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Dissertations / Theses on the topic 'LFPP'

Author: Grafiati
Published: 3 June 2025
Last updated: 20 July 2025

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1

Schachter, Mike J. "Decoding the rhythms of avian auditory LFP." Thesis, University of California, Berkeley, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10192590.

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<p> We undertook a detailed analysis of population spike rate and LFP power in the Zebra finch auditory system. Utilizing the full range of Zebra finch vocalizations and dual-hemisphere multielectrode recordings from auditory neurons, we used encoder models to show how intuitive acoustic features such as amplitude, spectral shape and pitch drive the spike rate of individual neurons and LFP power on electrodes. Using ensemble decoding approaches, we show that these acoustic features can be successfully decoded from the population spike rate vector and the power spectra of the multielectrode LFP with comparable performance. In addition we found that adding pairwise spike synchrony to the spike rate decoder boosts performance above that of the population spike rate alone, or LFP power spectra. We also found that decoder performance grows quickly with the addition of more neurons, but there is notable redundancy in the population code. Finally, we demonstrate that LFP power on an electrode can be well predicted by population spike rate and spike synchrony. High frequency LFP power (80-190Hz) integrates neural activity spatially over a distance of up to 250 microns, while low frequency LFP power (0-30Hz) can integrate neural activity originating up to 800 microns away from the recording electrode. </p><p> To understand how an auditory system processes complex sounds, it is essential to understand how the temporal envelope of sounds, i.e. the time-varying amplitude, is encoded by neural activity. We studied the temporal envelope of Zebra finch vocalizations, and show that it exhibits modulations in the 0-30Hz range, similar to human speech. We then built linear filter models to predict 0-30Hz LFP activity from the temporal envelopes of vocalizations, achieving surprisingly high performance for electrodes near thalamorecipient areas of Zebra finch auditory cortex. We then show that there are two spatially-distinct subnetworks that resonate at different frequency bands, one subnetwork that resonates around 19Hz, and another subnetwork that resonates at 14Hz. These two subnetworks are present in every anatomical region. Finally we show that we can improve predictive performance with recurrent neural network models. </p>
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2

Seiscio, Andrew R. "The Role of GABAergic Transmission in Mediation of Striatal Local Field Potentials (LFPs)." Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/psych_theses/63.

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In the present study, electrophysiological and behavioral effects of compromised Gama-Aminobutyric Acid (GABAergic) transmission were investigated in adult Rhesus macaque monkeys (N=2). GABAergic transmission was perturbed in the putamen by administration of a GABAa receptor antagonist, gabazine (10 and 500 μM), via a microdialysis-local field potential (MD-LFP) probe. Resultant changes in striatal local field potentials (LFPs) were measured as an assay of synchrony. Gabazine perfusion evoked discrete large amplitude spikes in LFPs in all subjects, and the frequency and shape of individual spikes were concentration-dependent. Pre-treatment with the GABAa receptor agonist, muscimol (100 μM) blocked the gabazine-induced events, confirming a role for GABAa receptors in the effects. Behavioral manifestations of gabazine treatment were observed only at the maximum concentration. Unusual facial movements suggested aberrant electrical activity was propagated from striatum to motor cortex, perhaps via reentrant circuits. These results support a role for GABAergic transmission in segregation of striatal circuits.
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3

Kühnen, Tanja [Verfasser]. "Chronische Depression. Entwicklung und Evaluation des Lübecker Fragebogens zur Erfassung präoperatorischen Denkens (LFPD) / Tanja Kühnen." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2013. http://d-nb.info/1043953167/34.

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4

Travaini, Job Nicolau. "Descritores de textura local para reconhecimento biométrico da íris humana." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18152/tde-09112015-161059/.

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Técnicas biométricas procuraram identificar usuários pela textura da íris, impressão digital, traços faciais, entre outros. A íris humana apresenta características de textura que a classificam como uma peculiaridade biométrica de grande poder de discriminação no reconhecimento de pessoas. O objetivo deste trabalho é avaliar a eficiência de uma nova metodologia de análise de texturas em desenvolvimento no LAVI (Laboratório de Visão Computacional da EESC-USP) na identificação de indivíduos por meio da textura de sua íris. A metodologia denomina-se Local Fuzzy Pattern e tem sido utilizada com excelente desempenho com texturas gerais, naturais e artificiais. Este documento detalha as técnicas utilizadas para extração e normalização da textura da íris, a utilização e os resultados obtidos com o método Local Fuzzy Pattern aplicado à classificação biométrica da íris humana. Os resultados obtidos apresentam sensibilidade de até 99,7516% com a aplicação da metodologia proposta em bancos de imagens de íris humana disponíveis na internet demonstram a viabilidade da técnica proposta.<br>Biometric techniques sought to identify users by the texture of the iris, fingerprint, facial features, among others. The human iris have texture characteristics that rank it as a powerful biometric peculiarity on human recognition. The objective of this masters proposal is to investigate the efficiency of a new methodology of iris texture analysis currently in development in LAVI (Laboratório de Visão Computacional da EESC-USP). The methodology is called LFP (Local Fuzzy Pattern) and has been used with excellent overall performance on artificial and natural textures. This document details the techniques used for the extraction and normalization of the iris texture, the use and results of the local fuzzy pattern method applied to biometric classification of the human eye. The results show a sensibility of value up to 99.7516%, obtained by applying the proposed methodology on human iris photos from image database available on the internet does showing the viability of the technique.
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5

Ribeiro, Patricia Pedroso Estevam. "Aplicação de técnicas de processamento de imagens para diferenciação do greening de outras pragas." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18152/tde-29072014-160016/.

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O greening ou Huanglongbing (HLB) é uma das mais graves doenças dos citros presentes nos pomares do Brasil. Causada pela bactéria Candidatus Liberibacter spp, é transmitida pelo inseto psilídeo Diaphorina citri, que ao se alimentar de uma planta doente transmite a doença às demais plantas. O greening apresenta como sintoma, manchas amareladas nas folhas, muitas vezes confundidas com deficiências nutricionais. A erradicação da planta e o controle do inseto transmissor são as únicas formas de prevenção para evitar a sua propagação. Este trabalho teve por objetivo avaliar uma metodologia baseada em segmentação por cor e outra baseada em análise de textura para avaliação de folhas de citros sintomáticas, identificando se estão contaminadas com o greening ou outras doenças e deficiências nutricionais. Foram fornecidas pelo grupo FISHER, 324 amostras de folhas cítricas, contendo folhas com doenças (greening, CVC e rubelose) e deficiências nutricionais (manganês, magnésio e zinco). As folhas foram digitalizadas por um scanner de mesa, com duas resoluções, utilizando somente a parte frontal da folha. Foram montados três bancos de imagens. Os resultados gerados com a metodologia baseada em segmentação por cor utilizando RNA PMC, mostraram que essa metodologia não é eficiente. Na metodologia baseada na análise por textura foram avaliados os descritores LBP, LFP e os de Haralick. Para estes descritores foram extraídas amostras por folha e por quadrantes das folhas nos canais de cores vermelho e verde e amostras em níveis de cinza. Os resultados gerados pelos descritores foram classificados pela distância &#9672 e pelos algoritmos IBK e RNA PMC do toolbox Weka. Os melhores resultados foram para os descritores LBP e LFP-s para distância &#9672, com valores de sensibilidade acima de 97% e 93%, respectivamente, e para o LBP com o algoritmo IBK, com valores de sensibilidade acima de 98,5%. Os resultados obtidos evidenciam que o descritor LBP é o mais eficiente seguido pelo LFP-s na diferenciação do greening das outras pragas.<br>The greening or Huanglongbing (HLB) is one of the most serious diseases of citrus orchards present in Brazil. HLB is caused by the bacterium Candidatus Liberibacter spp, it is transmitted by the psyllid insect (Diaphorina citri) that, when feeding on a diseased plant, it transmits the disease to other plants. One of the symptoms of the greening are yellowish spots on the leaves, often confused with nutritional deficiencies. The eradication of plants and control of insect are the only forms of prevention. This work aims to evaluate two methodologies: one based on color segmentation and the other based on texture analysis for assessment of symptomatic citrus leaves, identifying whether they are infected with greening and other diseases and nutritional deficiencies. A number of 324 samples of citrus leaves were provided by FISHER group, infected with diseases (greening, CVC, rubelose) and nutritional deficiencies ( manganese, magnesium, zinc) . The leaves were acquired by a flatbed scanner with two different resolutions, using only the front side of the leaf. Three datasets of images were constructed. The results generated using the methodology based on color segmentation with ANN MLP, showed that this methodology is not efficient. In the methodology based on texture analysis it was evaluated the LBP, LFP and the Haralick descriptors. For these descriptors it was extracted samples from the leaves and quadrants of leaves, in red and green color channels and grayscale. The results generated by the descriptors were classified by &#9672 distance and the algorithms IBK and ANN MLP from the toolbox Weka. The best results were for LBP descriptor and LFP-s for &#9672 distance with values of sensitivity above 97% and 93%, respectively, and the LBP with IBK algorithm, with values of sensitivity above 98.5%. The results showed that the LBP descriptor is the most efficient followed by LFP-s in the differentiation of the greening from other pests.
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6

Jarre, Guillaume. "Etude des réseaux neuronaux du cortex somatosensoriel au cours de l'épileptogenèse dans un modèle d'épilepsie génétique." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV064.

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Le cerveau est composé de réseaux de neurones interconnectés dont la mise en place au cours du développement cérébral est hautement régulée par des processus cellulaires, moléculaires et fonctionnels. Un dysfonctionnement de ces processus peut perturber l’établissement de ces réseaux et conduire à des pathologies neurologiques. L’épilepsie absence est une pathologie génétiquement déterminée qui apparait au cours de l’enfance. Les crises d’absences sont caractérisées par une altération de la conscience et par la présence de décharges de pointe-ondes (DPO) sur l’électroencéphalogramme initiées au sein d’un zone restreinte du cortex. Cependant, on sait peu de choses sur les mécanismes conduisant à la mise en place des décharges épileptiques récurrentes au cours de l’enfance (i.e. l’épileptogenèse). Nous avons fait l’hypothèse que des anomalies du processus de maturation cérébrale sont à l’origine de l’apparition des DPO.J’ai vérifié cette hypothèse chez un modèle génétique d’épilepsie absence, le rat GAERS. Dans un premier temps, j’ai étudié l’épileptogenèse du GAERS grâce à l’enregistrement in vivo du potentiel de champs local et de l’activité intracellulaire des neurones pyramidaux au niveau du site d’initiation des DPO, le cortex somatosensoriel (SoCX). Nous avons mis en évidence que les DPO se développent progressivement après la fin d’une période de maturation hautement sensible et malléable du SoCx (i.e. période critique). La maturation des décharges épileptiques consiste en une augmentation de leur fréquence, de leur durée et en l’évolution du motif de décharge jusqu’à l’âge adulte, période à laquelle ces paramètres atteignent une relative stabilité. De plus, ces changements sont associés à une altération graduelle des propriétés intrinsèques des neurones pyramidaux qui s’accompagne d’une augmentation progressive de la force de l’activité synaptique locale et d’une propension accrue des neurones du SoCx à générer des oscillations synchrones.Nous avons ensuite recherché les raisons de cette prédisposition anormale des neurones du SoCx à se synchroniser chez le GAERS. Dans ce but, nous avons cherché à mettre en évidence des anomalies de la maturation corticale au niveau de la structure et de l’organisation fonctionnelle du SoCx avant l’apparition des DPO. En combinant l’IRM, des marquages immunohistochimiques et le traçage rétrograde monosynaptique des connexions longue distance par le virus de la rage modifié, nous avons pu montrer qu’aucune anomalie globale du cerveau et du SoCx n’est présente chez le GAERS avant l’apparition des DPO. Afin de déterminer la présence d’anomalies fonctionnelles nous avons utilisé l’imagerie calcique biphoton et enregistré in vivo la dynamique de l’activité spontanée du réseau de neurones des couches 2-3 du SoCx. Chez le GAERS, nous avons mis en évidence que ces neurones sont plus actifs et dévoilent une organisation fonctionnelle différente de celle des animaux contrôles. Enfin, pour comprendre comment cette organisation fonctionnelle anormale est médiée, nous avons étudié la structure dendritique et synaptique du SoCx en combinant la microscopie électronique et la reconstruction morphologique de neurones. Nous avons mis en évidence un élargissement des épines dendritiques associé à un allongement de la densité post-synaptique au sein du SoCx chez le GAERS.L’ensemble de ces résultats démontrent la nature progressive du développement de l’épilepsie absence ainsi que l’existence d’anomalies de la maturation corticale qui affectent la structure et la fonction du réseau neuronal, avant l’apparition des crises épileptiques. Ces altérations constituent une prédisposition à l’établissement et l’évolution des DPO et sont une cible thérapeutique potentielle qui pourrait permettre de bloquer la mise en place des crises d’absences<br>The brain is organized into several interconnected neuronal networks whose formation is highly regulated by cellular, molecular and functional processes. The dysfunction of these processes during brain development could disrupt neuronal circuit establishment and lead to neurological pathologies. Absence epilepsy is a genetically determined disease with a childhood onset. Absence seizures are characterized by an impairment of the consciousness associated on the electroencephalogram with spike and wave discharges (SWD). However, little is known about the mechanisms leading to the establishment of recurrent epileptic discharges (i.e. epileptogenesis). We hypothesized that SWD onset originates from an abnormal brain maturation.During my PhD, I examined this hypothesis in a recognized genetic model of absence epilepsy, the GAERS rat. First, I studied the epileptogenic process by recording in vivo the local field potential and the intracellular activities of pyramidal neurons in the initiating area of SWD, the somatosensory cortex (SoCx), at different post natal days in GAERS. We showed that SWD progressively developed after the end of a highly sensitive and plastic maturation period of the SoCx (i.e critical period). Afterward, epileptic discharges maturation consists in an increase of their duration, their number and in an evolution of the pattern reaching a relative stability at adulthood. Moreover, these changes are associated with a gradual abnormal alteration of the intrinsic properties of pyramidal neurons which is accompanied with a progressive increase in the strength of the local synaptic activity and a growing propensity of SoCx neurons to generate synchronized oscillations.Then, we explored the reasons for this abnormal susceptibility of SoCx neurons to be more synchronized in GAERS. We sought to bring to light anomalies of SoCx maturation at the structural and functional organization level prior to SWD onset in GAERS. Combining MRI, immunohistochemistry labeling and rabies-mediated retrograde monosynaptic tracing to reveal long-range connectivity, we showed that, prior to SWD onset, no brain and SoCx architecture abnormalities could be observed in GAERS. Then, using two photon calcium imaging we recorded in vivo the spontaneous activity of SoCx layers 2-3 neurons to evidence their functional organization. We found that these neurons were more active and unveiled a different functional organization in GAERS compared to control animals. Finally, to understand how is mediated this abnormal functional organization, we studied the dendritic and synaptic fine structure of SoCx neurons by combining electron microscopy and morphological neuron reconstruction. We highlighted an enlargement of the dendritic spines as well as an increase of the post-synaptic density length in the GAERS SoCx.Taken together, these findings showed the progressive nature of absence epilepsy development and the presence of abnormalities in the cortical maturation which affect the structure and the functional of the neuronal network the prior to SWD. These alterations constitute a breeding ground for the establishment and evolution of SWD. Future studies will aim at interfering with the epileptogenesis process should target these early alterations to stop seizure development
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7

Keller, Christopher. "Photolysis of 1-(4-azidomethyl-phenyl)-ethanone and matrix/LFP studies of 2-benzoyl-3-methyl-2H-azirine." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1121442210.

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8

Gilliers, Frédéric. "Dévelopement par prototypage et génération de code à partir de LfP, un langage de modélisation de haut niveau." Paris 6, 2005. http://www.theses.fr/2005PA066302.

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9

Tippmann, Eric M. "Studies of carbene-solvent interactions." Connect to this title online, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1070405724.

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Thesis (Ph. D.)--Ohio State University, 2003.<br>Title from first page of PDF file. Document formatted into pages; contains xxviii, 310 p.; also includes graphics (some col.) Includes bibliographical references (p. 181-183). Available online via OhioLINK's ETD Center
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Polshakov, Dmitrii A. "Ultrafast spectroscopy and dynamics of nitrenes and carbenes." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1130968887.

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11

Zhou, Pengcheng. "Computational Tools for Identification and Analysis of Neuronal Population Activity." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/1015.

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Recently-developed technologies for monitoring activity in populations of neurons make it possible for the first time, in principle, to ask many basic questions in neuroscience. However, computational tools for analyzing newly available data need to be developed. The goal of this thesis is to contribute to this effort by focusing on two specific problems. First, we used a point-process regression framework to provide a methodology for statistical assessment of the link between neural spike synchrony and network-wide oscillations. In simulations, we showed that our method can recover ground-truth relationships, and in two types of spike train data we illustrated the kinds of results the method can produce. The approach improves on methods in the literature and may be adapted to many different experimental settings. Second, we considered the problem of source extraction in calcium imaging data, i.e., the detection of neurons within a field of view and the extraction of each neuron’s activity. The data we mainly focus on are recorded with a microendoscope, which has the unique advantage of imaging deep brain regions in freely behaving animals. These data suffer from high levels of background fluorescence, as well as the potential for overlapping neuronal signals. Based on the existing constrained nonnegative matrix factorization (CNMF) framework, we developed an efficient method to process microendoscopic data. Our method utilizes a novel algorithm to initialize the spatial shapes and temporal activity of the neurons from the raw video data independently from the strong fluctuating background. This step ensures the efficiency and accuracy of solving a nonconvex CNMF problem. Our method also models the complicated background by including its low-spatial frequency structure and the locally-low-rank feature to avoid absorbing cellular signals into the background term. We developed a tractable solution to estimate the background activity using this new model. After subtracting the approximated background, we followed the CNMF framework to demix neural signals and recover denoised and deconvolved temporal activity. We optimized several algorithms in solving the CNMF problems to get accurate results. In practice, our method outperforms all existing methods and has been adopted by many experimental labs.
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12

Rothé, Marie. "Activités spécifiques du cortex cingulaire antérieur et du cortex préfrontal dorsolatéral et interactions lors de l’adaptation des comportements." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10268/document.

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Agir de façon optimale dans un environnement incertain nécessite d'évaluer et de comparer les coûts et bénéfices des différentes alternatives. Cela implique aussi de réguler et de contrôler le comportement de façon flexible pour optimiser les périodes de recherche de gains ou de ressources et les périodes d'exploitation des acquis. Une des hypothèses actuelles sur les mécanismes neurobiologiques impliqués, propose que cortex cingulaire antérieur (CCA), associé à l’évaluation de l’action, et cortex préfrontal dorsolatéral (CPFdl), associé au contrôle cognitif, interagiraient pour réguler le comportement. Les travaux réalisés au cours de cette thèse ont permis de préciser le rôle joué par le CCA dans la détection et l’évaluation des performances ainsi que ses interactions avec le CPFdl au sein d'une boucle du contrôle cognitif. Menés grâce à des enregistrements électrophysiologiques chez le singe en comportement, ils apportent des précisions sur la séquence d’activation du CCA et du CPFdl dans la bande de fréquences gamma lors de l'adaptation du comportement. L’étude des potentiels de champs locaux de ces deux régions amènent à poser des hypothèses sur les mécanismes oscillatoires sous-jacents et notamment sur le rôle des communications basses fréquences entre le CCA et le CPFdl et leur implication différentielle entre recherche et exploitation<br>Acting optimally in uncertain environments requires evaluating costs and benefits of choosing each alternative. It also requires to flexibly regulate between exploration for and exploitation of resources. One current hypothesis is that the anterior cingulate cortex (ACC), involved in action valuation, and dorsolateral prefrontal cortex (dlPFC), involved in cognitive control, interact to elaborate an optimal regulation of behaviour. Studies achieved during this thesis allowed to precise the role of ACC in the detection and valuation of action outcomes as well as to describe the interactions with dlPFC in a cognitive control loop. Thanks to neurophysiological recordings in behaving monkey our work give new clues on the sequential activation of ACC and dlPFC during adaptation. The analyses of local field potentials allowed us to suggest hypotheses on the underlying oscillatory mechanisms, in particular on low frequency communications between ACC and dlPFC, and their modulation during exploration and exploitation
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Gabaldón, López María Victoria. "Estudio de la estructura dinámica de las interacciones funcionales en el hipocampo mediante procesado de registros electrofisiológicos cerebrales en rata." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/30777.

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El hipocampo es una de las regiones del cerebro más ampliamente estudiadas, y es de interés para gran parte de los neurocientíficos, desde aquellos que estudian su estructura y funcionalidad hasta los que estudian su mal funcionamiento en diversas enfermedades y condiciones patológicas. El hipocampo tiene un papel fundamental, entre otras cosas, en la adquisición y consolidación de la memoria episódica, así como en la orientación espacial. De todas las propiedades de las sinapsis en el hipocampo, quizás la más atractiva, y seguramente la estudiada con mayor entusiasmo, es su habilidad de responder a patrones de activación específicos con aumentos o disminuciones de larga duración en la eficiencia sináptica. Esta propiedad plástica de las sinapsis en general, y de las del hipocampo en particular, es considerada por muchos neurocientíficos como la base celular del aprendizaje de ciertos tipos de recuerdos y memorias. El objetivo principal de esta Tesis Doctoral, fruto de una estrecha colaboración entre el Centro de Biomateriales e Ingeniería Tisular de la Universitat Politècnica de València y el Laboratorio de Plasticidad de las Redes Neuronales del Instituto de Neurociencias (Consejo Superior de Investigaciones Científicas ¿ Universidad Miguel Hernández) de San Juan (Alicante), es aportar nuevos conocimientos sobre los mecanismos que regulan el flujo de información entre las distintas áreas del hipocampo y por tanto, contribuir a un mejor entendimiento de los mecanismos neurofisiológicos que subyacen al aprendizaje y la memoria mediante el análisis de señales adquiridas mediante registros electrofisiológicos de alta densidad, correspondientes a distintas partes del hipocampo y la corteza parietal asociativa, adquiridas en distintos instantes de tiempo antes y después de la potenciación sináptica a largo plazo. Para ello, se ha desarrollado una metodología que nos ha permitido estudiar la actividad espontánea del sistema, y con la que hemos observado la dependencia espacial y temporal de la desviación típica tanto en los cálculos de correlación como en los de coherencia. Además, se ha trabajado tanto con los potenciales de campo locales (LFP por sus siglas en inglés), como con sus componentes independientes, haciendo una comparativa entre los resultados obtenidos para cada caso, en cuanto a correlación y coherencia se refiere, utilizando fragmentos pertenecientes a diferentes etapas durante la potenciación sináptica a largo plazo (LTP por sus siglas en inglés), para conocer los cambios que se dan en esta estructura tras dicha potenciación sináptica. En el caso de la coherencia, hemos podido observar los cambios que se producen debido a la potenciación sináptica en las diferentes bandas de frecuencia. Todos estos cálculos se han realizado de forma ipsilateral, comparando señales pertenecientes a un mismo hemisferio cerebral, y de forma bilateral, comparando señales pertenecientes a hemisferios cerebrales diferentes. Por último, a partir de la experiencia en el manejo de estos registros electrofisiológicos y de sus componentes independientes, se han identificado patrones de correlación interregional, que se suceden en el tiempo como entidades singulares y a los que hemos denominado ¿ministates¿ por su duración menor de un segundo. Dichos patrones, que aparecen de forma repetida en los registros, podrían estar asociados a eventos electrofisiológicos identificables en la señal y estar modulados por procesos de plasticidad sináptica. Así, se ha desarrollado una metodología adecuada para el análisis de señales adquiridas mediante registros electrofisiológicos de alta densidad, mediante el cálculo de la correlación y la coherencia de estas señales electrofisiológicas y de sus componentes independientes, y se ha programado en entorno MATLAB. Gracias a las herramientas desarrolladas y aplicadas hemos comprobado la dependencia temporal y espacial de la dispersión de los valores de correlación y coherencia y hemos analizado la estructura funcional en reposo de los circuitos de la formación hipocampal, obteniendo evidencias a favor de la existencia de dos vías de procesamiento paralelo e independiente en el sistema. Además, hemos hallado patrones de comunicación, a los que hemos denominado ¿ministates¿, que se suceden en el tiempo en secuencias controladas por procesos de plasticidad sináptica, apareciendo repetidamente en las distintas fases estudiadas de nuestro modelo experimental de aprendizaje. Aún nos encontramos lejos de poder describir cómo el aprendizaje modifica el `estado interno¿ del cerebro. Entre las dificultades encontradas cabe destacar la enorme variabilidad en las señales electrofisiológicas registradas en los distintos estados por los que, de forma espontánea, transcurre la actividad cerebral. De esta forma la huella del aprendizaje o la memoria se encuentra enmascarada por grandes fluctuaciones de actividad. Sin embargo, gracias a las herramientas desarrolladas hemos podido aportar datos nuevos sobre cómo tiene lugar la comunicación en la formación hipocampal y constatar que la plasticidad sináptica modula dicha comunicación.<br>Gabaldón López, MV. (2013). Estudio de la estructura dinámica de las interacciones funcionales en el hipocampo mediante procesado de registros electrofisiológicos cerebrales en rata [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/30777<br>TESIS
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14

Ocazionez, Sergio Andr?s Conde. "The influence of visual inter-hemispheric connections on spiking, assembly and LFP activities, and their phase relationship during figure-ground stimulation." Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17032.

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Made available in DSpace on 2014-12-17T15:29:22Z (GMT). No. of bitstreams: 1 SergioACO_TESE.pdf: 4589227 bytes, checksum: 062baf399b5377e444d02b747586f12b (MD5) Previous issue date: 2014-03-31<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior<br>Desde os descobrimentos pioneiros de Hubel e Wiesel acumulou-se uma vasta literatura descrevendo as respostas neuronais do c?rtex visual prim?rio (V1) a diferentes est?mulos visuais. Estes est?mulos consistem principalmente em barras em movimento, pontos ou grades, que s?o ?teis para explorar as respostas dentro do campo receptivo cl?ssico (CRF do ingl?s classical receptive field) a caracter?sticas b?sicas dos est?mulos visuais como a orienta??o, dire??o de movimento, contraste, entre outras. Entretanto, nas ?ltimas duas d?cadas, tornou-se cada vez mais evidente que a atividade de neur?nios em V1 pode ser modulada por est?mulos fora do CRF. Desta forma, ?reas visuais prim?rias poderiam estar envolvidas em fun??es visuais mais complexas como, por exemplo, a separa??o de um objeto ou figura do seu fundo (segrega??o figura-fundo) e assume-se que as conex?es intr?nsecas de longo alcance em V1, assim como as conex?es de ?reas visuais superiores, est?o ativamente envolvidas neste processo. Sua poss?vel fun??o foi inferida a partir da an?lise das varia??es das respostas induzidas por um est?mulo localizado fora do CRF de neur?nios individuais. Mesmo sendo muito prov?vel que estas conex?es tenham tamb?m um impacto tanto na atividade conjunta de neur?nios envolvidos no processamento da figura quanto no potencial de campo, estas quest?es permanecem pouco estudadas. Visando examinar a modula??o do contexto visual nessas atividades, coletamos potenciais de a??o e potenciais de campo em paralelo de at? 48 eletrodos implantados na ?rea visual prim?ria de gatos anestesiados. Estimulamos com grades compostas e cenas naturais, focando-nos na atividade de neur?nios cujo CRF estava situado na figura. Da mesma forma, visando examinar a influ?ncia das conex?es laterais, o sinal proveniente da ?rea visual isot?pica e contralateral foi removido atrav?s da desativa??o revers?vel por resfriamento. Fizemos isso devido a: i) as conex?es laterais intr?nsecas n?o podem ser facilmente manipuladas sem afetar diretamente os sinais que est?o sendo medidos, ii) as conex?es inter-hemisf?ricas compartilham as principais caracter?sticas anat?micas com a rede lateral intr?nseca e podem ser vistas como uma continua??o funcional das mesmas entre os dois hemisf?rios e iii) o resfriamento desativa as conex?es de forma causal e revers?vel, silenciando temporariamente seu sinal, permitindo conclus?es diretas a respeito da sua contribui??o. Nossos resultados demonstram que o mecanismo de segmenta??o figurafundo se reflete nas taxas de disparo de neur?nios individuais, assim como na pot?ncia do potencial de campo e na rela??o entre sua fase e os padr?es de disparo produzidos pela popula??o. Al?m disso, as conex?es laterais inter-hemisf?ricas modulam estas vari?veis dependendo da estimula??o feita fora do CRF. Observamos tamb?m uma influ?ncia deste circuito lateral na coer?ncia entre potenciais de campo entre eletrodos distantes. Em conclus?o, nossos resultados d?o suporte ? ideia de um mecanismo complexo de segmenta??o figura-fundo atuando desde as ?reas visuais prim?rias em diferentes escalas de frequ?ncia. Esse mecanismo parece envolver grupos de neur?nios ativos sincronicamente e dependentes da fase do potencial de campo. Nossos resultados tamb?m s?o compat?veis com a hip?tese que conex?es laterais de longo alcance tamb?m fazem parte deste mecanismo<br>Since Hubel and Wiesel s pioneer finding a vast body of literature has accumulated describing neuronal responses in the primary visual cortex (V1) to different visual stimuli. These stimuli mainly consisted of moving bars, dots or gratings which served to explore the responses to basic visual features such as orientation, direction of motion or contrast, among others, within a classical receptive field (CRF). However, in the last two decades it became increasingly evident that the activity of V1 neurons can be modulated by stimulation outside their CRF. Thus, early visual areas might be already involved in more complex visual tasks like, for example, the segmentation of an object or a figure from its (back)-ground. It is assumed that intrinsic long-range horizontal connections within V1 as well as feedback connections from higher visual areas are actively involved in the figure-ground segmentation process. Their possible role has been inferred from the analysis of the spike rate variations induced by stimuli placed outside the CRF of single neurons. Although it is very likely that those connections also have an impact on the joined activity of neurons involved in processing the figure and on their local field potentials (LFP), these issues remain understudied. In order to examine the context-dependent modulation of those activities, we recorded spikes and LFPs in parallel from up to 48 electrodes in the primary visual cortex of anesthetized cats. We stimulated with composite grating and natural scene stimuli focusing on populations of neurons whose CRFs were situated on the foreground figure. In addition, in order to examine the influence of horizontal connections we removed the inter-hemispheric input of the isotopic contralateral visual areas by means of reversible cooling deactivation. We did so because i) the intrinsic horizontal connections cannot be easily manipulated without directly affecting the measured signals, ii) because inter-hemispheric connections share the major anatomical features with the intrinsic lateral network and can be seen as a functional continuation of the latter across the two hemispheres and iii) because cooling causally and reversibly deactivates input connections by temporarily silencing the sending neurons and thus enables direct conclusions on their contribution. Our results demonstrate that the figure-ground segmentation mechanism is reflected in the spike rate of single neurons, as well as in their LFP power and its phase-relationship to the spike patterns produced by the population. In addition "lateral" inter-hemispheric connections modulate spike rates and LFP power depending on the stimulation of the neurons CRF surround. Further, we observe an influence of this lateral circuit on field- field coherences between remote recording sites. In conclusion, our findings support the idea of complex figure-ground segmentation mechanism acting already in early visual areas on different time scales. This mechanism seems to involve groups of neurons firing synchronously and dependent on the LFP s phase. Our results are also compatible with the hypothesis that long-range lateral connections contribute to that mechanism
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15

Juventin, Maxime. "Can the respiratory rhythm be a global signal promoting long-range communication in the brain?" Thesis, Lyon, 2021. https://tel.archives-ouvertes.fr/tel-03789626.

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Le cerveau est le siège d’une activité rythmique intense, chaque aire cérébrale exprimant un ou plusieurs rythmes. Une question centrale en neurosciences est de comprendre comment ces activités rythmiques peuvent se coordonner à travers des zones très distantes du cerveau pour résoudre des fonctions aussi complexes que la perception de l’environnement, des réponses motrices adaptées ou la formation de mémoires. Une possibilité est que le système utilise une référence temporelle commune, sorte d’horloge centrale, à partir de laquelle les différents réseaux neuronaux impliqués dans une fonction pourraient se coordonner. Nous faisons l’hypothèse que le rythme respiratoire pourrait être l’une de ces horloges centrales, constituant un signal de référence pour la coordination des différentes aires cérébrales. Comme horloge centrale, la respiration présente des avantages majeurs : fiabilité flexibilité, faible. Dans le système olfactif, le lien entre rythme respiratoire et l'activité neuronale est indéniable. La respiration entraîne des oscillations lentes à la fréquence respiratoire, des bursts de d'oscillations rapides et la décharge des neurones. La littérature récente, à laquelle mon équipe participe, a montré que cette influence respiratoire de l'activité neuronale n'est pas restreinte au système olfactif, mais bien au contraire s'étend au cerveau entier (néocortex, amygdale, hippocampe, thalamus). Dans la plupart des aires non-olfactives enregistrées le rythme respiratoire module également la décharge des neurones et les oscillations rapides. Les oscillations lentes liées à la respiration semblent donc bien affecter la dynamique globale du cerveau. Mon projet de thèse est composé de deux parties. Dans un premier temps, de manière à confirmer une influence du rythme respiratoire sur les neurones, j’ai réalisé des enregistrements intracellulaires dans quatre aires non-olfactives chez des rats anesthésiés. Les structures ciblées étaient le cortex préfrontal médian, le cortex somesthésique primaire, le cortex visuel primaire et enfin l’hippocampe. J’ai effectivement pu observer une modulation respiration dans la plupart de ces neurones. La quantification de ces données montre que les évènements de modulation respiratoire sont courts mais observés dans un nombre conséquent de neurones. Ces données apportent aussi la preuve que la modulation respiratoire des diverses aires cérébrales n’est pas uniquement due à de la conduction volumique. Dans un second temps, de manière à étudier la coordination d’aires cérébrales par le rythme respiratoire, j’ai analysé des enregistrements de potentiels de champ locaux (LFP) multisites chez le rat vigile. Les enregistrements contiennent sept aires cérébrales (bulbe olfactif, cortex piriforme antérieur, cortex visuel primaire, cortex préfrontal médian, cortex somesthésique primaire, CA1, gyrus denté) et la respiration. J’ai pu observer des oscillations lentes liées à respiration dans tous les états cérébraux. Mais c’est pendant l’éveil calme que la modulation respiratoire est la plus importante et apparaît dans toutes les aires enregistrées. En parallèle, ces oscillations lentes sont couplées avec plusieurs types d’oscillations rapides. Enfin, j’ai voulu savoir si, lors de l’état d’éveil calme, où les LFP d’un large réseau cérébral sont synchronisés à la respiration, les activités unitaires pouvaient aussi se synchroniser par rapport au signal respiratoire. Pour cela, j’ai mis en place un poste d’enregistrement électrophysiologique chez le rat vigile contraint permettant d’enregistrer de nombreux neurones dans des paires de structures cérébrales avec des « silicon probes ». Le poste est aujourd’hui fonctionnel et j’ai pu enregistrer 6 animaux. Ces dernières données ne seront pas entièrement traitées au moment où je soutiendrai ma thèse. Je présenterai des résultats préliminaires qui nous permettent d’ores et déjà de montrer que la respiration peut synchroniser<br>The brain is the site of intense rhythmic activity, each area of the brain expressing one or more rhythms. A central question in neuroscience is to understand how these rhythmic activities can coordinate across very distant areas of the brain to solve functions as complex as environmental perception, adapted motor responses or memory formation. One possibility is that the system uses a common time reference, a sort of central clock, from which the different neural networks involved in a function could coordinate. Today, the existence and nature of this clock are still debated. We hypothesize that the respiratory rate could be one of these central clocks, constituting a reference signal for the coordination of different areas of the brain. As a central clock, breathing has major advantages: reliability (because it is a vital function), flexibility (because it adapts to the needs of the organism), low cost (because it is a rhythm which is not not created specifically for this function). In the olfactory system, the link between respiratory rate and neuronal activity is undeniable. Respiration causes slow oscillations in the respiratory rate, bursts of rapid oscillations (gamma and beta) and the discharge of neurons. Recent literature, in which my team participates, has shown that this respiratory influence of neuronal activity is not restricted to the olfactory system, but on the contrary extends to the entire brain (neocortex, amygdala, hippocampus, thalamus). In most of the non-olfactory areas recorded the respiratory rate also modulates the discharge of neurons and rapid oscillations. The slow oscillations associated with breathing therefore seem to affect the overall dynamics of the brain. My thesis project is made up of two parts. First, in order to confirm an influence of the respiratory rate on neurons, I made intracellular recordings in four non-odor areas in anesthetized rats. The targeted structures were the median prefrontal cortex, the primary somatic cortex, the primary visual cortex and finally the hippocampus. I was able to observe respiration modulation in most of these neurons. The quantification of these data shows that the respiratory modulation events are short but observed in a significant number of neurons. These data also provide evidence that the respiratory modulation of various brain areas is not solely due to volume conduction. In a second step, in order to study the coordination of cerebral areas by the respiratory rhythm, I analyzed recordings of multisite local field potentials (LFP) in the vigilant rat. The recordings contain seven areas of the brain (olfactory bulb, anterior piriformis cortex, primary visual cortex, median prefrontal cortex, primary somatic cortex, CA1, dentate gyrus) and respiration. I was able to observe slow oscillations related to respiration in all brain states. But it is during calm awakening that respiratory modulation is greatest and appears in all recorded areas. In parallel, these slow oscillations are coupled with several types of fast oscillations. Finally, I wanted to know if, during the calm state of wakefulness, where LFPs of a large brain network are synchronized with respiration, unit activities can also synchronize with the respiratory signal. To do this, I set up an electrophysiological recording station in constrained vigilant rats allowing the recording of numerous neurons in pairs of cerebral structures with "silicon probes". The station is now functional and I was able to register 6 animals. These last data will not be fully processed when I am defending my thesis. I will present preliminary results which already allow us to show that respiration can synchronize the unit activities of many cells in even spatially distant regions of the brain
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16

Nilsson, Johan Fredrik. "Low temperature Li-ion battery ageing." Thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-251356.

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Different kinds of batteries suit different applications, and consequently several different chemistries exist. In order to better understand the limitations of low temperature performance, a Li-ion battery chemistry normally intended for room temperature use, graphite-Lithium Iron Phosphate, with 1 M LiPF6 ethylene carbonate:diethylene carbonate electrolyte, is here put under testing at -10°C and compared with room temperature cycling performance. Understanding the temperature limitations of this battery chemistry will give better understanding of the desired properties of a substitute using alternative materials. The experimental studies have comprised a combination of battery cycle testing, and surface analysis of the electrodes by Scanning Electron Microscopy and X-Ray Photoelectron Spectroscopy. Results showed that with low enough rate, temperature is less of a problem, but with increased charge rate, there are increasingly severe effects on performance at low temperatures. XPS measurements of low charge rate samples showed similar Solid Electrolyte Interface layers formed on the graphite anode for room- and low temperature batteries, but with indications of a thicker layer on the former. A section of the report handles specific low temperature battery chemistries. The conclusions- and outlook were made by comparing the results found in the study with earlier findings on low temperature Li-ion batteries and present possible approaches for modifying battery performance at lowered temperatures.<br>I detta projekt har litium-jon-batterier testats i avseende på sina lågtemperaturprestanda. Arbetet gjordes genom att testa och jämföra prestantda mellan prover vid -10°C och rumstemperaturprover. Med analytiska instrument studerades både den morfologiska och kemiska förändring som skett under användning. Vald batterikemi har varit av slaget grafit-litiumjärnfosfat med en typisk organisk elektrolyt. Denna batterikemi är inte på något sätt anpassad för lågtemperaturprestanda och med det hoppas kunna påvisas de effekter som en mer lämpligt lågtemperaturkemi åtgärdar, och förstå hur de gör det. Med låg temperatur uppkommer en större ’tröghet’ för de kemiska reaktioner som sker i ett batteri. Om designen inte är särskilt gjord för låg temperatur kan effekterna bli osäkra, rent av farliga. Risken ökar nämligen för plätering av metalliskt litium på den negativa elektroden, och skulle litiumdeponeringen växa i den riktning som kopplar samman batteriets poler så kortsluts systemet. Med den höga energidensitet som karaktäriserar litium-jon-batterier vore en kortslutning extra beklaglig då den organiska elektrolyten kan antändas, med en potentiell explosion som följd.Inom särskilda applikationer kan lågtemperaturmiljöer förväntas för ett batteri, till exempel för fordon. En elbil i skandinaviskt klimat skulle behöva fungera ohindrat även vintertid, då temperaturerna ofta når -10°C och lägre. Samtidigt får man påminnas om att litium-jon-batterierna är relativt moderna och ännu inte har fått något stort genomslag som framdrivningsmedel. Detta försätter bilindustrin i ett krafigt behov av omfattande forskning för att kunna ta strategiskt sunda beslut för att möjliggöra en ordentlig introducering av elbilar som trovärdig ersättare till de fossilt drivna bilarna. I linje med trenden att ständigt bygga säkrare bilar måste elbilarna kunna visa upp förutsägbarhet, och med detta pålitlighet och säkerhet. I detta arbetet erhölls resultat som visade på batterifunktion även vid den sänkta temperaturen, men med gränser för hur snabbt laddningöverföring kunde ske jämfört med i rumstemperatur. Bevis för bildande av skyddsfilm på anod efter 1.5 battericykler, snarlik komposition för -10°C - och rumstemperaturbatterier – men med vissa indikationer på ett tjockare bildat lager hos den senare. Därtill gjordes jämförelser med specifika lågtemperaturselektrolyter, där en skillnad i framförallt innehåll utav etylkarbonat (mindre andel vid lågtemperaturapplikationer) uppvisar stora förbättringar i kallare klimat. En sådan provblandning gjordes och uppvisade bättre prestanda vid -10°C än rumstemperaturbatterier med standardelektrolyt. Arbetet har utförts vid Institutionen för Kemi-Ångström vid Uppsala universitet.
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17

Wong, Alexander T. "A Techno-Economic Analysis of Employing Lithium Iron Phosphate Battery Energy Storage System for Peak Demand Reduction of Industrial Manufacturing System." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1613159189785232.

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18

Martínez, Berríos Aquiles Nicolás. "Diseño de un biomarcador electrofisiológico para caracterizar un modelo animal de la enfermedad de Parkinson usando la potencia oscilatoria y scale-free de señales LFP." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/170045.

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Memoria para optar al título de Ingeniero Civil Eléctrico<br>La enfermedad de Parkinson (EP) es la segunda enfermedad neurodegenerativa más común en el mundo. La EP produce un desequilibrio del circuito sensoriomotor del sistema nervioso, provocando los síntomas motores clásicos de esta enfermedad, tales como rigidez, temblor y falta de movimiento. Las enfermedades motoras que presentan estos síntomas son catalogadas como Parkinsonismos, siendo la EP la más común. Debido a que el diagnóstico de la EP se realiza con criterios clínicos basados en los síntomas motores, es común confundirlo con otros Parkinsonismos. Se han estudiado varios biomarcadores de la EP para ayudar a mejorar el diagnóstico, pero hasta ahora ninguno ha mostrado resultados confiables. Un hecho importante que ocurre en la EP son los cambios en los patrones electrofisiológicos del circuito sensoriomotor del cerebro, donde se destaca el aumento de potencia oscilatoria en la banda α-β. Estos cambios son característicos de esta enfermedad y podrían servir para establecer un biomarcador. En este estudio se estableció un biomarcador basado en características de la potencia espectral de señales electrofisiológicas para caracterizar un modelo de la EP. Para esto, se registraron señales de 3 áreas del circuito sensoriomotor del cerebro; corteza motora primaria (M1), núcleo estriado (STR) y núcleo ventral posterolateral del tálamo (VPL) de ratas lesionadas con 6-OHDA (n=4), usadas como modelo de la EP. Además, se registró una rata sana (n=1), usada como control. Se consideraron 4 condiciones para evaluar la progresión temporal; condición control (C), condición de lesión temprana (LTe), condición de lesión intermedia (LIn) y condición de lesión tardía (LTa). De la potencia espectral de las señales registradas se extrajeron 5 características espectrales provenientes de: la potencia oscilatoria en la banda α-β (Po), la potencia scale-free en la banda ancha (Psf), la pendiente scale-free entre [10-20]Hz (D2), la pendiente scale-free entre [20-30]Hz (D3) y la pendiente scale-free entre [30-40]Hz (D4). Se diseñó un clasificador Support Vector Machine (SVM) multiclase con el que, a través de un ranking, se seleccionaron las características más relevantes para cada condición, las que fueron usadas como entrada del clasificador. También, se determinó un índice de Parkinsonismo consistente en la distancia euclidiana de las características seleccionadas anteriormente hasta el origen del espacio de características. Finalmente, el biomarcador se estableció usando como componente discreto al clasificador SVM multiclase y como componente continuo el índice de Parkinsonismo, para determinar la condición a la que pertenece cada registro y el grado de severidad de la condición, respectivamente. El uso del biomarcador fue evaluado con un conjunto ejemplo y un conjunto de sujetos tratados. Las características seleccionadas fueron D3 de M1 y Po de STR, obteniendo una precisión del 75% en ambas características. El clasificador y el índice de Parkinsonismo consiguieron identificar y separar en un 100% las condiciones C, LTe y LIn, pero la condición LTa fue confundida con las condiciones LTe y LIn, obteniendo un rendimiento general del 75%. Además, el biomarcador pudo evidenciar la respuesta terapéutica de los sujetos tratados. La componente scale-free mostró ser relevante para describir los cambios electrofisiológicos de la EP, especialmente las características basadas en la pendiente scale-free. La confusión de la condición LTa con las condiciones LTe y LIn se puede deber a que se usó un modelo agudo de la EP, por lo que sería adecuado emplear este modelo sólo hasta el periodo de la condición LIn. Finalmente, el biomarcador electrofisiológico mostró ser sensible, confiable y robusto al separar la condición sana de las condiciones de Parkinsonismo y al evidenciar la respuesta a un tratamiento, siendo un excelente candidato para mejorar el diagnóstico de la EP.
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19

Waheed, Abdul [Verfasser], and Dieter [Akademischer Betreuer] Schramm. "Modellierung, Echtzeitsimulation und genaue Prognose der Lebensdauer und Kosten einer LFP-Batterie am Beispiel eines A- und C-Segment E-Autos / Abdul Waheed. Betreuer: Dieter Schramm." Duisburg, 2016. http://d-nb.info/1106854519/34.

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20

Zbrzeski, Adeline. "Circuits intégrés d’enregistrement et d’analyse en temps réel des potentiels de champ neuronaux : application au traitement de la maladie de Parkinson, par contrôle adaptatif de stimulations cérébrales profondes." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14328/document.

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La maladie de Parkinson est la seconde maladie neuro-dégénérative la plus fréquente à travers le monde. Dans ce contexte, le projet de recherche associé à cette thèse vise à améliorer le traitement symptomatique de la maladie de Parkinson, par le développement de procédés de stimulation cérébrale profonde adaptative. Le travail de cette thèse repose sur la conception d’un ASIC d’enregistrement et de traitement de signaux neuronaux, répondant à divers enjeux :un traitement continu et en temps réel focalisé sur des bandes spécifiques très basses-fréquences et largement configurables. L’objectif est d’utiliser l’information traitée pour le contrôle et la génération d’un signal de stimulation. Cet ASIC a été développé, caractérisé électroniquement et utilisé dans un contexte in vivo. Un système en boucle fermée a été réalisé à partir de cet ASIC, se montrant fonctionnel. Ces validations expérimentales in vivo ouvrent de nombreuses possibilités d’investigation du concept de stimulation cérébrale en boucle fermée<br>Parkinson’s disease is the second most common neurodegenerative diseases throughout theworld. In this context, the research project associated with this thesis is to improve the symptomatictreatment of Parkinson’s disease through the development process of deep brain stimulationadaptive. The work of this thesis is based on the design of an ASIC for recording andprocessing of neural signals, in response to a variety of issues : ongoing treatment and real-timefocus on specific bands of very low-frequency and highly configurable. The goal is to use theprocessed information to the control and generation of a stimulation signal. This ASIC wasdeveloped, characterized and used electronically in a context in vivo. A closed-loop system wasmade from the ASIC, showing functional. These in vivo validations open up many possibilitiesfor investigation of the concept of closed-loop brain stimulation
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21

Rothé, Marie. "Activités spécifiques du cortex cingulaire antérieur et du cortex préfrontal dorsolatéral et interactions lors de l'adaptation des comportements." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00710536.

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Agir de façon optimale dans un environnement incertain nécessite d'évaluer et de comparer les coûts et bénéfices des différentes alternatives. Cela implique aussi de réguler et de contrôler le comportement de façon flexible pour optimiser les périodes de recherche de gains ou de ressources et les périodes d'exploitation des acquis. Une des hypothèses actuelles sur les mécanismes neurobiologiques impliqués, propose que cortex cingulaire antérieur (CCA), associé à l'évaluation de l'action, et cortex préfrontal dorsolatéral (CPFdl), associé au contrôle cognitif, interagiraient pour réguler le comportement. Les travaux réalisés au cours de cette thèse ont permis de préciser le rôle joué par le CCA dans la détection et l'évaluation des performances ainsi que ses interactions avec le CPFdl au sein d'une boucle du contrôle cognitif. Menés grâce à des enregistrements électrophysiologiques chez le singe en comportement, ils apportent des précisions sur la séquence d'activation du CCA et du CPFdl dans la bande de fréquences gamma lors de l'adaptation du comportement. L'étude des potentiels de champs locaux de ces deux régions amènent à poser des hypothèses sur les mécanismes oscillatoires sous-jacents et notamment sur le rôle des communications basses fréquences entre le CCA et le CPFdl et leur implication différentielle entre recherche et exploitation.
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22

Moreno, Andrea. "Short and long-term plasticity modulates the brain-wide interactions of the hippocampus : a combined electrophysiology-fMRI study." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29019.

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This thesis examines the functional connectivity of the hippocampus with the rest of the brain, with a focus on the neocortex. The hypothesis explored, in an animal model, is whether the frequency-dependent behaviour of certain brain connectivity relationships applies to hippocampal-neocortical connections. To encompass the temporal and spatial resolution necessary to do this, two main techniques are used in combination in most of the experimental work hereby presented: (1) electrophysiological recordings of local field potentials (LFPs), and (2) functional activity recordings of blood oxygenation level dependent (BOLD) signal using functional magnetic resonance imaging (fMRI). The main hypothesis is that the frequency-dependent behaviour of specific hippocampal synapses imposes the rules of extra-hippocampal activity propagation and hippocampal-neocortical interactions. The main discovery is that short and long-term plasticity modulates network activation, a finding suggesting a possible mechanism that could mediate the encoding and consolidation of memory traces. Chapters 1 to 3 introduce the vast literature review in which this project lies, and the general methods utilised. Chapter 4 (first experimental chapter) describes, using electrophysiology in rats, the evoked response of the main hippocampal output (CA1 neurons) when its major input (CA3 pyramidal cells) is activated at frequencies that in subsequent experiments were used to build brain-wide functional maps. CA1 spiking activity is found to be optimal in maintaining the amplitude of the population spike (PS) at beta frequencies (10-20 Hz), whereas lower (< 10 Hz) and higher (> 20 Hz) frequencies are normally less effective. Chapter 5 describes, using fMRI, how these intra-hippocampal activity patterns relate to long-range activity propagation in fMRI experiments. Hippocampal activation exhibits a linear monotonic increase with evoked frequency, whilst a network of selected structures is activated preferentially when beta frequencies are applied (mainly neocortical structures like the prefrontal and parietal cortices, motor and sensory cortices, and some subcortical structures like the nucleus accumbens and the striatum). This data is highly correlated with the PS recorded in CA1 and with multi-unit activity (MUA) and single-unit activity (SUA) simultaneously recorded in the medial prefrontal cortex (mPFC), one of the structures receiving propagated activity at beta frequencies, as described in Chapter 6. As mPFC also receives hippocampal input at a restricted beta frequency range stimulation of the dorsal hippocampus, Chapter 7 describes the use of a combined electrophysiology/fMRI approach to identify the pathway responsible for activity propagation. We performed microsurgery lesions to investigate the pathway responsible for the polysynaptic propagation of activity. Findings indicate that the septo-temporal longitudinal pathway is the one leading information transfer from dorsal to ventral hippocampus in the rat, and from there directly to the ventral subiculum, apparently by-passing entorhinal cortex. Last, in Chapter 8 the effect of durable modifications of synaptic weights by long-term potentiation (LTP) in the previously described frequency-dependent activity propagation is also described and contextualized in the memory trace consolidation framework, both electrophysiologically (Chapter 5) and with fMRI (Chapter 6). LTP is a long-lasting change in synaptic weights that, at the CA3-CA1 synapse, is capable of modifying hippocampal-neocortical connections such as to open the opportunity for higher frequency patterns (> 40 Hz) to propagate to neocortical structures. These results suggest that, by means of frequency-coding, the hippocampus normally regulates propagation of selected information to the neocortex, but that at specific moments (e.g. when the hippocampus undergoes LTP) this regulation broadens to permit high-frequency information to pass through and affect neural activity in the cortex. It is a beautifully simple mechanism that merits further detailed examination in a multi-disciplinary manner as outlined in Chapters 9 and 10.
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23

Girin, Baptiste. "Influence de la respiration sur les rythmes du cerveau chez le Rat : une étude électrophysiologique au cours des cycles veille / sommeil." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSE1024.

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La communication entre les différentes aires cérébrales nécessite une bonne coordination entre les structures. Cette coordination peut notamment passer par une synchronisation des rythmes électrophysiologiques. Nous avons émis l’hypothèse que le rythme respiratoire pourrait agir comme une horloge centrale pour la coordination des rythmes cérébraux. Si cela est vrai nous pouvons nous attendre à ce que l’activité neuronale soit influencée par la respiration dans un large réseau cérébral. Nous avons testé cette hypothèse en enregistrant la respiration et l’activité neuronale dans différentes zones du cerveau chez le rat pendant les différents états de vigilance. En accord avec les publications récentes, nous avons observé que toutes les structures pouvaient être modulées par la respiration. Cependant, nous montrons pour la première fois que cette modulation varie selon l’état de vigilance, chaque état étant associé à un régime respiratoire spécifique. En particulier, une synchronisation à grande échelle, de toutes les structures enregistrées, sur le rythme respiratoire n’est observable que dans l’état d’éveil calme, où la respiration présente une fréquence basse (2Hz), avec un débit d’air relativement élevé. En même temps, nous observons aussi une modulation du rythme rapide gamma (35-80 Hz) dans toutes les aires, seulement dans l’état d’éveil calme. Pour savoir si cette synchronisation respiratoire générale était une conséquence de l’état lui-même ou du régime respiratoire, nous avons cherché à décorréler l’état cérébral du régime respiratoire. Les animaux ont été enregistrés alors qu’ils respiraient un air enrichi en CO2, où les caractéristiques respiratoires (fréquence et amplitude) sont augmentées par rapport à la condition air seul. Nous avons alors observé que la synchronisation respiratoire, observée en état d’éveil calme, peut s’étendre aux autres stades de vigilance, notamment les états de sommeil (REM et NREM). Nous montrons que l’entrainement du cerveau par la respiration est lié à l’effet combiné de l’amplitude et de la durée d’inspiration. Pour finir nous avons voulu évaluer la part respective des flux d’air liés à la respiration et du contrôle central de la respiration sur l’entrainement du cerveau par la respiration. Nous avons décorrélé la respiration de l’animal des flux d’air dans la cavité nasale grâce à une expérience de double trachéotomie chez l’animal anesthésié. Les premiers résultats semblent montrer que les flux d’air circulant dans la cavité nasale lors des inspirations successives ont une part prépondérante dans l’entrainement du cerveau. En conclusion, la respiration peut entrainer un large réseau cortical via l’activation du système olfactif par les flux d’air circulant dans la cavité nasale. Le régime respiratoire optimal pour cet entrainement est une respiration lente et profonde. Cette étude est importante pour comprendre le mode d’action des méthodes de relaxation et de méditation sur le cerveau<br>Inter-area communication requires the different brain rhythms to be coordinated across areas. This coordination can be achieved by synchronizing electrophysiological rhythms. As others, we hypothesized respiratory rhythm could act as a central clock for cerebral rhythms coordination. If true, one can expect neuronal activity to be influenced by respiration in a large brain network. We tested that by recording respiration and neuronal activity in different brain areas in the freely-moving rat during different vigilance states. In agreement with recent publications, we observed that all structures could be modulated by breathing. We provided the additional observation that such a modulation varies according to the vigilance state, each state being associated with a specific respiratory regime. Particularly, we observed a large-scale synchronization of all recorded structures on the respiratory rhythm is only observable in the calm awake state, where the breathing has a low frequency (2Hz), with a relatively high air flow. At the same time, we also observe a modulation of the fast gamma rhythm (35-80 Hz) in all areas, only in the calm awake state. To determine whether this general respiratory synchronization was a consequence of the state itself or of the respiratory regime, we sought to uncorrelated the brain state of the respiratory regime. Animals were thus recorded while breathing a CO2-enriched air, where the respiratory characteristics (frequency and amplitude) are increased compared to the normal air condition. We observed the across-areas respiratory synchronization observed in quiet state can be extended, under CO2 condition, to other vigilance states including sleep states (REM and non-REM).We show that the coordination of the brain by breathing is related to the combined effect of the amplitude and duration of inspiration. Finally, we wanted to evaluate the respective share of air flows related to breathing and central breathing control on the brain's training by breathing. We uncorrelated the animal's breathing from the air flows in the nasal cavity through a double tracheotomy experiment in the anesthetized animal. The first results seem to show that the air flows circulating in the nasal cavity during successive breaths have a preponderant part in the entrainment of the brain. In conclusion, breathing can lead to a large cortical network via the activation of the olfactory system by the air flows circulating in the nasal cavity. The optimal breathing regime for this training is slow and deep breathing. This study is important to understand how relaxation and meditation methods work on the brain
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24

Chakraborty, Mrinal. "Chemistry of the Putative Metabolite of a Model Anti-tumor Drug." Miami University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1344305348.

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25

Krejčí, Pavel. "Elektrochemická příprava grafen oxidu a jeho využití v elektrodových kompozitech s LiFePO4." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-376908.

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This work deals with issues of application of the graphene material in the field of electrochemical energy storage. It includes basic graphene properties, the overview of methods for the production of lithium-iron-phosphate/graphene composites and results of different research approaches. The general aim is to present growing opportunity of application of graphene based composites in the electrochemical energy storage field. In the experimental part of this work, a electrochemical exfoliation of graphite and a production of LFP/G composites with different amount of graphene material and with different types of graphene material are carried out. This work includes also x-ray diffraction spectroscopy measurements and the evaluation of impacts of graphene additives on final properties of the electrochemical energy storage.
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26

Burini, Franz Homero Paganini. "Resposta dos componentes da Síndrome metabólica a programa de mudança do estilo de vida em adultos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/89/89131/tde-26082013-144014/.

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A síndrome metabólica (SM) é um conjunto de patologias caracterizadas pela obesidade abdominal, resistência insulínica, hipertensão arterial e dislipidemia aterogênica. Pelos seus desfechos, ocupa posição de destaque dentre as doenças crônicas com impacto crescente na economia do SUS. Não há modelo curativo efetivo para SM, restando a atenção primária pelo combate ao sedentarismo e a inadequação alimentar, mediante modificação do estilo de vida (MEV). O objetivo deste trabalho foi estudar o efeito de programa de mudança do estilo de vida (MEV) sobre a SM em adultos. Preencheram os critérios de inclusão 131 indivíduos (55 ± 9 anos), 74% do sexo feminino 68,7% abaixo de 60 anos. Todos foram submetidos a programa de MEV composto de exercícios aeróbios dinâmicos (caminhadas - 65-80% V02máx.)supervisionados, 80minutos/sessão, 3-5x/semana. Adicionalmente, houve aconselhamento nutricional mensal. A duração do MEV foi de 6 meses com avaliações nos momentos inicial (M0) e final (M1). As avaliações incluíram dados clínicos, antropométricos, dietéticos, capacidade aeróbia e bioquímica sanguínea. O diagnóstico de SM foi feito pelo ATP III - NCEP (2003). Os resultados foram analisados estatisticamente pelas variáveis contínuas (teste t de Student ou de Wilcoxon) ou categóricas (qui-quadrado), mediante software Stat for Windows 6.0 p=0,05. Em M0 a SM era de 50,3% tendo como principal componente a adiposidade abdominal (63,4%). Os portadores (G1) diferiram dos não portadores (G2) de SM pelos maiores valores de IMC e uricemia, e menor desempenho físico em esteira. O programa de MEV aumentou a pontuação do índice de alimentação saudável (IAS) e da ingestão de fibras, e reduziu a ingestão energética. Adicionalmente, aumentou o tempo de esteira e reduziu os valores plasmáticos de proteína C reativa (PCR-us), &#947;-glutamil transpeptidase (&#947;-GT) e ácido úrico. A redução da SM foi de 6,8%, resultante da redução de circunferência abdominal (CA), pressão arterial sistólica (PAS) e aumento do HDL-colesterol. O aparecimento de SM durante a MEV decorrente da elevação da glicemia, trigliceridemia e uricemia, acompanhada da menor ingestão de fibras durante o programa. Os dados mostram as características dos pacientes que respondem positiva e negativamente a este programa de MEV na atenção primária à SM.<br>Metabolic Syndrome (MS) is a cluster of cardiovascular risk factors as abdominal obesity, insulin resistance, hypertension and atherogenic lipid profile, having an enormous economic impact on the national health system. There is no curative model for the MS, being the primary prevention, such as the combat of sedentary behavior and food intake inadequacy the aim of the primary care system. The objective of this study was to evaluate the effectiveness of a lifestyle changing program (LFCP) on MS components in free-living adults. 131 individuais (55 ± 9 years, 74% females and 68,7% under 60 years of age) were submitted to the program, characterized by supervised aerobic exercise (65-80% V02max.) for 80 minutes per session, 3-5 times per week, additionally to monthly dietary counseling. The program lasted 6 months, involving clinic evaluations followed by anthropometric, nutritional and biochemistry, along with a maximal cardiorespiratory fitness test on a treadmill (Balke protocol), at baseline and at end (6 months). MS diagnosis was made according to ATP III - NCEP (2003), being the glycemic index altered as suggested (AHA, 2005). All results were analyzed with Statistic Software, with Student t test and Wilcoxon, when properly, being 5% the statistical level of significance (p<0,05). At baseline, MS prevalence was 50,3%, being elevated waist circumference the most prevalent component (63,4%). MS patients (G1) were different from non MS patients for higher BMI, high levels of uric acid and lower cardiorespiratory fitness. LFCP resulted in higher scores of health eating index (HEI) and dietary fiber intake, and lowered the caloric iintake. Additionaly, it improved the cardiorespiratory fitness and lowered C reactive protein (CRP-hs), &#947;-glutamil transpeptidase (&#947;-GT) and uric acid. MS prevalence dropped 6,8%, resulted from a reduction in waist circumference (WC) and blood pressure, and an increase in HDL-c levels. MS diagnosis after the program were due glycemic, tryclicerides and uric acid elevation, followed by reduction in fiber intake during the 6 months period. Datas presented in this study evidence patients characteristics with and without improvements with LFCP focusing MS prevention and treatment.
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27

Zachrisson, Love. "Investigation of coherence between limbic structures in a rodent model of Parkinson's Disease." Thesis, Umeå universitet, Institutionen för psykologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-186674.

