degradation due to disease, anthropogenic damage, and climate change, particularly in the Tropical Western Atlantic. Mesophotic coral ecosystems (MCEs) have been recently gaining attention through increased characterization as continuations of shallow reefs below traditional SCUBA depths (>30 m). As MCEs appear to be sheltered from many stressors affecting shallow reefs, MCEs may act as a coral refuge and provide larvae to nearby shallow reefs. The Deep Reef Refugia Hypothesis (DRRH) posits that shallow and mesophotic reefs may be genetically connected and that some coral species are equally compatible in both habitats. The research presented here addresses key questions that underlie this theory and advances our knowledge of coral connectivity and MCE ecology using the depth-generalist coral Montastraea cavernosa. Chapter 1 presents an overview of the DRRH, a description of MCEs in the Gulf of Mexico (GOM), and the framework of research questions within existing reef management infrastructure in the GOM. Through microsatellite genotyping, Chapter 2 identifies high connectivity among shallow and mesophotic reefs in the northwest GOM and evidence for relative isolation between depth zones in Belize and the southeast GOM. Historical migration and vertical connectivity models estimate Gulf-wide population panmixia. Chapter 3 focuses on population structure within the northwest GOM, identifying a lack of significant population structure. Dominant migration patterns estimate population panmixia, suggesting mesophotic populations currently considered for National Marine Sanctuary protection benefit the Flower Garden Banks. Chapter 4 quantifies the level of morphological variation between shallow and mesophotic M. cavernosa, revealing two distinct morphotypes possibly representing adaptive tradeoffs. Chapter 5 examines the transcriptomic mechanisms behind coral plasticity between depth zones, discovering a consistent response to mesophotic conditions across regions. Additionally, variable plasticity of mesophotic corals resulting from transplantation to shallow depths and potential differences in bleaching resilience between shallow and mesophotic corals are identified. The dissertation concludes with a synthesis of the results as they pertain to connectivity of shallow and mesophotic corals in the Gulf of Mexico and suggests future research that will aid in further understanding of MCE ecology and connectivity. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Partial differential equations having diffusive, convective and reactive terms appear naturally in the modeling of a large variety of processes of practical interest in several branches of science such as biology, chemistry, economics, physics, physiology and materials science. Moreover, in some instances several species or components interact with each other requiring to solve strongly coupled systems of convection-diffusion-reaction equations. Of special interest for us is the numerical treatment of the advection dominated continuum dislocation transport equations used to describe the plastic behavior of crystalline materials.Analytical solutions for such equations are extremely scarce and practically limited to linear equations with homogeneous coefficients and simple initial and boundary conditions. Therefore, resorting to numerical approximations is the most affordable and often the only viable strategy to deal with such models. However, when classical numerical methods are used to approximate the solutions of such equations, even in the simplest one dimensional case in the steady state regime for a single equation, instabilities in the form of node to node spurious oscillations are found when the convective or reactive terms dominate over the diffusive term.To address such issues, stabilization techniques have been developed over the years in order to handle such transport equations by numerical means, overcoming the stability difficulties. However, such stabilization techniques are most often suited for particular problems. For instance the Streamline Upwind Petrov-Galerkin method, to name only one of the most well-known, successfully eliminates spurious oscillations for single advection-diffusion equations when its advective form is discretized, but have been shown useless if the divergence form is used instead. Additionally, no extensive work has been carried out for systems of coupled equations. The reason for this immaturity is the lack of a maximum principle when going from a single transport equation towards systems of coupled equations.The main aim of this work is to present a stabilization technique for systems of coupled multidimensional convection-diffusion-reaction equations based on coefficient perturbations. These perturbations are optimally chosen in such a way that certain compatibility conditions analogous to a maximum principle are satisfied. Once the computed perturbations are injected in the classical Bubnov-Galerkin finite element method, they provide smooth and stable numerical approximations.Such a stabilization technique is first developed for the single one-dimensional convection-diffusion-reaction equation. Rigorous proof of its effectiveness in rendering unconditionally stable numerical approximations with respect to the space discretization is provided for the convection-diffusion case via the fulfillment of the discrete maximum principle. It is also demonstrated and confirmed by numerical assessments that the stabilized solution is consistent with the discretized partial differential equation, since it converges to the classical Bubnov-Galerkin solution if the mesh Peclet number is small enough. The corresponding proofs for the diffusion-reaction and the general convection-diffusion-reaction cases can be obtained in a similar manner. Furthermore, it is demonstrated that this stabilization technique is applicable irrespective of whether the advective or the divergence form is used for the spatial discretization, making it highly flexible and general. Subsequently the stabilization technique is extended to the one-dimensional multiple equations case by using the superposition principle, a well-known strategy used when solving non-homogeneous second order ordinary differential equations. Finally, the stabilization technique is applied to mutually perpendicular spatial dimensions in order to deal with multidimensional problems.Applications to several prototypical linear coupled systems of partial differential equations, of interest in several scientific disciplines, are presented. Subsequently