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1
Ghimouz, Rym. "Caractérisation du rôle des facteurs de transcription Homez et CBFbeta au cours de la neurogenèse et de la formation de la crête neurale chez Xenopus laevis". Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209568.
Testo completoAbstract (sommario):
Le but des recherches du laboratoire de génétique du développement est de mieux comprendre les mécanismes moléculaires qui contrôlent le développement neural des vertébrés. C’est la raison pour la quelle, j’ai identifié deux EST (BC071005 et BC077938) spécifiques de l’expression génique chez le Xenopus laevis. Sur base de la littérature, ces deux gènes présentent des profils d’expression intéressants, caractéristiques des gènes impliqués dans la neurogenèse.Le premier clone d’ADNc code pour l’homologue du facteur de transcription Homez, contenant trois homéodomaines et deux motifs leucine zipper et dont la fonction est inconnue. Mes résultats ont montré que chez l’embryon de xénope au stade neurula, Homez est exprimé préférentiellement dans la plaque neurale, l’expression la plus forte étant détectée dans les domaines où les neurones primaires apparaissent. Plus tard, Homez est détecté dans le tube neural dans des cellules neurales postmitotiques en cours de différenciation. En accord avec ce profil d’expression, j’ai observé que Homez est régulé positivement par l’atténuation des signaux BMPs et par le facteur proneural Ngnr1 et négativement par la voie Notch. Bien que le facteur Homez ne soit pas suffisant pour induire une expression ectopique de marqueurs neuronaux dans l’embryon de xénope, j’ai pu montrer, en utilisant une approche de morpholino antisens, que celui-ci est requis en aval du facteur Ngnr1 pour la différenciation des précurseurs neuraux en neurones primaires.
Le deuxième clone code pour l’homologue du facteur CBFβ qui s’associe avec une famille de protéines CBFα1-3/Aml1-3/Runx1-3 pour former un complexe hétérodimérique liant l’ADN. Alors que chez la souris, les facteurs Runx1 et Runx3 jouent un rôle important dans la neurogenèse dans les ganglions spinaux et que chez le xénope, Runx1 est requis pour la formation des neurones Rohon-Beard, le rôle de CBFβ au cours du développement du système nerveux est actuellement mal connu. Mes résultats ont montré que chez l’embryon de xénope au stade neurula, CBFβ est coexprimé avec les facteurs Runx1-3 en bordure de la plaque neurale, mais de manière plus étendue et plus précoce. Comme attendu pour un marqueur de la bordure de la plaque neurale, j’ai observé que l’expression de CBFβ est régulée par les signaux BMP, Wnt, FGF et Notch. De manière intéressante, son expression est induite par les facteurs proneuraux alors que celle de Runx1 est inhibée. Des expériences de perte de fonction à l’aide de morpholinos antisens bloquant la traduction de CBFβ ont été réalisées. Ces expériences suggèrent que le facteur CBFβ est nécessaire à la mise en place de la CN et à la différenciation des neurones de Rohon-Beard.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
2
Panasenkava, Veranika. "Utilisation de cellules souches pluripotentes induites combinée à une approche transcriptomique pour améliorer le diagnostic moléculaire des troubles du neurodéveloppement chez l’homme". Electronic Thesis or Diss., Université de Rennes (2023-....), 2024. http://www.theses.fr/2024URENB060.
Testo completoAbstract (sommario):
L'holoprosencéphalie (HPE) est une maladie rare qui affecte le développement de la ligne médiane du cerveau antérieur dès les premiers stades embryonnaires, rendant son diagnostic moléculaire complexe. Elle résulte principalement d’altérations génétiques entraînant une réduction de l'activité de la voie de signalisation Sonic Hedgehog (SHH). Cependant, un diagnostic moléculaire précis n’est possible que pour 30% des patients, ce qui souligne l’importance de développer des nouvelles approches diagnostiques. Le principal obstacle réside dans l'impossibilité d'accéder au tissu primaire affectée par la pathologie, soit le neuroectoderme antérieur. Pour surmonter cet obstacle, j’ai mis au point un modèle in vitro du développement du neuroectoderme antérieur en utilisant des cellules souches pluripotentes induites. Ce modèle m’a permis de produire des données transcriptomiques permettant d’évaluer les impacts moléculaires de la déficience en SHH et de définir des signatures transcriptomiques décrivant les variations de l'activité de la voie SHH pouvant être corrélées à la sévérité des phénotypes d’HPE. Ce travail a également révélé de nouveaux gènes co-exprimés et régulés par SHH, qui pourraient constituer de nouveaux marqueurs génétiques de l'HPE. Ces avancées ouvrent la voie à la création d’outils de diagnostic innovants, visant à améliorer la précision du diagnostic pour les patients atteints d'HPEAbstract : Holoprosencephaly (HPE) is a rare disorder that affects the development of the midline of the forebrain during the earliest stages of embryogenesis, making molecular diagnosis challenging. It primarily results from genetic alterations that lead to a reduction in the activity of the Sonic Hedgehog (SHH) signaling pathway. However, a precise molecular diagnosis is only possible for 30% of patients, highlighting the importance of developing new diagnostic approaches. The main challenge is the inaccessibility of the primary tissue, specifically the anterior affected by HPE, namely the anterior neuroectoderm. To overcome this challenge, I established an in vitro model of anterior neuroectoderm using induced pluripotent stem cells. This model allowed me to generate transcriptomic data to assess the molecular impacts of SHH deficiency and define transcriptomic signatures that describe variations in SHH pathway activity, which may correlate with the severity of HPE phenotypes. This work also revealed new co-expressed and SHH-regulated genes, which could serve as new genetic markers for HPE. These advances pave the way for innovative diagnostic tools aimed at improving diagnostic accuracy for patients with HPE
3
Kolluru, Chaitanya Kolluru. "Deep neural networks for A-line based plaque classification in intravascular optical coherence tomography images". Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1530626730008246.
Testo completo
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Qurashi, Abrar Ahmad. "Neuronal remodeling in Drosophila melanogaster with WAVE/SCAR complex and its implication in cognitive functions". Université Louis Pasteur (Strasbourg) (1971-2008), 2006. http://www.theses.fr/2006STR13112.
Testo completoAbstract (sommario):
La morphogenèse neurale et la plasticité neuronale dépendent du remodelage du cytosquelette d’actine et sont induits en réponse à des signaux extra cellulaires qui sont interprétés par la famille des petites Rho GTPases. Pendant ma thèse, j’ai cherché à comprendre comment les voies de signalisations en aval des protéines Rac, petites Rho GTPases, sont utilisés pour réguler la morphogenèse neurale et la plasticité structurelle. Récemment, le complexe WAVE/SCAR, un ensemble de cinq protéines conservées durant l’évolution [WAVE (SCAR), PIR121 (Sra-1 or CYFIP), Hem-2 (NAP1 or Kette),Abi et HSPC300] a été identifié comme le lien essentiel entre Rac1 et Arp2/3 (un complexe moléculaire induisant la polymérisation d’actine). Les premières études suggéraient que Rac1 agissait en dissociant le complexe WAVE/SCAR conduisant à la libération et à l’activation de la protéine WAVE (SCAR). Des études ultérieures proposent un autre mode d’action et suggèrent que le complexe WAVE/SCAR ne se dissocie pas mais qu’à la place il est nécessaire dans son ensemble pour localiser et activer la protéine WAVE (SCAR). Au cours de ma thèse, j’ai utilisé la drosophile comme modèle pour étudier la fonction et le mode d’action du complexe WAVE/SCAR au cours de différents processus du développement neuronal comme la navigation axonale et le développement synaptique. J’ai plus particulièrement isolé des mutants du gène HSPC300 et caractérisé génétiquement et moléculairement cette protéine. Ensuite, j’ai étudié le rôle des autres membres du complexe WAVE/SCAR, ce qui m’a permis de proposer un modèle expliquant comment les divers signaux reçus par les différents membres du complexe sont interprétés. Pendant ma thèse, j’ai démontré que WAVE (SCAR), Kette et HSPC300 forment aussi un complexe chez la drosophile. J’ai observé que toutes ces protéines sont très fortement exprimées dans le système nerveux et tout particulièrement dans les neurones du système nerveux central et les neurones moteurs. De manière intéressante, j’ai observé que muter n’importe quel membre du complexe conduit toujours à des défauts similaires non seulement au niveau du guidage et de la croissance axonale mais aussi au niveau de la morphologie des jonctions neuromusculaires. Nous avons ensuite recherché les raisons de cette similarité phénotypique. Par des expériences de génétique et de biochimie, nous avons démontré que la perte d’un des composants du complexe conduit à l’instabilité des autres composants ce qui fournit une base physique à la similarité des phénotypes observés avec les différentes mutations individuelles. De manière intéressante, les mutations individuelles des composants du complexe n’affectent pas seulement la stabilité des autres membres mais aussi les voies de signalisations en aval. Par exemple, muter n’importe quel membre du complexe WAVE/SCAR a un effet sur la signalisation de CYFIP vers une autre protéine FMRP (Fragile X Mental Retardation Protein : une proteine impliquée dans la mémoire et l’apprentissage chez les humains). De la même manière, la signalisation SCAR-Arp2/3 est affectée par toutes les différentes mutation individuelles. Nous avons aussi étudié la fonction de ce complexe dans le développement de l’oeil de drosophile et montré qu’il contrôle notamment la morphologie et l’intégrité des différents types cellulaires, photorécepteurs (neurones) y inclus. En conclusion, j’ai démontré que le complexe WAVE/SCAR se trouve au centre (physiquement et fonctionnellement) de nombreuses voix de signalisations impliquées et dans le développement de nombreux types cellulaires. Ainsi mon travail s’inscrit dans la lignée des études qui supportent que la régulation de différents évènements morphogénétiques passent par un même noyau de signalisation. Enfin, ma thèse suggère que les autre petites Rho GTPases Rac2 et Mtl sont elles aussi impliqués dans plasticité et la croissance synaptiqueNeuronal morphogenesis and plasticity during development as well as in cognitive functions rely on actin cytoskeleton remodeling in response to extra-cellular signals that are interpreted by Rho family of small GTPases. The key subject of my thesis is to understand how signaling pathways downstream of Rac proteins, members of the Rho GTPase family, are utilized to orchestrate distinct aspects of neuronal morphogenesis and structural plasticity. WAVE/SCAR complex, an evolutionarily-conserved assembly of five proteins: WAVE (SCAR), PIR121 (CYFIP), Hem-2 (Kette), Abi and HSPC300 has emerged as a critical link between Rac1 and Arp2/3, molecular complex triggering actin nucleation. During my thesis I have used Drosophila melanogaster as a model system to understand the physiological significance of WAVE/SCAR complex. We have elucidated its role in neuronal actin remodeling underlying axon as well synapse development. Specifically, I have isolated mutations in the HSPC300 gene, and present its detailed characterization both at genetic and biochemical level. My thesis work provides evidence that in Drosophila melanogater SCAR, CYFIP, Kette and HSPC300 associate together to form a complex. All these proteins are highly expressed in the embryonic nervous system and show strong accumulation in central and motor neurons. Interestingly, in many processes examined, there are striking similarities between the phenotypes resulting from the mutations in any member of the complex, for example defects in axon path-finding, axon growth and Neuromuscular Junction (NMJ) morphology, thus demonstrating their pivotal roles for precise neuronal development. By biochemical and genetic experiments, we demonstrated that loss of any of the complex components leads to instability in other components. Therefore, the results provide an unequivocal reason for the common pathological condition noticed in single mutation of the WAVE/SCAR complex. Interestingly, mutation in individual components of the complex not only affects the stability of other complex components but also affects the multiple downstream pathways associated with them. For example, mutation in any component of the complex has an impact on CYFIP signaling to the Fragile X Mental Retardation Protein (FMRP) implicated in learning and memory in humans. Thus, our results identify the Drosophila WAVE/SCAR complex as a multifunctional unit orchestrating different pathways and aspects of neuronal connectivity and support an emerging theme: different aspects of xv morphogenesis may involve the regulation of common core signaling pathways. Additionally, my thesis also demonstrates the interaction of all three Racs (Rac1, Rac2 and Mtl) with CYFIP and suggests their requirement during NMJ growth and plasticity
5
Ravel-Chapuis, Aymeric. "Etude du contrôle des modifications de la chromatine musculaire par les facteurs neuraux". Lyon, École normale supérieure (sciences), 2006. http://www.theses.fr/2006ENSL0379.