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Parkinson’s Disease affects 10 million people worldwide, with 40% of patients developing an associated psychosis which has been identified by studies as the number one source of caretaker distress and is related to increased mortality. This is further complicated by the fact that typical antipsychotic drugs worsen many of the motor symptoms implicated in Parkinson’s Disease, with only one commercially available drug able to ameliorate both symptoms. This problem ushers the development of novel drugs to treat these symptoms, as first tested on research animals. Complicating matters, drug effectiveness on the degree of psychosis is hard to obtain in animals without a reliable biomarker. However, a hallmark of psychotic states is thought to be the reduced coordination between brain structures, through neuronal synchronization, as demonstrated by steady-state responses and is suggested to be a potential biomarker of psychosis. By building a MATLAB software we were able to analyze the degree of neural synchronization between structures, during an auditory steady-state response, in rats that had been unilaterally lesioned by the 6-Hydroxydopamine model of Parkinson’s Disease, before and after administration of the psychotomimetic drug MK801. These rats had been chronically implanted with 128-channel multi electrode array, enabling us to measure the strength of coherence between several limbic structures, associated with auditory processing, from the sampled local field potential, identifying the degree of synchronization in the animal brain. As our data demonstrate that coherence levels dropped in the psychotic drug state, for structures in both the healthy and the Parkinsonian hemisphere, we are able to further demonstrate the validity of coherence measures as a biomarker for psychosis. These results demonstrate that our software can be used as a tool to assess the therapeutic response of drugs developed, aimed at treating Parkinson’s associated psychosis.<br>Parkinsons sjukdom drabbar 10 miljoner världen över, där 40% av patienterna utvecklar en associerad psykos vilket har visats vara en av de största stressfaktorerna för deras vårdgivare och är även förknippat med en högre dödlighetsgrad. Denna situation förvärras av det faktum att de vanliga antipsykotiska drogerna kan förvärra många av de motoriska symptom som utgörs av Parkinsons sjukdom och det finns i dagsläget enbart en enda kommersiell drog som kan dämpa bägge symptom samtidigt. Detta problem frammanar vidare utveckling av nya läkemedel som kan behandla dessa symptom, som innebär att de först måste testas på försöksdjur. En komplikation som uppstår i relation till detta är svårigheten att utvärdera om läkemedel har någon terapeutisk effekt på de psykotiska tillstånden, enbart genom att observera försöksdjurens beteenden, och en pålitlig biomarkör krävs istället. En lösning kan dock finnas i det faktum att psykotiska tillstånd karaktäriseras av en reducerad förmåga för olika hjärnområden att koordinera genom neural synkronisering vilket demonstreras av ‘steady- state’ responser. Detta föreslår att ett mått på graden av koordineringsförmåga kan agera som en möjlig biomarkör för psykotiska tillstånd. Genom att konstruera ett MATLAB-program kunde vi analysera graden av synkronicitet mellan hjärnstrukturer, under den auditiva steady- state responsen i råttor som hade blivit ensidigt lesionerade genom 6-Hydroxiddopamin modellen av Parkinsons sjukdom, före och efter administration av den psykotomimetiska drogen MK801. Dessa råttor hade blivit kroniskt implanterade med 128 elektroder vilket möjliggjorde att vi kunde mäta styrkan i koherens i den lokala fält potentialen mellan limbiska strukturer, som är associerade med auditiv processering, vilket möjliggjorde identifiering av3dessa strukturers synkronicitet. Vår data demonstrerar att koherensen minskade under det psykotiska drogtillståndet för limbiska strukturer både i den intakta och den lesionerade hjärnhalvan. Detta är en vidare demonstration av att koherensnivåer kan agera som en biomarkör för det psykotiska tillståndet, liksom att vår mjukvara kan nyttjas som ett verktyg för att utvärdera nya läkemedels behandlingsförmåga på Parkinsons psykos.
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28

Xiong, Bao Kou. "Quantification des gaz générés lors du fonctionnement d'une batterie Li-ion : effet des conditions opératoires et rôle de l'électrolyte." Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4003/document.

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Le fonctionnement des batteries lithium-ion, qu’il soit normal ou dans des conditions abusives, est accompagné d’une génération de gaz en particulier lors des premiers cycles. Celle-ci est intrinsèque au dispositif et est soumise à de nombreux paramètres tels que les matériaux d’électrodes utilisés, l’électrolyte ou encore les conditions opératoires. Cette génération de gaz est délétère : elle conduit à l’augmentation de la pression interne des batteries et pose donc des problèmes de sécurité. Cette étude vise à quantifier les volumes de gaz générés et à comprendre les mécanismes liés à la surpression dans les batteries. A cet effet, le format de batterie « pouch cell » a été adopté tout au long de ce travail de thèse. L’électrolyte choisi est le mélange EC:PC:3DMC + 1 mol.L-1 LiPF6. La première partie de ce travail est dédiée à la mise au point d’un protocole expérimental basé sur (i) l’analyse des matériaux d’électrodes (NMC, LFP, Gr, et LTO), (ii) la solubilité de gaz (O2, H2) comparées à (CO2, CH4) par PVT, et (iii) la quantification des volumes de gaz générés durant le cyclage en pouch cell, corrélée aux performances électrochimiques. Une analyse préalable en demi-piles et en dispositifs complets Gr//NMC et LTO//LFP a également été réalisée afin d’anticiper les performances attendues en pouch cells. Une analyse critique des données (de la littérature et de nos mesures) a permis de définir une procédure optimisée pour obtenir des résultats reproductibles et comparables lors des mesures de volume en pouch cells. La seconde partie de cette thèse consiste en la quantification du volume de gaz produit au cours du cyclage des pouch cells Gr//NMC, Gr//LFP, LTO//LFP et LTO//NMC. Ainsi, les tensions de fin de charge, l’effet du sel et de la température ont été discutés pour dégager les paramètres déterminants dans la génération de gaz en particulier lors de la formation de la SEI. Enfin, une analyse de la composition du gaz récupéré a été effectué par GC-MS et FTIR. A partir de résultats obtenus, des mécanismes ont été proposés et discutés<br>The functioning of lithium-ion batteries, may it be under normal use or under abusive conditions, is accompanied by gas generation, especially during the first cycles. This extent of gas generation is dependent on the choice of electrode materials, the electrolyte, and the operating conditions. This gas generation is detrimental: the build-up of pressure leads to the over-pressure in the battery, raising serious concerns. This study is aimed at understanding the fundamental mechanisms governing these reactions. To do so, the « pouch cell » configuration was adopted throughout this thesis. The electrolyte we worked on is the mixture EC:PC:3DMC + 1 mol.L-1 LiPF6. The first chapter of this work is dedicated to development of an experimental protocol based on (i) the analysis of the electrodes materials (NMC, LFP, Gr and LTO), (ii) the gas solubilities (O2, H2) compared to (CO2, CH4) by PVT method, and (iii) the quantification of the volume of generated gases during the cycling of pouch cells which was correlated to the electrochemical performances. A preliminary analysis of half-cells and full cells Gr//NMC and LTO//LFP were also conducted to foresee the performances of the pouch cells. A critical analysis of data taken from the literature and from our own experiments enabled the optimization of a proper procedure to get reproducible and comparable results. The second part of this thesis consists in the quantification of the volume of gases generated during the cycling of Gr//NMC, Gr//LFP, LTO//LFP and LTO//NMC pouch cells. In that respect, the voltages of the end of charge and the effect of salt and of temperature were discussed to figure out the essential parameters in the gas generation and in particular during the formation of SEI. Lastly, a compositional analysis of gases was performed using GC-MS and FTIR. Based on those results, a mechanism is proposed and discussed herein
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29

Vialatte, François Benoît. "Modélisation en bosses pour l'analyse de motifs oscillatoires reproductibles dans l'activité de populations neuronales: applications à l'apprentissage olfactif chez l'animal et à la détection précoce de la maladie d'Alzheimer." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://pastel.archives-ouvertes.fr/pastel-00001508.

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Le travail décrit dans ce mémoire a été effectué dans le cadre d'une collaboration entre le Laboratoire d'Électronique de l'École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), et l'équipe "Neurobiologie de la mémoire olfactive" de l'Institut des Sciences Cognitives de Lyon. L'étude des dynamiques neuronales associées aux processus cognitifs peut être abordée par l'analyse de l'activité électrique de populations neuronales enregistrée par des électrodes placées sur le scalp (électroencéphalogramme ou EEG); ou en profondeur (local field potential ou LFP) qui fournissent une meilleure résolution spatiale sur l'origine du signal. On détecte ainsi des motifs d'activité rythmiques divisés en bandes de fréquences (rythmes alpha, bêta, gamma...) et qui traduisent différents "états cérébraux" comme le niveau de vigilance et d'attention ou certains états pathologiques comme l'épilepsie. On ignore toutefois si ce type d'activité révèle également des aspects plus fins du traitement de l'information comme par exemple la réponse neuronale sélective ("code neuronal") à une stimulation sensorielle donnée. S'il en est ainsi, on devrait pouvoir mettre en évidence que la présentation d'un stimulus sensoriel donné évoque un pattern reproductible d'activité oscillatoire. C'est pourquoi dans un premier volet nous nous intéressons, dans ce travail, à l'analyse des représentations temps-fréquence des signaux LFP enregistrés chez le rat libre de se mouvoir en réponse à différents odorants. Dans un second volet, nous analysons des enregistrements EEG de courte durée obtenus chez des patients dont on soupçonne qu'ils développeront la maladie d'Alzheimer. Nous cherchons à détecter des patterns d'activité oscillatoires qui pourraient contribuer au diagnostic. Ces deux approches sont rendues possibles par une nouvelle méthode d'analyse des cartes temps-fréquence qui fait l'objet de cette thèse. La méthode que nous présentons ici, la "modélisation en bosses", fournit une représentation simple, parcimonieuse en nombre de paramètres, des cartes temps-fréquence obtenues par décomposition du signal en ondelettes. Cette modélisation permet l'extraction de caractéristiques temps-fréquence, à l'aide desquelles l'analyse statistique d'enregistrements nombreux, et la détection de motifs temps-fréquence reproductibles, peuvent être effectuées. La méthode est d'abord validée sur des signaux artificiels (simulation de signaux réels). Elle est ensuite appliquée en premier lieu à l'analyse de plusieurs centaines de réponses aux odeurs obtenues dans le bulbe olfactif du rat (signaux LFP). Nous montrons d'une part que chacun des 4 odorants évoquent des patterns d'activité oscillatoire reproductibles et que certains de ces patterns diffèrent entre eux de façon significative. Ces motifs spécifiques d'activité, principalement observés dans la bande beta (15-35 Hz), pourraient refléter le recrutement successif d'assemblées neuronales associées à la représentation du stimulus. Pour les signaux EEG, nous présentons les premiers résultats d'une étude effectuée en collaboration avec le laboratoire LABSP du Riken Brain Science Institute (Wako, Japon). Nous montrons que notre méthode permet une détection précoce de la maladie (18 à 24 mois avant le diagnostic de la pathologie) avec une précision largement améliorée par rapport aux prédictions effectuées par d'autres méthodes sur la même base de données. En conclusion, notre approche montre qu'il est possible d'extraire à partir de l'analyse des motifs complexes d'activités oscillatoires générées par de larges populations neuronales des corrélats du traitement de l'information sensorielle et la signature encore discrète d'états pathologiques.
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30

Jokar, Ali. "An inverse method for estimating the electrochemical and the thermophysical parameters of lithium-ion batteries with different positive electrode materials." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11799.

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La sécurité de plusieurs systèmes électriques est fortement dépendante de la fiabilité de leur bloc-batterie à base de piles aux ions lithium (Li-ion). Par conséquent, ces batteries doivent être suivis et contrôlés par un système de gestion des batteries (BMS). Le BMS interagit avec toutes les composantes du bloc-batterie de façon à maintenir leur intégrité. La principale composante d’un BMS est un modèle représentant le comportement des piles Liion et capable de prédire ses différents points d’opération. Dans les industries de l’électronique et de l’automobile, le BMS repose habituellement sur des modèles empiriques simples. Ceux-ci ne sont cependant pas capables de prédire les paramètres de la batterie lorsqu’elle vieillit. De plus, ils ne sont applicables que pour des piles spécifiques. D’un autre côté, les modèles électrochimiques sont plus sophistiqués et plus précis puisqu’ils sont basés sur la résolution des équations de transport et de cinétique électrochimique. Ils peuvent être utilisés pour simuler les caractéristiques et les réactions à l’intérieur des piles aux ions lithium. Pour résoudre les équations des modèles électrochimiques, il faut connaître les différents paramètres électrochimiques et thermo-physiques de la pile. Les variables les plus significatives des piles Li-ion peuvent être divisées en 3 catégories : les paramètres géométriques, ceux définissant les matériaux et les paramètres d’opération. Les paramètres géométriques et de matériaux peuvent être facilement obtenus à partir de mesures directes ou à partir des spécifications du manufacturier. Par contre, les paramètres d’opération ne sont pas faciles à identifier. De plus, certains d’entre eux peuvent dépendre de la technique de mesure utilisée et de l’âge. Finalement, la mesure de certains paramètres requiert le démantèlement de la pile, une procédure risquée et destructive. Plusieurs recherches ont été réalisées afin d’identifier les paramètres opérationnels des piles aux ions lithium. Toutefois, la plupart de ces études ont porté sur l’estimation d’un nombre limité de paramètres et se sont attardées sur un seul type de matériau pour l’électrode positive utilisé dans la fabrication des piles Li-ion. De plus, le couplage qui existe entre les paramètres électrochimiques et thermo-physiques est complètement ignoré. Le but principal de cette thèse est de développer une méthode générale pour identifier simultanément différents paramètres électrochimiques et thermo-physiques et de prédire la performance des piles Li-ion à base de différents matériaux d’électrodes positives. Pour atteindre ce but, une méthode inverse efficace a été introduite. Des modèles directs représentatifs des piles Li-ion à base de différents matériaux d’électrodes positives ont également été développés. Un modèle rapide et précis simulant la performance de piles Li-ion avec des électrodes positives à base de LiMn2O4 ou de LiCoO2 est présenté. Également, deux modèles ont été développés pour prédire la performance des piles Li-ion avec une électrode positive de LiFePO4. Le premier, appelé modèle mosaïque modifié (MM), est basé sur une approche macroscopique alors que le deuxième, appelé le modèle mésoscopique, est plutôt basé sur une approche microscopique. Des études d’estimation de paramètres ont été conduites en utilisant les modèles développés et des données expérimentales fournies par Hydro-Québec. Tous les paramètres électrochimiques et thermo-physiques des piles Li-ions ont été simultanément identifiés et appliqués à la prédiction de la performance des piles. Finalement, une technique en temps réel reposant sur des réseaux de neurones est introduite dans la méthode d’estimation des paramètres intrinsèques au piles Li-ion.<br>Abstract : The safety of many electrical systems is strongly dependent on the reliable operation of their lithium-ion (Li-ion) battery packs. As a result, the battery packs must be monitored by a battery management system (BMS). The BMS interacts with all the components of the system so as to maintain the integrity of the batteries. The main part of a BMS is a Li-ion battery model that simulates and predicts its different operating points. In the electronics and in the automobile industries, the BMS usually rests on simple empirical models. They are however unable to predict the battery parameters as it ages. Furthermore, they are only applicable to a specific cell. Electrochemical-based models are, on the other hand, more sophisticated and more precise. These models are based on chemical/electrochemical kinetics and transport equations. They may be used to simulate the Li-ion battery characteristics and reactions. In order to run the electrochemical-based mathematical models, it is imperative to know the different electrochemical and thermophysical parameters of the battery. The significant variables of the Li-ion battery can be classified into three groups: geometric, material and operational parameters. The geometric and material parameters can be easily obtained from direct measurements or from the datasheets provided by the manufacturer. The operational properties are, on the other hand, not easily available. Furthermore, some of them may vary according to the measurement techniques or the battery age. Sometimes, the measurement of these parameters requires the dismantling of the battery itself, which is a risky and destructive procedure. Many investigations have been conducted to identify the operational parameters of Li-ion batteries. However, most of these studies focused on the estimation of limited parameters, or considered only one type of the positive electrode materials used in Li-ion batteries. Moreover, the coupling of the thermophysical parameters to the electrochemical variables is ignored in all of them. The main goal of this thesis is to develop a general method to simultaneously identify different electrochemical and thermophysical parameters and to predict the performance of Li-ion batteries with different positive electrode materials. To achieve this goal, an effective inverse method is introduced. Also, direct models representative of Li-ion batteries are developed, applicable for all of the positive electrode materials. A fast and accurate model is presented for simulating the performance of the Li-ion batteries with the LiMn2O4 and LiCoO2 positive electrodes. Moreover, two macro- and micro-based models are developed for predicting the performance of Li-ion battery with the LiFePO4 positive electrode, namely the Modified Mosaic (MM) and the mesoscopic-based models. The parameter estimation studies are then implemented by means of the developed direct models and experimental data provided by Hydro-Québec. All electrochemical and thermophysical parameters of the Li-ion batteries are simultaneously identified and applied for the prediction of the battery performance. Finally, a real-time technique resting on neural networks is used for the estimation of the Li-ion batteries intrinsic parameters.
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31

Schlasza, Christian. "Analysis of aging mechanisms in Li-ion cells used for traction batteries of electric vehicles and development of appropriate diagnostic concepts for the quick evaluation of the battery condition." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0155.