the stabilization technique is applied to the continuum dislocation transport equations, involving their non-linearity, their strongly coupled character and the special boundary conditions used in this context; a combination of additional difficulties which most traditional stabilization techniques are unable to deal with. The proposed stabilization scheme has been successfully applied to these equations. Its effectiveness in stabilizing the classical Bubnov-Galerkin scheme and being consistent with the discretized partial differential equation are both demonstrated in the numerical simulations performed. Such effectiveness remains unaffected when different types of dislocation transport models with constant or variable length scales are used.These results allow envisioning the use of the developed technique for simulating systems of strongly coupled convection-diffusion-reaction equations with an affordable computational effort. In particular, the above mentioned crystal plasticity models can now be handled with reasonable computation times without the use of extraordinary computational power, but still being able to render accurate and physically meaningful numerical approximations. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

O protocolo conhecido como Dynamic Clamp consiste em utilizar um computador para introduzir condutâncias artificiais em um neurônio biológico. O modo como estas condutâncias dependem da voltagem da membrana ou do tempo são modelado por equações diferenciais que são integradas em tempo real por um computador conectado ao neurônio biológico. Resumidamente, o computador tem acesso ao potencial de membrana dos neurônios através de eletrodos intracelulares conectados a conversores analógico-digitais (ADCs), calcula as correntes a serem injetadas nos neurônios e produz os sinais de saída através de conversores digitalanalógicos (DACs) que produzem a injeção das correntes nos eletrodos intracelulares. De um certo modo, o Dynamic Clamp utiliza os neurônios como simuladores, permitindo investigar a importância de um tipo de condutância para a atividade elétrica de um neurônio, assim como determinar o efeito produzido pelas sinapses em uma rede, combinando o controle e flexibilidade de uma simulação no computador com a acurácia e o realismo de um experimento em eletrofisiologia. Descrevemos a implementação de um protocolo de Dynamic Clamp utilizando um computador pessoal tipo IBM-PC que permitiu contornar 3 das principais limitações que apresentam alguns dos programas de Dynamic Clamp comerciais/gratuitos disponíveis atualmente: (a) Garantia de que o sistema roda em tempo real - nossa implementação é baseada em um programa de Dynamic Clamp que roda em uma plataforma Linux Real-Time que além de controlar os experimentos em tempo real consiste em software livre com codigo fonte aberto e que pode ser instalado gratuitamente; (b) Não necessita de hardware de aquisição de dados dedicado para eletrofisiologia - utilizamos uma placa ADC/DAC comercial comum marca National Instruments modelo PCIMIO16E4. Com o driver COMEDI instalado para placas de aquisição de dados Linux, a maioria das placas ADC/DAC tipo PCI disponíveis no mercado podem ser utilizadas em implementações futuras; (c) Aumentar o número de neurônios que podem ser conectados simultaneamente - desenvolvemos um circuito demultiplex analógico que permite controlar até 8 neurônios biológicos/artificiais a partir das duas saídas analógicas que as placas DAC comerciais possuem e ainda atingir frequências de atualização da corrente de até 3 kHz (para 8 correntes de saída). Apresentamos os resultados de diversos testes que fizemos usando o programa adaptado e o circuito demultiplex para produzir sinapses em tempo real e conectar diversos neurônios artificiais em pequenas redes. Também mostramos alguns resultados preliminares obtidos com a primeira implementação de um modelo de neurônio estocástico tipo Hodgkin-Huxley em um programa de Dynamic Clamp. / The Dynamic Clamp protocol consists in using a computer to introduce artificial conductances in a biological neuron. The voltage- and time-dependency of each conductance is modeled by differential equations integrated in real-time by the computer connected to the biological neurons. In short, the computer executes a 3-phase cycle in which the membrane potential of the neurons is measured by intracellular electrodes and digitized by analog-to-digital converters (ADCs), the currents are calculated based in the digitized membrane potentials and current signals are generated by digital-to-analog converters (DACs). These currents are actually injected in the neurons by other intracellular electrodes. In some extent the Dynamic Clamp uses the neurons as simulators, allowing one to investigate the role of a specific conductance in the intrinsic activity of a neuron as well as to look for the effects of a synapse in the behavior of a small network. The Dynamic Clamp combines the control and flexibility of a computer simulation with the reality of an experiment in electrophysiology. We describe an implementation of a Dynamic Clamp protocol that allowed us to surmount 3 of the main drawbacks present in some commercial/freely available Dynamic Clamp programs: (a) Runs in real time - our implementation is based in a program that runs in a Real-Time Linux platform. This operating system not only ensures the experiments will be controlled in real time but also consists in open source software that can be freely downloaded and installed; (b) No need of special electrophysiology acquisition hardware - we used a commercial ADC/DAC acquisition board model PCI-MIO16E4 from National Instruments. With the COMEDI Linux package driver that is used most of the PCI commercial ADC/DAC boards can be used in future implementations with no change needed in the program itself. (c) We can connect more than two neurons with artificial synapses - we developed an analog demultiplex circuit that allowed us to control simultaneously up to 8 biological/artificial neurons from the two analog outputs available in most of the commercial ADC/DAC boards and we could still reach current update rates of about 3 kHz (for 8 current outputs enabled). We present the results of several tests we performed using the program adapted to control the analog demultiplex to establish synapses and to connect several artificial neurons in small neural networks. Preliminary results from the first implementation of a stochastic whole cell Hodgkin-Huxley model neuron in a real time Dynamic Clamp program are also shown.