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1
Wright, Kristina M. "Revising the Role of the Ventrolateral Periaqueductal Gray in the Fear Circuit:". Thesis, Boston College, 2021. http://hdl.handle.net/2345/bc-ir:109159.
Testo completoAbstract (sommario):
Thesis advisor: Michael A. McDannaldThesis advisor: John P. Christianson
The ability to accurately evaluate and respond to threats is vital to survival. Disruptions in neural circuits of fear give rise to maladaptive threat responding, and have clinical implications in fear and anxiety disorders. To better inform therapeutic interventions, it is imperative that roles for regions classically associated with fear continue to be refined, and that novel nodes are incorporated into what is most certainly a larger fear circuit. In the canonical view, threat estimates are generated at the level of the amygdala and sent to the ventrolateral periaqueductal gray (vlPAG), which organizes an appropriate behavioral response, most notably freezing. Despite a multitude of studies successfully linking the vlPAG and Pavlovian fear behavior, evidence of a direct neural correlate for fear expression in the vlPAG is lacking. By contrast, a role for the caudal substantia nigra (cSN) in fear, stands apart from its canonical associations with movement and reward processes. Although there is new interest in examining a role for the nigra in fear modulation, this is essentially an uncharted area of discovery. The goals of this dissertation are three-fold. First, to propose a role for vlPAG activity in threat estimation, a function previously restricted to the upstream amygdala. Second, to scrutinize vlPAG neural activity using a novel multi-cue Pavlovian procedure and identify the long-anticipated, direct neural correlate for fear expression. Third, to present causal evidence supporting the cSN as a potential node in a circuit that most certainly extends beyond regions canonically associated with fear
Thesis (PhD) — Boston College, 2021
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Psychology
2
Yuzhe, Li. "Computational Investigations on Uncertainty-Dependent Extinction of Fear Memory". 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225756.
Testo completo
3
Pagani, Jerome H. "The medial hypothalamic defensive circuit and predator odor-induced fear a comparison of electrolytic and neurotoxic lesions /". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 127 p, 2007. http://proquest.umi.com/pqdweb?did=1397903941&sid=8&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Testo completo
4
Aime, Mattia. "Circuit mechanisms for encoding discriminative learning in the dorsal prefrontal cortex of behaving mice". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0805/document.
Testo completoAbstract (sommario):
Chez les mammifères, le néocortex constitue une structure remarquablement plastique assurant leurs multiples capacités d’adaptation et d’apprentissage. Par exemple, l’apprentissage associatif permet à chaque individu d’apprendre les relations entre un événement particulier (un danger par exemple) et les signaux environnementaux qui y sont associés, afin d’en anticiper les conséquences s’il se reproduit dans le futur. Dans le cas de la peur conditionnée, l'apprentissage associatif améliore les capacités de discrimination des signaux de menace et de sécurité, garantissant ainsi une représentation précise de l'environnement. Ce processus comportemental est en partie dépendant de l'interaction entre deux structures cérébrales: le cortex préfrontal (PFC) et le complexe basolatéral de l'amygdale (BLA). Bien que le PFC puisse encoder à la fois les mémoires de menace et de sécurité qui seraient recrutées préférentiellement après l'apprentissage, on ignore toujours si une telle représentation discriminative existe réellement, et si oui, les mécanismes neuronaux et synaptiques qui en sont à l'origine. Au cours de mon travail de thèse, j'ai démontré que l'activité des neurones excitateurs du PFC est nécessaire à la discrimination entre les signaux de menace et de sécurité grâce à la formation d'ensembles spécifiques de neurones. Au cours de l'apprentissage, les neurones pyramidaux sont potentialisés et recrutés au sein de ses ensembles grâce à l'association au niveau dendritique d'événements synaptiques non-linéaires issus des entrées sensorielles avec des entrées synaptiques provenant de la BLA. En conclusion, nos données fournissent la preuve d'un nouveau mécanisme synaptique qui associe, pendant l'apprentissage, l'expérience perçue avec l’état émotionnel transmis par la BLA permettant ainsi la formation d'ensembles neuronaux dans le cortex préfrontalThe ability of an organism to predict forthcoming events is crucial for survival, and depends on the repeated contingency and contiguity between sensory cues and the events (i.e. danger) they must predict. The resulting learned association provides an accurate representation of the environment by increasing discriminative skills between threat and safety signals, most likely as a result of the interaction between the prefrontal cortex (PFC) and the basolateral amygdala (BLA). Although it suggests that local neuronal networks in the PFC might encode opposing memories that are preferentially selected during recall by recruiting specific cortical or subcortical structures, whether such a discriminative representation is wired within discrete prefrontal circuits during learning and by which synaptic mechanisms remain unclear. Here, the work at issue demonstrates that discrimination learning of both safe and fear-conditioned stimuli depends on full activity of the frontal association cortex, and is associated with the formation of cue-specific neuronal assemblies therein. During learning, prefrontal pyramidal neurons were potentiated through sensory-driven dendritic non-linearities supported by the activation of long-range inputs from the basolateral amygdala (BLA). Taken together, these data provide evidence for a new synaptic level mechanism that coincidently link (or meta-associate) during learning features of perceived experience with BLA mediated emotional state into prefrontal memory assemblies
5
Lima, Miguel Antonio Xavier de. "Investigação da circuitaria cortical envolvida no processamento do medo contextual à ameça predatória". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/42/42131/tde-17022016-135344/.
Testo completoAbstract (sommario):
Lesões na parte ventral do núcleo anteromedial do tálamo (AMv) interferem no processamento da memória aversiva predatória sem no entanto influenciar as respostas de defesa inatas do animal frente a um predador. O escopo deste trabalho foi entender melhor o papel do AMv e investigar se seus alvos de projeção corticais também interferem no processamento da memória aversiva. No primeiro experimento detectamos que o AMv participa da aquisição da memória aversiva. As áreas corticais pré-límbica, cingulada anterior, visual anteromedial e retroesplenial ventral, recebem e integram entre si projeções oriundas do AMv, além de enviar projeções para a amígdala e hipocampo. Estas áreas corticais estão seletivamente recrutadas durante a exposição ao predador, e observamos que lesões neuroquímicas afetaram severamente a formação da memória aversiva. Nossos dados sugerem que há um circuito de áreas corticais que está criticamente envolvido no processo mnemônico aqui abordado, e fornece as primeiras evidências para a hipótese de módulos corticais a partir do conectoma do rato.Neurochemical lesions placed into ventral part of anteromedial thalamic nucleus (AMv) disrupt contextual, but not innate, fear responses to predatory threats. In the present investigation, we determined whether the AMv is involved in the acquisition and/or retrieval of the conditioned responses, and if its cortical targets are involved in the fear memory processing. In the first assay, we found that AMv has a critical role in the acquisition of conditioned responses. The cortical areas prelimbic (PL), anterior cingulate area (ACA), anteromedial visual area (VISam) and the ventral part of retrosplenial area (RSPv), receive projections from AMv and are recruited during predator exposure. The integrity of these cortical areas is required for the processing of the mnemonic processes here addressed. Our data corroborate current ideas on functional cortical modules, and help to elucidate how they are involved in the acquisition of fear memories related to life threatening situations.
6
Bouarab, Chloe. "Modifications post-traductionnelles des histones au sein du circuit hippocampo-amygdalien déterminant le passage d'une mémoire de peur normale à une mémoire traumatique". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0261/document.
Testo completoAbstract (sommario):
Les altérations mnésiques associées au trouble de stress post-traumatique (TSPT) constituent un aspect fondamental de la symptomatologie de cette pathologie. Cette altération qualitative de la mémoire inclut à la fois une hypermnésie, c’est-à-dire une intensification de la mémoire vis-à-vis du coeur de l’événement traumatique, et une amnésie de type déclaratif pour les éléments contextuels péri-traumatiques. Les données chez l’Homme suggèrent que ces altérations mnésiques pourraient être sous-tendues par une hyper-activation amygdalienne et un dysfonctionnement hippocampique, respectivement. Cependant, les bases neurobiologiques, et en particulier moléculaires, du TSPT restent largement méconnues. Un modèle comportemental développé chez la souris au laboratoire et basé sur un conditionnement aversif permet précisément de comparer une mémoire de peur normale, c’est-à-dire « contextualisée » et adaptée, à une mémoire pathologique de type TSPT, c’est-à-dire « décontextualisée » et focalisée sur un élément saillant du trauma. Dans la mesure où il a été montré que le développement d’une mémoire de peur contextuelle implique certaines modifications épigénétiques spécifiques, nos travaux ont eu pour objectif de déterminer les altérations des modifications post-traductionnelles d’histones qui sous-tendent le développement d’une mémoire traumatique au lieu d’une mémoire de peur normale. Nos résultats révèlent (1) que des profils spécifiques différents des états d’acétylation/méthylation de l’histone H3 dans le réseau hippocampo-amygdalien sont associés à une mémoire de peur normale et à une mémoire traumatique de type TSPT. Spécifiquement, une mémoire de peur normale est associée à une forte acétylation de H3K9 hippocampique, tandis qu’une mémoire traumatique de type TSPT s’accompagne d’une hyperméthylation de H3K9 dans l’hippocampe, traduisant une répression transcriptionnelle, ainsi que d’une diminution de la tri-méthylation de H3K27 dans l’amygdale latérale, caractéristique d’une activation transcriptionnelle. De plus, nos travaux montrent (2) qu’une modulation pharmacologique de la balance des états d’acétylation/méthylation de H3K9 dans l’hippocampe permet de promouvoir ou de prévenir le développement d’une mémoire traumatique. Enfin, (3) une dernière série d’expériences révèle (i) qu’un stress prénatal est un facteur de risque au développement d’une mémoire traumatique, (ii) que cette dernière est associée à des profils épigénétiques spécifiques, et (iii) qu’une telle vulnérabilité peut se transmettre de manière intergénérationnelleMemory alterations associated with post-traumatic stress disorder (PTSD) are a fundamental feature of this pathology. PTSD is characterized both by hypermnesia for simple salient trauma-related stimuli and amnesia for peri-traumatic contextual cues. In humans, this disorder is associated with hippocampal hypofunction and amygdalar hyperfunction, which may underlie such paradoxical memory pattern. However, neurobiological bases of PTSD, particularly at the molecular level, remain largely unknown. A behavioral model based on aversive conditioning was developed in mice by our team. This model allows the comparison between a normal, i.e. “contextualized” and adaptive, fear memory, and a PTSD-like pathological fear memory, i.e. “decontextualized” and focused on a salient cue of the trauma. Since specific epigenetic alterations have been involved in the development of contextual fear memory, our aim was the identification of the alterations in post-translational histone modifications underlying the development of traumatic memory instead of normal fear memory. Our results first reveal that normal and PTSD-like fear memory are associated with distinct acetylation/methylation profiles of histone H3 in the hippocampal-amygdalar network. Specifically, we show that, compared to normal fear memory, PTSD-like memory is associated with a switch from H3K9 hyperacetylation (marker of transcriptional activation) to H3K9 hypermethylation (marker of transcriptional repression) in hippocampal CA1, as well as a significant reduction of H3K27 trimethylation, which results in an increased transcription, in the lateral amygdala. Second, we show that the pharmacological manipulation of the acetylation/methylation balance of H3K9 in the hippocampus can prevent or promote the development of PTSD-like memory. Finally, a last series of experiments shows that (i) prenatal stress is a risk factor for the development of PTSD-like memory, (ii) which is associated with specific epigenetic alterations and (iii) that such vulnerability to stress can be transmitted to subsequent generations
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SILVA, BIANCA AMBROGINA. "INDEPENDENT HYPOTHALAMIC CIRCUITS FOR SOCIAL AND PREDATOR FEAR". Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/229915.
Testo completoAbstract (sommario):
Fear is a distressing negative sensation induced by a perceived threat. This emotion is necessary for the survival of the individual, since it guarantees appropriate responses
to life challenging threats. In the last decades research on the neural mechanisms underling such emotion both in humans and in animal models have been mostly focused on the amygdala. In particular fear models in rodents typically rely on foot shock based paradigms. However, innate and learned fear elicited by other stimuli such as predators or aggressive members of the same species has been shown to be regulated by other circuits where the triggering, coordination and the expression of fear seem to be centered in the hypothalamus and periaqueductal grey. Nevertheless very little is known about the function and physiology of these structures in fear processing.
To study the function of the medial hypothalamic fear circuit, we developed a novel behavioral paradigm to measure innate and conditioned fear responses to social and predator threats in mice. We subsequently created tools to selectively inhibit specific hypothalamic nuclei during the fear and we observed the inhibition of the
ventromedial hypothalamus, a nucleus previously studied for its function in feeding, sex and aggression, specifically impaired social and predator fear but not foot shock
fear. Moreover we demonstrated that different portions of this nucleus account for fear to different threats with the dorsomedial portion, previously implicated in feeding
function, processing predator fear, and the ventrolateral portion, previously implicated in sex and aggression, processing social fear. Our results demonstrate that the hypothalamus plays a crucial role in fear processing
even if it is not recruited during foot shock exposure, suggesting that it might be a good target for the treatment of fear related disorders like panic or phobias and we are
now trying to identify possible drugs specifically acting in this area. On the other hand, we showed that specific hypothalamic subnuclei are recruited selectively during social or predator fear, corroborating the hypothesis that different types of fear are processed by separate brain circuits. Such evidence opens the possibility of targeted therapy of pathological fear in humans. Interestingly these same hypothalamic structures are fundamental regulators of non-fear motivated behaviors that are essential for survival such as feeding behavior, aggression and sex and we are now
investigating how the same nuclei can orchestrate multiple functions.