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Dans cette thèse, les mécanismes de vieillissement des cellules Li-ion sont analysés sur un niveau théorique,assisté par une AMDEC (Analyse des modes de défaillance, de leurs effets et de leur criticité). L'accent est mis surla famille des cellules lithium fer phosphate (LFP) utilisées comme batteries de traction dans les applicationsvéhicules électriques.L'objectif de la partie xpérimentale de cette thèse est le développement d'un concept d'un outil de diagnostic pourla détermination rapide d'état de la batterie. Une expérience de vieillissement accélérée est réalisée avec un groupede cellules LFP de haute capacité (70Ah). Les cellules sont analysées en utilisant des méthodes de mesured'impédance dans les domaines temporel et fréquentiel. La pectroscopie d'Impédance Électrochimique (SIE, ouEIS en anglais) s'est trouvée être un bon outil pour révéler des informations intéressantes sur l'état de santé (Stateof-Health, SOH) de la batterie.Des modèles de batterie sont utilisés pour l'interprétation des résultats de mesure. En comparant différents modèlesdu circuit équivalent (ECMs), un modèle est choisi. Ce modèle est utilisé pour la détermination du SOC et étendupour la détermination du SOH. Un concept pour la détermination du SOH est développé, permettant uneapproximation de la capacité de la batterie dans une période de temps de moins de 30s, si les onditions de labatterie et d'environnement, comme la température et l'état de charge de la batterie, sont connus<br>In this thesis, the aging mechanisms withing Li-ion cells are analyzed on a theoretical level, supported by an FMEA(Failure ode and Effects Analysis). The focus lies on the group of lithium iron phosphate (LFP) cells used fortraction batteries in electric vehicles. Scope of the experimental part of the thesis is the development of a diagnosticconcept for the quick battery state determination. A group of high capacity LFP cells (70Ah) designed for tractionpurposes in electric vehicles is aged artificially and investigated afterwards by impedance measurements in the timeand frequency domain. Electrochemical impedance spectroscopy (EIS) is found to reveal interesting information onthe battery's State-of-Health (SOH).For the interpretation of the measurement results, battery models are employed. Different equivalent circuit models(ECMs) are compared and an appropriate model is chosen, which is used for the SOC (State-of-Charge)determination and extended for the SOH (State-of-Health) determination. An SOH determination concept isdeveloped, which allows the approximation of the cell capacity in less than 30s, if the battery and environmentalconditions, such as the temperature and the cell's SOC, are known
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32

Gomes, Jean-Marie. "Etude expérimentale et théorique de la genèse des potentiels de champs locaux par les neurones corticaux." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066409/document.

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Les potentiels de champs locaux (LFP) sont des événements de fréquence inférieure à 200-500 Hz, résultant de l'activité cérébrale. Leur signification et les mécanismes contribuant à leur formation sont encore très débattus. Ainsi, l'existence et l'importance d'un filtrage des courants ioniques par le tissu cérébral est controversée. Certains auteurs concluent que le milieu est résistif, alors que d'autres suggèrent que le tissu cérébral pourrait exercer un filtrage passe-bas significatif sur les courants électriques. Une méthode de mesure nouvelle est présentée ici, s'appuyant sur le concept d'impédance naturelle, mesurée en utilisant un neurone comme " électrode " . Ceci permet d'obtenir l'impédance la plus pertinente d'un point de vue physiologique, en termes d'interface électrode-milieu, d'intensité des courants et d'échelle spatiale. L'impédance mesurée est stable, reproductible, plus forte que celle mesurée traditionnellement, et possède une dépendance en fréquence en 1/vf. Un modèle physique prenant en compte la diffusion ionique dans le milieu est capable de reproduire cette impédance. Une méthode similaire permet de calculer la fonction de transfert entre les potentiels intra- et extracellulaire d'un neurone. Des modèles sont proposés pour expliquer sa forme, prédire les LFP d'après l'activité cellulaire et vice-versa. Ces résultats pourraient aider à l'interprétation des signaux de LFP et d'électroencéphalographie, permettant une compréhension plus profonde du fonctionnement cérébral physiologique et pathologique<br>Local field potentials (LFPs) are low-frequency (&lt; 200-500 Hz) events resulting from brain activity. Their meaning and the mechanisms shaping them have been highly debated for decades. The existence and importance of a frequency-dependant filtering of ionic currents by brain tissue is controversial. Some authors conclude that the medium is resistive, while others suggest that brain tissue may exert significative low-pass filtering on electrical currents. A new measurement method is presented here, relying on the concept of natural impedance, which is measured using a neuron as an ''electrode''. This allows to obtain the most relevant impedance from a physiological point of view, in terms of electrode-medium interface, current intensity and spatial scale. The measured impedance is stable, reproducible, stronger than what is traditionally measured, and has a 1/\√f frequency dependance. A physical model, taking into account ionic diffusion in the medium, is able to reproduce this impedance. A similar method allows to compute the transfer function between the intra- and extracellular potentials of a neuron. Models are proposed to explain its structure, predict LFPs from cell activity and vice-versa. These results may help interpreting LFP and electroencephalography signals, yielding a deeper understanding of the physiological and pathological brain function
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33

Toledo, Luciana Dias Leal [UNESP]. "Um estudo sobre o uso de vocabulário rico por aprendizes de inglês na sessão oral do teletandem institucional integrado." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151765.

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Submitted by LUCIANA DIAS LEAL TOLEDO null (lucianatoledo@iftm.edu.br) on 2017-09-29T00:40:17Z No. of bitstreams: 1 TOLEDO, dissertação versão de publicação repositório UNESP.pdf: 2270514 bytes, checksum: 564ee2f75603507e914c127ed1286837 (MD5)<br>Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-29T18:34:54Z (GMT) No. of bitstreams: 1 toledo_ldl_me_sjrp.pdf: 2270514 bytes, checksum: 564ee2f75603507e914c127ed1286837 (MD5)<br>Made available in DSpace on 2017-09-29T18:34:54Z (GMT). No. of bitstreams: 1 toledo_ldl_me_sjrp.pdf: 2270514 bytes, checksum: 564ee2f75603507e914c127ed1286837 (MD5) Previous issue date: 2017-09-01<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>O projeto Teletandem Brasil (TELLES, 2006) é um projeto pedagógico e de pesquisa, que se apresenta como uma opção de prática telecolaborativa (O‟DOWD, 2013), e tem como um de seus objetivos proporcionar a aprendizagem de línguas estrangeiras e a aproximação de pessoas que estão distantes geograficamente dentro das instituições de ensino usando, principalmente, ferramentas de videoconferência. O projeto Teletandem tem hoje diferentes modalidades, conforme as oportunidades e necessidades das universidades envolvidas. Nesse contexto, investigamos o uso de vocabulário rico (MALVERN; RICHARDS, 2012) na produção oral de dois aprendizes brasileiros de inglês como língua estrangeira que participaram das sessões de teletandem (TTD) na modalidade institucional integrada (ARANHA; CAVALARI, 2014) em parceria com aprendizes norte-americanos de português. Nosso objetivo é caracterizar as sessões orais de teletandem (SOT) em relação ao uso de vocabulário rico (VR), e descobrir quais características do cenário de aprendizagem (FOUCHER, 2010) mostram-se mais relevantes ao uso de VR nas SOTs. Nosso estudo se caracteriza como uma pesquisa de métodos mistos (DÖRNYEI, 2007), e nosso principal instrumento de coleta de dados é um programa de computador usado para registrar as interações em áudio e vídeo, o Evaer®. Para proceder à análise quantitativa dos dados, transcrevemos as sete SOTs de dois interagentes e submetemos os textos ao programa computacional RANGE, que traça o LFP, ou perfil lexical (LAUFER; NATION, 1995) dos interagentes. O perfil lexical é uma medida de qualidade da linguagem que mostra o percentual de utilização de VR, bem como percentual utilizado de vocabulário básico e intermediário. Os resultados nos apontaram as SOTs que se destacaram quanto à utilização de VR, bem como as ocorrências específicas. Esses dados foram usados na análise qualitativa, em que identificamos as características do cenário de aprendizagem (CA) que se mostraram mais relevantes à produção oral de VR. Para a análise qualitativa, examinamos cada ocorrência de VR e identificamos o tipo de discurso do CA que era predominante no momento de sua ocorrência. Nossos resultados mostraram que as características do CA que foram mais relevantes ao uso de VR foram aquelas relacionadas ao tipo de discurso predominante na SOT, mais especificamente quando havia direcionamento através da tarefa em língua estrangeira.<br>Teletandem Brasil (TELLES, 2006) is a pedagogical and research project that is an option in telecollaborative practice (O'Dowd, 2013). One of its objectives is to provide foreign language learning, and the approximation of people who are geographically distant within the educational institutions, using mainly videoconferencing tools. The Teletandem project has different modalities, according to the opportunities and needs of the universities involved. In this context, we investigated the use of rich vocabulary (MALVERN; RICHARDS, 2012) in the oral production of two Brazilian learners of English as a foreign language who participated in the teletandem (TTD) sessions in the integrated institutional modality (ARANHA; CAVALARI, 2014). The Brazilians were working in partnership with North American learners of Portuguese. Our goal with this study is to characterize oral teletandem sessions (OTS) regarding the use of rich vocabulary (RV), and to discover which characteristics of the learning scenario (FOUCHER, 2010) are more relevant to the use of RV in the OTS. Our study is characterized as a mixed methods research (DÖRNYEI, 2007), and our main data collection tool is a computer program used to record the audio and video interactions: Evaer®. In order to quantitatively analyze data, we transcribed the seven OTS of the two students and submitted the texts to the computer program RANGE, which shows the lexical frequency profile (LFP) (LAUFER; NATION, 1995) of the students. The LFP is a measure of language quality that shows the percentage of RV use as well as the percentage of basic and intermediate vocabulary used. The results showed us the OTS that stood out regarding the use of RV, as well as the specific occurrences. These data were used in the qualitative analysis, in which we identified the characteristics of the learning scenario (LS) that were most relevant to oral RV production. For the qualitative analysis, we examined each occurrence of RV and identified the type of discourse of the LS that was predominant at the time of its occurrence. Our results showed that the characteristics of the LS that were most relevant to the use of RV were those related to the type of discourse that was predominant in the OTS, more specifically when the students were carrying out a task in the foreign language.<br>CAPES: 33004153069P-5
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34

Haglund, Robin. "Automated analysis of battery articles." Thesis, Uppsala universitet, Strukturkemi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-403738.

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Journal articles are the formal medium for the communication of results among scientists, and often contain valuable data. However, manually collecting article data from a large field like lithium-ion battery chemistry is tedious and time consuming, which is an obstacle when searching for statistical trends and correlations to inform research decisions. To address this a platform for the automatic retrieval and analysis of large numbers of articles is created and applied to the field of lithium-ion battery chemistry. Example data produced by the platform is presented and evaluated and sources of error limiting this type of platform are identified, with problems related to text extraction and pattern matching being especially significant. Some solutions to these problems are presented and potential future improvements are proposed.
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35

TANTILLO, Elena. "Bidirectional Neuron-glioma interactions: effects of Glioma Cells on Synaptic activity and its impact on tumor growth." Doctoral thesis, Scuola Normale Superiore, 2020. http://hdl.handle.net/11384/94546.

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Gliomas grow in a neuronal environment, but the interactions between glioma cells and peritumoral neurons remain poorly understood. Understanding this complex relationship could add useful information to develop more effective therapeutic approaches for the treatment of this deadly disease. In recent years, the interaction between cancer cells and tumor microenvironment has emerged as one important regulator of tumor progression. Thus, my thesis aimed to investigate the crosstalk between neural peritumoral tissue and glioma cells; in particular, I assessed i) functional impairments of peritumoral tissue occurring during tumor progression and ii) the impact of neural activity on glioma proliferation. To monitor longitudinal changes in network activity, I recorded visual evoked potentials (VEP) and local field potentials (LFP) after transplant of GL261 glioma cells (or PBS) in mouse visual cortex. Gliomas were injected in visual cortex to allow a detailed investigation of peritumoral neurons using several physiological parameters. Thanks to this analysis, I detected a progressive deterioration of VEP amplitudes along with tumor progression and changes in the LFP power spectra typical of focal epilepsy, with an increase of the power of delta band and the deterioration of alpha rhythm in glioma-bearing mice. To understand the molecular alterations that underlie these perturbed patterns of neuronal activity, I analysed the gene expression profile of microdissected peritumoral pyramidal neurons in the cortical superficial layers (i.e., II-III). The data were clear in indicating that glioma induces alterations in both pre- and post-synaptic markers, demonstrating that its progression shapes the network activity of peritumoral areas towards hyperexcitability. Indeed, I recorded the occurrence of seizures in a subset of glioma-bearing animals, finding alterations in the LFP power spectra just before the onset of ictal events. To investigate how levels of cortical activity affects tumor cell proliferation, I inoculated GL261 glioma cells into the mouse neocortex and modulated neuronal activity by different methods. Second, I dissected the role of inhibitory and excitatory circuitries on tumor proliferation and I found that while the activation of excitatory networks exacerbate glioma proliferation (confirming the data in literature), inhibitory circuits decrease GL261 cell proliferation. Based on these data, I investigated whether a sensory stimulation of the visual cortex may also impact on tumor growth. I found that a reduction of visual cortical activity via Dark Rearing enhanced the density of proliferating glioma cells, while a Visual Stimulation had the opposite effect. Intriguingly the effect was region-specific, as visual deprivation had no significant effect on glioma proliferation in motor cortex. I found that local blockade of neurotransmission via administration of the synaptic blocker botulinum neurotoxin A (BoNT/A) enhances glioma cell proliferation, underlying the importance of neural activity in controlling glioma progression. In addition, the stimulation with visual patterns combined with temozolomide treatment delayed the deterioration of visual responses induced by glioma growth. Altogether, these data demonstrate complex effects of different neuronal subtypes and afferent sensory input in the control of glioma proliferation.
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36

Ortiz, Cantin. "Study of neural correlates of attention in mice with spectro-spatio-temporal approaches." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-220948.

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While signatures of attention can be observed in widespread areas within and outside of cortex, the control of attention is thought to be regulated by higher cognitive brain areas, such as the prefrontal cortex. In their recent study on mice Kim et al. could show that successful allocation of attention is characterized by increased spiking of a specific type of inhibitory interneurons, the parvalbumin neurons, and higher oscillatory activity in the gamma band in the local prefrontal network. It was recently demonstrated that encoding of working memory in prefrontal areas is linked to bursts of gamma oscillations, a discontinuous network process characterized by short periods of intense power in the gamma band. The relationship between attention and working memory is unclear, and it is possible that these two cognitive processes share encoding principles. To address this gap, the electrophysiological data collected in the Carlén Lab have been analyzed with advanced spatio-temporal approaches. In particular, we have analyzed bursting gamma activity in medial prefrontal cortex during attentional processing and investigated the similarities to gamma bursting observed during working memory. Gamma-band bursts during attention were reliably detected with several methods. We have characterized several features of the bursts, including the occurrence, duration and amplitude. The neuronal firing rates during and outside of bursts have also been computed. We investigated the correlation between different criteria characterizing the gamma burst and successful vs failed allocation of attention. Control data were generated to discuss the obtained results. The aim of the study was to explore the hypothesis that the medial prefrontal cortex encodes attention trough gamma bursts, which could reveal some similarities and differences in coding of central cognitive processes. No clear difference was found in the characterization between successful and failed allocation of attention. In addition, results were very similar in control set and original data. No underlying mechanism could be identified from this analysis. Therefore, as the bursts occurring in the gamma band in the prefrontal cortex (PFC) were not discriminative with respect to the different tested conditions, they do not seem to encode information related to attention.<br>Även fast flera olika hjärnområdens aktivitet kan korreleras med uppmärksamhet, anses kontrollen av uppmärksamhet regleras av högre kognitiva hjärnområden, såsom främre hjärnbarken. I en nyligen publicerad artikel studerade Kim et al. hjärnaktiviteten hos möss och kunde visa att en framgångsrik uppmärksamhet kännetecknas av en ökad aktivitet av en specifik typ av inhiberande nervceller, parvalbumin celler, och högre oscillerande aktivitet i gammafrekvens i främre hjärnbarkens lokala nätverk. Det har nyligen visats att kodning av arbetsminne i främre hjärnbarken är kopplat till utbrott av gamma-oscillationer, en diskontinuerlig nätverksprocess som kännetecknas av korta perioder av intensiva oscillationer av det lokala nätverket i gammafrekvens . Relationen mellan uppmärksamhet och arbetsminne är oklar, och det är möjligt att dessa två kognitiva processer delar kodningsprinciper. För att minska detta gap av kunskap har den elektrofysiologiska datan som samlats in i Carlén Lab analyserats med avancerade spatio-temporala tillvägagångssätt. I synnerhet har vi analyserat utbrott i gammaaktivitet i främre hjärnbarken under uppmärksamhet och undersökt likheterna med gamma- utbrott observerade under arbetsminne. Gamma-bandutbrott under uppmärksamhet påvisades på ett tillförlitligt sätt med flera metoder. Vi har karaktäriserat flera funktioner hos utbrotten, inklusive förekomsten, varaktigheten och amplituden. De enskilda cellernas aktivitet undersöktes även under och utanför utprotten av gamma-oscillationer. Vi undersökte sambandet mellan de olika kriterier som karakteriserar gamma-utbrott under framgångsrik mot misslyckad allokering av uppmärksamhet. Kontrolldata genererades för att diskutera de erhållna resultaten. Syftet med studien var att utforska hypotesen att den främre hjärnbarken kodar uppmärksamhet genom gamma-utbrott, vilket kan avslöja vissa likheter och skillnader i kodning av centrala kognitiva processer. Ingen klar skillnad hittades i karaktäriseringen mellan framgångsrik och misslyckad allokering av uppmärksamhet. Dessutom var resultaten mycket likartade i kontrolluppsättningen och den ursprungliga datan. Ingen underliggande mekanism kunde identifieras ur denna analys. Eftersom de utbrott som uppstod i gamma-bandet i främre hjärnbarken inte var unika med hänsyn till de olika testade förhållandena, tycks de därför inte koda information relaterad till uppmärksamhet.
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37

Sheth, Sujitraj. "Synthesis and characterization of catalysts for photo-oxidation of water." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00981124.

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Artificial photosynthesis is often considered to have great potential to provide alternative, renewable fuels by harvesting, conversion and storage of solar energy. One promising approach is the development of modular molecular photocatalysts inspired by natural photosynthetic enzymes. The first part of this thesis deals with artificial mimics of the water oxidizing photosystem II composed of a chromophore and an electron relay as synthetic counterpart of the P680-TyrZ/His190 ensemble of photosystem II. Three ruthenium polypyridyl - imidazole - phenol complexes with varying position of a methyl group on the phenol ring (Ru-xMe) were synthesized and characterized by electrochemical and photophysical methods. As an improvement compared to earlier complexes the increased redox potential (~0.9 V vs. Ferrocene) of the phenol groups makes their function as an electron relay in a photocatalytic system for water oxidation thermodynamically possible. Time-resolved absorption studies revealed fast intramolecular electron transfer (<5-10 µs in aprotic solvent and <100 ns in water) despite the low driving force and the importance of the hydrogen bond between the phenol and the imidazole group was put in evidence. Slight differences between the three Ru-xMe complexes and investigation of the effect of external bases allowed to derive a mechanistic picture in which the imidazole is involved in a "proton domino" reaction. Accepting the phenolic proton upon ligand oxidation (within the H-bond) renders its second nitrogen site more acidic and only deprotonation of this site pulls the overall equilibrium completely towards oxidation of the ligand. Another part of this thesis comprises a chromophore-tryptophan construct synthesized using a click chemistry approach. Light-induced oxidation of Trp in this Ru-tryptophan complex was shown to follow ETPT mechanism. Depending on the pH conditions tryptophan radicals, either Trp* or TrpH*⁺ were detected and spectral measurement at different time showed the transition between the two forms. Deprotonation of the radical was dependent on the concentration of water as proton acceptor. Later part of the thesis deals with efforts to covalently bind a catalytic unit to the previously characterized chromophore-electron relay module. The click chemistry approach was not successful to obtain the final photocatalytic assembly. Therefore bimolecular activation of a Mn salen catalyst was performed and formation of Mn(IV) species was observed. As a step towards utilization of these types of photocatalysts in a photoelectrochemical cell a [Ru(bpy)₃]²⁺ chromophore with phosphonate anchoring groups (Ru-Phosphonate) was synthesized and grafted on the surface of a TiO₂ mesoporous semiconductor surface anode to perform photocurrent measurements.
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38

Thompson, Garth John. "Neural basis and behavioral effects of dynamic resting state functional magnetic resonance imaging as defined by sliding window correlation and quasi-periodic patterns." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49083.

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While task-based functional magnetic resonance imaging (fMRI) has helped us understand the functional role of many regions in the human brain, many diseases and complex behaviors defy explanation. Alternatively, if no task is performed, the fMRI signal between distant, anatomically connected, brain regions is similar over time. These correlations in “resting state” fMRI have been strongly linked to behavior and disease. Previous work primarily calculated correlation in entire fMRI runs of six minutes or more, making understanding the neural underpinnings of these fluctuations difficult. Recently, coordinated dynamic activity on shorter time scales has been observed in resting state fMRI: correlation calculated in comparatively short sliding windows and quasi-periodic (periodic but not constantly active) spatiotemporal patterns. However, little relevance to behavior or underlying neural activity has been demonstrated. This dissertation addresses this problem, first by using 12.3 second windows to demonstrate a behavior-fMRI relationship previously only observed in entire fMRI runs. Second, simultaneous recording of fMRI and electrical signals from the brains of anesthetized rats is used to demonstrate that both types of dynamic activity have strong correlates in electrophysiology. Very slow neural signals correspond to the quasi-periodic patterns, supporting the idea that low-frequency activity organizes large scale information transfer in the brain. This work both validates the use of dynamic analysis of resting state fMRI, and provides a starting point for the investigation of the systemic basis of many neuropsychiatric diseases.
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39

Muralidharan, Prasanna. "Hand-Movement Prediction Using LFP Data." Thesis, 2010. https://etd.iisc.ac.in/handle/2005/1342.

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The last decade has seen a surge in the development of Brain-Machine Interfaces (BMI) as assistive neural devices for paralysis patients. Current BMI research typically involves a subject performing movements by controlling a robotic prosthesis. The neural signal that we consider for analysis is the Local Field Potential (LFP). The LFP is a low frequency neural signal recorded from intra-cortical electrodes, and has been recognized as one containing movement information. This thesis investigates hand-movement prediction using LFP data as input. In Chapter 1, we give an overview of Brain Machine Interfaces. In Chapter 2, we review the necessary concepts in time series analysis and pattern recognition. In the final chapter, we discuss classification accuracies when considering Summed power and Coherence as feature vectors.
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40

Muralidharan, Prasanna. "Hand-Movement Prediction Using LFP Data." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/1342.

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The last decade has seen a surge in the development of Brain-Machine Interfaces (BMI) as assistive neural devices for paralysis patients. Current BMI research typically involves a subject performing movements by controlling a robotic prosthesis. The neural signal that we consider for analysis is the Local Field Potential (LFP). The LFP is a low frequency neural signal recorded from intra-cortical electrodes, and has been recognized as one containing movement information. This thesis investigates hand-movement prediction using LFP data as input. In Chapter 1, we give an overview of Brain Machine Interfaces. In Chapter 2, we review the necessary concepts in time series analysis and pattern recognition. In the final chapter, we discuss classification accuracies when considering Summed power and Coherence as feature vectors.
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KHARB, SACHIN. "THEORETICAL MODELLING AND SIMULATION OF PRISTINE LFP AND Ni DOPED LFP AS CATHODE MATERIAL OF LITHIUM ION BATTERY." Thesis, 2019. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16716.

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A simulation model for electrochemical impedance spectroscopy (EIS) of pristine LiFePO4 (LFP), doped with various concentrations of Ni such as LiNi.03Fe0.97PO4 (LFNP3), LiNi.05Fe0.95PO4 (LFNP5) and LiNi.07Fe0.93PO4 (LFNP7) in place of Fe has been developed in COMSOL Multiphysics. The model was studied under constant frequency domain perturbation using AC current impulses of 5-10 mA in frequency range 10kHz-10mHz. The simulated model parameters, which depict ideal conditions were varied one at a time, and then, two at a time to bring them close to experimental performance as extracted from experimental data. Among all the undoped and Ni doped LFP samples, lithium iron phosphate doped with 3% Ni i.e. LiNi.03Fe0.97PO4 comes close to 92% of the theoretical predicted yield [55], which translates to a maximum electrode state of charge of 0.9-0.92. The dielectric constant of pristine LFP, LFNP3, LFNP5 and LFNP7 is dependent on frequency of operation and affects the capacitance of electrode as the frequency domain perturbation is investigated. At low level of doping, the electrochemical performance improves, but on increasing the doping content of Ni more than 5 %, the resistances increase beyond that of pristine LPF.
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Fu, Chih-jian, and 傅志堅. "Study on Parameters Acquirement and Stare-of-Charge Assessment of LFPO Batteries." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/66319333131955748001.

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碩士<br>國立臺灣科技大學<br>電機工程系<br>101<br>A state-of-charge (SOC) assessment method for Lithium Iron Phosphorous Oxide (LFPO) Cell are proposed in this thesis. This SOC estimating method includes both “open circuit voltage method” and “coulomb-counting method.” To establish the SOC estimation method, we need to investigate and analyze the LFPO cell’s characteristics by a battery-testing system. In the part of the open circuit voltage method, we can find the relative equation between open circuit voltage and SOC by the open circuit voltage test; in the part of the improved coulomb counting method, it is improved that the quantity of discharging current causes differences of the output capacity. Therefore, we can use Least squares to find relative equation between discharge current and correct current by the data of discharge test. The state-of-charge estimation hardware circuit is implemented by HT66F50 microcontroller. It can communicate with the computer by UART/USB communication protocols, and the man-machine is implemented interface by LabVIEW, The accuracy of the SOC estimation methodology is then verified by conducting experiments. Experimental results show that the deviation rate of the estimation is below 1.2% when SOC is within the range of 30% to 100%. As a consequence, the proposed method with implemented hardware is justified for SOC assessment.
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Liu, Kung-Nan, and 劉恭男. "Preparation of LFP/C Composite Cathode Material from Milled Iron Source by Solid-phase Reaction." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/9449c4.

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碩士<br>明志科技大學<br>化學工程系碩士班<br>103<br>Lithium iron phosphate (LiFePO4, LFP) is a promising alternative cathode material because of its low raw material cost, environment friendliness, superior thermal safety and long operational life.In this study, lithium iron phosphate (LFP) materials were synthesized from LiCO3, Fe2O3 and H3PO4 as raw materials in furnace at 600-700 C for 10h under a 95%Ar+5%H2 atmosphere. The carbon-coated lithium iron phosphate (LFP/C) composite cathode materials were prepared by using spray drying and annealing from a glucose solution. Fe2O3 powders were ground to decrease the particle size and then to investigate its effects on the operating conditions of material preparation and properties of LFP/C.The structural, morphological and electrochemical properties were investigated by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Raman scattering spectra, and constant current charge–discharge cycling test. The results show that the cathode based on the ground Fe2O3 have the higher specific discharge capacities than those prepared from the original Fe2O3. In addition, the cathodes prepared from the ground Fe2O3 show the higher stability in material quality and thus the effects of annealing temperature on their discharge capacities could be negligible. The best specific discharge capacities of the prepared cathodes in this study are 141 mAh/g at 0.1C and 67 mAh/g at 10C, respectively.
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44

"Performance, Modeling, and Characteristics of LFP pack for HEV using FUDS (depleting) in Hot and Arid Conditions." Master's thesis, 2016. http://hdl.handle.net/2286/R.I.39424.

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abstract: There was a growing trend in the automotive market on the adoption of Hybrid Electric Vehicles (HEVs) for consumers to purchase. This was partially due to external pressures such as the effects of global warming, cost of petroleum, governmental regulations, and popularity of the vehicle type. HEV technology relied on a variety of factors which included the powertrain (PT) of the system, external driving conditions, and the type of driving pattern being driven. The core foundation for HEVs depended heavily on the battery pack and chemistry being adopted for the vehicle performance and operations. This paper focused on the effects of hot and arid temperatures on the performance of LiFePO4 (LFP) battery packs and presented a possible modeling method for overall performance. Lithium-ion battery (LIB) packs were subjected to room and high temperature settings while being cycled under a current profile created from a drive cycle. The Federal Urban Driving Schedule (FUDS) was selected and modified to simulate normal city driving situation using an electric only drive mode. Capacity and impedance fade of the LIB packs were monitored over the lifetime of the pack to determine the overall performance through the variables of energy and power fade. Regression analysis was done on the energy and power fade of the LIB pack to determine the duration life of LIB packs for HEV applications. This was done by comparing energy and power fade with the average lifetime mileage of a vehicle. The collected capacity and impedance data was used to create an electrical equivalent model (EEM). The model was produced through the process of a modified Randles circuit and the creation of the inverse constant phase element (ICPE). Results indicated the model had a potential for high fidelity as long as a sufficient amount of data was gathered. X-ray powder diffraction (XRD) and a scanning electron microscope (SEM) was performed on a fresh and cycled LFP battery. SEM results suggested a dramatic growth on LFP crystals with a reduction in carbon coating after cycling. XRD effects showed a slight uniformed strain and decrease in size of LFP olivine crystals after cycling.<br>Dissertation/Thesis<br>Masters Thesis Engineering 2016
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JYUN, JHANG-MING, and 張峻銘. "Study on the Effect of Combined Sinusoidal Wave Charging Method on the Internal Material of LFP Battery." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/z53h4j.