Testo completo
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Bosque-Freeman, Léorah. "Imagerie de la dégénérescence neuronale dans une maladie démyélinisante : la sclérose en plaques". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066522/document.
Testo completoAbstract (sommario):
La sclérose en plaques (SEP) a longtemps été considérée comme une affection inflammatoire démyélinisante de la substance blanche. (SB) Hors, de nombreuses études ont démontré l’implication extensive de la substance grise (SG). La souffrance neuronale joue un rôle majeur dans la détérioration physique et cognitive des patients atteints de SEP. Le développement de nouvelles techniques d’imagerie capables de quantifier cette atteinte neuronale est devenu crucial. Grace à la tomographie par émission de positons (TEP) et au radiotraceur [11C]flumazenil ([11C]FMZ), antagoniste du récepteur central aux benzodiazépines, nous avons quantifié de façon non-invasive la souffrance neuronale de la SG chez des patients atteints de SEP à différents stades de la maladie. Une cohorte de 18 patients atteints de SEP a été comparée à 8 sujets sains. Les participants ont bénéficié d’une évaluation clinique, cognitive, et radiologique par TEP au [11C]FMZ et IRM. Les données TEP ont été évaluées par région d’intérêt et vertex-à- vertex. Des réductions significatives de l’activité TEP au [11C]FMZ ont été mises en évidence au sein de la SG corticale et sous-corticale des patients comparés aux contrôles. Ces changements étaient présents dès le stade rémittent de la maladie et corrélaient modérément avec la charge lésionnelle de la SB. L’activité TEP corticale était aussi associée à la performance cognitive des patients. Cette étude pilote est la première à quantifier in vivo la souffrance neuronale chez des patients atteints de SEP. Nos résultats permettent de proposer la TEP au [11C]FMZ comme marqueur spécifique et discriminant de l’atteinte neuronale de la SG dans la SEPMultiple sclerosis (MS) has long been regarded as an inflammatory demyelinating disorder of the white matter. But post-mortem studies have recently shed light on the extensive involvement of the grey matter (GM). Neuronal damage, characterized by synaptic and dendritic loss as well as neuronal apoptosis, is thought to be a major substrate of physical and cognitive deterioration in MS patients. There is a crucial need for new imaging techniques able to specifically assess neuronal damage in MS. Using positron emission tomography (PET) with [11C]flumazenil ([11C]FMZ), an antagonist of the central benzodiazepine site located within the GABAA receptor, and a non-invasive quantification method, we measured and mapped neurodegenerative changes in the GM of patients with MS at distinct disease stages. A cohort of 18 MS patients was compared to 8 healthy controls and underwent neurological and cognitive evaluations, high-resolution dynamic [11C]FMZ PET imaging and brain MRI. PET data were evaluated using a region of interest and a surface-based approach. [11C]FMZ binding was significantly decreased in the cortical and subcortical GM of MS patients compared to controls. These changes were significant in both progressive and relapsing-remitting forms of the disease and correlated moderately with white matter lesion load. [11C]FMZ cortical binding was also associated with cognitive performance. This pilot study is the first to quantify in vivo the neurodegenerative changes occurring in MS. Our results show that PET with [11C]FMZ could be a promising and sensitive quantitative marker to assess and map the neuronal substrate of GM pathology in MS
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Lefevre, Fabien. "Caractérisation de structures du type plaque par ondes guidées générées et détectées par laser". Valenciennes, 2010. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/24980ba6-f06c-4c75-988a-16e1228d2e42.
Testo completoAbstract (sommario):
La réalisation de couches minces déposées sur substrats est très recherchée dans de nombreuses applications. C'est le cas par exemple des pièces nickelées destinées à des dispositifs à hautes performances techniques, où une couche anti-corrosion est déposée a n d'améliorer leur imperméabilité. L'utilisation de ces structures du type couche sur substrat étant grandissante, on comprend dès lors l'importance de disposer de moyens non destructifs permettant de les contrôler et de les caractériser. Dans ce travail, l'objectif a été de mettre à pro t les ondes acoustiques guidées pour le contrôle et la caractérisation de structures du type plaque. Pour la génération et la détection de ces ondes guidées, la technique laser-ultrasons a été privilégiée. C'est une méthode large bande et sans contact permettant d'éviter l'utilisation d'un milieu de couplage ou tout contact direct avec la structure et pouvant s'adapter à des géométries complexes. Pour tirer pro t au maximum de l'utilisation de cette technique, des réseaux de neurones lui ont été associés a n de résoudre le problème inverse posé par les ondes de plaque. Une méthode de caractérisation originale, e cace et polyvalente a ainsi été mise en oeuvre, permettant de déterminer les propriétés géométriques et/ou mécaniques de plaques simples ou de structures à couches. Des structures composées de silicium ont plus particulièrement été étudiées par le biais de cette méthode. Des simulations éléments nis, ainsi que des études sur certains défauts présents dans les couches minces, comme l'adhérence, sont présentéesThe deposition of thin layers on substrates is more and more required in many applications. For example, to reach high technical performance, bumpers or other parts are nickeled to improve their impermeability and resistance. Another example in microelectronics is the realization of transistors found in LCDs where they are associated with each pixel. The use of these layer/substrate structures is growing, so the importance of having non-destructive techniques to monitor and characterize them is well understood. The point in using ultrasonic waves for non-destructive testing and evaluation of various materials and structures is well known. In this work, the aim was to use guided waves to monitor and to characterize plaque-like structures. The main advantage of using these modes lies in their ability to test very large areas and inaccessible structures. For the generation and detection of guided waves, the laser ultrasonics technique was preferred. It is a broadband and non contact method which doesn't imply the use of coupling medium and which can be adapted to complex geometries. To take full advantage of this technique, it has been combined with neural networks in order to solve the inverse problem posed by the propagation of guided waves. As a result, an original, e cient and polyvalent characterization method has been obtained, which allowed us to determine the geometric properties and / or the elastic parameters of di erent plate-like structures. Structures made of silicon have been studied with this method. Finite element simulations and studies concerning the in uence of defects, including adhesion, on the waves propagation are also presented
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Schwartz, David, e David Schwartz. "Navigational Neural Coding and De-noising". Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625322.
Testo completoAbstract (sommario):
The work discussed in this thesis is the product of investigation on information and coding theoretic properties of colluding populations of navigationally relevant mammalian neurons. For brevity and completeness, that work is presented chronologically in the order in which it was investigated.
This thesis details coding theoretic properties of (and develop a model for communication between) colluding populations of spatially responsive neurons in the hippocampus (HC) and medial entorhinal cortex (MEC) through a hypothetical layer of interneurons (each of which posesses exclusively excitatory or inhibitory synapses). This work presents analysis of the changes in network structure induced by an anti-Hebbian learning process and translate these analyses into biologically testable hypotheses. Further, it is demonstrated that for appropriately parameterized codes (i.e. populations of grid and place cells in MEC and HC, respectively), this network is able to learn the code and correct for errors introduced by neural noise, potentially explaining the results of a correlational study: Place cell variability sharply decreases at a time that coincides with the maturation of the grid cell network in developing mice. Further, this work predicts that disruption of the grid cell network (e.g. via optogenetic inactivation and lesioning) should increase the variability of place cell firing, and impair decoding from these place cells' activities.
Continuing down this avenue, we consider how the inclusion of a population of the somewhat controversial time cells (purportedly residing in HC and MEC) impacts de-noising network structure, coding properties of the population of populations of all three classes of navigatory neuron, and denoisability. These results are translated to testable neurobiological predictions. Additionally, to ensure realistic stimulus statistics, locations and times are taken from real rat paths recorded from navigating rats in the Computational and Experimental Neuroscience Laboratory at the University of Arizona. Interestingly, while time cells exhibit some of the coding and information theoretic trends described in chapter 4, in certain cases, they admit surprising connectivity trends. Most surprisingly, after including time cells in this framework it was discovered that some classes of neural noise appear to improve decoding accuracy over the entire path while simultaneously impairing accuracy of decoding position and time independently.
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Blair, Joel. "Building a better Placode: Modeling Neural Plate Border interactions with hPSCs". University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627663141272833.
Testo completo
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Thelander, Jenny. "Neural Mechanisms Underlying Self-Localization in Rodents". Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-11339.
Testo completoAbstract (sommario):
The ability to self-localize and navigate in both stable and changing environments is crucial for the survival of many species. Research conducted on the non-human mammalian hippocampus and surrounding brain structures has uncovered several classes of spatial related cells. These cells provide the rest of the brain with knowledge of the animal’s location and direction—knowledge that is subsequently used in spatial navigation. This thesis provides an overview of three types of cells underlying this ability in rodents. First, place cells located in the hippocampus encode the animal’s specific location in the environment. Second, head direction cells found throughout the Papez circuit convey the angular direction of the animal’s head. Last, grid cells in the medial entorhinal cortex generate a regular triangular grid spanning the entire explored setting. The focus of this review lies on the most salient features of these types of cells. It is also considered how the cells respond to manipulations of external and internal information, as well as how different lesions affect their activity.
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Kreuzberger, Moritz. "Neuronale Verteilung des Enzyms Glutaminylzyklase im Kortex und der hippocampalen Formation des humanen Gehirns". Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-160140.
