Dans cette thèse, nous avons étudié le codage prédictif and sa relation avec la perception et les oscillations. Nous avons, dans l'introduction, fait une revue des connaissances sur les neurones et le néocortex et un état de l'art du codage prédictif. Dans les chapitres principaux, nous avons tout d'abord, proposé l'idée, au travers d'une étude théorique, que la temporalité de la décharge crée une inhibition sélective dans les réseaux excitateurs non-sélectifs rétroactifs. Ensuite, nous avons montré les effets perceptuels du codage prédictif: la perception de la forme améliore la perception du contraste. Enfin, nous avons montré que le codage prédictif peut utiliser des oscillations dans différentes bandes de fréquences pour transmettre les informations en avant et en rétroaction. Cette thèse a fourni un mécanisme neuronal viable et innovant pour le codage prédictif soutenu par des données empiriques démontrant des prédictions rétroactives excitatrices et une relation forte entre codage prédictif et oscillations. / In this thesis, we investigated predictive coding and its relationship with perception and oscillations. We first reviewed my current understanding about facts of neuron and neocortex and state-of-the-arts of predictive coding in the introduction. In the main chapters, firstly, we proposed the idea that correlated spike times create selective inhibition in a nonselective excitatory feedback network in a theoretical study. Then, we showed the perceptual effect of predictive coding: shape perception enhances perceived contrast. At last, we showed that predictive coding can use oscillations with different frequencies for feedforward and feedback. This thesis provided an innovative and viable neuronal mechanism for predictive coding and empirical evidence for excitatory predictive feedback and the close relationship between the predictive coding and oscillations.

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Many problems in fluid mechanics and material sciences deal with liquid-vapour flows. In these flows, the ideal gas assumption is not accurate and the van der Waals equation of state is usually used. This equation of state is non-convex and causes the solution domain to have two hyperbolic regions separated by an elliptic region. Therefore, the governing equations of these flows have a mixed elliptic-hyperbolic nature. Numerical oscillations usually appear with standard finite-difference space discretization schemes, and they persist when the order of accuracy of the semi-discrete scheme is increased. In this study, we propose to use a Chebyshev pseudospectral method for solving the governing equations. A comparison of the results of this method with very high-order (up to tenth-order accurate) finite difference schemes is presented, which shows that the proposed method leads to a lower level of numerical oscillations than other high-order finite difference schemes, and also does not exhibit fast-traveling packages of short waves which are usually observed in high-order finite difference methods. The proposed method can thus successfully capture various complex regimes of waves and phase transitions in both elliptic and hyperbolic regimes

Les aires cérébrales frontales et pariétales sont impliquées dans différents processus cognitifs importants pour la performance visuelle, tels que l'attention ou la conscience. Malgré les preuves existantes en faveur d'une implication de ces régions dans la cognition visuelle, leurs contributions dans le traitement de stimuli non masqués de faible contraste ainsi que l'activité spatio-temporelle sous-tendant ces contributions restent largement inexplorées, tout particulièrement en termes de causalité. Nous avons mené une exploration approfondie de ces contributions chez l'humain, en mettant l'accent sur la dynamique de l'activité neurale et les améliorations perceptives potentielles qui peuvent résulter de la manipulation non invasive de l'activité cérébrale. À cette fin, nous avons testé chez des sujets sains les effets d'impulsions simples ou de rafales courtes de stimulation magnétique transcrânienne (SMT) réelle versus fausse, délivrée sur le champ oculomoteur frontal ou le sillon intrapariétal avant la présentation d'un filtre de Gabor de faible contraste, sur la discrimination et la détection consciente de ce filtre de Gabor. Nos résultats montrent que chez l'humain, la distribution spatio-temporelle de l'activité frontale et pariétale joue un rôle causal dans la performance visuelle. Nos recherches contribuent à mieux comprendre les bases oscillatoires de la cognition visuelle et les comportements associés et à préparer le terrain pour le développement de nouvelles thérapies basées sur la manipulation non-invasive de l'activité cérébrale oscillatoire avec, pour objectif ultime, l'amélioration des pathologies neuropsychiatriques. / Frontal and parietal areas have been shown to subtend different cognitive processes such as attentional orienting, decision making and access to consciousness, with bearing on visual performance. In spite of prior evidence supporting an implication of those regions in visual cognition, their contributions to the processing of low-contrast unmasked stimuli and the characteristic spatiotemporal activity patterns underlying them remain to be fully explored and causation is lacking. We here addressed a thorough exploration of such contributions in humans, with an emphasis on the dynamics of neural activity and visual performance enhancements as probed by patterns of noninvasive manipulation of local brain oscillatory activity. To this end, we tested in healthy participants the effects of either single pulses or short bursts of active vs. sham transcranial magnetic stimulation (TMS), delivered to the frontal eye field (FEF) and the intraparietal sulcus (IPS) prior to the presentation of a lateralized low-contrast near-threshold Gabor stimulus, on the visual discrimination and conscious detection of such stimulus. Our findings contribute to better substantiate the oscillatory basis of visual cognition and its associated behaviors and to set the stage for the development of novel therapies based on noninvasive manipulation of dysfunctional brain oscillatory activity.