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碩士<br>國立臺北科技大學<br>車輛工程系<br>107<br>In this study, the effects of CC-CV charging method and Combined Sinusoidal Wave charging method on the internal structure of lithium iron phosphate battery were discussed. From the experimental results, it is found that after 600 cycles, the battery using the charging method still retains about 94% of SOH, and in the electrochemical impedance analysis and cyclic voltammetry test, the portion of the SEI film impedance is increased about 0.08 mΩ. In the microstructured portion, no significant SEI film formation was observed on the surface of the negative electrode using the battery of the present charging method. Finally, in the analysis of the SEI film composition, it was found that the Li_2 CO_3 and Li_2 O content in the Li element was only about 15.97% and 4.42% in the battery using this charging method, and the battery component content in the CC-CV charging method was 27.2%. 6.69%.
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46

MANISH and PINKI. "STRUCTURAL AND ELECTROCHEMICAL STUDY OF OLIVINE TYPE LIFEPO4 AS CATHODE MATERIAL." Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/20117.

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This study is intended to synthesize the olivine-type pristine LiFePO4 (LFP) using the solid-state ball milling method. The structural, electrical, and electrochemical properties of as synthesized pristine LiFePO4 has been analyzed. The synthesized sample was characterized using X-ray diffraction (XRD) to confirm the single/mixed phase formation of the olivine type LFP as a cathode material. Hence, the Rietveld refinement analysis of the observed XRD pattern indicates that olivine type orthorhombic single phase with the space group, Pnma is formed without any impurity. Fourier Transform Infrared Spectroscopy (FTIR) is also performed to see the groups developed, bond strength and bond stretching and bond vibrations in the LFP. The dc conductivity and activation energy were estimated by the source measurement unit using Arrhenius equation. The electrochemical performance of LFP has been carried using Cyclic Voltammetry (CV), Electrochemical impedance spectroscopy (EIS) and Galvanostatic charge/discharge (GCD) methods. Here, it is found that the 1st cycle of pristine LFP delivers a specific discharge capacity of 52(±5) mAh g-1 at 0.5C rate and after 50 charge/discharge cycles a noticeable retention in the capacity is observed which implies that, the electrochemical Li+ insertion/extraction process is extremely reversible and that the structure of pristine LiFePO4 is quite stable and also the pristine LFP has a coulombic efficiency of greater than 99 %.
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47

Padovani, Laura. "Reconsolidation of appetitive memory and sleep: functional connectomics and plasticity." Doctoral thesis, 2020. http://hdl.handle.net/11562/1015855.

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Introduzione: La dipendenza da cibo è un disturbo comportamentale caratterizzato da modelli maladattativi di consumo alimentare, in cui alimenti ricchi in zuccheri, sale e/o grassi possono indurre una dipendenza tale da essere paragonata ai disturbi relativi all’abuso di sostanze. Alla base di questo processo vi è l’associazione tra questi cibi altamente palatabili e la sensazione piacevole e rinforzante indotta dal loro consumo, che può essere codificata in una nuova memoria maladattativa sottostante il disturbo di dipendenza. Infatti, le nuove informazioni che riceviamo quotidianamente dall’esterno vengono processate dal nostro cervello tramite un primo stadio di codifica e un secondo stadio di consolidamento, durante il quale vengono stabilizzate in una nuova memoria e integrate nella rete cerebrale di conoscenze preesistenti. Tuttavia, dopo il suo consolidamento, una memoria può essere destabilizzata e riportata ad uno stato di labilità che ne permette la modifica e l’eventuale integrazione con nuove informazioni. Infine, un nuovo processo di stabilizzazione chiamato riconsolidamento è necessario affinché la traccia mnemonica aggiornata sia nuovamente stabilizzata. Da recenti studi, è noto come il sonno sia rilevante sia per il consolidamento che per il riconsolidamento della memoria. Tuttavia, mentre è chiaro come il consolidamento che avviene durante il sonno permetta la stabilizzazione a lungo termine delle tracce mnemoniche, non è ancora stato del tutto chiarito il ruolo del sonno nel processo di riconsolidamento. Scopo: Date queste premesse, e nota l’importanza dell’interazione tra amigdala basolaterale (BLA) e ippocampo nel riconsolidamento delle memorie appetitive, gli obiettivi della presente tesi erano: i) valutare come l’amigdala BLA e ippocampo interagiscono in termini di potenziali locali durante la riattivazione della memoria strumentale effettuata o durante la fase di attività o durante la fase di inattività del ciclo circadiano dei roditori; ii) valutare come il richiamo della memoria effettuato durante la fase attiva o quella inattiva possa influenzare il successivo processo di riconsolidamento, e iii) trovare, in-vivo, un marker di riattivazione della memoria appetitiva. Metodi: Sono stati utilizzati 32 ratti maschi, ceppo Sprague Dawley, a cui sono stati impiantati due elettrodi profondi: uno in BLA e uno in ippocampo, per la registrazione dei potenziali locali. I ratti sono stati sottoposti ad un protocollo comportamentale in gabbia operante di auto-somministrazione di saccarosio, composto da quattro stadi: addestramento (i), in cui i ratti imparavano l’associazione tra la pressione di una leva e l’emissione di un pellet di saccarosio; astinenza (ii), durante la quale i soggetti non venivano esposti al contesto di addestramento; riattivazione o non riattivazione (iii) della memoria strumentale in gabbia operante, svolta o durante la fase di attività, o durante la fase di inattività; test di ricaduta (iv). I potenziali locali sono stati analizzati per lo stadio (iii) in modo da ottenere la potenza delle oscillazioni theta e gamma per i due elettrodi profondi; tali frequenze sono state scelte in quanto rilevanti per i processi mnemonici. Infatti, il richiamo della memoria è correlato alla sincronizzazione delle onde theta (4-12 Hz) tra BLA e altre aree cerebrali quali l’area CA1 dell’ippocampo, ed è inoltre correlato alle basse gamma (30-60 Hz) nell’ippocampo. Infine, l’accoppiamento tra le onde theta e gamma nell’ippocampo è un noto metodo di comunicazione tra sotto-aree ippocampali nel corso dei processi di memoria. Risultati: I risultati hanno mostrato la presenza di una correlazione inversa tra la potenza delle basse gamma nell’area CA1 ippocampale e il tasso di risposta durante lo stadio di richiamo della memoria nella fase di attività, indipendentemente dal fatto che i soggetti stessero o meno premendo la leva. Le basse gamma potrebbero quindi rappresentare un marker di correlazione per il richiamo della memoria appetitiva. Inoltre, la potenza di basse e alte gamma ippocampali aumenta durante le epoche di pressione di leva quando il richiamo della memoria viene effettuato nella fase di inattività, suggerendo che le onde gamma potrebbero essere dei marker correlazionali specifici per la componente strumentale del richiamo della memoria effettuato durante la fase di inattività. Conclusioni e limitazioni: Per concludere, i risultati hanno mostrato l’importanza delle frequenze basse gamma nel richiamo delle memorie appetitive, tuttavia non hanno mostrato alcuna differenza a livello delle onde theta, né a livello della BLA. Di conseguenza, si conclude che il protocollo utilizzato nella presente tesi non ha mostrato una sensibilità sufficientemente elevata nell’evidenziare i cambiamenti ipotizzati a livello dei potenziali locali. Lo svolgimento di ulteriori esperimenti che andranno a determinare misure di connettomica quali coerenza e accoppiamento, sia intra- che inter- area, aiuterà a determinare se e come le due aree comunicano tra di loro.<br>Introduction: Food addiction is a behavioural disorder in which individuals develop maladaptive patterns of food consumption. Particularly, food containing processed sugars, salt, fat etc. can be addictive, and refined food consumption behaviours may meet the criteria for substance use disorders. For these characteristics, food addiction can also be considered a memory disorder. Memories in the brain are processed as follows: new information is encoded and then long-term consolidated through a process allowing its integration into already existing knowledge networks. After a memory has been consolidated, it can be destabilized and brought back to a labile state, requiring a new re-stabilization process called reconsolidation. Memory consolidation is known to require sleep. In fact, sleep allows new memory traces to long-term stabilize. Sleep also seems to influence memory reconsolidation; however, its involvement in this process is not yet clear. Aim: Given these premises, the goals of the project were: to evaluate how basolateral amygdala (BLA) and hippocampus interact in terms of local field potentials (LFPs) when appetitive instrumental memory is retrieved either during active or inactive phase of rats circadian rhythm; to evaluate how retrieving the memory in the activity vs inactivity phase influences following memory reconsolidation; and to find an in vivo electrophysiological marker of appetitive memory retrieval. In fact, it has been shown that BLA and dorsal hippocampus interaction is crucial for appetitive memory reconsolidation. Methods: Thirty-two male Sprague Dawley rats were implanted with in-depth electrodes for LFPs recordings in BLA and dorsal hippocampal CA1 and subject to a behavioural protocol apt to induce appetitive memory retrieval. The behavioural procedure consisted of four stages: training (i), in which animals learned lever pressing – sucrose reward association; abstinence (ii), during which subjects were not exposed to the training context; memory retrieval or no retrieval (iii): instrumental memory reactivation or no reactivation, performed either during active or inactive phase; and relapse test (iv), during which sucrose-seeking behaviour was analysed. Theta and gamma oscillations powers were analysed during stage (iii). In fact, they are known to be involved in memory processes. Memory retrieval has been shown to correlate with theta (4-12 Hz) synchronization between BLA and other brain areas (such as hippocampal CA1) and with low gamma (30-60 Hz) in hippocampus. Particularly, theta-gamma cross-frequency coupling has been shown to be used as a mean of communication between hippocampal sub-areas during memory processing. Results: Results showed an inverse correlation between hippocampal CA1 low gamma power and reactivation rate of responding (either when rats were lever pressing or not) when reactivation was performed during the active phase. This suggests that low gamma may be a correlational marker of instrumental sucrose memory retrieval, independent of whether rats were lever-pressing or not. Moreover, hippocampal CA1 gamma bands increased when lever pressing during instrumental memory reactivation while in the inactive phase, suggesting that both low and high gamma bands may be correlational markers to actual instrumental responding retrieval during the inactive phase. Conclusions and limitations: In conclusion, results showed that low gamma is relevant in sucrose appetitive memory retrieval. However, no difference was observed in the theta frequency band, nor at the level of BLA. Therefore, the current protocol did not have the sensitivity to detect predicted changes in LFPs. Further experiments would help investigating if and how the two areas interact, by determining connectomics measures such as coherence and coupling within and between areas.
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48

Wu, Jo-Yu, and 吳若瑜. "A Band-Tunable, Low-Noise, Multichannel Amplifier with AP/LFP Separation for Neuronal Recording and Dual-threshold adaptive AP detector." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/62058010356408671785.

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碩士<br>國立清華大學<br>電機工程學系<br>100<br>Biological prosthetic system had developed for a long time. The progress in CMOS technology and increasing demand of health management make implantable system become a main stream. The application of such a system including Parkinson's disease, epilepsy, neuromuscular disorders, stroke, paralysis, artificial silicon retina, silicon cochlea, physiology signal monitor, etc. 　The neural amplifier amplifies and filters the indistinct signal after it is recorded by electrode array. For deceasing design trade-off between power and noise, a two-stage structure is used in this article. A balanced tunable pseudo-resistor is used to acquire local field potential (LFP) and action potential (AP) separately while rejecting unwanted offset voltage induced by tissue-electrode interface. In recent years, the research about interaction between neurons is more and more popular, the multi-channel neural amplifier is essential in this application. However, low power design is desirable, heat produced from the power-hungry chip can eventually injury the deep-skin cells. Action potential detector is usually a choice to reduce power consumption of processor and transmitter. The proposed AP detector combines dual-threshold technique to adaptive threshold setting circuit and only consumes 12.65uW. 　　The article is fabricated by TSMC 0.18um process.　The measurement results show that the system achieved input referred noise 4.96mVrms and noise efficiency factor (NEF)3,69 with mid-band gain of 50.4dB and power consumption of 7uW.　The bandwidth is highly tunable in the range of 15Hz-436.9Hz for high-pass corner and 317Hz-11kHz for low-pass corner. The results show that the proposed low-power, low-noise biomedical system is suitable for implantable device applications.
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49

"Neural Mechanisms of Sensory Integration: Frequency Domain Analysis of Spike and Field Potential Activity During Arm Position Maintenance with and Without Visual Feedback." Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.46363.

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abstract: Understanding where our bodies are in space is imperative for motor control, particularly for actions such as goal-directed reaching. Multisensory integration is crucial for reducing uncertainty in arm position estimates. This dissertation examines time and frequency-domain correlates of visual-proprioceptive integration during an arm-position maintenance task. Neural recordings were obtained from two different cortical areas as non-human primates performed a center-out reaching task in a virtual reality environment. Following a reach, animals maintained the end-point position of their arm under unimodal (proprioception only) and bimodal (proprioception and vision) conditions. In both areas, time domain and multi-taper spectral analysis methods were used to quantify changes in the spiking, local field potential (LFP), and spike-field coherence during arm-position maintenance. In both areas, individual neurons were classified based on the spectrum of their spiking patterns. A large proportion of cells in the SPL that exhibited sensory condition-specific oscillatory spiking in the beta (13-30Hz) frequency band. Cells in the IPL typically had a more diverse mix of oscillatory and refractory spiking patterns during the task in response to changing sensory condition. Contrary to the assumptions made in many modelling studies, none of the cells exhibited Poisson-spiking statistics in SPL or IPL. Evoked LFPs in both areas exhibited greater effects of target location than visual condition, though the evoked responses in the preferred reach direction were generally suppressed in the bimodal condition relative to the unimodal condition. Significant effects of target location on evoked responses were observed during the movement period of the task well. In the frequency domain, LFP power in both cortical areas was enhanced in the beta band during the position estimation epoch of the task, indicating that LFP beta oscillations may be important for maintaining the ongoing state. This was particularly evident at the population level, with clear increase in alpha and beta power. Differences in spectral power between conditions also became apparent at the population level, with power during bimodal trials being suppressed relative to unimodal. The spike-field coherence showed confounding results in both the SPL and IPL, with no clear correlation between incidence of beta oscillations and significant beta coherence.<br>Dissertation/Thesis<br>Doctoral Dissertation Biomedical Engineering 2017
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50

Zbrzeski, Adeline. "Circuits intégrés d'enregistrement et d'analyse en temps réel des potentiels de champ neuronaux. Application au traitement de la maladie de Parkinson, par contrôle adaptatif de stimulations cérébrales profondes." Phd thesis, 2011. http://tel.archives-ouvertes.fr/tel-00674478.

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La maladie de Parkinson est la seconde maladie neuro-dégénérative la plus fréquente à travers le monde. Dans ce contexte, le projet de recherche associé à cette thèse vise à améliorer le traitement symptomatique de la maladie de Parkinson, par le développement de procédés de stimulation cérébrale profonde adaptative. Le travail de cette thèse repose sur la conception d'un ASIC d'enregistrement et de traitement de signaux neuronaux, répondant à divers enjeux :un traitement continu et en temps réel focalisé sur des bandes spécifiques très basses-fréquences et largement configurables. L'objectif est d'utiliser l'information traitée pour le contrôle et la génération d'un signal de stimulation. Cet ASIC a été développé, caractérisé électroniquement et utilisé dans un contexte in vivo. Un système en boucle fermée a été réalisé à partir de cet ASIC, se montrant fonctionnel. Ces validations expérimentales in vivo ouvrent de nombreuses possibilités d'investigation du concept de stimulation cérébrale en boucle fermée.
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