Testo completoAbstract (sommario):
Intra- und extrazelluläre ß-Amyloid-Ablagerungen (Abeta) sind ein neuropathologisches Hauptmerkmal der Alzheimerschen Demenz (AD). Aktuelle Studien belegen, dass nicht Abeta-Plaques, sondern Abeta-Oligomere die Schädigung von Synapsen und Nervenzellen verursachen und dass ihre Konzentration gut mit der Schwere der kognitiven Dysfunktion korreliert. Allerdings sind Abeta-Peptide eine heterogene Gruppe schwer wasserlöslicher Peptide mit zahlreichen C- und N-terminalen Modifikationen. Dabei hängt die Tendenz von Abeta-Peptiden Oligomeren zu bilden, ihre proteolytische Resistenz und ihr neurotoxisches Potential maßgeblich von ihrer N-terminalen Struktur ab. Abeta-Peptide, die N-terminal einen Pyroglutamyl-Laktamring (pE-Abeta) aufweisen, machen einen Hauptbestandteil der Abeta-Last in den frühen Stadien der AD aus. Diese modifizierten Abeta-Peptide aggregieren schneller als unmodifiziertes Abeta, sind gegen Proteolyse geschützt und wirken als Aggregationskeim für andere Abeta-Spezies. Das Enzym Glutaminylzyklase (QC) katalysiert die n-terminale pE-Modifikation von Abeta in vitro und in vivo und wird in Neuronenpopulationen gefunden, für die ein starker Verlust von Synapsen und Neuronen im Zusammenhang mit der AD beschrieben wurde. Diese Arbeit stellt die schichtspezifische Verteilung von QC im temporalen Kortex und der hippocampalen Formation von Alzheimerpatienten und Kontrollen vergleichend dar und zeigt einen direkten Zusammenhang zwischen der Überexpression von QC und der Vulnerabilität betreffender Neuronenpopulationen auf. Darüber hinaus bestätigen die vorgestellten Ergebnisse die These, wonach QC und pE-Abeta das Potential haben, nach axonalem Transport eine Kaskade in efferenten Hirnregionen zu initiieren, an deren Ende der Verlust von Nervenzellen steht. Diese Erkenntnisse unterstützen das Interesse an QC als Gegenstand zukünftiger Grundlagenforschung und Wirkstoffentwicklungen für die Therapie der ADIntra- and extracellular s-amyloid (Abeta) deposits are a major neuropathological hallmark of Alzheimer\'s disease (AD). Recent studies demonstrate that Abeta oligomers rather than Abeta plaques cause severe damage of synapses and nerve cells and in addition the concentration of Abeta oligomers correlates well with the severity of cognitive dysfunction. However, Abeta peptides are a heterogeneous group of poorly water-soluble peptides with various C- and N-terminal modifications. Biophysical properties of these peptides such as their propensity to form oligomers, their proteolytic resistance and their neurotoxic potential particularly depends on their N-terminal structure. Abeta-peptides that contain a pyroglutamyl-a-lactam ring at their N-Terminus (pE-Abeta) constitute a major component of the Abeta load in the early stages of AD. These modified Abeta-peptides aggregate faster than unmodified Abeta, are protected against proteolysis and act as aggregation seed for other Abeta-species. The enzyme glutaminyl cyclase (QC)catalyzes the cyclization of Abeta to pE-Abeta in vitro and in vivo and is found in neuronal populations for which a strong loss of synapses and neurons in the context of AD is described. This thesis presents the layer-specific distribution of QC in the temporal cortex and the hippocampal formation of Alzheimer\'s patients and controls, showing a direct correlation between the overexpression of QC and the vulnerability of respective neuronal populations. Moreover, the presented results confirm the hypothesis that QC and pE-Abeta have the potential to initiate a cascade leading to the loss of nerve cells due to axonal transport and release in efferent brain regions. These findings support the interest in QC as a subject of fundamental research and future drug developments for the treatment of AD
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Rossi, Christy Cortez. "Early development of two cell populations at the neural plate border : rohon-beard sensory neurons and neural crest cells /". Connect to full text via ProQuest. Limited to UCD Anschutz Medical Campus, 2008.
Cerca il testo completoAbstract (sommario):
Thesis (Ph.D. in Neuroscience) -- University of Colorado Denver, 2008.Includes bibliographical references (leaves 112-120). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;
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Grieves, Roderick McKinlay. "The neural basis of a cognitive map". Thesis, University of Stirling, 2015. http://hdl.handle.net/1893/21878.
Testo completoAbstract (sommario):
It has been proposed that as animals explore their environment they build and maintain a cognitive map, an internal representation of their surroundings (Tolman, 1948). We tested this hypothesis using a task designed to assess the ability of rats to make a spatial inference (take a novel shortcut)(Roberts et al., 2007). Our findings suggest that rats are unable to make a spontaneous spatial inference. Furthermore, they bear similarities to experiments which have been similarly unable to replicate or support Tolman’s (1948) findings. An inability to take novel shortcuts suggests that rats do not possess a cognitive map (Bennett, 1996). However, we found evidence of alternative learning strategies, such as latent learning (Tolman & Honzik, 1930b) , which suggest that rats may still be building such a representation, although it does not appear they are able to utilise this information to make complex spatial computations. Neurons found in the hippocampus show remarkable spatial modulation of their firing rate and have been suggested as a possible neural substrate for a cognitive map (O'Keefe & Nadel, 1978). However, the firing of these place cells often appears to be modulated by features of an animal’s behaviour (Ainge, Tamosiunaite, et al., 2007; Wood, Dudchenko, Robitsek, & Eichenbaum, 2000). For instance, previous experiments have demonstrated that the firing rate of place fields in the start box of some mazes are predictive of the animal’s final destination (Ainge, Tamosiunaite, et al., 2007; Ferbinteanu & Shapiro, 2003). We sought to understand whether this prospective firing is in fact related to the goal the rat is planning to navigate to or the route the rat is planning to take. Our results provide strong evidence for the latter, suggesting that rats may not be aware of the location of specific goals and may not be aware of their environment in the form of a contiguous map. However, we also found behavioural evidence that rats are aware of specific goal locations, suggesting that place cells in the hippocampus may not be responsible for this representation and that it may reside elsewhere (Hok, Chah, Save, & Poucet, 2013). Unlike their typical activity in an open field, place cells often have multiple place fields in geometrically similar areas of a multicompartment environment (Derdikman et al., 2009; Spiers et al., 2013). For example, Spiers et al. (2013) found that in an environment composed of four parallel compartments, place cells often fired similarly in multiple compartments, despite the active movement of the rat between them. We were able to replicate this phenomenon, furthermore, we were also able to show that if the compartments are arranged in a radial configuration this repetitive firing does not occur as frequently. We suggest that this place field repetition is driven by inputs from Boundary Vector Cells (BVCs) in neighbouring brain regions which are in turn greatly modulated by inputs from the head direction system. This is supported by a novel BVC model of place cell firing which predicts our observed results accurately. If place cells form the neural basis of a cognitive map one would predict spatial learning to be difficult in an environment where repetitive firing is observed frequently (Spiers et al., 2013). We tested this hypothesis by training animals on an odour discrimination task in the maze environments described above. We found that rats trained in the parallel version of the task were significantly impaired when compared to the radial version. These results support the hypothesis that place cells form the neural basis of a cognitive map; in environments where it is difficult to discriminate compartments based on the firing of place cells, rats find it similarly difficult to discriminate these compartments as shown by their behaviour. The experiments reported here are discussed in terms of a cognitive map, the likelihood that such a construct exists and the possibility that place cells form the neural basis of such a representation. Although the results of our experiments could be interpreted as evidence that animals do not possess a cognitive map, ultimately they suggest that animals do have a cognitive map and that place cells form a more than adequate substrate for this representation.
14
Bagušinskas, Donatas. "Automobilio numerio identifikavimo algoritmai". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110615_135256-26171.
Testo completoAbstract (sommario):
Šiame darbe aprašytas automobilio numerio identifikavimo uždavinys, šio uždavinio skaidymas į smulkesnes užduotis, tokias kaip numerio lokalizavimas nuotraukoje, numerio suskaidymas į atskirus simbolius, bei rastų simbolių identifikavimas. Kiekvienai šiai užduočiai realizuota po du algoritmus. Numerio lokalizavimo algoritmai remiasi kontūrų išskyrimu ir spalvų intensyvumu, bei morfologinėmis operacijomis nuotraukoje. Surasto numerio skaidymo į simbolius algoritmai remiasi statistiniu pasiskirstymu bei objektų išskyrimu. Simboliams atpažinti panaudota koreliacijos skaičiavimas tarp šablonų ir atpažįstamojo simbolio, bei dirbtinis neuroninis tinklas. Taip pat apžvelgta šiuo metu pasaulyje naudojamas technologijas ir algoritmai, sprendžiantys šį uždavinį bei palyginti rezultatai su savais.This paper describes the task of vehicle number identification. It is further divided into smaller tasks, such as the localization of the number in the picture, the splitting of the number into individual symbols and the identification of the located symbols. Two algorithms were allocated for each task. The number localization algorithm is based on the exclusion of the contours, colour intensity and morphological operations in the picture. The algorithms used to divide the symbols of the identified number are based on the statistical distribution and object separation. Correlation calculation is used between the templates, identifiable symbol and artificial neural network. Moreover, the paper discusses the technologies and algorithms currently used across the world when dealing with such task, and compares it with the results of this paper.
15
Audoin, Bertrand. "Etude par IRM cérébrale multimodalitaire des supports morphologiques et fonctionnels des troubles cognitifs au stade initial de la sclérose en plaques". Aix-Marseille 2, 2004. http://www.theses.fr/2004AIX20686.
Testo completo
16
Lyttle, David Nolan. "Modeling inhibition-mediated neural dynamics in the rodent spatial navigation system". Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/311105.
Testo completoAbstract (sommario):
The work presented in this dissertation focuses on the use of computational and mathematical models to investigate how mammalian brains construct and maintain stable representations of space and location. Recordings of the activities of cells in the hippocampus and entorhinal cortex have provided strong, direct evidence that these cells and brain areas are involved in generating internal representations of the location of an animal in space. The emphasis of the first two portions of the dissertation are on understanding the factors that influence the scale and stability of these representations, both of which are important for accurate spatial navigation. In addition, it is argued in both cases that many of the computations observed in these systems emerge at least in part as a consequence of a particular type of network structure, where excitatory neurons are driven by external sources, and then mutually inhibit each other via interactions mediated by inhibitory cells. The first contribution of this thesis, which is described in chapter 2, is an investigation into the origin of the change in the scale of spatial representations across the dorsoventral axis of the hippocampus. Here it will be argued that this change in scale is due to increased processing of nonspatial information, rather than a dorsoventral change in the scale of the spatially-modulated inputs to this structure. Chapter 3 explores the factors influencing the dynamical stability of class of pattern-forming networks known as continuous attractor networks, which have been used to model various components of the spatial navigation systems, including head direction cells, place cells, and grid cells. Here it will be shown that network architecture, the amount of input drive, and the timescales at which cells interact all influence the stability of the patterns formed by these networks. Finally, in chapter 4, a new technique for analyzing neural data is introduced. This technique is a spike train similarity measure designed to compare spike trains on the basis of shared inhibition and bursts.
17
Chen, Zetao. "Biologically-inspired place recognition with neural networks". Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/98550/1/Zetao_Chen_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis explores two aspects of biologically inspired methods for place recognition, a key component of navigation. The first key theme is to explore the multi-scale mapping principles inspired by the recent discovery of overlapping, multi-scale spatial maps in the rodent brain, while the second develops biologically inspired Convolutional Neural Networks (CNNs) for place recognition. We presented a series of studies comprehensively demonstrating for the first time how both a rodent brain-inspired multi-scale mapping system and CNN-based techniques enable state of the art place recognition performance.
18
Josse, Goulven. "Variabilité inter-individuelle des bases neurales du langage : relations avec la préférence manuelle, l'anatomie du planum temporale et le volume cérébral". Caen, 2003. http://www.theses.fr/2003CAEN3100.
Testo completoAbstract (sommario):
Depuis quelques années, la neuroimagerie autorise l'étude de la variabilité inter-individuelle des aires du langage chez le sujet sain. Permettant à la fois une étude anatomique et fonctionnelle, cette nouvelle approche nous a servi à décrire la variabilité des bases neurales de la compréhension et de la production orale. La taille du planum temporale gauche et le volume cérébral ont permis d'expliquer une part importante de cette variabilité. Ces facteurs pourraient être des marqueurs de la spécialisation hémisphérique pour le traitement rapide des sons, potentiellement à la base de la spécialisation hémisphérique pour le langage. En accord avec la littérature, nous avons aussi observé un lien entre préférence manuelle et variabilité neurofonctionnelle. Ce résultat est en faveur d'une origine gestuelle du langage, impliquant l'aire de Broca. D'une manière générale, cette thèse montre la complexité mais aussi l'utilité de l'étude de la variabilité des bases neurales du langage.
19
Reuter, Françoise. "Perturbations cognitives au stade initial de la sclérose en plaques : Corrélats structuraux et application d'un modèle d'accès à la conscience". Aix-Marseille 2, 2008. http://www.theses.fr/2008AIX20698.
Testo completo
20
Kolibacz, Eric. "Classification of incorrectly picked components using Convolutional Neural Networks". Thesis, KTH, Robotik, perception och lärande, RPL, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230732.
Testo completoAbstract (sommario):
Printed circuit boards used in most ordinary electrical devices are usually equipped through an assembly line. Pick and place machines as part of those lines require accurate detection of incorrectly picked components, and this is commonly performed via image analysis. The goal of this project is to investigate if we can achieve state-of-the-art performance in an industrial quality assurance task through the application of artificial neural networks. Experiments regarding different network architectures and data modifications are conducted to achieve precise image classification. Although the classification rates do not surpass or equal the rates of the existing vision-based detection system, there remains great potential in the deployment of a machine-learning-based algorithm into pick and place machines.Tryckta kretskort som används i de flesta vanliga elektroniska produkter är vanligtvis monterade i monteringslinjer. Ytmonteringsmaskinerna i dessa monteringslinjer kräver exakt detektering av felaktigt plockade komponenter, vilket ofta genomförs med hjälp av bildanalys. Målet med detta projekt är att undersöka om vi kan uppnå framstående resultat i en industriell kvalitetssäkringsuppgift genom användandet av artificiella neuronnätverk. Experiment utförs med olika nätverksarkitekturer och datamodifikationer för att uppnå exakt bildklassificering. Även om klassificeringsgraderna inte uppnår klassificeringsgraderna hos existerande synbaserade detekteringssystem, finns en stor potential för användandet av maskininlärningsbaserade algoritmer i ytmonteringsmaskiner.
21
Masante-Roca, Ingwild. "Attraction de l'eudémis de la vigne par la plante hôte : gènes, cerveau et comportement". Bordeaux 2, 2004. http://www.theses.fr/2004BOR21109.
Testo completoAbstract (sommario):
L'olfaction joue un rôle majeur dans la recherche de la plante hôte chez les papillons de nuit. La compréhension des mécanismes d'attraction d'un ravageur, l'Eudémis de la vigne, Lobesia botrana, par sa plante hôte est essentielle pour développer de nouvelles méthodes de lutte biologique. J'ai étudié le comportement olfactif ainsi que les bases neurophysiologiques et génétiques chez ce tortricide. Les expériences en tunnel de vol ont montré que seules les femelles accouplées répondent aux odeurs de plante. Les expériences d'électrophysiologie ont révélé que la structure et ka fonction des neurones dans le lobe antennaire (AL), étaient corrélées et varient suivant le sexe et l'état sexuel. Un atlas du AL en 3D a été construit et des glomérules ayant des arborisations dendritiques de neurones caractérisés physiologiquement ont été identifiés. J'ai identifié et cloné un gène, Lbfor (L. Botrana foraging). Son expression dans le cerveau étant plus élevée chez les femelles accouplées que chez les vierges, cela suggère un rôle dans la plasticité comportementaleOlfaction plays a major role in the process of host plant finding in moths. The understanding of the host plant attraction is essential to develop new biological control methods against a serious pest insect, the European grapevine moth, Lobesia botrana. I studied olfactory guided behaviour, as well as its neurological basis in this tortricid species. Wind tunnel experiments showed that only mated females responded to grapevine plant odours. Electrophysiological experiments revealed that structure and function of neurons in the primary olfactory centre, the antennal lobe (AL), were correlated and varied depending on sex and mating status. A complete 3D-AL atlas was reconstructed and glomeruli housing arborisations of physiologically characterised neurons were identified. I identified and cloned a gene, Lbfor (L. Botrana foraging). Its expression in the brain being is higher in mated than in virgin females, thus suggesting a role in behavioural plasticity
22
BJOERKLUND, TOMAS PER ROLF. "License Plate Recognition using Convolutional Neural Networks Trained on Synthetic Images". Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2709876.
Testo completoAbstract (sommario):
In this thesis, we propose a license plate recognition system and study the feasibility
of using synthetic training samples to train convolutional neural networks for a
practical application.
First we develop a modular framework for synthetic license plate generation; to
generate different license plate types (or other objects) only the first module needs
to be adapted. The other modules apply variations to the training samples such as
background, occlusions, camera perspective projection, object noise and camera
acquisition noise, with the aim to achieve enough variation of the object that the
trained networks will also recognize real objects of the same class.
Then we design two convolutional neural networks of low-complexity for license
plate detection and character recognition. Both are designed for simultaneous
classification and localization by branching the networks into a classification and a
regression branch and are trained end-to-end simultaneously over both branches, on
only our synthetic training samples.
To recognize real license plates, we design a pipeline for scale invariant license
plate detection with a scale pyramid and a fully convolutional application of the
license plate detection network in order to detect any number of license plates and
of any scale in an image. Before character classification is applied, potential plate
regions are un-skewed based on the detected plate location in order to achieve an as
optimal representation of the characters as possible. The character classification is
also performed with a fully convolutional sweep to simultaneously find all characters
at once.
Both the plate and the character stages apply a refinement classification where
initial classifications are first centered and rescaled. We show that this simple, yet
effective trick greatly improves the accuracy of our classifications, and at a small
increase of complexity. To our knowledge, this trick has not been exploited before.
To show the effectiveness of our system we first apply it on a dataset of photos
of Italian license plates to evaluate the different stages of our system and which
effect the classification thresholds have on the accuracy. We also find robust training
parameters and thresholds that are reliable for classification without any need for
calibration on a validation set of real annotated samples (which may not always be
available) and achieve a balanced precision and recall on the set of Italian license
plates, both in excess of 98%.
Finally, to show that our system generalizes to new plate types, we compare our
system to two reference system on a dataset of Taiwanese license plates. For this, we
only modify the first module of the synthetic plate generation algorithm to produce
Taiwanese license plates and adjust parameters regarding plate dimensions, then we
train our networks and apply the classification pipeline, using the robust parameters,
on the Taiwanese reference dataset. We achieve state-of-the-art performance on plate
detection (99.86% precision and 99.1% recall), single character detection (99.6%)
and full license reading (98.7%).
23
Drottsgård, Alexander, e Jens Andreassen. "Effektivisering av automatiserad igenkänning av registreringsskyltar med hjälp av artificiella neurala nätverk för användning inom smarta hem". Thesis, Malmö universitet, Fakulteten för teknik och samhälle (TS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-20803.
Testo completoAbstract (sommario):
Konceptet automatiserad igenkänning och avläsning av registreringsskyltarhar utvecklats mycket de senaste åren och användningen av Artificiellaneurala nätverk har introducerats i liten skala med lovande resultat. Viundersökte möjligheten att använda detta i ett automatiserat system förgarageportar och implementerade en prototyp för testning. Den traditionellaprocessen för att läsa av en skylt kräver flera steg, i vissa fall upp till fem.Dessa steg ger alla en felmarginal som aggregerat kan leda till över 30% riskför ett misslyckat resultat. I denna uppsats adresseras detta problem och medhjälp av att använda oss utav Artificiella neurala nätverk utvecklades enkortare process med endast två steg för att läsa en skylt, (1) lokaliseraregistreringsskylten (2) läsa karaktärerna på registreringsskylten. Dettaminskar antalet steg till hälften av den traditionella processen samt minskarrisken för fel med 13%. Vi gjorde en Litteraturstudie för att identifiera detlämpligaste neurala nätverket för uppgiften att lokalisera registreringsskyltarmed vår miljös begränsningar samt möjligheter i åtanke. Detta ledde tillanvändandet av Faster R-CNN, en algoritm som använder ett antal artificiellaneurala nätverk. Vi har använt metoden Design och Creation för att skapa enproof of concept prototyp som använder vårt föreslagna tillvägagångssätt föratt bevisa att det är möjligt att implementera detta i en verklig miljö.The concept of automated recognition and reading of license plates haveevolved a lot the last years and the use of Artificial neural networks have beenintroduced in a small scale with promising results. We looked into thepossibility of using this in an automated garage port system and weimplemented a prototype for testing. The traditional process for reading alicense plate requires multiple steps, sometimes up to five. These steps all givea margin of error which aggregated sometimes leads to over 30% risk forfailure. In this paper we addressed this issue and with the help of a Artificialneural network. We developed a process with only two steps for the entireprocess of reading a license plate, (1) localize license plate (2) read thecharacters on the plate. This reduced the number of steps to half of theprevious number and also reduced the risk for errors with 13%. We performeda Literature Review to find the best suited algorithm for the task oflocalization of the license plate in our specific environment. We found FasterR-CNN, a algorithm which uses multiple artificial neural networks. We usedthe method Design and Creation to implement a proof of concept prototypeusing our approach which proved that this is possible to do in a realenvironment.
24
Wei, Wen. "Apprentissage automatique des altérations cérébrales causées par la sclérose en plaques en neuro-imagerie multimodale". Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4021.
Testo completoAbstract (sommario):
La sclérose en plaques (SEP) est la maladie neurologique évolutive la plus courante chez les jeunes adultes dans le monde et représente donc un problème de santé publique majeur avec environ 90 000 patients en France et plus de 500 000 personnes atteintes de SEP en Europe. Afin d'optimiser les traitements, il est essentiel de pouvoir mesurer et suivre les altérations cérébrales chez les patients atteints de SEP. En fait, la SEP est une maladie aux multiples facettes qui implique différents types d'altérations, telles que les dommages et la réparation de la myéline. Selon cette observation, la neuroimagerie multimodale est nécessaire pour caractériser pleinement la maladie. L'imagerie par résonance magnétique (IRM) est devenue un biomarqueur d'imagerie fondamental pour la sclérose en plaques en raison de sa haute sensibilité à révéler des anomalies tissulaires macroscopiques chez les patients atteints de SEP. L'IRM conventionnelle fournit un moyen direct de détecter les lésions de SEP et leurs changements, et joue un rôle dominant dans les critères diagnostiques de la SEP. De plus, l'imagerie par tomographie par émission de positons (TEP), une autre modalité d'imagerie, peut fournir des informations fonctionnelles et détecter les changements tissulaires cibles au niveau cellulaire et moléculaire en utilisant divers radiotraceurs. Par exemple, en utilisant le radiotraceur [11C]PIB, la TEP permet une mesure pathologique directe de l'altération de la myéline. Cependant, en milieu clinique, toutes les modalités ne sont pas disponibles pour diverses raisons. Dans cette thèse, nous nous concentrons donc sur l'apprentissage et la prédiction des altérations cérébrales dérivées des modalités manquantes dans la SEP à partir de données de neuroimagerie multimodaleMultiple Sclerosis (MS) is the most common progressive neurological disease of young adults worldwide and thus represents a major public health issue with about 90,000 patients in France and more than 500,000 people affected with MS in Europe. In order to optimize treatments, it is essential to be able to measure and track brain alterations in MS patients. In fact, MS is a multi-faceted disease which involves different types of alterations, such as myelin damage and repair. Under this observation, multimodal neuroimaging are needed to fully characterize the disease. Magnetic resonance imaging (MRI) has emerged as a fundamental imaging biomarker for multiple sclerosis because of its high sensitivity to reveal macroscopic tissue abnormalities in patients with MS. Conventional MR scanning provides a direct way to detect MS lesions and their changes, and plays a dominant role in the diagnostic criteria of MS. Moreover, positron emission tomography (PET) imaging, an alternative imaging modality, can provide functional information and detect target tissue changes at the cellular and molecular level by using various radiotracers. For example, by using the radiotracer [11C]PIB, PET allows a direct pathological measure of myelin alteration. However, in clinical settings, not all the modalities are available because of various reasons. In this thesis, we therefore focus on learning and predicting missing-modality-derived brain alterations in MS from multimodal neuroimaging data
25
Chancan, Leon Marvin Aldo. "The role of motion-and-visual perception in robot place learning and navigation". Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/229769/8/Marvin%20Aldo_Chancan%20Leon_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis was a step forward in developing new robot learning-based localisation and navigation systems using real world data and simulation environments. Three new methods were proposed to provide new insights on the role of joint motion-and-vision-based end-to-end robot learning in both place recognition and navigation tasks, within modern reinforcement learning and deep learning frameworks. Inspired by biological neural circuits underlying these complex tasks in insect and rat mammalian brains, these methods were shown to be orders of magnitude faster than classical techniques, while setting new state-of-the-art performance standards in terms of accuracy, throughput and latency.
26
Liu, Boqi. "The gene regulatory network in the anterior neural plate border of ascidian embryos". Kyoto University, 2020. http://hdl.handle.net/2433/253119.
Testo completo
27
Patthey, Cédric. "Induction of the isthmic organizer and specification of the neural plate border". Doctoral thesis, Umeå universitet, Umeå centrum för molekylär medicin (UCMM), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1811.
Testo completoAbstract (sommario):
The vertebrate nervous system is extremely complex and contains a wide diversity of cell types. The formation of a functional nervous system requires the differential specification of progenitor cells at the right time and place. The generation of many different types of neurons along the rostro-caudal axis of the CNS begins with the initial specification of a few progenitor domains. This initial coarse pattern is refined by so-called secondary organizers arising at boundaries between these domains. The Isthmic Organizer (IsO) is a secondary organizer located at the boundary between the midbrain and the hindbrain. Although the function and maintenance of the IsO are well understood, the processes underlying its initial specification have remained elusive. In the present work we provide evidence that convergent Wnt and FGF signals initiate the specification of the IsO during late gastrulation as part of the neural caudalization process. The initial step in the generation of the nervous system is the division of the embryonic ectoderm into three cell populations: neural cells giving rise to the CNS, neural plate border cells giving rise to the peripheral nervous system, and epidermal cells giving rise to the outer layer of the skin. While the choice between neural and epidermal fate has been well studied, the mechanism by which neural plate border cells are generated is less well understood. At rostral levels of the neuraxis, the neural plate border gives rise to the olfactory and lens placodes, thickenings of the surface ectoderm from which sensory organs are derived. More caudally, the neural plate border generates neural crest cells, a transient population that migrates extensively and contributes to neurons and glia of the peripheral nervous system. How the early patterning of the central and peripheral nervous systems are coordinated has remained poorly understood. Here we show that the generation of neural plate border cells is initiated at the late blastula stage and involves two phases. During the first phase, neural plate border cells are exposed to Wnt signals in the absence of BMP signals. Simultaneous exposure to Wnt and BMP signals at this early stage leads to epidermal induction. Wnt signals induce expression of Bmp4, thereby regulating the sequential exposure of cells to Wnt and BMP signals. During the second phase, at the late gastrula stage, BMP signals play an instructive role to specify neural plate border cells of either placodal or neural crest character depending on the status of Wnt signaling. At this stage, Wnt signals promote caudal character simultaneously in the neural plate border and in the neural ectoderm. Thus, the choice between epidermal and neural plate border specification is mediated by an interplay of Wnt and BMP signals that represents a novel mechanism involving temporal control of BMP activity by Wnt signals. Moreover, the early development of the central and peripheral nervous systems are coordinated by simultaneous caudalization by Wnt signals.
28
Chen, Songqing. "Development of a neural network based software package for the automatic recognition of license plate characters". Ohio : Ohio University, 1992. http://www.ohiolink.edu/etd/view.cgi?ohiou1172092299.
Testo completo
29
Rosay, Sophie. "A statistical mechanics approach to the modelling and analysis of place-cell activity". Thesis, Paris, Ecole normale supérieure, 2014. http://www.theses.fr/2014ENSU0010/document.
Testo completoAbstract (sommario):
Les cellules de lieu de l’hippocampe sont des neurones aux propriétés intrigantes, commele fait que leur activité soit corrélée à la position spatiale de l’animal. Il est généralementconsidéré que ces propriétés peuvent être expliquées en grande partie par les comporte-ments collectifs de modèles schématiques de neurones en interaction. La physique statis-tique fournit des outils permettant l’étude analytique et numérique de ces comportementscollectifs.Nous abordons ici le problème de l’utilisation de ces outils dans le cadre du paradigmedu “réseau attracteur”, une hypothèse théorique sur la nature de la mémoire. La questionest de savoir comment ces méthodes et ce cadre théorique peuvent aider à comprendrel’activité des cellules de lieu. Dans un premier temps, nous proposons un modèle de cellulesde lieu dans lequel la localisation spatiale de l’activité neuronale est le résultat d’unedynamique d’attracteur. Plusieurs aspects des propriétés collectives de ce modèle sontétudiés. La simplicité du modèle permet de les comprendre en profondeur. Le diagrammede phase du modèle est calculé et discuté en comparaison avec des travaux précedents.Du point de vue dynamique, l’évolution du système présente des motifs particulièrementriches. La seconde partie de cette thèse est à propos du décodage de l’activité des cellulesde lieu. Nous nous demandons quelle est l’implication de l’hypothèse des attracteurs surce problème. Nous comparons plusieurs méthodes de décodage et leurs résultats sur letraitement de données expérimentalesPlace cells in the hippocampus are neurons with interesting properties such as the corre-lation between their activity and the animal’s position in space. It is believed that theseproperties can be for the most part understood by collective behaviours of models of inter-acting simplified neurons. Statistical mechanics provides tools permitting to study thesecollective behaviours, both analytically and numerically.Here, we address how these tools can be used to understand place-cell activity withinthe attractor neural network paradigm, a theory for memory. We first propose a modelfor place cells in which the formation of a localized bump of activity is accounted for byattractor dynamics. Several aspects of the collective properties of this model are studied.Thanks to the simplicity of the model, they can be understood in great detail. The phasediagram of the model is computed and discussed in relation with previous works on at-tractor neural networks. The dynamical evolution of the system displays particularly richpatterns. The second part of this thesis deals with decoding place-cell activity, and theimplications of the attractor hypothesis on this problem. We compare several decodingmethods and their results on the processing of experimental recordings of place cells in afreely behaving rat
30
Lucas, Marsha E. "Requirement of Hand2 in Noradrenergic Differentiation of Sympathetic Neurons and Zebrafish Hatchback Required for Neural Crest and Lateral Mesoderm Development". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1211997609.
Testo completo
31
An, Min. "Positional cloning and functional analysis of the SF3B1gene in zebrafish". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180528932.
Testo completo
32
Liu, Youhua. "Efficient Methods for Structural Analysis of Built-Up Wings". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/77972.
Testo completoAbstract (sommario):
The aerospace industry is increasingly coming to the conclusion that physics-based high-fidelity models need to be used as early as possible in the design of its products. At the preliminary design stage of wing structures, though highly desirable for its high accuracy, a detailed finite element analysis(FEA) is often not feasible due to the prohibitive preparation time for the FE model data and high computation cost caused by large degrees of freedom. In view of this situation, often equivalent beam models are used for the purpose of obtaining global solutions. However, for wings with low aspect ratio, the use of equivalent beam models is questionable, and using an equivalent plate model would be more promising.
An efficient method, Equivalent Plate Analysis or simply EPA, using an equivalent plate model, is developed in the present work for studying the static and free-vibration problems of built-up wing structures composed of skins, spars, and ribs. The model includes the transverse shear effects by treating the built-up wing as a plate following the Reissner-Mindlin theory (FSDT). The Ritz method is used with the Legendre polynomials being employed as the trial functions. Formulations are such that there is no limitation on the wing thickness distribution. This method is evaluated, by comparing the results with those obtained using MSC/NASTRAN, for a set of examples including both static and dynamic problems.
The Equivalent Plate Analysis (EPA) as explained above is also used as a basis for generating other efficient methods for the early design stage of wing structures, such that they can be incorporated with optimization tools into the process of searching for an optimal design. In the search for an optimal design, it is essential to assess the structural responses quickly at any design space point. For such purpose, the FEA or even the above EPA, which establishes the stiffness and mass matrices by integrating contributions spar by spar, rib by rib, are not efficient enough.
One approach is to use the Artificial Neural Network (ANN), or simply called Neural Network (NN) as a means of simulating the structural responses of wings. Upon an investigation of applications of NN in structural engineering, methods of using NN for the present purpose are explored in two directions, i.e. the direct application and the indirect application. The direct method uses FEA or EPA generated results directly as the output. In the indirect method, the wing inner-structure is combined with the skins to form an "equivalent" material. The constitutive matrix, which relates the stress vector to the strain vector, and the density of the equivalent material are obtained by enforcing mass and stiffness matrix equities with regard to the EPA in a least-square sense. Neural networks for these material properties are trained in terms of the design variables of the wing structure. It is shown that this EPA with indirect application of Neural Networks, or simply called an Equivalent Skin Analysis (ESA) of the wing structure, is more efficient than the EPA and still fairly good results can be obtained.
Another approach is to use the sensitivity techniques. Sensitivity techniques are frequently used in structural design practices for searching the optimal solutions near a baseline design. In the present work, the modal response of general trapezoidal wing structures is approximated using shape sensitivities up to the second order, and the use of second order sensitivities proved to be yielding much better results than the case where only first order sensitivities are used. Also different approaches of computing the derivatives are investigated. In a design space with a lot of design points, when sensitivities at each design point are obtained, it is shown that the global variation in the design space can be readily given based on these sensitivities.Ph. D.
33
Zhao, Ping. "Low-Complexity Deep Learning-Based Light Field Image Quality Assessment". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25977.
Testo completoAbstract (sommario):
Light field image quality assessment (LF-IQA) has attracted increasing research interests due to the fast-growing demands for immersive media experience. The majority of existing LF-IQA metrics, however, heavily rely on high-complexity statistics-based feature extraction for the quality assessment task, which will be hardly sustainable in real-time applications or power-constrained consumer electronic devices in future real-life applications.
In this research, a low-complexity Deep learning-based Light Field Image Quality Evaluator (DeLFIQE) is proposed to automatically and efficiently extract features for LF-IQA. To the best of my knowledge, this is the first attempt in LF-IQA with a dedicatedly designed convolutional neural network (CNN) based deep learning model.
First, to significantly accelerate the training process, discriminative Epipolar Plane Image (EPI) patches, instead of the full light field images (LFIs) or full EPIs, are obtained and used as input for training and testing in DeLFIQE. By utilizing the EPI patches as input, the quality evaluation of 4-D LFIs is converted to the evaluation of 2-D EPI patches, thus significantly reducing the computational complexity. Furthermore, discriminative EPI patches are selected in such a way that they contain most of the distortion information, thus further improving the training efficiency. Second, to improve the quality assessment accuracy and robustness, a multi-task learning mechanism is designed and employed in DeLFIQE. Specifically, alongside the main task that predicts the final quality score, an auxiliary classification task is designed to classify LFIs based on their distortion types and severity levels. That way, the features are extracted to reflect the distortion types and severity levels, which in turn helps the main task improve the accuracy and robustness of the prediction. The extensive experiments show that DeLFIQE outperforms state-of-the-art metrics from both accuracy and correlation perspectives, especially on benchmark LF datasets of high angular resolutions.
When tested on the LF datasets of low angular resolutions, however, the performance of DeLFIQE slightly declines, although still remains competitive. It is believed that it is due to the fact that the distortion feature information contained in the EPI patches gets reduced with the decrease of the LFIs’ angular resolutions, thus reducing the training efficiency and the overall performance of DeLFIQE.
Therefore, a General-purpose deep learning-based Light Field Image Quality Evaluator (GeLFIQE) is proposed to perform accurately and efficiently on LF datasets of both high and low angular resolutions. First, a deep CNN model is pre-trained on one of the most comprehensive benchmark LF datasets of high angular resolutions containing abundant distortion features. Next, the features learned from the pre-trained model are transferred to the target LF dataset-specific CNN model to help improve the generalisation and overall performance on low-resolution LFIs containing fewer distortion features. The experimental results show that GeLFIQE substantially improves the performance of DeLFIQE on low-resolution LF datasets, which makes it a real general-purpose LF-IQA metric for LF datasets of various resolutions.
34
Gróf, Zoltán. "Realizace rozdělujících nadploch". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219781.
Testo completoAbstract (sommario):
The main aim of this master's thesis is to describe the subject of the implementation of decision boundaries with the help of artificial neural networks. The objective is to present theoretical knowledge concerning this field and on practical examples prove these statements. The work contains basic theoretical description of the field of pattern recognition and the field of feature based representation of objects. A classificator working on the basis of Bayes decision is presented in this part, and other types of classificators are named as well. The work then deals with artificial neural networks in more detail; it contains a theoretical description of their function and their abilities in the creation of decision boundaries in the feature plane. Examples are shown from literature for the use of neural networks in corresponding problems. As part of this work, the program ANN-DeBC was created using Matlab, for the generation of practical results about the usage of feed-forward neural networks for the implementation of decision boundaries. The work contains a detailed description of this program, and the achieved results are presented and analyzed. It is shown as well, how artificial neural networks are creating decision boundaries in the form of geometrical shapes. The effects of the chosen topology of the neural network and the number of training samples on the success of the classification are observed, and the minimal values of these parameters are determined for the successful creation of decision boundaries at the individual examples. Furthermore, it's presented how the neural networks behave at the classification of realistically distributed training samples, and what methods can affect the shape of the created decision boundaries.
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Langlet, Jonatan. "Towards Machine Learning Inference in the Data Plane". Thesis, Karlstads universitet, Institutionen för matematik och datavetenskap (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-72875.
Testo completoAbstract (sommario):
Recently, machine learning has been considered an important tool for various networkingrelated use cases such as intrusion detection, flow classification, etc. Traditionally, machinelearning based classification algorithms run on dedicated machines that are outside of thefast path, e.g. on Deep Packet Inspection boxes, etc. This imposes additional latency inorder to detect threats or classify the flows.With the recent advance of programmable data planes, implementing advanced function-ality directly in the fast path is now a possibility. In this thesis, we propose to implementArtificial Neural Network inference together with flow metadata extraction directly in thedata plane of P4 programmable switches, routers, or Network Interface Cards (NICs).We design a P4 pipeline, optimize the memory and computational operations for our dataplane target, a programmable NIC with Micro-C external support. The results show thatneural networks of a reasonable size (i.e. 3 hidden layers with 30 neurons each) can pro-cess flows totaling over a million packets per second, while the packet latency impact fromextracting a total of 46 features is 1.85μs.
36
Jiang, Nan. "Plasticité de la transmission synaptique dans l’hippocampe et excitabilité intrinsèque dans un modèle murin de la maladie d’Alzheimer". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0137/document.
Testo completoAbstract (sommario):
La maladie d'Azheimer (MA) est une pathologie neurodégénérative qui est liée dans ses stades précoces à un dysfonctionnement synaptique et une perte de synapses. De nombreuses données cliniques obtenues chez des patients mais également des données expérimentales obtenues sur des modèles murins de la MA montrent qu'il existe un dimorphisme sexuel s'exprimant par un dépôt de plaques amyloïdes supérieur et une apparition précoce de troubles mnésiques chez les souris femelles par rapport aux souris mâles. Dans ce travail, nous avons étudié les altérations moléculaires et cellulaires de la MA ainsi que les déficits cognitifs associés chez la souris femelle APP/PS1, un modèle murin double transgénique de la MA. En parallèle nous avons étudié les altérations de la transmission et de la plasticité synaptique dans le stratum moleculare, une couche proche du gyrus dentelé (DG) en raison de la forte densité de plaques amyloïdes dans cette région de l'hippocampe.Nous avons mis en évidence la présence de nombreuses plaques amyloïdes dans le DG en quantité supérieure chez les femelles âgées de 6 mois par rapport aux mâles du même âge ainsi qu'une forte activation des cellules gliales astrocytes et microglie. Ces altérations moléculaires et cellulaires s'accompagnent de déficits mnésiques hippocampo-dépendants (test du comportement de peur conditionné et test de la nouvelle localisation spatiale d'un objet) dès l'âge de 4 mois chez les femelles alors que les mâles ne présentent aucun déficit jusqu'à l'âge de 12 mois.Nous avons alors étudié les propriétés électriques des neurones du gyrus dentelé (DG), la transmission et la plasticité de la synapse voie perforante - neurones du gyrus dentelé (synapse PP-DG) chez la souris femelle âgée de 6 mois en comparant les deux génotypes APP/PS1 vs sauvage.Les neurones du DG présentent deux populations distinctes en terme de résistance d'entrée et de patron de décharge de potentiels d'action (PAs). A l'inverse, le potentiel membranaire de repos, la résistance d'entrée, le seuil d'activation et l'amplitude du potentiel d'action ne sont pas modifiés chez la souris APP/PS1 vs la souris sauvage. La fréquence de décharge des potentiels d'action est augmentée chez la souris APP/PS1 sans que la probabilité de décharge en fonction de la pente du pied du potentiel d'action (courbe E-S) soit différente entre la souris APP/PS1 et la souris sauvage. La transmission basale à la synapse PP-DG est modifiée chez la souris APP/PS1 vs la souris sauvage sans altérations du ratio AMPA/NMDA ni de l'index de rectification AMPA. La fréquence des courants miniatures NMDA est augmentée dans les neurones DG de la souris APP/PS1 vs la souris sauvage ce qui suggère le démasquage de synapses silencieuses qui n'expriment peu ou pas de récepteurs AMPA. La potentialisation à long terme (PLT) de l'amplitude des potentiels d'action synchrone est diminuée d'environ 50% chez la souris APP/PS1. La diminution de la PLT observée chez la souris APP/PS1 est en partie liée à des altérations des propriétés intrinsèques des neurones du DG comme le montre le déplacement des courbes E-S induit par la PLT qui traduit une augmentation d'excitabilité de la souris APP/PS1.En conclusion nos résultats montrent un dimorphisme sexuel important avec un dépôt des plaques amyloïdes et une activation neuroinflammatoire des cellules gliales plus précoce chez la souris femelle vs mâle. En parallèle, des déficits importants de la mémoire hippocampale-dépendante sont observés ainsi que des altérations de la transmission et de la plasticité synaptique à la synapse voie perforante - neurones du gyrus dentelé, une synapse clé de l'intégration des informations mnésiques en provenance du cortex enthorhinalAzheimer's disease (AD) is a neurodegenerative disease that is linked in its early stage to synaptic dysfunction and loss of synapses. Numerous clinical data obtained from patients but also experimental data obtained on mouse models of AD show that there is a sexual dimorphism evidenced by a higher amyloid plaque deposition and an early onset of memory disorders in female mice compared to male mice.In this work, we investigated the molecular and cellular alterations of AD as well as the associated cognitive deficits in female APP/PS1 mice, a double transgenic murine model of AD. In parallel we studied the alterations of hippocampal synaptic transmission and plasticity in the stratum moleculare, a layer in the vicinity of the dentate gyrus (DG) which specifically displayed a high density of amyloid plaques. We showed the presence of numerous amyloid plaques in the DG in a larger amount in 6 month old females compared to age-matched males as well as a strong activation of astrocyte and microglia glial cells. These molecular and cellular alterations are accompanied by hippocampo-dependent memory deficits (contextual fear conditioning and novel object place recognition task) from the age of 4 months in females whereas males have no deficit until the age of 12 months. We then studied the electrical properties of DG neurons, the transmission and the plasticity of the perforant pathway - DG neurons (PP-DG synapse) in the 6-month old female mouse by comparing the two genotypes APP/PS1 vs wild type (WT).In both genotypes, DG neurons displayed two distinct populations in terms of input resistance and action potential discharge pattern (APs). In contrast, the resting membrane potential, the input resistance, the activation threshold and the amplitude PAs were not modified in APP/PS1 vs WT. The frequency of discharge of APs was increased in APP/PS1 without shift of E-S curve which relates EPSP-slopes to the associated AP firing probability.Basal transmission at the PP-DG synapse was altered in the APP/PS1 mouse vs WT without alterations in the AMPA/NMDA ratio or the AMPA rectification index. The frequency of the NMDA miniature currents was increased in APP/PS1 DG neurons vs WT which suggests the unmasking of silent synapses that express almost no AMPA receptors. The long term potentiation (LTP) of population spike amplitude was decreased by approximately 50% in APP/PS1 mice. The decrease in LTP observed in APP/PS1 was partly related to alterations in the intrinsic properties of DG neurons as evidenced by LTP-induced shifts of E-S curves, which reflects an increased excitability for APP/PS1 mice.In conclusion our results show a prominent sexual dimorphism with much earlier amyloid plaque deposition, neuroinflammatory glial activation in female vs male APP/PS1. In parallel, significant deficits in hippocampal-dependent memory are observed as well as alterations of synaptic transmission and plasticity at the PP-DG synapse, a key synapse of the integration of mnesic informations originated from the entorhinal cortex
37
Varga, Adrienn Gabriella. "The Neural Basis of Head Direction and Spatial Context in the Insect Central Complex". Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1487249074487484.
Testo completo
38
Wittler, Lars. "Anteriore Musterbildung im Wirbeltierembryo die Induktion von Vorderhirn und Herz /". Doctoral thesis, [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=967365570.
Testo completo
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Skřivánková, Barbora. "Anonymizace SPZ vozidel". Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2016. http://www.nusl.cz/ntk/nusl-255442.
Testo completoAbstract (sommario):
While browsing an online map server, continuous photographs of certain places can be browsed as well. When the map service takes pictures of a public space, there are some personal data captured as well (i.e. faces, car licence plates). The goal of this thesis is the design of automated car licence plates anonymization system, optimized for the Panorama service provided by the Seznam.cz a.s. corporation. In this thesis, the process of car licence plate anonymization is divided into two parts: the first one solves a detection of cars and the second solves a car licence plate localization in the selected image. The car detection is based on the deep neural network approach, the car licence plate localization is solved by using a fully connected neural network performing a regression task. The goal of this thesis is to get over the disadvantages of commercial solution used nowadays. These are false posititive results and high computational complexity. Results of this thesis are not as good as expected. The reason could be a dataset provided by Seznam.cz a.s. corporation, which seemed to be robust enough in the beginning, but in the end it showed up to be not suffice enough to train the neural network.
40
Borg, Denis. "Implementação de uma rede neural em ambiente foundation fieldbus para computação de vazão simulando um instrumento multivariável". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-29072011-100528/.
Testo completoAbstract (sommario):
Esta dissertação propõe o desenvolvimento de uma rede neural artificial (RNA) direcionada a ambientes foundation fieldbus para realização do cálculo de vazão em dutos fechados. Para tanto, a metodologia proposta utiliza-se de medidas de pressão, temperatura e pressão diferencial, as quais normalmente estão disponíveis em plantas industriais. A principal motivação do emprego das redes neurais reside no seu baixo custo e simplicidade de implementação, o que possibilita o emprego de apenas blocos fieldbus padrões tornando a metodologia independente do fabricante. Foi utilizada uma rede perceptron multicamadas com algoritmo de treinamento backpropagation de Levenberg-Marquardt. O treinamento foi realizado numa programação elaborada para o software Matlab TM. A arquitetura da rede neural foi determinada por métodos empíricos variando-se o número de neurônios e de camadas neurais até se atingir um erro aceitável na prática. Após esses treinamentos foi desenvolvida uma programação para realizar os cálculos de vazão em um ambiente foundation fieldbus utilizando-se para tanto o software DeltaV TM do fabricante Emerson Process Management. Foram obtidos resultados com erro relativo médio de valor de vazão em torno de 1.43% para um primeiro cenário utilizando uma placa de orifício e ar como fluido, e de 0,073% para um segundo cenário utilizando uma placa de orifício e gás natural como fluido, com relação aos valores obtidos através do instrumento multivariável 3095MV TM do fabricante Rosemount. Os valores de erro encontrados validam o método desenvolvido nessa dissertação.This dissertation proposes the development of an artificial neural network (ANN) directed to foundation fieldbus environment for calculation of flow in closed ducts. The proposed methodology uses measurements of pressure, temperature and differential pressure, which are usually available in industrial plants. The main motivation of the use of neural networks lies in their low cost and simplicity of implementation, which allows the use of standard fieldbus blocks by just making the method independent of the manufacturer. It was used a multilayer perceptron network with backpropagation training and algorithm from Levenberg-Marquardt. The training was programmed in the software Matlab TM. The architecture of the ANN was determined by empirical methods by varying the number of neurons and neural layers until it reaches an acceptable error. After such trainings, it was developed a program to perform the flow calculations in an foundation fieldbus environment using Emerson Process Management\'s DeltaV TM software. The results were obtained with an average relative error of flow rate of 1.43% for the first scenario using an orifice plate and air as a process fluid, and 0.073% for a second scenario using an orifice plate and natural gas as the fluid related to the values obtained from Rosemount 3095MV TM multivariable instrument. The values of error found validate the method developed in this dissertation.
41
Youssef, Ihsen. "Étude des mécanismes moléculaires impliqués dans la mort neuronale induite par le peptide de ß-amyloïde soluble : recherche et validation fonctionnelle de cibles cellulaires". Thesis, Vandoeuvre-les-Nancy, INPL, 2006. http://www.theses.fr/2006INPL068N/document.
Testo completoAbstract (sommario):
Le vieillissement des populations est corrélé à l’augmentation des pathologies neurodégénératives liées à l’âge, plus particulièrement la maladie d’Alzheimer. La recherche de marqueurs précoces de la maladie ainsi que l’élaboration de nouvelles stratégies thérapeutiques constituent un enjeu de taille. Parmi les mécanismes moléculaires de la formation des plaques amyloïdes actuellement explorés, les formes oligomériques tronquées de peptide amyloïde (Aß), notamment le peptide Aß3(?pE)??42? retrouvé à des stades précoces de la maladie, joueraient un rôle déterminant. Ces travaux de thèse ont permis de montrer, dans un premier temps, que l’injection intracérébrale de ce peptide chez la souris entraîne des altérations de la mémoire de travail et des capacités d’apprentissage, associées à une accumulation d’espèces réactives dérivées de l’oxygène dans des régions cérébrales spécifiques (hippocampe et bulbes olfactifs) de ces animaux. Des essais menés in vitro sur des cultures primaires de neurones de souris montrent leur implication dans les voies apoptotiques impliquant l’activation des caspases et la cascade métabolique de l’acide arachidonique. La seconde étape de ces travaux a constitué en l’étude des effets protecteurs d’un peptide antiapoptotique d’origine endogène, l’humanine (HN) et son variant S14G (HNG). In vitro, un effet protecteur de ces peptides a été mesuré après traitement de neurones en culture par le peptide A[bêta]3?(pE)42.??? Les résultats les plus marquants résident dans les observations faites in vivo : en effet, ces peptides inhibent l’effet délétère de l’injection intracérébroventriculaire du peptide Aß3?(pE??)42?? en restaurant les performances mnésiques des animaux dans les tests comportementaux. A la lumière de ces résultats, les peptides HN pourraient constituer de nouveaux outils thérapeutiques dans le traitement ou la prévention des dommages cellulaires précoces liés à la présence des oligomères solubles du peptide AßAging of population is correlated to the increase of neurodegenerative disease, more particularly Alzheimer disease. Defining early diagnostic markers and new therapeutic strategies are highly relevant. Among the molecular pathways which are currently developed, N-terminal-truncated forms of amyloid-ß (Aß) peptide have been recently suggested to play a pivotal role in the disease. Among them, Aß3(?pE)42 ?peptide is the dominant Aß species in amyloid plaques. We first investigated the effects of soluble oligomeric Aß3(pE) 42 after intracerebroventricular injection on mice learning capacities and the molecular mechanisms of in vitro neurotoxicity. Mice injected with soluble Aß3(pE) 42 displayed impaired spatial working memory and delayed memory acquisition. These cognitive alterations were associated with free radical overproduction in hippocampus and olfactory bulbs. In vitro, Aß3(pE) 42 oligomers induced a redox-sensitive neuronal apoptosis involving caspase activation and an arachidonic acid-dependent pathway. The second goal of this work was to investigate the protective effects of the apoptosis rescue endogenous peptide humanin (HN) and its S14G mutant (HNG). In vitro, we measured their inhibitory effect on neuronal death and apoptotic events resulting from soluble Ab oligomer treatment. What’s of particular interest is the in vivo restoration of soluble Aß3(pE) 42 oligomer-induced mnesic impairment. Thus, HN peptides might serve as new drug candidates for treatment or prevention of early cellular damages linked to soluble A[bêta] oligomers
42
Taelman, Vincent. "Etude du facteur de transcription XHRT1 dans le développement embryonnaire chez le xénope". Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211002.
Testo completoAbstract (sommario):
Le laboratoire d’Embryologie Moléculaire étudie les mécanismes moléculaires contrôlant le développement embryonnaire et utilise comme système expérimental l’embryon de xénope. En collaboration le laboratoire du Dr Daniel Christophe, nous avons abordé l’étude du gène XHRT1 chez le xénope. Ce gène est l’orthologue du gène HRT-1/Hey1/Hesr-1/HERP2/CHF2 de souris. Celui-ci, avec deux autres protéines apparentées (HRT2 et HRT3) forme une sous-famille de facteurs de transcription de type bHLH-O qui se différencient des autres facteurs bHLH-O par l’absence d’un motif carboxy-terminal de séquence « WRPW » et par la présence d’un nouveau motif carboxy-terminal conservé de séquence « TEI/VGAF ». Le rôle de ces facteurs HRT dans le développement est encore actuellement mal connu. Dans un premier temps, nous avons déterminé le profil d’expression de XHRT1 au cours de l’embryogenèse. Nous avons observé que ce gène est fortement exprimé au stade neurula dans le plancher du tube neural, et que plus tardivement celui-ci est exprimé dans différentes régions du système nerveux, dans les somites et le dans le pronéphros. Comme attendu pour un membre de la famille des facteurs bHLH-O, nous avons également observé que l’expression précoce de HRT1 au niveau du plancher du tube neural est bien régulée par la voie de signalisation Notch.
Dans un deuxième temps, nous nous sommes intéressés au rôle et au mode d’action du facteur XHRT1 dans le développement du plancher du tube neural. Nous avons pu montrer que XHRT1 agit comme répresseur transcriptionnel et que cette répression nécessite la présence du domaine bHLH et de séquences en aval de celui-ci. Nous avons montré en embryon que la surexpression précoce de XHRT1 induit un blocage de l’expression des marqueurs du mésoderme et une augmentation de marqueur du plancher du tube neural, ce qui est en accord avec le modèle selon lequel la voie de signalisation Notch interviendrait dans le choix de la destinée des cellules de la région médiane en inhibant la différenciation des cellules en notocorde et en favorisant leur différenciation en cellules du plancher du tube neural. XHRT1 n’étant cependant activé qu’à partir du stade neurula, nous avons conclu que les effets observés n’étaient probablement pas dus à XHRT1 mais à un autre facteur bHLH-O apparenté exprimé plus précocement dans les cellules de la ligne mediane de l’embryon. Afin d’éviter ces effets non spécifiques précoces, nous avons utilisé un vecteur d’expression de XHRT1 permettant un contrôle temporel de l’activité de la protéine. Nous avons ainsi montré que l’activation de XHRT1 au stade neurula dans l’ectoderme inhibe la différenciation des cellules précurseurs neurales en neurones et qu’il pourrait ainsi jouer un rôle important dans le développement du plancher du tube neural. Nos résultats ont montré également que XHRT1 est capable d’homo- et hétérodimériser in vivo avec les facteurs Xhairy1 et Xhairy2b coexprimés avec XHRT1 dans le plancher du tube neural. Enfin, nous avons montré que les propriétés de dimérisation de XHRT1 sont dépendantes non seulement du domaine bHLH, mais aussi du domaine Orange et des séquences situées en aval, séquences jouant un rôle important dans le choix du partenaire.
Des travaux récents ayant montré que la voie de signalisation Notch joue un rôle important dans le développement du rein, nous avons voulu déterminer l’importance de XHRT1 dans le développement du pronéphros. Nos résultats ont montré que XHRT1 ainsi que d’autres facteurs bHLH-O sont exprimés de manière dynamique, d’abord dans le glomus puis dans la partie dorso-antérieure de l’ébauche du pronéphros à l’origine des tubules proximaux, et que leur expression est régulée positivement par Notch. La surexpression de XHRT1 à la fin de la neurulation inhibe la formation du canal et du tubule distal, tandis que l’inhibition de la traduction de la protéine entraîne une réduction de l’expression de marqueurs spécifiques des tubules proximaux et du glomus. Ces résultats démontrent que XHRT1 joue un rôle important comme médiateur de la voie de signalisation Notch dans le pronéphros.
Doctorat en sciences, Spécialisation biologie moléculaire
info:eu-repo/semantics/nonPublished
43
Bruce, Jake. "Learning from limited experience: Real-world robot navigation from a single traversal". Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/205492/1/Jacob_Bruce_Thesis.pdf.
Testo completoAbstract (sommario):
If you want to do something, first you have to go somewhere. Navigation is a crucial capability for any intelligent agent that is expected to operate in the world, be they human, animal, or robot. In this work, we present techniques for teaching robots to navigate in the real world, given only a single prior traversal of the environment. We employ an online adaptive approach to sequence-based localization, and a novel framework for model-based deep reinforcement learning, to develop robot systems that can successfully localize and navigate in a city.
44
Stella, Federico. "Spatial Representations in the Entorhino-Hippocampal Circuit". Doctoral thesis, SISSA, 2014. http://hdl.handle.net/20.500.11767/4121.
Testo completoAbstract (sommario):
After a general introduction and a brief review of the available experimental data on spatial representations (chapter 2), this thesis is divided into two main parts. The first part, comprising the chapters from 3 to 6, is dedicated to grid cells. In chapter 3 we present and discuss the various models proposed for explaining grid cells formation. In chapter 4 and 5 we study our model of grid cells generation based on adaptation in the case of non-planar environments, namely in the case of a spherical environment and of three-dimensional space. In chapter 6 we propose a variant of the model where the alignment of the grid axes is induced through reciprocal inhibition, and we suggest that that the inhibitory connections obtained during this learning process can be used to implement a continuous attractor in mEC.
The second part, comprising chapters from 7 to 10 is instead focused on place cell representations. In chapter 7 we analyze the differences between place cells and grid cells in terms on information content, in chapter 8 we describe the properties of attractor dynamics in our model of the Ca3 net- work, and in the following chapter we study the effects of theta oscillations on network dynamics. Finally, in Chapter 10 we analyze to what extent the learning of a new representation, can preserve the topology and the exact metric of physical space.
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Dubruc, Franck. "Modulation de la fidélité temporelle de la décharge neuronale par l'activité GABAergique et le système des endocannabinoïdes dans l'hippocampe". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5011/document.
Testo completoAbstract (sommario):
Les neurones pyramidaux sont constamment bombardés par une activité GABAergique spontanée qui régule le comportement de la décharge neuronale. Des résultats récents ont montré que cette activité spontanée GABAergique pouvait moduler l'excitabilité mais aussi la fidélité temporelle de décharge d'un neurone définie comme sa capacité à reproduire à l'identique un patron de décharge lors de la présentation répétée d'un même stimulus. D'autre part, de nombreuses études ont caractérisé l'existence d'une plasticité à court-terme de l'activité GABAergique médiée par les endocannabinoïdes. Ce phénomène, connu sous le nom de DSI (Depolarization-induced Suppression of Inhibition) a été décrit dans de nombreuses structures comme le cervelet, le cortex ou encore l'hippocampe.Au cours de ma thèse, j'ai étudié quelles pouvaient être les conséquences fonctionnelles de la production d'endocannabinoïdes sur l'activité neuronale et en particulier sur la fidélité temporelle de la décharge. Dans un premier temps nous avons montré que le profil de décharge in vivo des cellules de lieu de l'hippocampe pouvait induire, quand il était rejoué in vitro, le phénomène de DSI. Nous avons observé ensuite que cette diminution transitoire de la transmission GABAergique était associée à une amélioration de la fidélité temporelle de la décharge.En conclusion, nos travaux suggèrent que l'activité des cellules de lieu de la région CA1 de l'hippocampe peut provoquer, par la synthèse et la libération rétrograde d'endocannabinoïdes, une diminution à court-terme de l'activité GABAergique reçue par ces cellules avec pour conséquence des modifications de la précision temporelle de la décharge neuronalePyramidal neurons are constantly bombarded by spontaneous GABAergic activity that regulates their firing behaviour. Recent results have shown that this spontaneous GABAergic activity can modulate both the excitability and the temporal fidelity of action potential discharge (Caillard, 2011). Many studies have characterized the existence of short-term plasticity of GABAergic activity mediated by endocannabinoids. This phenomenon, known as DSI (Depolarization-induced Suppression of Inhibition) has been described in many brain structures such as the cerebellum, cortex or hippocampus (for review see Freund et al., 2003; Kano et al. 2009).During my PhD thesis, I have evaluated the functional consequences of the endocannabinoid production on neuronal activity and in particular on the spike-time precision of the CA1 pyramidal neurons. As a first step we have shown that the in vivo firing pattern of place cells could induce, when replayed in vitro, a decrease in spontaneous GABA release by the endocannabinoid signalling pathway. We then observed that this transient depression of GABAergic transmission improved spike-time precision of CA1 pyramidal neurons.In conclusion, our work suggests that, in the hippocampus, CA1 place cell firing can induce, following the synthesis and retrograde release of endocannabinoids, a short-term decrease in the GABAergic activity received by these cells that consequently affects their spike-time precision
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Ouallet, Jean-Christophe. "Encéphalomyélite autoimmune expérimentale : expression neuronale du TNFalpha, expression du système FAS/FAS-L et apoptose des cellules immunes chez le rat DA : thérapies de tolérance immune par injections intraveineuses de peptides immunodominants de la MOG chez le primate ouistiti/marmoset commun : sclérose en plaques". Paris 6, 2002. http://www.theses.fr/2002PA066280.
Testo completo
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Hok, Vincent. "Bases neurales des comportements orientés vers un but : étude des corrélats de l'activité unitaire préfrontale et hippocampique dans une tâche de navigation". Toulouse 3, 2007. http://thesesups.ups-tlse.fr/174/.
Testo completoAbstract (sommario):
L'hippocampe est aujourd'hui reconnu pour jouer un rôle majeur dans le traitement des informations spatiales. Bien que son rôle ne se limite pas simplement à ce type de traitement, la présence de cellules de lieu, neurones déchargeant lorsque l'animal occupe certaines localisations spatiales, a suscité nombre d'études, visant à déterminer la nature de la représentation spatiale au sein de cette structure. Néanmoins, il n'existe pas de consensus sur l'implication de l'hippocampe dans la genèse des trajets de navigation ou dans le codage des buts spatiaux. D'autre part, du fait de son rôle probable dans les comportements de planification, le cortex préfrontal apparaît comme une structure clé dans la réalisation d'un comportement orienté vers un but. L'objectif des recherches réalisées au cours de cette thèse est donc de tenter de comprendre comment ces deux structures (hippocampe et cortex préfrontal) participent à la genèse des comportements orientés vers un but. Nous montrons, dans une première expérience, que les neurones du cortex préfrontal médian (aires prélimbique et infralimbique) enregistrés chez des animaux réalisant une tâche de navigation, présentent une activité spatio-sélective. Les lieux à forte valeur motivationnelle semblent être particulièrement représentés par cette activité préfrontale. Dans une seconde expérience, nous montrons que les cellules de lieu enregistrées chez des animaux réalisant la tâche de navigation présentent une activité liée au but, en plus de leur activité spatio-sélective classique. Cette décharge est spécifiquement liée à certaines phases temporelles de la tâche. Ce type de signal, en conjonction avec l'activité des neurones préfrontaux, pourrait servir de base à un système de planification de trajet. Dans la dernière partie de cette thèse, nous présentons des données récentes concernant les interactions entre l'hippocampe et le cortex préfrontal, et plus particulièrement les conséquences de l'inactivation du cortex préfrontal sur l'activité hippocampique. .The hippocampus is well known to play a key role in spatial information processing as shown by the existence of place cells. Such cells are active when the animal occupies particular locations in particular behavioural contexts. However, little evidence has been found in support of the hypothesis that the hippocampus could be involved in the generation of navigation paths and coding of spatial goals. On the other hand, the prefrontal cortex, in line with its role in planning, could be a key structure in the mechanisms involved in goal-directed behaviour. The objective of the research carried out during this thesis is thus to attempt to understand how these two structures (hippocampus and prefrontal cortex) take part in the emergence of goal-directed behaviour. In a first study, we show that prefrontal cortex neurons recorded while the animal performed a goal-oriented navigation task, display spatio-selective activity, especially at locations with a high motivational value. In a second study, we show that hippocampal place cells recorded in animals trained in the same goal navigation task do have a goal firing pattern, i. E. Out-of-field goal related activity, that is time-locked to particular phases of the task. This kind of signal could serve for path planning in combination with prefrontal neurons activity. In the last study, we present recent data that deal with the interactions between these two structures in the same task, looking for particular modulations of hippocampal place cells activity after prefrontal inactivation. .
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Heathcote, Jonathan David. "Building and operating large-scale SpiNNaker machines". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/building-and-operating-largescale-spinnaker-machines(6151916a-ed71-42e4-97d2-2993a4caf5f6).html.
Testo completoAbstract (sommario):
SpiNNaker is an unconventional supercomputer architecture designed to simulate up to one billion biologically realistic neurons in real-time. To achieve this goal, SpiNNaker employs a novel network architecture which poses a number of practical problems in scaling up from desktop prototypes to machine room filling installations. SpiNNaker's hexagonal torus network topology has received mostly theoretical treatment in the literature. This thesis tackles some of the challenges encountered when building `real-world' systems. Firstly, a scheme is devised for physically laying out hexagonal torus topologies in machine rooms which avoids long cables; this is demonstrated on a half-million core SpiNNaker prototype. Secondly, to improve the performance of existing routing algorithms, a more efficient process is proposed for finding (logically) short paths through hexagonal torus topologies. This is complemented by a formula which provides routing algorithms with greater flexibility when finding paths, potentially resulting in a more balanced network utilisation. The scale of SpiNNaker's network and the models intended for it also present their own challenges. Placement and routing algorithms are developed which assign processes to nodes and generate paths through SpiNNaker's network. These algorithms minimise congestion and tolerate network faults. The proposed placement algorithm is inspired by techniques used in chip design and is shown to enable larger applications to run on SpiNNaker than the previous state-of-the-art. Likewise the routing algorithm developed is able to tolerate network faults, inevitably present in large-scale systems, with little performance overhead.
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Garg, Sourav. "Robust visual place recognition under simultaneous variations in viewpoint and appearance". Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/134410/1/Sourav%20Garg%20Thesis.pdf.
Testo completoAbstract (sommario):
This thesis explores the problem of visual place recognition and localization for a mobile robot, particularly dealing with the challenges of simultaneous variations in scene appearance and camera viewpoint. The proposed methods draw inspiration from humans and make use of semantic cues to represent places. This approach enables effective place recognition from similar or opposing viewpoints, despite variations in scene appearance caused by different times of day or seasons. The research contributions presented in the thesis advance visual place recognition techniques, making them more useful for deployment in a wide range of robotic and autonomous vehicle scenarios.
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Kvapilová, Aneta. "Pořízení a zpracování sbírky registračních značek vozidel". Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2019. http://www.nusl.cz/ntk/nusl-403115.
Testo completoAbstract (sommario):
This master thesis focuses on creating and processing a dataset, which contains semi-automatically processed images of vehicles licence plates. The main goal is to create videos and a set of tools, which are able to transform input videos into a dataset used for traffic monitoring neural networks. Used programming language is Python, graphical library OpenCV and framework PyTorch for implementation of neural network.