8
Carey, Guillaume. "Imaging anxiety in Parkinson's disease". Electronic Thesis or Diss., Université de Lille (2022-....), 2024. https://pepite-depot.univ-lille.fr/ToutIDP/EDBSL/2024/2024ULILS023.pdf.
Testo completoAbstract (sommario):
L'anxiété dans la maladie de Parkinson (MP) est un symptôme non-moteur fréquent et invalidant dont la prise en charge est difficile. La faible connaissance des mécanismes impliqués est une limite à sa prise en charge. L'objectif de ce travail était d'identifier les mécanismes sous-jacents de l'anxiété liée à la MP, via une approche IRM cérébrale multimodale.Une revue systématique de la littérature portant sur les données d'imagerie dans l'anxiété liée à la MP a d'abord été réalisée, permettant de générer de premières hypothèses. Ensuite, plusieurs études incluant des analyses en IRM cérébrale structurale et fonctionnelle ont été menées chez des patients atteints de MP et présentant ou non une anxiété cliniquement significative. Nos analyses se sont focalisées sur le circuit de la peur, connu pour être impliqué dans les troubles anxieux, et le circuit cortico-striato-thalamo-cortical limbique, connu pour son implication dans les symptômes psycho-comportementaux de la MP.Nos résultats suggèrent que l'anxiété liée à la MP serait la conséquence d'un déséquilibre fonctionnel et structural entre ces deux circuits. Certaines structures communes, comme le thalamus, le striatum ou les noyaux du tronc cérébral, pourraient être des zones clés dont l'altération pourrait expliquer la forte prévalence de ces troubles dans la MP. D'autres travaux s'appuyant notamment sur les avancées technologiques en imagerie et sur de nouveaux concepts concernant la physiopathologie de la MP, seront nécessaires pour répondre à ces questionsAnxiety in Parkinson's disease (PD) is a frequent and disabilitating non-motor symptom. It is difficult to manage, partly due to a poor knowledge of the underlying mechanisms. The objective of this thesis was to identify the underlying mechanisms of PD-related anxiety, using multimodal brain MRI.A systematic review of the literature on imaging data in PD-related anxiety was first carried out, allowing the generation of initial hypotheses. Then, several studies including structural and functional brain MRI analyses were carried out in PD patients with or without clinically significant anxiety. Our analyses focused on the fear circuit, known to be involved in anxiety disorders and fear processing, and the limbic cortico-striato-thalamo-cortical circuit, known for its involvement in the neuropsychiatric symptoms of PD.Our results suggest that PD-related anxiety is the consequence of a functional and structural imbalance between these two circuits. Certain overlapping structures, such as the thalamus, the striatum or the brainstem nuclei, could be key areas whose alteration could explain the high prevalence of these disorders in PD. Further works based in particular on technological advances in imaging and new concepts concerning the pathophysiology of PD will be necessary to answer the remaining questions
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Joly, Fanny. "Impacts d’une perturbation de la voie TSC2/mTOR dans l’amygdale dès l’adolescence sur le comportement de peur et la fonctionnalité du cortex préfrontal chez le rat adulte Disruption of Amygdala Tsc2 in Adolescence Leads to Changed Prelimbic Cellular Activity and Generalized Fear Responses at Adulthood in Rats". Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASL016.
Testo completoAbstract (sommario):
L’adolescence est une période développementale vulnérable marquée par d’intenses modifications structurelles et fonctionnelles des réseaux qui assurent la régulation des comportements émotionnels et cognitifs. Les processus de maturation de ces réseaux sont influencés par les facteurs environnementaux et génétiques. Le syndrome de stress post-traumatique (PTSD) est un trouble psychiatrique caractérisé par des peurs exagérées, des généralisations de la peur et des déficits d’extinction de peur. Les facteurs de prédisposition au PTSD sont peu connus, mais nous savons qu’un stress intense subi au cours de l’adolescence favorise son apparition à l’âge adulte lorsqu’un individu est confronté à un nouvel événement traumatique.Au cours de cette thèse, nous avons étudié la fonctionnalité de deux structures du circuit de la peur, l’amygdale et le cortex préfrontal, qui suivent une maturation asynchrone. L’amygdale étant fonctionnellement mature à l’âge juvénile, elle est en position de modifier la maturation tardive du cortex préfrontal (mPFC). Nous avons donc voulu tester l’impact d’une dérégulation de la voie Tsc2/mTOR dans les cellules excitatrices du noyau basolatéral de l’amygdale (BLA) du rat au début (25 jours post-natal, PN25), ou à la fin (PN50) de l’adolescence. Le comportement émotionnel à l’âge adulte a été évalué à l’aide d’un conditionnement Pavlovien et l’activité basale du mPFC par la mesure de l’expression du gène immédiat précoce c-FOS. Nous montrons que seuls les rats altérés à l’adolescence (PN25) présentent à l’âge adulte des symptômes typiques du PTSD (déficit d’extinction et généralisation de la peur), associés à une augmentation de l’activité basale du mPFC, en particulier dans les couches corticales impliquées dans le maintien de la mémoire de peur. Ainsi, une modification de la fonctionnalité de l’amygdale au début de l’adolescence pourrait être un facteur de prédisposition à l’apparition d’un PTSD à l’âge adulteAdolescence is a highly sensitive developmental period characterized by massive structural and functional changes in networks regulating emotional and cognitive behaviors, with maturational processes influenced by environmental and genetical factors. Post-traumatic stress disorder (PTSD) is a psychiatric disorder characterized by an exaggerated fear, overgeneralization, and deficits in fear extinction. Nowadays, genetical and/or environmental predisposal factors for PTSD are not fully understood, but we know that an intense stress or a trauma endured during adolescence promotes the appearance of PTSD at adulthood following a novel trauma exposure.In this thesis, we particularly studied two structures that belong to the fear-network, the amygdala and prefrontal cortex, which follow an asynchronous maturation. While the amygdala is functionally mature at a juvenile age, its activity could impact the late maturation of the medial prefrontal cortex (mPFC). We aimed to study the impact of a disruption of Tsc2/mTOR pathway in the excitatory cells of the basolateral nucleus of the amygdala (BLA) in rats at young adolescence (post-natal day 25, PN25) or at the end of adolescence (PN50). When animals had reached adulthood, we assessed emotional behavior through a Pavlovian fear conditioning protocol, and the basal mPFC activity through the measure of expression of immediate early gene c-FOS. We show that only animals altered during young adolescence presented at the adult age typical symptoms of PTSD (fear extinction deficits, overgeneralization of fear), associated with an increase of mPFC basal activity, especially in cortical layers known to be involved in the maintenance of fear memory and expression. Thus, we suggest that a developmental dysfunction of the amygdala early in adolescence could be a predisposal factor to PTSD appearance at adulthood
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Hancock, Kate. "Women's perceptions of safety : CCTV in an inner city setting". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2004. https://ro.ecu.edu.au/theses/801.
Testo completoAbstract (sommario):
To date, most research on closed circuit television (CCTV) has come out of the United Kingdom (UK) where the growth of CCTV has reached immense proportions with wide support and funding from the Home Office. There are 33 systems operating in Australia, with the focus of this research on the first system installed in Perth, Western Australia in 1991. There is a dearth of information on CCTV in Australia, and little research looking at the link between CCTV, women’s safety and fear of crime. The literature on fear of crime shows that women are more fearful than men even though they are less likely to be offended against. Many reasons are proposed in the literature including vulnerability, victimisation and past experience of crime, environmental factors, and psychological factors to explain women’s fear. Many methodological problems are presented in the fear of crime literature. The core aim of this research was to collect information attitudes, knowledge and opinions about closed circuit television (CCTV) and women’s safety. Six qualitative interviews were conducted with women who work in the fields related to CCTV and women’s safety or who have a keen interest in the field. A further 295 women in the community were surveyed about issues relating to the purpose and effectiveness of CCTV, attitudes about CCTV and general feelings towards crime and safety. The findings show that women are overwhelmingly supportive of CCTV in public spaces and believe CCTV reduces crime and increases feelings of safety. However, women consider the current level of surveillance to be sufficient, and would like to see more police officers, women police and improved street lighting. Women are fearful for their safety at night and are afraid of personal crimes more than property crimes. Women are fearful at the railway station, when they are alone, in car parks and walkways and when waiting for taxis. Older women are more supportive of CCTV than younger women and all women would like to be made more aware the CCTV system.
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Sengupta, Ayesha. "Mechanisms of serotonergic control in fear-related neural circuits and behaviour". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:333590cf-964d-44dd-8f5b-4d492e15f8b2.
Testo completoAbstract (sommario):
Serotonin (5-HT) neurotransmission is strongly implicated in affective psychopathologies, with first-line drugs selectively targeting the 5-HT system. Further evidence for the role of 5-HT as an important regulator of emotional states comes from human gene association studies. These have identified polymorphic variants of the 5-HT transporter (5-HTT) gene with reduced transcription efficacy. Lower 5-HTT expression associates with susceptibility to affective disorders and heightened amygdala reactivity to fearful stimuli. The mechanisms by which 5-HTT gene variation leads to altered amygdala function and fear-related behaviour are unknown. The experiments presented in this thesis study these associations in tractable animal models that allow temporal- and circuit-specific control over 5-HT signalling. Specifically, a translationally relevant mouse model of 5-HTT expression variation and an optogenetic approach are used to probe how changes in 5-HT transmission shape fear-related behaviours. Using an array of behavioural tests, it was found that 5-HTT overexpressing (OE) mice exhibit a low-fear/anxiety phenotype that is already established in adolescence, indicating a possible neurodevelopmental trajectory. Acute pharmacological blockade of the 5-HTT at the time of behavioural testing did not rescue the low-fear phenotype in adolescent 5-HTT OE mice, whereas 5-HTT blockade during an early postnatal period did reverse it. These results identify a developmental origin of the fear-related phenotype associated with 5-HTT expression variation. Next, in vivo optogenetic tools were employed during a fear learning task to control neuromodulation of the basal amygdala (BA) by 5-HT neurons arising from the dorsal raphe (DRN). Photoexcitation of the DRN-BA 5-HT projection pathway enhanced fear learning and impaired fear extinction, while photoinhibition caused a fear learning deficit and facilitated fear extinction. Thus, a bidirectional functional role in fear learning for the BA-targeting 5-HT pathway was characterised. The effect of optogenetic photoexcitation of the DRN-BA 5-HT pathway on BA single unit and network activity during the fear learning task was then recorded in vivo. The study revealed that 5-HT projection activation promoted a neurophysiological state (both in terms of individual neuron activity and network oscillations) in the BA that has previously been associated with fear expression. Ex vivo electrophysiology experiments then explored the effect of optogenetic activation of the DRN-BA 5-HT pathway on the BA microcircuitry. These latter experiments identified clear evidence of 5-HT and glutamate co-transmission within the BA, which functioned in a cell type-specific and frequency-dependent manner. Finally, a combination of retrograde tracing and immunohistochemistry was applied to analyse the neurochemical identity of DRN neurons that project to the BA. The majority of these neurons were found to co-express markers for 5-HT and glutamate. To evaluate the contribution of 5-HT transmission from DRN-BA 5-HT projections to fear learning, optogenetics was combined with local infusion of 5-HT receptor antagonists. This experiment demonstrated that photoexcitation-induced enhancement of fear learning was mediated by 5-HT-dependent mechanisms. In summary, this thesis presents new evidence that DRN-BA 5-HT projections exert circuit-, temporal-, and 5-HT receptor-specific regulation of fear-related behaviour. These results highlight the importance of elucidating precise actions of 5-HT transmission in moving towards a more accurate understanding of how the 5-HT system influences emotional states.
12
Angelhuber, Martin. "The neural circuitry of fear conditioning : a theoretical account". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ082/document.
Testo completoAbstract (sommario):
Conditionnement à la peur est un paradigme réussi pour comprendre les substrats neuronaux de l’apprentissage et de l’émotion. Dans cette thèse, je présente deux modèles informatiques des structures du cerveau qui sous-tendent l'acquisition de la peur conditionnée. Le première modèle est utilisé pour enquêter sur l’effet des changements de l’inhibition tonique sur le traitement des informations reçues. On confirme que la diminution de l’inhibition tonique d’une population augmente la réactivité du réseau. Ensuite, le modèle est analysé d’une perspective fonctionnelle et des prédictions qui découlent de cette proposition sont discutées. En outre, je présenterai un modèle systématique, basé sur un type de modèle de conditionnement récemment introduit utilisant des variables latentes. Je propose que l’interaction entre les neurones dans l’amygdale basale code pour l’interface entre ces variables latentes. Le modèle couvre une large gamme d’effets et l’analyse produit un certain nombre de prédictions vérifiablesFear conditioning is a successful paradigm for studying neural substrates of emotional learning. In this thesis, two computational models of the underlying neural circuitry are presented. First, the effects of changes in neuronal membrane conductance on input processing are analyzed in a biologically realistic model. We show that changes in tonic inhibitory conductance increase the responsiveness of the network to inputs. Then, the model is analyzed from a functional perspective and predictions that follow from this proposition are discussed. Next, a systems level model is presented based on a recent high-level approach to conditioning. It is proposed that the interaction between fear and extinction neurons in the basal amygdala is a neural substrate of the switching between latent states, allowing the animal to infer causal structure. Important behavioral and physiological results are reproduced and predictions and questions that follow from the main hypothesis are considered
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Wagner, Viola [Verfasser], e Jens V. [Akademischer Betreuer] Schwarzbach. "The Neural Core of Fear and Anxiety – Commonalities and Differences of Fear and Anxiety Circuits / Viola Wagner ; Betreuer: Jens V. Schwarzbach". Regensburg : Universitätsbibliothek Regensburg, 2021. http://d-nb.info/1225935881/34.
Testo completo
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Tarpley, Jason William. "Molecules, neuronal firing, and circuits for the learning and expression of conditioned fear". Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1679374151&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Testo completo
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Winter, Andrew. "Novel insights on panic: emerging role of the subfornical organ (SFO) mechanisms and circuits". University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1572877989104869.
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Alves, Sandra Priscila. "O circuito espacial da produ??o petrol?fera no Rio Grande do Norte". Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/18939.
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Previous issue date: 2012-03-22Our study refers to the state of Rio Grande do Norte against the deployment of oil activity in their territory. In this sense the aim of this work was to analyze the presence of the loop space of the oil production system linked to objects and actions on the Rio Grande do Norte territory. From the so-called "oil shock", an event that caused global developments in several countries, Petr?leo Brasileiro S/A (PETROBRAS) increased investments in drilling geological basins in Brazil. In the year 1973 was drilled in the sea area well which led to commercial production of oil and gas in Rio Grande do Norte. From that point on were added in some parts of the Potiguar territory, large systems of coupled objects to actions caused by several agents. In this context, geographic situations have been reorganized due to an unprecedented space circuit production accompanied by a new circle of cooperation. In the state happen all instances of the circuit: the production, distribution and consumption. In light of the theory of the geographical area seek to direct our thoughts to the operation of these bodies, and they are linked to material and immaterial flows multiscales. This perspective allows us to think the territory of Rio Grande do Norte entered into a new territorial division of labor characterized by specialization regional production. Oil activity was implemented in the territory of Rio Grande do Norte at a time marked by productive restructuring of various economic sectors. The oil sector has been acting increasingly linked the scientific and informational, with a view to increasing productivity. The presence of this circuit demanded the territory, specifically the Mossor?, an organizational structure that is different from the vast system nationally integrated private commercial corporations to small corporations, all of them relating directly or indirectly to PETROBRAS. The flows between companies whose headquarters are located in distant states and even countries have generated a continuous movement of goods, people, information and ideas, which is also causing new materialities in the territory
Nosso estudo se remete ao estado do Rio Grande do Norte frente ? implanta??o da atividade petrol?fera em seu territ?rio. Nesse sentido o objetivo geral do trabalho consistiu em analisar a presen?a do circuito espacial da produ??o petrol?fera vinculado ao sistema de objetos e de a??es presentes no territ?rio norte-rio-grandense. A partir do chamado choque do petr?leo , acontecimento mundial que causou desdobramentos em v?rios pa?ses, a Petr?leo Brasileiro S/A (PETROBRAS) aumentou os investimentos em perfura??es nas bacias geol?gicas brasileiras. No ano de 1973 foi perfurado em ?rea mar?tima o po?o que deu origem ? produ??o comercial de petr?leo e g?s no Rio Grande do Norte. Desse momento em diante foram acrescentados em algumas parcelas do territ?rio potiguar, grandes sistemas de objetos, juntamente, ?s a??es provocadas por agentes diversos. Nesse contexto, situa??es geogr?ficas foram reorganizadas em fun??o de um in?dito circuito espacial de produ??o acompanhado de um novo c?rculo de coopera??o. No estado acontecem todas as inst?ncias do circuito: a produ??o, a distribui??o e o consumo. ? luz da teoria do espa?o geogr?fico procuramos direcionar as nossas reflex?es ao funcionamento destas inst?ncias, estando elas ligadas a fluxos materiais e imateriais multiescalares. Essa perspectiva nos autoriza a pensar o territ?rio norte-rio-grandense inserido em uma nova divis?o territorial do trabalho marcada pela especializa??o regional produtiva. A atividade petrol?fera implantou-se no territ?rio norte-rio-grandense em um momento marcado pela reestrutura??o produtiva de diversos segmentos econ?micos. O setor petrol?fero passou a atuar cada vez mais atrelado ?s bases cient?ficas e informacionais, tendo em vista o aumento da produtividade. A presen?a desse circuito demandou ao territ?rio, mais especificamente a Mossor?, uma diversa estrutura organizacional que ocorre desde o vasto sistema nacionalmente integrado de corpora??es comerciais privadas at? as pequenas empresas, todas elas relacionando-se diretamente ou indiretamente com a PETROBRAS. Os fluxos entre empresas, cujas sedes localizam-se em estados e mesmo pa?ses distantes, t?m gerado um movimento cont?nuo de produtos, pessoas, informa??es e ideias, o que vem provocando tamb?m novas materialidades no territ?rio
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Reppucci, Christina Jean. "The functional forebrain circuitry of fear-cue inhibited feeding in food-deprived rats: Evidence from complementary pathway tracing and Fos induction maps studies". Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104569.
Testo completoAbstract (sommario):
Thesis advisor: Gorica D. PetrovichThe drive to eat, like most motivated behaviors, is controlled by both intrinsic signals from the body as well as extrinsic signals from the environment. Although these factors often act in concert, in some instances environmental cues can override the body’s homeostatic signals. Prior work investigating the ability of learned cues to promote overeating in the absence of hunger identified a critical forebrain network composed of the amygdala, medial prefrontal cortex (mPFC), and lateral hypothalamus (LHA). We hypothesized that a similar forebrain network may also be critical when learned fear-cues inhibit eating despite hunger. The amygdala, mPFC and LHA are each anatomically and functionally positioned to influence feeding, and evidence suggests they could work together to support the fear-cue’s ability to inhibit feeding by overriding homeostatic hunger signals triggered by food-deprivation. Prior anatomical work identified direct pathways between these three large, heterogeneous regions; however, less is known about the organization of the underlying circuitries, especially between distinct nuclei and/or subdivisions that comprise these structures. Study 1 used a dual retrograde tract tracing design to map the topographical organization of the connections between the amygdala, mPFC, and LHA in detail, and to determine whether amygdalar pathways to the mPFC and to LHA originated from the same or different neurons. We found evidence for multiple, topographically organized, direct pathways from the amygdala to the LHA, and separate pathways from the amygdala to areas of the mPFC that send direct projections to the LHA. Importantly, nearly all amygdalar projections to the mPFC and to the LHA originated from different neurons, suggesting that amygdala and amygdala-mPFC processing influence the LHA independently. Study 2 used immediate early gene induction to map the patterns of functional activation within this amygdala-prefrontal-lateral hypothalamic network during the expression of fear-cue inhibited feeding behavior, and to assess whether these patterns were similar in males and females. We found differential activation across the network, and activation patterns related to the presentation of fear-cues, the presence of food-related cues, and the amount of food consumed were associated within distinct cell groups in the amygdala, mPFC, and LHA. Together, the studies presented in this dissertation provide anatomical and functional maps for future interrogation of the circuitry underlying fear-cue inhibited feeding
Thesis (PhD) — Boston College, 2015
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Psychology
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Bernot, Alix. "Modélisation et optimisation d'une machine électrique homopolaire en poudre de fer". Thesis, CentraleSupélec, 2015. http://www.theses.fr/2015SUPL0025/document.
Testo completoAbstract (sommario):
Cette thèse présente l’étude d’une machine électrique à stator à flux transverse à griffes. Après une étude du SMC et des structures à flux transverse, une structure associant un stator à griffes à un rotor à aimants permanents est choisie. Un modèle de la machine par réseau de réluctances est développé, en s’appuyant sur des simulations éléments finis. Il est ensuite amendé par l’introduction d’hypothèses d’inclinaison de flux dans l’entrefer, puis il est validé par le test d’un prototype. L’architecture est alors optimisée après une analyse détaillée de la circulation des flux, qui permet d’identifier le problème de la saturation du pied de dents. Après des simulations éléments finis de la machine améliorée, un prototype est ensuite testé qui confirme l’apport de la nouvelle architecture.Une version alternative de la machine, avec un bobinage d’excitation au stator et un rotor massif est ensuite proposée. Cette machine promet une fabrication économique et une bonne robustesse. Un modèle analytique est proposé, accompagné d’une étude éléments finis, puis pour finir un prototype est testé. Une version améliorée de cette machine avec un rotor à dents isolés est ensuite proposée : un modèle analytique et des études éléments finis permettent de valider l’intérêt de cette évolutionThis thesis presents the study of a claw-pole transverse flux electric machine. At first, SMC material properties and transverse flux structures are studied, leading to the choice of a structure combining a claw-pole stator and a permanent magnet rotor. The machine is modelled by the means of a magnetic equivalent circuit, with a reluctance network, developed with the help of finite elements simulation. The model is then changed with the introduction of the hypothesis that the flux is bent inside the airgap; it is then validated by the test of a prototype.The architecture of the machine is optimized after a detailed analysis of the flux circulation, leading to the identification of the tooth-tip saturation issue. After finite element simulation of the improved machine, a prototype is later tested, which confirms the gain brought by the new architecture.An alternative version of the machine, with a field winding attached to the stator and a massive rotor is then proposed. This machine promises to be cost-effective to build and robust thanks to its massive rotor. An analytical model of the machine is introduced, along with a finite element simulation, to end with the test of a prototype which confirms the possibilities of this new concept. An improved version of the machine with a rotor with isolated teeth is finally studied, with an analytical model and a finite element leading to the validation of the interest of this evolution
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Han, Sijing. "Design and Modeling Environment for Nano-Electro-Mechanical Switch (NEMS) Digital Systems". Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1354568246.
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Darwaz, Khamsa. "Etude expérimentale et en simulation comportementale des"pertes fer"dans des circuits magnétiques de géométrie simple". Lyon, INSA, 1995. http://www.theses.fr/1995ISAL0016.
Testo completoAbstract (sommario):
Les dissipations d'énergie constituent une des limitations principales rencontrées dans la construction des transformateurs d'énergie et des machines électriques. De nouvelles conditions d'utilisation imposées par les convertisseurs de l'électronique de puissance font supporter de nouvelles contraintes aux circuits magnétiques que les outils classiques de calcul ne peuvent prendre facilement en compte. Le travail présenté s'inscrit dans le développement d'outils adaptés à ces nouvelles sollicitations. Nous avons choisi une technique de représentation qui décrit de façon globale le comportement dynamique donc évalue les pertes à l'échelle du circuit. Le modèle comportemental présenté permet d'estimer avec une bonne précision les pertes fer dans un matériau ferromagnétique doux dans des conditions variées d'excitation. Les simulations implantées sur PC demandent des temps de calcul d'environ la minute. L'extraction des paramètres nécessaires du modèle est réalisée automatiquement sur station UNIX à partir d'un nombre très réduit de données expérimentales et en très peu de temps. Ces paramètres sont calculés une fois pour toutes à l'issue d'une étape de caractérisation et gardés constants pour n'importe quelles conditions de fonctionnement du matériau étudié. Les apports et les limites de la validité de la méthode utilisée sont évalués à partir de la précision obtenue avec le modèle par rapport à une mesure directe réalisée en laboratoire dans des conditions voisines des applications les plus courantes de l'électrotechnique[Energy losses are constituting one of the principal limitations met with energy transformers and electrical machines construction. In the mean time, electronic converters are imposing new working conditions to magnetic circuits, that classical calculation methods can't easily take into account. The work exposed in this paper is about the development of adapted tools, designed to respond to these new constraints. We have chosen a technical representation that globally describes the dynamic behavior and evaluates iron losses on a circuit scale. The behavioral model used allows us to estimate with a good accuracy the losses in ferromagnetic materials, under various excitation conditions. The simulations are running on persona! computer and calculation time takes about a minute. The parameters used in the mode! are automatically and quickly obtain from UNIX station using a limited number of experimental data. These parameters are calculate once and remain constant throughout the simulations. The conditions and the validity's limits of the described method are evaluate using the mode! Accuracy, obtained by comparing results with a direct measure realised in a laboratory under the most widely encountered electrical conditions. ]
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Goyon, Stéphanie. "Circuits neuronaux sous-tendant la régulation émotionnelle par le système ocytocinergique". Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAJ046/document.
Testo completoAbstract (sommario):
L’ocytocine (OT) est un neuropeptide synthétisé au sein de l’hypothalamus. On sait aujourd’hui que l’OT est fortement impliquée dans la modulation de nombreux comportements et émotions. Pourtant, il reste encore difficile d’expliquer comment s’organise le système ocytocinergique, par exemple en sous-ensembles spécifiques. De même, les circuits neuronaux impliqués dans leur recrutement restent obscures, tout comme leur potentielle plasticité. C’est pourquoi, au cours de ma thèse, je me suis attachée à mieux comprendre ces différents points. Les résultats obtenus ont montré que i) un sous-ensemble spécifique de neurones OT est recruté par la peur ; ii) le système OT fait preuve d’une grande plasticité après une exposition à un contexte effrayant ; iii) le neuropeptide S est capable de recruter une sous-population de neurones OT afin d’exercer une action anxiolytique ; iv) les neurotransmetteurs monoaminergiques sont eux-mêmes capables de recruter différents sous-ensembles de neurones OT. En conclusion, mon travail a mis en évidence la plasticité de ce système peptidergique et différentes manières de recruter de manière spécifiques certains sous-ensembles existants de neurones OTOxytocin (OT) is a peptide synthesized within the hypothalamus. We now know that OT is strongly involved in the modulation of many behaviors and emotions. However, it is still difficult to explain how the oxytocinergic system is organized, for example in specific sub-populations. Similarly, the neuronal circuits involved in their recruitment remain obscure, like their potential plasticity. That is why, during my thesis, I tried to better understand these different points. The results obtained showed that i) a specific sub-population of OT neurons is recruited by fear; ii) the OT system exhibits great plasticity after exposure to a scary context; iii) the neuropeptide S is able to recruit an OT neuron sub-population in order to exert an anxiolytic effect; iv) monoaminergic neurotransmitters are themselves able to recruit different sub-populations of OT neurons. In conclusion, my work has highlighted the plasticity of this peptidergic system and different ways to recruit in a specific manner some existing sub-populations of OT neurons
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Kuerbitz, Jeffrey S. "Formation and Function of Amygdala Circuitry: Differentiation and Migration of Intercalated Cells (ITCs) and their Role in Fear, Depression and Social Behavior". University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535457845286194.
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Almada, Rafael Carvalho. "Mediação do medo condicionado contextual por mecanismos serotoninérgicos do circuito núcleo mediano da rafe-hipocampo dorsal". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/59/59134/tde-01082013-103214/.
Testo completoAbstract (sommario):
Vários estudos mostram que o núcleo mediano da rafe (NMR) e o hipocampo dorsal (HD) estão envolvidos no medo condicionado Pavloviano. Além disso, mecanismos serotoninérgicos do NMR parecem participar da expressão da resposta de medo condicionado contextual. Entretanto, ainda não existe uma abordagem experimental que integre os mecanismos do circuito NMR-HD. Neste trabalho, o paradigma do medo condicionado foi utilizado para testar a influência dos mecanismos serotoninérgicos do circuito NMR-HD no medo condicionado contextual. As respostas de sobressalto e congelamento foram avaliadas após a administração de drogas serotoninérgicas intra-NMR e no HD, 6 h depois a sessões treino, nas quais os ratos eram condicionados com choques nas patas. A redução da transmissão serotoninérgica no NMR é devido a microinjeção do 8-hidroxi-2(di-n-propilamino)-tetralin (8-OH-DPAT), um agonista de receptores 5-HT1A, no NMR promoveu redução das respostas de congelamento, mas não alterou a resposta de sobressalto. Estes resultados são consistentes com a ideia de que mecanismos serotoninérgicos no NMR regulam as respostas de congelamento a um contexto aversivo. A diminuição pós-sináptica da serotonina nas áreas de projeção do NMR ocorre devido a ativação de autoreceptores 5-HT1A nesta estrutura. Com relação ao hipocampo, a microinjeção de cetanserina, um antagonista de receptores 5-HT2, não promoveu alteração nas respostas de congelamento e sobressalto potencializado pelo medo, porém a ativação de receptores 5-HT1A pela injeção de 8-OH-DPAT 6 h após o treino inibiu essas respostas. De acordo com esses resultados, um mecanismo inibitório deva se interpor entre os processos associados à chegada de informação aversiva e os associados à saída delas no HD. As projeções HD-amígdala e córtex pré-frontal medial podem constituir a porta de saída dos processos neurais subjacentes a expressão do medo condicionado contextual, conforme foi observado no experimento em que estudou a imunorreatividade destas estruturas á proteína Fos em ratos submetidos ao mesmo procedimento experimental de medo condicionado contextualSeveral studies have shown that the median raphe nucleus (MRN) and dorsal hippocampus (DH) are involved in Pavlovian conditioned fear. Moreover, previous findings have also implicated serotonergic mechanisms of the MRN in the retrieval of contextual conditioned fear. However, studies that examine the integrated involvement of serotonergic mechanisms of the MRN-DH are lacking. This study, a fear conditioning paradigm was used to test whether the serotonergic projections from the MRN to DH can influence contextual fear conditioning. Startle and freezing responses were avaliated after administration of serotoninergics drugs into the MRN or DH, 6 h previously rats received footshocks in the training session. A reduction of 5-HT transmission in the MRN by local infusions of the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) decreased freezing in response to the CS but did not reduce fear-potentiated startle. This pattern of results is consistent with the hypothesis that MRN serotonergic mechanisms selectively modulate the freezing response to the aversive context. As for the DH, a decrease in postsynaptic 5-HT receptor activity at projection areas has been proposed to be the main consequence of 5-HT1A receptor activation in the MRN. Infusions of the 5-HT2 receptor antagonist ketanserin into the DH had no effect, but activation of 5-HT1A receptors through intra-DH injections of 8-OH-DPAT inhibited both the freezing and fear-potentiated startle response to the CS. To reconcile these findings, an inhibitory mechanism may exist between the incoming DH 5-HT pathway from the MRN and the presynaptic 5-HT neurons that are part of the DH output to other structures. The DH-amygdala and medial prefrontal cortex projections could well be this output circuit modulating the expression of contextual fear conditioning as revealed by measurements of Fos immunoreactivity in these areas.
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Meurer, Ywlliane da Silva Rodrigues. "Participa??o do circuito dopamin?rgico nas altera??es do comportamento de medo inato de camundongos infectados pelo Toxoplasma gondii". Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17339.
Testo completoAbstract (sommario):
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Previous issue date: 2012-04-26The protozoan parasite Toxoplasma gondii transforms the innate aversion of rats for cat urine into a fatal attraction, that increases the likelihood of the parasite completing its life cycle in the cat s intestine. The neural circuits implicated in innate fear, anxiety, and learned fear all overlap considerably, raising the possibility, that T. gondii may disrupt all of these nonspecifically. In this study, we evaluated immunoreactivity for tyrosine hydroxylase (TH) in areas associated with innate fear of infected male swiss mice. The latent Toxoplasma infection converted the aversion of mice to feline odors into attraction. This loss of fear is remarkably specific, as demonstrated by Vyas et al (2007), because infection did not diminish learned fear, anxiety-like behavior, olfaction, or nonaversive learning. However, the neurochemical mechanism related to alterations in innate fear due to T. gondii infection remains poorly studied. 20 mice were inoculated with bradyzoites (25 cysts) from a Toxoplasma gondii (Me-49 strain). The brains were removed after 60 days, sectioned and processed for TH immunohistochemistry. The correlation between the amount of cysts per area and the densitometric analysis of neurotransmitter reactivity was low in the areas implicated in innate fear of infected animals, when comparated with noninfected controls
O protozo?rio Toxoplasma gondii transforma a avers?o inata de ratos ? urina de gato em atra??o. Essa mudan?a pode aumentar a probabilidade de transmiss?o do parasito para o seu hospedeiro definitivo, os felinos, onde pode se reproduzir sexualmente. Os circuitos neurais envolvidos no medo inato, ansiedade ou medo aprendido se sobrep?em consideravelmente, aumentando a possibilidade de que o T. gondii possa interferir com todos de maneira n?o-espec?fica. Neste estudo, foi avaliada a imunorreatividade para tirosina hidroxilase (TH) em ?reas dopamin?rgicas relacionadas com o medo inato em camundongos sui?os machos infectados. A infec??o latente pelo parasita inverteu a avers?o aos odores de felinos. Esta modifica??o pode estar relacionada com a presen?a dos cistos na am?gdala, pois a infec??o n?o diminui medo aprendido, a ansiedade, o olfato, ou a aprendizagem n?o-aversiva. No entanto, o mecanismo neuroqu?mico relacionado a estas altera??es no medo inato durante a infec??o permanece pouco estudado. Os animais foram infectados com bradizo?tos (25 cistos) da cepa ME-49 de T. gondii. Os c?rebros foram removidos ap?s 60 dias, seccionados e processados para revelar a reatividade da enzima TH. Os cistos foram contados nas ?reas associadas ao circuito dopamin?rgico, bem como em regi?es relacionadas ao medo inato. A contagem por ?rea e a an?lise densitom?trica mostrou baixa rela??o entre a presen?a de cistos e a reatividade para TH regi?es de interesse nos animais infectados, quando comparados aos controles n?o-infectados
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Jelassi, Sana. "Impact d'un court-circuit interne au stator d'une machine asynchrone sur les phénomènes générés par la denture". Thesis, Artois, 2011. http://www.theses.fr/2011ARTO0203/document.
Testo completoAbstract (sommario):
D’une manière générale l’étude des machines électriques peut être entreprise suivant différents niveaux de complexité. L’approche la plus simple considère une machine idéalisée pour laquelle on s’intéresse aux phénomènes principaux, notamment ceux qui génèrent le couple électromagnétique moyen. Si on s’intéresse aux phénomènes secondaires, parfois difficiles à appréhender, comme les bruits et vibrations, les pertes fer, ou le flux de dispersion des machines électriques, il est nécessaire d’avoir une approche plus complexe. C’est dans ce contexte que s’inscrit notre travail dans lequel on s’intéressera plus particulièrement à la machine asynchrone fonctionnant dans des régimes nonconventionnels. L’originalité de notre étude réside dans l’analyse, par une approche semi analytique, des phénomènes précités dans des cas d’une machine présentant un défaut de court-circuit entre spires statoriques. Les objectifs de ce travail sont multiples, on s’intéressera tout d’abord à l’étude de l’effet du défaut sur les phénomènes générés par la denture de manière à pouvoir apprécier son importance sur les dégradations des performances de la machine. Le deuxième point consiste à étudier les moyens de minimisation des pertes fer et des vibrations par conception, en ajustant certains paramètres géométriques de la machine, évitant ainsi le recours à des actions extérieures comme l’injectiond’harmoniques de courant. Le dernier point consiste à corréler les pertes fer et les vibrations avec le champ magnétique de dispersion. Cette corrélation permet par exemple d’estimer le niveau de dégradation des performances lors d’un fonctionnement non conventionnel de la machineIn a general way the electrical machines study can be undertaken according to various levels of complexity. The simplest approach considers an idealized machine for which we are interested in the main phenomena, in particular those that generate the average electromagnetic torque. If we are interested in the secondary phenomena, sometimes difficult to analyze, as the vibrations and noise, the iron losses, or the external magnetic field of the electrical machines, it is necessary to have a more complex approach. It is in this context that joins our work in which we shall be interested more particularly in the induction machine working in unconventional conditions. The originality of our study lies in the analysis, by a semi analytical approach, of aforesaid phenomena in cases of a machine presenting an inter turn short circuit. The objectives of this work are multiple, we shall be interested first in the study of the effect of the default on the phenomena generated by the slotting effect so as to be able to appreciate its importance on the machine performances degradation. The second point is to explore the ways to minimize iron losses and vibration by conception, by adjusting some machine geometrical parameters, so avoiding the recourse to outside actions as the current harmonic injection. The last point consists in correlating the iron losses and the vibrations to the external magnetic field. This correlation allows for example to estimate the performance degradation level during a machine unconventional running
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Bandelier, Bernard. "Contribution à la modélisation des machines sans fer par séries de Fourier : étude d'un cas de couplage d'harmoniques, calcul des performances liées à la structure de divers bobinages". Paris 6, 1986. http://www.theses.fr/1986PA066013.
Testo completoAbstract (sommario):
Equations générales de la modélisation d'une machine asynchrone à rotor massif et sans noyau sloctorique. Etude de la culasse magnétique externe. Etude des différents types d'enroulement utilisables. Analyse de l'influence de la structure du circuit magnétique sur les caractéristiques.
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Alzoubi, Khawla Ali. "NANO-ELECTRO-MECHANICAL SWITCH (NEMS) FOR ULTRA-LOW POWER PORTABLE EMBEDDED SYSTEM APPLICATIONS: ANALYSIS, DESIGN, MODELING, AND CIRCUIT SIMULATION". Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1278511770.
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Lopez, Samuel. "Définition de nouvelles structures de circuits magnétiques de machines AC utilisant des tôles à grains orientés". Thesis, Artois, 2011. http://www.theses.fr/2011ARTO0202/document.
Testo completoAbstract (sommario):
Le travail présenté porte sur la définition et le développement d’un circuit magnétique pour moteurs à haut rendement de faible et moyenne puissances. Il est réalisé avec des tôles à Grains Orientés (GO) non-segmentées. Des expérimentations réalisées en champ unidirectionnel, destinées à comparer les caractéristiques globales de la structure GO à celles obtenues sur un assemblage classique composé de tôles à grains Non-Orientés (NO), permettent de conclure quant à l’efficacité de l’association proposée en termes de pertes fer. Des investigations au niveau local, accompagnées d’une modélisation numérique, conduisent à une analyse de la répartition interne du flux magnétique dans la structure, permettant de l’optimiser. Cette technique d’assemblage est ensuite testée en champ tournant sur des moteurs statiques. Les performances obtenues, sont de nouveau comparées à celles relevées sur une maquette NO. L’étape finale consiste à tester le principe développé sur des moteurs à induction réalisés avec la configuration GO. Diverses caractéristiques sont relevées ou estimées (norme CEI) et comparées à celles de la machine NO d’origine. L’efficacité de la structure GOse traduit par une réduction notable des pertes fer, notamment statiques, conduisant à accroître sensiblement le rendement global de la machineThe work presented is focused on the design and development of a magnetic circuit for high efficiency motors of medium and small powers. It is built with non-segmented laminations of Grain Oriented (GO) steel. Experimentations on magnetic circuits excited under unidirectional magnetic field are performed. Such tests aim the comparison of the GO structure global characteristics with those of a classic one composed of Non-Oriented (NO) steel, allowing seeing the superiority of the GO structure in terms of iron losses. Local experimentations, followed by a numerical model, allow the analysis of the local distribution of the magnetic flux within the structure, leading to its optimisation. Such technique of assembly is then tested under rotational magnetic field. In that context, several experimentations are performed and its performance is compared with the one of a NO prototype. The final stage consists in testing the developed structure in induction motors built withthis GO assembly. Several characteristics are measured or estimated (IEC standard) and compared with those obtained on the initial NO motor. The GO structure efficiency leads to a remarkable reduction of the static losses, allowing the increase of the global efficiency of the motor
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Hasan, Iftekhar Hasan. "Modeling and Analysis of High Torque Density Transverse Flux Machines for Direct-Drive Applications". University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1515582377354583.
Testo completo
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Silva, Juliana Almeida da. "Estudo neurofarmacológico da interação entre circuitos endocanabinoides e opioides da substância negra, parte reticulada, sobre a atividade da via GABAérgica Nigro-Tectal, e de seu papel na modulação da analgesia induzida pelo medo inato". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/17/17133/tde-14082013-123119/.
Testo completoAbstract (sommario):
Existe um grande interesse científico voltado para a busca das bases neuropsicofarmacológicas dos comportamentos que têm sido associados ao medo e ao pânico. Muitos estudos sugerem o teto mesencefálico (TM) como responsável pelo controle de respostas defensivas elaboradas durante situações de perigo iminente. A substância cinzenta periaquedutal (SCP), as camadas profundas do colículo superior (cpCS) e o colículo inferior (CI) têm sido considerados importantes estruturas na elaboração do medo inato e do comportamento de defesa, assim como na organização da antinocicepção induzida pelo medo inato. Contudo, muitos estudos têm implicado a via neoestriado-nigro-tectal no controle de respostas defensivas elaboradas no mesencéfalo dorsal, permeadas pela interação entre vias opioides e GABAérgicas. O presente trabalho tem por objetivo o estudo neurofarmacológico da anatomia conectiva funcional entre a substância negra (SN) e estruturas do TM, como a SCP e as cpCS, ligadas à organização do comportamento relacionado ao medo e à elaboração de processos antinociceptivos, avaliando-se o envolvimento da interação entre os sistemas opioide e canabinoide e a via nigro-tectal GABAérgica na modulação do comportamento de defesa e da antinocicepção induzida pelo medo evocado pela microinjeção de antagonista GABAérgico no continuum compreendido pela coluna dorsolateral da SCP e pelas cpCS. Com esse propósito, foram estudados os efeitos de microinjeções de agonistas e de antagonistas de receptores opioides ou canabinoides não-seletivos e seletivos na substância negra, parte reticulada (SNpr), sobre a antinocicepção que segue as diversas respostas comportamentais evocadas por microinjeções de bicuculina na SCPdl/cpCS de Rattus norvegicus (Rodentia, Muridae). O presente trabalho mostrou que a microinjeção do antagonista de receptores GABAA, bicuculina no TM, induziu comportamentos defensivos, elaborados concomitantemente com processos antinociceptivos, a interação entre vias opioides e aquelas mediadas por endocanaboinoides SNpr modula o comportamento de defesa organizado no mesencéfalo dorsal sem alteração na antinocicepção induzida pelo medo. O pré-tratamento na substância negra, parte reticulada com agonistas opioides e canabinoides aumentou os limiares nociceptivos e a microinjeção de antagonistas opioides e canabinoides, causou redução dos limiares nociceptivos. Esses dados sugerem uma interação entre vias opioides e endocanabinoides da SNpr, na modulação do comportamento que tem sido relacionado ao medo inato e a ataques de pânico, sendo recrutados receptores endocanaboinoides do tipo CB1 e CB2 do mesencéfalo ventral, ao lado de receptores opioides do tipo µ1 e na modulação de vias GABAérgicas de projeção nigro-tectal.There is a great scientific interest in searching the neuropsychopharmacological bases of behavioural reactions associated to fear and panic. Many studies suggest that the mesencephalic tegmentum (MT) a mesencephalic division rich GABA, opiod and endocannabinoid containing neurons and/or receptors complex control on defensive responses during imminent danger conditions. It is also known that the periaquedutal grey matter (PAG), the deep layers of colliculus superior (cpCS) and the colliculus inferior (CI) are important structures related to innate fear and defence as well as to the organization of fear-induced antinociception. In addition neo-striatal-nigrotectal pathways are involved in the modutation of defensive responses elaborated in the dorsal midbrain, the central mesencephalic is rich in endocannabinoids. There are interactions between opioid and GABAergic pathways in these processes. The aim of this work is to study the role of the interaction between opioid anda endocannabinoide-mediated neurotransmission on the activity of GABAergic nigro-collicular pathways. Microinjections of non-selective ande selective agonist and antagonists of opioid an canabinoid receptor were performed in the SNpr before the GABAA receptor blockade in the dorsal midbrain (SCPdl/cpCS). The GABAA receptor blockade in the Mesencephalic tectum elicited vigorous defensive behaviour. This explosive escape behaviour was followed by significant antinociception. Microinjection of opioid and cannabinoid agonists in the SNpr increased the fear-induced antinociception and the treatment of the ventral midbrain with antagonists caused opposite effect .These data suggest a clear interaction between opioids and endocannabinoids pathways of the SNpr, in the modulation of the behaviour that has been related to the innate fear and the attacks of panic, being enlisted receiving endocannabinoids of type CB1 and CB2 of mesencephalic tegmentum, to the side of opioids receptors (-opioid receptor antagonist and µ1-opioid receptor antagonist) in the modulation of nigro-tectal GABAergic pathways.
31
JOUBERT, HERVE. "Analyse de couches d'oxyde formees a la surface d'alliages a base de nickel et de fer dans les conditions du circuit primaire d'une centrale nucleaire a eau sous pression". Université Louis Pasteur (Strasbourg) (1971-2008), 1997. http://www.theses.fr/1997STR13262.
Testo completoAbstract (sommario):
Notre etude s'inscrit dans le cadre de la reduction de la contamination radioactive du personnel travaillant lors de certaines operations de maintenance des centrales nucleaires a eau sous pression. Il est possible de diminuer une part de cette contamination en oxydant les tubes de generateur de vapeur cote primaire avant leur mise en service. La preoxydation est satisfaisante si elle conduit a une couche d'oxyde qui limite le relachement de metal dans le milieu primaire et d'autre part l'incorporation de produits de corrosion actives. A l'aide de techniques physiques de caracterisation, nous avons etudie les couches d'oxyde se formant sur alliages 690, 600 et 800 a la suite de quatre preoxydations (lioh 150 heures, lioh 300 heures, lioh + b et vapeur) et d'une exposition en autoclave simulant le milieu primaire. Notre objectif consistait -i) a ameliorer la connaissance des films d'oxyde formes dans de telles conditions, -ii) a definir lequel des trois alliages et le plus interessant, et -iii) a determiner si l'une des preoxydations testees est susceptible de diminuer l'incorporation et le relachement. Les observations par microscopie a force atomique (afm) ont montre que les traitements conduisent a une microrugosite plus importante sur l'alliage a base de fer que sur les alliages a base de nickel. La complementarite des analyses tem, xps, ftir, xrd, mossbauer permet de conclure a la presence des phases spinelle nifecro#4, nife#2o#4 et fe#3o#4, des oxydes de chrome cr#3o#4 et cr#2o#3 et de nio. Les donnees morphologiques (tem et afm) ainsi que les profils d'etat d'oxydation xps indiquent l'apparition de grains de ferrite de nickel sur les alliages 690 et 600 lors de l'exposition au milieu de type primaire. Les criteres d'epaisseur, d'homogeneite, de composition et de rugosite montrent l'interet -i) de preoxyder les tubes de generateur de vapeur en milieu aqueux et -ii) d'utiliser les alliages a base de nickel plutot qu'un alliage a base de fer.
32
Faye, Wagane Koli. "Contribution à la modélisation des pertes par courants de Foucault dans les circuits magnétiques feuilletés des machines électriques". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT038.
Testo completoAbstract (sommario):
Dans le cadre de la lutte contre l'augmentation des gaz à effet de serre et la préservation de l'environnement, l'efficacité énergétique est un enjeu majeur du XXIème siècle. Par exemple, les moteurs et actionneurs électriques sont de plus en plus nombreux dans le monde, les transformateurs de distribution affichent une efficacité énergétique de 97 à 99 %. Cependant, en raison de leur utilisation intensive, leur impact environnemental est loin d'être négligeable. De ce fait une compréhension et une détermination plus précise des pertes dans ces machines électriques permettraient d'améliorer l'efficacité énergétique des dispositifs d'électronique de puissance et des machines électriques. Ces dispositifs sont le siège de pertes dans les bobinages et dans les circuits magnétiques. L'objectif de cette thèse est de pouvoir modéliser, par des méthodes numériques de type éléments finis, les pertes dans les circuits magnétiques feuilletés des machines électriques.Cependant le laminage de ces circuits magnétiques, qui permet de réduire les courants de Foucault, induit de fortes contraintes de modélisation. En effet la nécessité de disposer d'au moins deux éléments finis dans l'épaisseur de peau pour obtenir une solution de qualité, conduit à la réalisation de maillages de taille très importante, incompatible avec les moyens de calcul disponibles aujourd'hui.L'objectif de ce travail est de développer des modèles de lois de comportement homogénéisé des matériaux magnétiques feuilletés dans le cadre de l'utilisation de la méthode des éléments finis en 2D et 3D, avec application aux machines tournantes et aux transformateurs. Ces modèles à priori permettront de prendre en compte les pertes en cours de résolution, afin d'obtenir des résultats précis sur les grandeurs locales et globales, et notamment les pertes, en fonction du tempsEnergy efficiency becomes a global major issue of XXIst century as we are dealing with greenhouse emissions. For instance electric rotating machines and actuators are globally more used than before. Distribution transformers do have 97 to 99% efficiency rate, with a non negligible environmental impact due to their intensive use. A thorough understanding and modeling of losses in those electric devices could help improving and maintaining that level of environmental impact and energy efficiency. This could be productive to many electrical devices from power electronics devices to electric machines and networks, because of losses in windings and magnetic cores. The main aim of this study is to model eddy current losses in laminated magnetic cores of electric machines by means of numerical methods such as Finite Element Methods (FEM).Laminating magnetic cores besides reducing eddy current loops, induces new modeling constraints . The necessary assignment of at least two elements in the skin depth in order to have good quality solutions, leads sometimes to unsolvable problems using actual computation solutions.The purpose will be to develop source code of homogenized behavior laws of laminated magnetic cores using 2D and 3D finite element methods, applied to transformers and electrical motors. Those a priori models consider losses in the main solving process allowing to have accurate results on local and macroscopic entities varying temporally
33
Hilal, Alaa. "Magnetic components modeling including thermal effects for DC-DC converters virtual prototyping". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10313/document.
Testo completoAbstract (sommario):
La complexité croissante des dispositifs en électronique de puissance nécessite l'intervention de la conception assistée par ordinateur. Le développement de systèmes électriques/électroniques est effectué à l'aide du prototypage virtuel dans lequel les logiciels de simulation sont utilisés pour prédire le comportement des composants. De ce fait, le prototypage virtuel permet une économie de temps et d'argent pour la réalisation de prototypes. La demande croissante d'appareils à faible puissance et à haut rendement a obligé les concepteurs à analyser précisément les pertes de chaque composant constituant du système. Les composants magnétiques constituent une partie importante des appareils en électronique, par conséquent la modélisation précise des matériaux magnétiques est nécessaire afin de prédire leur comportement réaliste dans des conditions de fonctionnement variables selon l'application. Notre travail s'inscrit dans ce contexte et propose un modèle dynamique non linéaire de composants magnétiques pour une utilisation dans des simulateurs de circuits électriques. Ce modèle de composant magnétique inclut le comportement d'hystérésis non linéaire du matériau et permet une modélisation précise des pertes fer et des pertes joule avec de plus la prise en considération des effets thermiques qui, généralement, ne sont pas pris en compte par les modèles existants. Le modèle est basé sur le principe de la séparation des contributions statiques et dynamiques des pertes fer et s'appuie sur la théorie de Bertotti. Le langage de programmation VHDL-AMS est utilisé en raison de sa fonctionnalité de modélisation multidomaines, permettant un couplage avec un modèle thermique. Le modèle de composant magnétique est mis en oeuvre dans le logiciel de simulation de circuit "Simplorer". Il est ensuite testé dans une application de convertisseur de puissance, le convertisseur abaisseur qui permet de fournir une excitation non-conventionnelle. Le modèle est validé pour différents noyaux d'inductances, différentes ondulations de courant et niveaux de charge, différentes températures et une large gamme de fréquenceThe increasing complexity of power electronic devices requires the intervention of computer-aided design in electrical engineering. Development of electric/electronic systems nowadays is carried out by the help of virtual prototyping, in which simulation software are used to predict components behavior without investing time and money to build physical prototypes. The increasing demand of low power, high efficiency devices forced designers to precisely analyze losses in each component constituting the system. Magnetic components constitute a major part of electronics devices. Therefore accurate modeling of magnetic materials is mandatory in order to predict their realistic behavior under variable operating conditions. Our work takes place in this context by proposing a non-linear dynamic model of magnetic components for use in circuit simulators. It includes the material nonlinear hysteretic and dynamic behaviors with accurate modeling of winding and core losses in addition to thermal effects that are not taken into account by existing models. The model is based on the principle of separation of static and dynamic contributions as well as Bertotti’s theory. VHDL-AMS is used as a modeling language due to its multi-domain modeling feature, allowing coupling with a thermal model. The magnetic component model is implemented in circuit simulation software “Simplorer” It is then tested in a widely used power converter application, the buck converter, to ensure non conventional excitation. The model is validated for different core inductors, different current ripples, different loads, different temperatures and a wide frequency range
34
Séméria, Marie-Noëlle. "Etude de circuits submicroniques implantés pour mémoire à bulles magnétiques". Grenoble 1, 1987. http://www.theses.fr/1987GRE10137.
Testo completoAbstract (sommario):
La technologie necessaire a la realisation de memoires a bulles magnetiques implantees de haute densite (au moins 16 mb/cm**(2)) est etudiee sous differents aspects: le report de motifs submicroniques (0. 3-0. 8 mu m) necessite d'optimiser les moyens classiques de lithographie optique par contact ou projection. A cette fin, une modelisation est utilisee et des experiences comparatives realisees; la realisation des circuits comporte des implantations ioniques: differents materiaux de masque sont proposes (or, silice, polymere). Dans chacun des cas, des realisations concretes de masques graves sont effectuees et analysees; enfin des implantations hydrogene sont realisees. Le fonctionnement des dispositifs est correle aux parametres de l'implantation et au dessin des motifs. Des conclusions pratiques sont tirees sur l'implantation et la technologie compatibles avec un bon fonctionnement des dispositifs
35
Solazzo, Rita. "Ceintures et crochets du territoire circum-alpin de l'Italie du Nord entre le VIIIe et le IIe siècle av. J.-C. : typologie et productions". Electronic Thesis or Diss., Paris 1, 2022. http://www.theses.fr/2022PA01H055.
Testo completoAbstract (sommario):
L'objectif de la thèse était l'étude typologique et technologique de ceintures provenant du nord de l'Italie à l'âge du fer. Cette étude a consisté à étudier les communautés qui circulaient et vivaient dans la zone transalpineThe aim of the thesis was the typological and technological study of belts from northern Italy in the Iron Age. This study involved a study of the communities that circulated and lived in the transalpine area
36
Flasquelle, Aurélie. "Contribution à la modélisation multi-physique : électro-vibro-acoustique et aérothermique de machines de traction". Ecole Centrale de Lille, 2007. http://tel.archives-ouvertes.fr/docs/00/19/65/74/PDF/These-A_FASQUELLE.pdf.
Testo completoAbstract (sommario):
Le développement important ces dernières années du secteur du transport s’est accompagné d’une inquiétude accrue pour le respect de l’environnement. Bien que le transport ferroviaire présente une efficacité énergétique élevée, il n’en est pas pour autant dénué de nuisances environnementales. L’intégration du développement durable lors de la conception optimale de machines électriques devient alors indéniable. Cela impose de tenir compte simultanément d’un grand nombre de phénomènes physiques. Cette thèse a alors pour objectif de mettre en avant une méthodologie de conception en accord avec la volonté actuelle d’optimisation économique et écologique. Un modèle multi-physique a alors été développé dans le but de représenter les phénomènes électromagnétiques, vibro-acoustiques et aérothermiques dans un moteur asynchrone fermé auto-ventilé dédié à la traction ferroviaire. Ce modèle est en fait composé de plusieurs modèles, analytiques ou semi-analytiques, interagissant entre eux. Chaque modèle représente des phénomènes physiques spécifiques. Un intérêt particulier a été porté au modèle aérothermique et au modèle de pertes, notamment pour la modélisation des pertes au sein du circuit magnétique. Bien qu’ils soient tous deux analytiques, le développement de ces deux modèles a fait appel à des études numériques préalables. L’efficacité du modèle multi-physique et son respect des tendances d’évolution ont pu être mis en évidence par une comparaison avec des résultats d’essais expérimentaux sur moteur réel et par une analyse de l’influence des incertitudesTransports have been developed for past few years. This major development has been followed by growing concern for the environment respect. Although railway transports present high energy efficiency, they also present environmental nuisances. It is then necessary to include the sustainable development from the moment of conception. It results in the consideration of numerous physical phenomena. Consequently, this PhD Thesis aims to emphasize a conception methodology in respect to the current will of economic and ecological optimisation. Then, a multi-physical model has been developed in order to represent electromagnetic, acoustic and thermal-flow phenomena in an enclosed induction motor of railway traction. In fact, this model is divided into several analytical interacting models. Each model represents a specific physical phenomenon. This work focuses on the thermal-flow model and the losses model, and in particular on the modelling of the iron losses. Although these models are analytical models, they both rely on numerical studies. The multi-physical model has shown to be efficient and to respect the main evolution trends thanks to comparison with experimental results and analysis of the uncertainties influence
37
Lin, Shao Hua. "Multi-Physics Model of Key Components In High Efficiency Vehicle Drive". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5971.
Testo completoAbstract (sommario):
Hybrid Electric Vehicles (HEVs) and Electric Vehicles (EVs) are crucial technologies for the automotive industry to meet society's demands for cleaner, more energy efficient transportation. Meeting the need to provide power which sustains HEVs and EVs is an immediate area of concern that research and development within the automotive community must address. Electric batteries and electrical motors are the key components in HEV and EV power generation and transmission, and their performance plays very important role in the overall performance of the modern high efficiency vehicles. Therefore, in this dissertation, we are motivated to study the electric batteries, interior permanent motor (IPM), in the context of modern hybrid electric/electric drive systems, from both multi-physics and system level perspectives. Electrical circuit theory, electromagnetic Finite Element Analysis (FEA), and Computational Fluid Dynamic (CFD) finite volume method will be used primarily in this work. The work has total of five parts, and they are introduced in the following.
Firstly, Battery thermal management design is critical in HEV and EV development. Accurate temperature distribution of the battery cells during vehicle operation is required for achieving optimized design. We propose a novel electrical-thermal battery modeling technique that couples a temperature dependent battery circuit model and a physics-based CFD model to meet this need. The electrical circuit model serves as a heat generation mechanism for the CFD model, and the CFD model provides the temperature distribution of the battery cells, which can also impact the heat generation of the electrical battery model. In this part of work, simulation data has been derived from the model respective to electrical performance of the battery as well as the temperature distribution simultaneously in consideration of the physical dimensions, material properties, and cooling conditions. The proposed model is validated against a battery model that couples the same electrical model with a known equivalent thermal model.
Secondly, we propose an accurate system level Foster network thermal model. The parameters of the model are extracted from step responses of the CFD battery thermal model. The Foster network model and the CFD model give the same results. The Foster network can couple with battery circuit model to form an electric-thermal battery model for system simulation.
Thirdly, IPM electric machines are important in high performance drive systems. During normal operations, irreversible demagnetization can occur due to temperature rise and various loading conditions. We investigate the performance of an IPM using 3d time stepping electromagnetic FEA considering magnet's temperature dependency. Torque, flux linkage, induced voltage, inductance and saliency of the IPM will be studied in details. Finally, we use CFD to predict the non-uniform temperature distribution of the IPM machine and the impact of this distribution on motor performance.
Fourthly, we will switch gear to investigate the IPM motor on the system level. A reduced order IPM model is proposed to consider the effect of demagnetization of permanent magnet due to temperature effect. The proposed model is validated by comparing its results to the FEA results.
Finally, a HEV is a vehicle that has both conventional mechanical (i.e. internal combustion engine) and electrical propulsion systems. The electrical powertrain is used to work with the conventional powertrain to achieve higher fuel economy and lower emissions. Computer based modeling and simulation techniques are therefore essential to help reduce the design cost and optimize system performance. Due to the complexity of hybrid vehicles, multi-domain modeling ability is preferred for both component modeling and system simulation. We present a HEV library developed using VHDL-AMS.Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
38
Juston, Maxime. "Suivi du vieillissement des batteries lithium embarquées, en usage ferroviaire". Thesis, Compiègne, 2021. http://www.theses.fr/2021COMP2596.
Testo completoAbstract (sommario):
Le modèle électrique classique d'une cellule considère celle-ci comme un ensemble homogène ayant des caractéristiques (résistance, capacités) uniques. Nous considérons au contraire qu'une cellule peut être subdivisés en un certains nombres de volumes qui sont eux considérés comme homogène d'un point de vue des propriétés électriques. La modélisation d'une cellule s'effectue alors par un ensemble de circuits électriques, à raison d'un par volume. Cette construction effectuée, nous cherchons à caractériser chacun des paramètres des circuits électriques grâce à des mesures expérimentales. Une nouvelle méthode de détermination des paramètres fonctionnant pour des cellules dont la tension à vide est non linéaire est proposée, ce qui permet de répondre à de nombreuses difficultés rencontrées dans nos travaux et des précédents. Les variations des paramètres avec la température et le courant sont également déterminées. Une seconde détermination, cette fois par optimisation permet d'introduire une différence des valeurs des paramètres afin de modéliser l'hétérogénéité. Des comparaisons expérimentales permettent de valider la pertinence du modèle hétérogène et ses performances. Les paramètres modélisant l'hétérogénéité sont représentatifs de l'interne de la cellule et le suivi de ces paramètres au cours de la vie de la cellule, et donc de son vieillissement, permettent de réaliser un diagnostic de celle-ci. Une application sur un pack de deux cellules constitué d'une neuve et d'une vieillie artificiellement permet une discrimination qualitative des cellules. Ceci permet de valider le potentiel de cette représentation comme outil de diagnosticThe classical electrical model of a cell considers it as a homogeneous whole With unique characteristics (resistance, capacitance). On the contrary, we consider that a cell can be subdivided into a certain number of volumes which are considered as homogeneous from the point of view of electrical properties. The modelling of a cell is then carried out by a set of electrical circuits, one per volume. Once this construction is completed, we seek to characterise each of the parameters of the electrical circuits by means of experimental measurements. A new method of determining the parameters for cells with a non-linear open circuit voltage is proposed, which makes possible to solve many of the difficulties encountered in our work and in previous ones. The variations of the parameters with temperature and current are also determined. A second determination, this time by optimization, allows to introduce a difference of the parameters values in order to model the heterogeneity. Experimental comparisons allow to validate the relevance of the heterogeneous model and its performances. The parameters modelling the heterogeneity are representative of the cell internals and the monitoring of these parameters during the life of the cell, and therefore its ageing, allows a diagnosis of the latter to be made. An application on a pack of two cells, one new and one artificially aged, allows a qualitative discrimination of the cells. This validates the potential of this representation as a diagnostic tool
39
Carvalho, da Silva Reginaldo. "Dyonisos par la voie de chemin de fer : cirque et théâtre dans l'intérieur de l'Etat de Bahia, Brésil, pendant la première moitié du XXe siècle". Thesis, Paris 10, 2014. http://www.theses.fr/2014PA100050/document.
Testo completoAbstract (sommario):
Cette thèse porte sur la circulation de la théâtralité du cirque, de la France aux régions intérieures du Brésil, en prenant comme référence la configuration du spectacle de cirque moderne et la présence du théâtre dans le Cirque Olympique de 1807 à 1836. Le théâtre y est considéré comme un des éléments de la pluralité du cirque qui arriva au Brésil au XIXe siècle. Pour comprendre la circulation de cette dramaturgie, l’étude se porte sur le système de transports du pays, en se focalisant sur les chemins de fer, afin de mesurer l’impact culturel du Bahia and São Francisco Railway et du Chemin de Fer São Francisco dans les régions intérieures de l’Etat de Bahia, pendant la première moitié du XXe siècle. Ce qui permet de réaliser une analyse de la vie culturelle de ce « réseau de villes » bénéficiaires des chemins de fer, en particulier les villes de Alagoinhas, Serrinha, Senhor do Bonfim et Juazeiro. A titre d’exemple de cette circulation, l’étude se concentre sur le mélodrame français Les deux sergents, de D’Aubigny, présenté pour la première fois au public au Théâtre de la Porte Saint-Martin en 1823. Traduit en portugais, il fut représenté par des cirques et des compagnies théâtrales, dans différentes villes du Brésil, dont celles étudiées ici, et illustre un vrai triomphe de la dramaturgie mélodramatique française au Brésil, pendant plus d’un siècleThis paper discusses the transit of the circus-theatricality from France to the interior of Brazil with reference to the configuration of the modern circus show and the presence of the theatre at the Cirque Olympique between the years 1807 and 1836. The theatre is therefore treated as an element of the plurality of the circus that came to Brazil in the nineteenth century. To understanding this circulation it is necessary to analyse the transport system in the country, focusing on the railroads, to point out the cultural impacts of the Bahia and San Francisco Railway and the Railway San Francisco on the interior of Bahia in the first half of the twentieth century and an analysis of the cultural life in the "network of cities" in Bahia, benefited by the railroads, especially the cities Alagoinhas, Serrinha, Senhor do Bonfim and Juazeiro. As an example of this movement, we discuss the French melodrama Les deux sergents from D'Aubigny, whose debut performance took place at the Théâtre de la Porte Saint-Martin in 1823. Translated into Portuguese, the piece was performed by circuses and theatre companies in several Brazilian cities, including those encompassed by this study, featuring a triumph of French melodramatic dramaturgy in Brazil over the course of more than a century
40
Fouassier, Patrick. "Modélisation électrique des composants magnétiques haute fréquence : prise en compte de la température et caractérisation des ferrites". Grenoble INPG, 1998. http://www.theses.fr/1998INPG0108.
Testo completoAbstract (sommario):
L'augmentation des fréquences de fonctionnement des convertisseurs statiques de l'Electronique de Puissance a rendu obligatoire une modélisation plus réaliste des composants magnétiques. Déduit uniquement de mesures extérieures au composant, le circuit électrique équivalent qui leur est associé comporte une vingtaine d'éléments discrets. Déterminé de façon systématique, grâce à une approche théorique et expérimentale rigoureuse, et rapide, grâce à l'utilisation de moyens informatiques adaptés, il permet de représenter l'ensemble des phénomènes physiques qui interviennent du continu jusqu'à une où deux décades au-delà de leur fréquence de travail. Une étude en température uniforme a montré que la possibilité de prédire le comportement électrique d'un transformateur à toute température, à partir de sa caractérisation à la température ambiante uniquement, était assurée pour les enroulements. Les données constructeur demeurent par contre insuffisantes pour quantifier correctement l'évolution du circuit magnétique. Les résistances du circuit équivalent, représentatives des pertes dans le composant, ont par ailleurs été validées par calorimétrie. Elles permettent ainsi d'estimer, avec une très bonne précision, les puissances dissipées pour une excitation et une charge données. En vue de répondre à l'absence de données complètes et réalistes de la part des fournisseurs de ferrites, une nouvelle méthode de caractérisation des matériaux magnétiques a été développée. Moyennant quelques précautions expérimentales, elle permet d'accéder, à toute fréquence et toute température uniforme, aux données perméabilité et permittivité complexes au moyen de relations analytiques simples. La méthode donne des grandeurs applicables à tout circuit magnétique, quelle que soit sa forme, et elle rend compte de tous les phénomènes physiques qui prennent naissance dans ie matériau lorsque la fréquence augmente, notamment du comportement capacitif que l'on observe dans les ferrites MnZn dès quelques dizaines de kHz. Cette méthode permet d'estimer les pertes fer jusqu'à environ 10 MHzThe increase of working frequencies in static converters used in power electronic applications requires a more realistic modeling of magnetic componems. The lumped équivalent electrical circuit assîgned to a comportent has about twenty éléments, derived by extemal impédance measurements only. This équivalent circuit, designed with a rigorous theoretical and expérimental approach, and quickly worked out using well ada^ted computer tools, enables ail the physical phenomena to be represented from DC to one or two décades beyond its operating frequency. A uniform température study has shown that the prédiction of the electric behavior of a transformer at any température, from its characterization at ambient température only, was possible for windings. On the other hand, suoplier data remain insufficient to correctly quantify the behavior of magnetic core. Moreover, résistances placed on the équivalent circuit to represent losses of the component hâve been validated by calorimetry. Thus, they allow dissipations to be determined with fine accuracy for a given source and load. To better characterize high frequency magnetic materials in the absence of complète and reliable data from ferrite manufacturers, a new origina! method has been developed. With this method requiring some expérimental précautions, simple analytical relations lead to the déduction of both complex permeability and complex permittivity at each frequency and uniform température. It also gives parameters applicable to any geometry of magnetic core and accounts for ail the physical phenomena occurring in the material when the frequency increases, notabiy the capacitive behavior that can be noticed in MnZn ferrites above tens of kHz. This method allows îron losses to be computed up to 10 MHz
41
Oplt, Tomáš. "Porovnání výsledků modální analýzy desky plošných spojů dosažených výpočtovým a experimentálním modelováním". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232000.
Testo completoAbstract (sommario):
Modal analysis of printed circuit board results, gained from computional and experimental modeling, have been compared. Anylyses have been performed on dummy boards (models without electronic components), created as one-layered at first, then as three-layered PCB. Board is usually clamped by its longer edges with wedgelock. In order to enable the realization of boundary conditions in computional and experimental modeling, real clamping has been simplified to simply supported. Computional models have used FEM elements, which are comomnly used in this type of problem. Determined results have been evaluated by comparing the experimental modeling results. Models‘ sensitivity on modification of element length and number of elements through thickness have been performed.
42
Retière, Nicolas. "Étude des défauts dans les associations onduleur-machine asynchrone : exemple d'une chaine de traction". Grenoble INPG, 1997. http://www.theses.fr/1997INPG0190.
Testo completoAbstract (sommario):
Les développements des composants de l'éléctronique de puissance ont permis l'utilisation des associations onduleur de tension - machine asynchrone pour la traction ferroviaire et de ce fait un gain de performances important. Afin que l'accroissement des performances ne se fasse pas au détriment de la sécurité et de la fiabilité, une étude s'avère indispensable pour maîtriser les conséquences des éventuelles défaillances. L'accent est particulièrement mis sur la machine asynchrone car, assurant la conversion électromécanique, elle répercute le défaut vers la transmission mécanique, élément vital pour la sécurité. Ainsi, une étude par la méthode des éléments finis des courts-circuits triphasés d'un moteur de traction ferroviaire est menée. Elle conduit à des résultats remarquables : sursaturation du parcours des flux de fuite, déplacement de courant dans les barres, contraintes sur les barres de l'ordre de grandeur de laforce centrifuge. Cette étude aboutit à la définition d'un schéma équivalent fin du moteur pour l'étude des régimes transitoires de grande amplitude. D'autre part, une formulation analytique extrêmement simple du court-circuit triphasée est obtenue pour facilitér l'interprétation physique. Enfin, une étude systématique des défauts de court-circuit des thyristors GTO de l'onduleur de tension est menée sur la base de la modélisation vectorielle de l'association, effectuant le lien entre l'état électromagnétique de la machine et les conditions du défaut.
43
Fonseca, Armando. "Comparaison de machines à aimants permanents pour la traction de véhicules électriques et hybrides". Phd thesis, Grenoble INPG, 2000. http://www.theses.fr/2000INPG0065.
Testo completoAbstract (sommario):
Ce travail se place dans le contexte de l'utilisation de machines à aimants permanents dans les véhicules hybrides ou électriques. Un modèle analytique, qui prend en compte les effets de la non linéarité du circuit magnétique, permet d'obtenir les pertes (Joule et fer) quel que soit le point de fonctionnement de la machine. Des cartes d'isorendement dans le plan couple-vitesse peuvent être tracées. Ce modèle a ensuite été utilisé pour étudier. Des variantes d'une machine synchrone à aimants. Des comparaisons de consommation sur cycles de route ont été effectuées sur ces machines, ainsi que l'étude d'autres structures de rotor à aimants. Un second modèle a été développé pour répondre à un besoin de' conception. Il a servi pour une optimisation sous contraintes dans un objectif de réduction de coût et de volumeA modelling methodology is proposed to study PM synchronous motor for electric drives. A non-linear model is presented to take saturation effects into account. FEM accuracy is combined. To analytical modelling to quicker reach motor performances whatever operating point. A new FEM magnetic 10ss estimation is exploited to obtain efficiency maps (Copper and core 10ss). Influence of active length shortening is stridied. Surface PM shape modification reduces high speed core. Loss. Inset and Interior PM motors are compared. Driving cycle consumption of Interior PM motor is improved by an airgap induction shape modification. Another analytical model is dedicated to conception. It uses a reluctance network. Constrained optimisation ofPM motors is then performed to reach cost and volume reduction
44
Park, Sehwan. "Les abus de puissance économique dans les relations commerciales déséquilibrées". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAA013.
Testo completoAbstract (sommario):
La loi doit trouver le moyen de prévenir et sanctionner de façon efficiente les abus de puissance économique constatés dans les relations commerciales déséquilibrés mais sans provoquer d’effets pervers sur le marché et sans ruiner l’efficacité des autres règles relevant du droit de la concurrence. Lorsque les rapports de force entre les parties sont particulièrement déséquilibrés, la partie forte peut imposer des conditions inégales à la partie faible, notamment à la faveur du « facteur crainte ». En effet, tant que le contrat est en cours d’exécution, la partie faible ne réagit pas de peur que la relation commerciale ne se termine. De ce fait, en dépit de la présence de nombreux textes réprimant les abus, la réalité montre qu’ils ne cessent de se répandre. Le législateur agit généralement dans la précipitation, abuse de palliatifs et néglige la faculté d’adaptation des entreprises les plus puissantes qui trouvent souvent le moyen de contourner les règles. En définitive, seul un marché plus équilibré, c’est-à-dire moins concentré, permettrait de remédier durablement aux abus de puissance économique. Dans ces conditions, la mise en place d’une véritable injonction structurelle mériterait d’être de nouveau envisagée. Le présent travail se propose de comparer les principales mesures de prévention et de sanction des abus mises en place en France et en Corée du sud qui, face à un phénomène similaire, adoptent parfois des réponses différentesCompetition provisions seek to regulate the abuse of economic power in unequal commercial relationships. However, in the process, such provisions should not have the effect of adversely impacting the market or harming the proper functioning of other competition rules. When there exists a significant power disparity between parties, the stronger party can impose unequal conditions on the weaker party, particularly through what is called the "fear factor". During the duration of the contractial relationship, the weaker party will not be able to stand up to the stronger party in fear of the commercial relationship being terminated. This is why oppressive behaviors continue in reality, despite the presence of numerous regulations designed to prevent such behaviors. Law makers have a tendency to react by hastily enacting ad hoc regulations. The adaptability of powerful corporations to circumvent the rules is often overlooked. Ultimately, abuses of economic power can only be regulated on a sustainable basis through the creation of a more balanced and less concentrated market. It is in this context that a truly structural approach should be considered. This analysis compares the principal measures against abuses of economic power employed in France and Korea, which sometimes adopt different responses to similar circumstances
45
Kolbeck, Carter. "A neurocomputational model of the mammalian fear conditioning circuit". Thesis, 2013. http://hdl.handle.net/10012/7897.
Testo completoAbstract (sommario):
In this thesis, I present a computational neural model that reproduces the high-level behavioural results of well-known fear conditioning experiments: first-order conditioning, second-order conditioning, sensory preconditioning, context conditioning, blocking, first-order extinction and renewal (AAB, ABC, ABA), and extinction and renewal after second-order conditioning and sensory preconditioning. The simulated neural populations used to account for the behaviour observed in these experiments correspond to known anatomical regions of the mammalian brain. Parts of the amygdala, periaqueductal gray, cortex and thalamus, and hippocampus are included and are connected to each other in a biologically plausible manner.
The model was built using the principles of the Neural Engineering Framework (NEF): a mathematical framework that allows information to be encoded and manipulated in populations of neurons. Each population represents information via the spiking activity of simulated neurons, and is connected to one or more other populations; these connections allow computations to be performed on the information being represented. By specifying which populations are connected to which, and what functions these connections perform, I developed an information processing system that behaves analogously to the fear conditioning circuit in the brain.
46
Lin, Pin-Shiuan, e 林品萱. "Fear Behavioral Effects and Pre-synaptically Monoaminergic Changes within Fear Circuit in a Rat Model of Posttraumatic Stress Disorder". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/11005309534182104707.
Testo completoAbstract (sommario):
碩士國防醫學院
生理學研究所
101
Posttraumatic stress disorder (PTSD) is a mental disorder of severe fear and anxiety may be ascribed largely to the abnormality of monoaminergic systems within the areas of fear circuit and lead to fear conditioning and extinction mechanism disruption, but the mechanism still unclear. Current exploration of behavioral and monoaminergic changes after extreme stress can provide useful evidence toward more understanding of the neurobiology of PTSD. The present study aimed to investigate the changes of fear conditioning-extinction mechanism and clarify the relationship between fear conditioning and extinction mechanism disruption and abnormality of presynaptic monoaminergic systems in fear circuit after single-prolonged stress (SPS). In this study, the cue-dependent fear conditioning-extinction process to assess the abnormality of fear conditioning-extinction after SPS, we confirmed that strengthen the fear conditioning and deficit the fear extinction consolidation in SPS rat. Further, the level and release capacity of dopamine (DA) reduction and increase homovanillic acid (HVA) level in brain areas of fear circuit were demonstrated by microdialysis in awake rat and high pressure liquid chromatography (HPLC) with electrochemical detection techniques. Finally, we also found the expression of synaptosome norepinephrine transporter (NET), dopamine transporter (DAT), serotonin transporter (SERT) and vesicular monoamine transporter 2 (VMAT2) decreases in several brain area. These studies confirmed that experienced extremely trauma may result in the presynaptic monoamine neurotransmitter system imbalance in fear circuit and disruption of fear conditioning-extinction mechanism, The results obtained from the present study will provide important information toward a further understanding of PTSD and the related fear mechanism.
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Lamoureux-Tremblay, Vickie. "L’anxiété et ses facteurs de risque chez les adolescents Inuits du Nunavik : les corrélats neuronaux d’une exposition prénatale et postnatale aux contaminants environnementaux". Thesis, 2019. http://hdl.handle.net/1866/24650.
Testo completoAbstract (sommario):
L’anxiété et l’exposition aux contaminants environnementaux sont actuellement deux enjeux internationaux majeurs en santé publique. Plusieurs études ont examiné empiriquement le développement des troubles intériorisés, soit ses corrélats neuronaux et ses facteurs de risque. Plus récemment, l’exposition prénatale et postnatale aux contaminants environnementaux a été soulevé comme un facteur de risque au développement de l’anxiété. Bien que les Inuits du Nunavik sont parmis les plus exposés aux contaminants environnementaux dans le monde et semble particulièrement à risque de développer des troubles intériorisés, la prévalence de l’anxiété et ses facteurs de risque demeurent à être clarifié dans cette population. Les corrélats neuronaux pouvant sous-tendre les liens entre une exposition aux contaminants environnementaux et l’anxiété chez l’humain demeure aussi à être étudié. Le premier article de ma thèse présente une revue de littérature afin de mettre en lumière les associations entre les troubles intériorisés et une exposition prénatale ainsi que postnatale au plomb, au mercure et aux biphényles polychlorés (BPC) dans diverses populations. Le deuxième article étudie empiriquement la présence d’anxiété auprès des adolescents Inuit du Nunavik ainsi que ses principaux facteurs de risque lors du développement, dont l’exposition prénatale et postnatale aux contaminants environnementaux. Cette étude a permis de confirmer des niveaux d’anxiété très élevé et de souligner les facteurs de risque pouvant y contribuer tels qu’être une femme, avoir un moindre quotient intellectuel, être plus exposé au mercure durant les périodes prénatale et posnatale, vivre davantage d’insécurité alimentaire, avoir un plus faible apport vitaminique et avoir été victime davantage d’intimidation. Finalement, le troisième article examine le fonctionnement du circuit neuronal de la peur avec l’imagerie par raisonance magnétique fonctionnelle (IRMf), grâce à une tâche de conditionnement et d’extinction de la peur, selon l’exposition prénatale et postnatale aux contaminants environnementaux. Des différences d’activation dans le cortex préfrontal ont ainsi été retrouvées, soit pour l’exposition prénatale aux BPC dans le cortex orbitofrontal lors du conditionnement ainsi que lors de l’extinction pour l’exposition prénatale au mercure dans le cortex cingulaire antérieur et l’exposition présente au plomb dans le cortex préfrontal dorsolatéral. Tous ces résultats convergent vers des pistes intéressantes pour la compréhension, la prévention et l’intervention.Anxiety and exposure to environmental contaminants are currently two major international issues in public health. Inuit of Nunavik appear at risk of developing psychological difficulties and more prone to be exposed to environmental contaminants. Several studies have empirically examined the development of anxiety, namely its neural correlates, as well as its risk factors. Environmental contaminants have recently emerged as contributing to the development of internalized disorders. The generalization of such risk factors remains to be validated within the Inuit population of Nunavik. Although closely related to anxiety, the relationship between exposure to environmental contaminants during development and the functioning of the neural circuit of fear remains to be examined. First, we reviewed the literature about association of internalized symptoms-related with prenatal and postnatal exposure to lead, mercury and polychlorinated biphenyls (PCB) in various populations. Next, we empirically examined anxiety levels in adolescent Inuit population of Nunavik and his risk factors, included environmental contaminants. This allowed to highlight very high levels of anxiety, as well as the implication of several risk factors, such as being a woman, higher exposure to mercury during prenatal and postnatal periods, more food insecurity, lower vitamin intake and more bullying experiences. Finally, we explored the functioning of the neural circuitry of fear with a task of conditioning and extinguishing fear, using functional magnetic resonance imaging, according to prenatal and postnatal exposure to environmental contaminants. Activation differences in prefrontal cortex were found, which are in the orbitofrontal cortex for prenatal exposure to PCB during fear conditioning, as well as during fear extinction in the anterior cingular cortex for prenatal exposure to mercury and in the dorsolateral prefrontal cortex for current lead exposure. All these results converge on interesting avenues for understanding, prevention and intervention.
48
Stujenske, Joseph Matthew. "Prefrontal-Amygdala Circuits Regulating Fear and Safety". Thesis, 2016. https://doi.org/10.7916/D8V69JFQ.
Testo completoAbstract (sommario):
Switching between a state of fear and safety is a critical aspect of adaptive behavior. Aversive and non-aversive associations must be formed quickly and reliably but remain malleable as these associations change dynamically. When these associations become biased towards aversive associations by traumatic and stressful circumstances, as in PTSD, fear generalization and impaired fear extinction arise. These changes are associated with reduced activity in the medial prefrontal cortex (mPFC) and enhanced activity in the basolateral amygdala (BLA). It has been hypothesized that the mPFC mediates top-down control of the BLA to signal safety. It has previously been demonstrated that synchronous activity within the mPFC-BLA circuit is strongly engaged during fear conditioning, but it is unknown how activity in this circuit changes to mediate aversive discrimination. We investigated how the mPFC and BLA cooperate to mediate successful discrimination between aversive and non-aversive stimuli both for learned and innately-valent associations. Extracellular elecrophysiological recordings were obtained simultaneously form the mPFC and BLA in mice during innate anxiety, fear discrimination, and fear extinction. Local field potentials were recorded in both structures along with single unit recordings from the BLA. We discovered that fear was associated with enhanced theta-frequency synchrony and theta-gamma coupling within the mPFC-BLA circuit. On the other hand, safety was associated with predominant mPFC-to-BLA directionality of synchronous information flow and enhanced fast gamma frequency activity in both structures. Interestingly, gamma oscillations in the BLA were strongly coupled to theta frequency activity arising in the mPFC. This data is consistent with entrainment of inhibitory circuits in the BLA by mPFC input to mediate safety.
49
Winke, Nȃnci Aléxia Vieira. "Contribution of the ventro-lateral periaqueductal grey matter to fear conditioned analgesia". Master's thesis, 2016. http://hdl.handle.net/10316/34181.
Testo completoAbstract (sommario):
Dissertação de Mestrado em Biologia Celular e Molecular apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.Fear conditioned analgesia (FCA) can be defined as a reduction of pain sensitivity resulting from the exposure to a stimulus previously associated with an aversive event. Indeed, among the classically studied fear reactions - like freezing or avoidance – analgesia has been observed after fear conditioning although the underlying neuronal circuits are largely unknown. The ventro-lateral part of the periaqueductal grey (vlPAG) has been shown to be necessary for fear expression but is also considered as a key structure in descending modulation of pain. Thus, the vlPAG, which is highly connected to brain regions involved in fear processing (such as the amygdala and the medial prefrontal cortex) but also to the spinal cord, could be an interface between fear and pain behaviours observable in FCA. In this context, the present project had two main objectives: the first aim was to investigate further the behavioural paradigm of FCA recently established in the laboratory. We observed that animals submitted to a hot-plate (HP) test show a delayed response when the trial is paired with a conditioned stimulus (CS+). This result suggests that CS+-evoked fear responses can alter the animals pain threshold. We verified that this effect could not be due to a specific stress effect, and observed that FCA can be replicated with the same strength when the HP test is repeated. The second goal of the study was to test whether the vlPAG is involved in FCA. To do so, we used optogenetic tools to manipulate two populations of inhibitory interneurons: the somatostatin-expressing (SOM+) and parvalbumin-expressing (PVa+) interneurons. We observed that the activation of these two subpopulations induced a pro-nociceptive behavior, while the inhibition of PVa+ interneurons induced an analgesic-like behaviour in the HP test. Importantly, these modulations of pain threshold were not any more visible when the animals were submitted to the FCA paradigm, suggesting that the fear-induced analgesia overcomes the optogenetic effects.
Analgesia condicionada por medo (FCA) pode ser definida como uma redução da sensibilidade à dor resultante da exposição de um estímulo que foi previamente associado a um evento aversivo. De facto, entre as respostas clássicas de medo, como imobilidade ou fuga , analgesia tem também sido observada depois de medo condicionado. Contudo, os circuitos neuronais inerentes são ainda desconhecidos. Apesar da parte ventro-lateral da substancia cinzenta periaquedutal (vlPAG) ser necessária para a expressão de medo esta estrutura é também considerada essencial na modulação da via descendente da dor. Assim, a vlPAG é uma área que está extensivamente conectada a regiões neuronais envolvidas no processamento do medo (como por exemplo a amigdala e o cortex pre-frontal) mas também à medula espinal, podendo funcionar como uma interface entre as manifestações de medo e dor observados em FCA. Desse modo, o presente estudo teve dois objectivos principais: o primeiro foi estudar em detalhe o paradigma comportamental de FCA que foi recentemente estabelecido no laboratório. Nós observamos que os animais quando sujeitos ao teste de placa quente (HP) demonstram um atraso na resposta quando o teste é emparelhado com o estímulo condicionado (CS+). Estes resultados sugerem que as respostas de medo elicitadas pelo CS+ podem alterar os limiares de dor dos animais. Além disso, verificámos que estes resultados não foram causados devido a um efeito de stress especifico e que quando o HP teste é repetido a FCA pode ser replicada, mantendo a mesma intensidade de resposta. O segundo objectivo deste estudo foi testar se a vlPAG está envolvida em FCA. Para tal, usamos ferramentas de optogenética para manipular duas subpopulações de interneurónios inibitórios: interneurónios expressando somatostatina (SOM+) e interneurónios expressando parvalbumina (PVa+). No teste de HP, constatámos que a activação destas duas subpopulações induz um comportamento pró-nociceptivo, enquanto que a inibição dos interneurónios de PVa+ resultam num comportamento analgésico. É importante salientar que a modulação destes limiares de dor não foi visível quando os animais foram submetidos ao paradigma de FCA, sugerindo que o efeito analgésico induzido por medo supera os efeitos da manipulação optogenética.
50
Reis, Sara Cristina Lourenço dos. "CONTROL OF FEAR MEMORY BY ADENOSINE RECEPTORS: role in the physiology of the related brain circuitry and implications for fear extinction and post-traumatic stress disorder". Master's thesis, 2017. http://hdl.handle.net/10316/82884.
Testo completoAbstract (sommario):
Dissertação de Mestrado em Biologia Celular e Molecular apresentada à Faculdade de Ciências e TecnologiaAnxiety- and trauma-related disorders such as post-traumatic stress disorder (PTSD) are characterized by pathological fear responses and impaired extinction of aversive memories. In both humans and rodents, caffeine intake in moderate doses correlates negatively with anxiety behavior, depression and cognitive dysfunction. These effects of caffeine are now known to be mediated mainly through the antagonism of adenosine A2A receptors (A2AR) in regions of the forebrain. In addition, A2AR in the hippocampus and in the amygdala were shown to modulate synaptic plasticity and control contextual associated fear memory. However, the role of these receptors in the extinction of fear is still unknown. In the present work, it was implemented and characterized a model of contextual fear conditioning and ‘retrieval-extinction’ paradigm. Next, the memory trace of contextual, fear and extinction memories was searched through c-fos immunohistochemistry on brain slices. Finally, it was investigated whether fear and extinction memories altered basal transmission, long-term potentiation (LTP) and depotentiation (metaplasticity) in the dorsal and ventral hippocampus and in the amygdala, through extracellular recordings on brain slices. The role of A2AR on fear extinction was investigated by injecting mice with the selective antagonist, SCH58261 (0.1mg/kg, intraperitoneal), 1 hour before each extinction trial and evaluating the fear response to the conditioning chamber, 24 hours after the last extinction trial. Moreover, it was also investigated if ex vivo blockade of A2AR modified basal transmission and plasticity on hippocampal and amygdala slices of naïve, fear conditioned and of mice that went through fear extinction.The results show that the global blockade of A2AR accelerates the extinction of contextual fear. Moreover, contextual fear conditioning increased activation of the hippocampus and of the amygdala whereas fear recall was associated with activation of other brain regions that orchestrate fear responses, namely the prelimbic area of the medial prefrontal cortex, the hypothalamus and the core region of the nucleus accumbens. Furthermore, contextual fear conditioning caused a stable increase of the LTP in the ventral hippocampus and of the basal excitability in the amygdala. Remarkably, ex vivo blockade of A2AR, which had no effect in the ventral hippocampal slices from naïve animals, in slices from fear conditioned mice reversed the conditioned-induced exacerbation of the LTP. Moreover, fear extinction also only reversed this effect of contextual fear conditioning in the ventral hippocampus.These results suggest a gain of function of the A2AR in the ventral hippocampus during the acquisition of contextual fear memories, and provides neurobiological evidence of a role for A2AR on fear extinction reinforcing the view of antagonists of these receptors as novel candidate drugs to manage fear- and anxiety-related disorders such as PTSD.
Patologias com sintomas de trauma e ansiedade, como por exemplo, stress pós-traumático (PTSD), são caraterizadas por respostas excessivas de medo e a incapacidade de extinguir memórias aversivas. Tanto em humanos como em roedores, pequenas doses de cafeína têm demonstrado ter efeitos benéficos em comportamentos de ansiedade, depressão e disfunção cognitiva. Já foi demonstrado que estes efeitos da cafeína são mediados, maioritariamente, pelo o antagonismo dos receptores de adenosina A2A (A2A). Estes receptores têm como, uma das suas funcções, modular processos de plasticidade sináptica, o que já mostrou ser vantajoso no controlo de memórias de medo. No entanto, nunca foi estudado o impacto destes receptores na extinção de memórias de medo.No estudo que vai ser apresentado, começou-se por implementar e caraterizar um modelo de medo contextual condicionado, assim como, um paradigma de ‘recuperação-extinção’ de memórias de medo. De seguida, caraterizou-se o padrão de ativação neuronal neste modelo através da imuno-histoquímica da proteína c-fos. Por fim, através de registos eletrofisiológicos extracelulares, investigou-se de que forma o medo e a extinção de memórias alterava a transmissão basal, a potenciação de longa duração e a despotenciação no hipocampo dorsal e ventral, e na amígdala. O papel dos receptores A2A foi estudado através da injeção intraperitoneal do antagonista seletivo destes receptores, SCH58261 (0,1mg/kg) 1 hora depois de cada teste de extinção. O efeito deste antagonista foi avaliado através da resposta de medo à câmara condicionada, 24horas depois do último teste de extinção. Além disto, ainda avaliamos se administração aguda ex-vivo do antagonista dos receptores A2A, modificava a transmissão basal e os processos de palsticidade em fatias de hipocampo e amigdala de animais control e animais submetidos ao protocolo de medo condicionado e extinção.Os resultados mostram que o bloqueio geral dos receptores A2A acelera a extinção do medo contextual, e ainda indicam que o medo contextual condicionado aumenta ativação neuronal tanto no hipocampo como na amigdala, mas que para relembrar a memória é necessário ativação de outras zonas cerebrais, nomeadamente, a zona pre-limbica do cortex pre-frontal, o hipotálamo e o núcleo accumbens. Os resultados da eletrofisiolofia mostram que o medo contextual condicionado levou a um aumento da magnitude da potenciação de longa duração no hipocampo ventral, e a um aumento da excitabilidade basal na amigdala. Notoriamente, o bloqueio ex-vivo dos receptores A2A normalizou a potenciação de longa duração no hipocampo ventral.Com isto, estes resultados sugerem que durante aquisição de medo existe uma hiperfunção dos receptores A2A no hipocampo ventral, e que antagonistas destes receptores poderão vir a ter um papel no tratamento de doenças de ansiedade como o PTSD.
Outro - 016684 - PTDC/NEU-NMC/4154/2014 (POCI-01-0145-FEDER-016684) - Papel dos astrócitos no controlo da memória- foco nos recetores adenosina A2A - Fundação para a Ciência e a Tecnologia
Outro - COMPETE POCI-01-0145-FEDER-007440 - Trabalho multidisciplinar no âmbito da neurociência cognitiva na saúde e na doença - Fundação para a Ciência e a Tecnologia