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Orientador: Vivaldo Fernando da Costa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T01:39:36Z (GMT). No. of bitstreams: 1 Magalhaes_AlinedaSilva_M.pdf: 1630763 bytes, checksum: a79cfa073b1e00a5a037e569e5a09bac (MD5) Previous issue date: 2006 / Resumo: Esta dissertação apresenta um estudo que avalia o desempenho do PST (Phase Shifting Transformer), equipado com um controlador suplementar, para o amortecimento de oscilações eletromecânicas de baixa freqüência em sistemas de energia elétrica. O modelo dinâmico que representa o PST é implementado no Modelo de Sensibilidade de Potência (MSP). A análise da estabilidade e o projeto de estabilizadores POD (Power Oscillation Damping) são baseados em análise modal, bifurcações de Hopf, gráficos do lugar das raízes e técnicas de resposta em freqüência e no tempo. É investigado o desempenho de diferentes sinais de entrada para os controladores. Os resultados obtidos revelam que o PST, quando equipado com estabilizadores, possui um grande potencial para manutenção da estabilidade de ângulo a pequenas perturbações de sistemas elétricos de potência / Abstract: This dissertation presents an assessment of the performance of PST (Phase Shifting Transformer) equipped with a supplemental controller for damping power systems low-frequency electromechanical oscillations. The dynamic model that represents the PST is implemented in the Power Sensitivity Model (PSM). The stability analysis and the design of POD (Power Oscillation Damping) stabilizers are based on modal analysis, Hopf bifurcations, root locus plots and time and frequency response techniques. The performance of different input signals to the controllers is investigated. The results obtained reveal that the PST, when equipped with stabilizers, has a great potential for keeping power systems small-signal angle stability / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Orientador: Hans Ingo Weber / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-24T05:43:03Z (GMT). No. of bitstreams: 1 Mattos_MarcioCoelhode_D.pdf: 10130294 bytes, checksum: 5b9cef82256f8fd05f78a1341b08ac10 (MD5) Previous issue date: 1998 / Resumo: Apresentamos neste trabalho uma investigação sobre as mudanças na dinâmica de sistemas com vibroimpacto. Particularmente estamos interessados no estudo da migração das freqüências características destes sistemas. Podemos considerar que um dado sistema com vibroimpacto tende a um sistema com impacto degenerado quando a folga deste sistema tende a zero ou a um valor maior que a amplitude de vibração do sistema na coordenada de impacto. Podemos também denominar estes sistemas como sistemas lineares associados ao sistema com impacto, se o impacto' for a única não linearidade presente no sistema. Mostramos que existe uma relação intrínseca entre a resposta do sistema com impacto e os sistemas lineares associados, ou sistemas degenerados. Para investigar esta relação, analisamos a resposta de sistemas com dois e três graus de liberdade com impacto em uma de suas coordenadas. Além disto, investigamos experimentalmente a resposta de uma viga engastada-livre excitada randomicamente e com impactos em sua extremidade livre. Observamos boa correlação entre os resultados numéricos e, experimentais. Propomos uma função para a migração da primeira freqüência característica da resposta de sistemas com vibroimpacto. O caminho da migração depende da distribuição da energia total fornecida ao sistema entre os diversos modos de vibração dos sistemas lineares associados / Abstract: This works presents an investigation on the changes in the dynamics of vibroimpact systems as their clearance is varied. Particularly we are interested in the migration of the characteristic frequencies of impact systems. We can consider that a given vibroimpact system reaches to a degenerated impact system when the clearance reaches to zero or to a value which is greater than the amplitude of the response of the system at the impact coordinate. We also can call these systems as associated linear systems of a given impact system, if the impact is the only nonlinearity which takes place. We show that there is an intrinsic relation between impact systems and their associated linear systems, or degenerated systems. To investigate this relation we consider the free response of 2-DOF and 3-DOF impact systems with impact in one of their coordinates. On the other hand, we have performed an experimental investigation in a randomly excited cantilever beam with impacts on its free end. We have found good agreement between numerical and experimental results. We have proposed a function for the migration of the first characteristic frequency of impact systems. The migration way depends on distribution of the total energy supplied to system among the vibration modes of the associated linear systems / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

Plusieurs études documentent des liens entre des habiletés dans des tâches liées au rythme et certaines compétences de base en lecture. Par exemple, des corrélations significatives sont observées chez des enfants et des adolescents entre des scores en décodage de la lecture et le niveau de réussite dans des tests qui impliquent de se synchroniser à une cadence ou une séquence rythmique. De plus, il est connu que la dyslexie s’accompagne souvent de plusieurs difficultés sur le plan rythmique, et des études récentes en électroencéphalographie (EEG) et magnétoencéphalographie (MEG) ont proposé que ces lacunes soient reliées à des patrons d’activité atypiques dans les oscillations neuronales de basse fréquence du système nerveux central. Comment expliquer que le rythme et la lecture soient ainsi liés sur le plan développemental? Dans plusieurs études, on fait référence à la conscience phonologique comme variable médiatrice pour comprendre cette association de façon indirecte. À la différence de ces théories, le présent mémoire propose une explication plus directe du lien entre rythme et lecture, dans laquelle on met l’accent sur le rôle intrinsèque du rythme pour le chunking d’information verbale en lecture à voix haute ou silencieuse. Pour tester cette hypothèse, on a mené une expérience durant laquelle 43 participants et participantes ont lu des textes alors que leur voix et leurs mouvements oculaires étaient enregistrés par un appareil d’oculométrie. Les résultats montrent que le rythme implicite d’un texte est suivi de façon stricte dans la lecture orale des participants, indépendamment d’amorces rythmiques auditives présentées avant le texte. De plus, certaines mesures probabilistes de fixations oculaires concordent avec ce comportement de la voix, suggérant que l’échantillonnage visuel d’un texte puisse générer une forme de comportement rythmique séquentiel. On termine en discutant des implications de ces résultats de recherche pour les théories de la lecture. / Numerous studies have documented links between abilities in tasks involving rhythm and some basic reading skills. For instance, significant correlations are observed between children or adolescent’s reading skills and their performance on tasks on motor synchronization to an auditory cadence or rhythmic sequence. Moreover, it is known that dyslexia is often accompanied by difficulties at the rhythmic level, and recent studies in electroencephalography (EEG) and magnetoencephalography (MEG) have suggested that these deficits may result from atypical patterns of activity in low-frequency neuronal oscillations of the central nervous system. How can these developmental links between rhythm and reading be explained? In some studies, phonological awareness is used to understand this association, hence proposing an indirect explanation relying on a third variable to make sense of the phenomenon. Unlike these theories, the present work proposes a more direct explanation of the link between rhythm and reading, where the emphasis is put on the intrinsic role of rhythm for the perceptual chunking of verbal information in oral or silent reading. To test this hypothesis, an experiment is presented in which 43 participants had to read sentences orally while their voice and eye-movements were recorded by an eye-tracking system. Results show that the implicit rhythm of the text is strictly followed in the participants’ oral reading, independently of a rhythmic priming that was presented before the text. In addition, probabilistic measures of eye fixations resemble the voice’s rhythmic chunks, highlighting possible rhythmic properties of visual sampling for text reading. We conclude by discussing the implications of these results for theories of reading.

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京都大学 / 新制・課程博士 / 博士(理学) / 甲第22986号 / 理博第4663号 / 新制||理||1669(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 松田 祐司, 教授 石田 憲二, 准教授 笠原 裕一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM