Teses / dissertações sobre o tema "Limbic circuit"
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Comte, Magali. "Neuro-imagerie fonctionnelle du circuit cortico-limbique lors du traitement émotionnel chez le patient schizophrène et le volontaire sain". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM5071/document.
Texto completo da fonteWithin the cortico-limbic circuit, complementary regions are believed to be involved in either the appraisal or the regulation of affective state. However, the respective contribution of these bottom-up and top-down mechanisms during emotion processing remains to be clarified. First, we validated a new fMRI paradigm designed to dissociate the components of the cortico-limbic circuit, that is, the dorsal cognitive circuit intertwined with the ventral affective circuit. We found that the amygdala and its connections to the dorsal circuit was engaged by bottom-up emotional processing. The dorsal anterior cingulate cortex (ACC) and its connections to the dorsolateral prefrontal cortex (DLPFC) and amygdala, was recruited by top-down resolution of emotional conflict. The DLPFC and its connections to dorsal ACC was engaged by top-down attentional control. Secondly, we investigated the impact of anxiety on the circuit. We demonstrated that higher levels of anxiety were associated with stronger conflict-related activation in ACC but with reduced connectivity between ACC and LPFC. Finally, we examined the variation in functional activity and connectivity in schizophrenia patients. In patients compared to controls, bottom-up processes were associated with reduced functional interaction between the amygdala and both dorsal and ventral ACC as well as DLPFC. Top-down resolution of emotional conflict led to stronger functional connectivity between the dorsal ACC and both ventral parts of ACC and DLPFC. Increased top-down attentional control caused higher functional coupling between the DLPFC and ventral ACC
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.
Texto completo da fonteAnxiety 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
Parkinson, John Anthony. "Limbic cortico-striatal circuitry underlying Pavlovian associative learning". Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625012.
Texto completo da fonteBuscher, Nathalie. "Cognition and the balance of excitation and inhibition in mouse cortico-limbic circuits". Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690894.
Texto completo da fonteZhu, Ning. "Advances in Non-Foster Circuit Augmented, Broad Bandwidth, Metamaterial-Inspired, Electrically Small Antennas". International Foundation for Telemetering, 2012. http://hdl.handle.net/10150/581683.
Texto completo da fonteThere are always some intrinsic tradeoffs among the performance characteristics: radiation efficiency, directivity, and bandwidth, of electrically small antennas (ESAs). A non-Foster enhanced, broad bandwidth, metamaterial-inspired, electrically small, Egyptian axe dipole (EAD) antenna has been successfully designed and measured to overcome two of these restrictions. By incorporating a non-Foster circuit internally in the near-field resonant parasitic (NFRP) element, the bandwidth of the resulting electrically small antenna was enhanced significantly. The measured results show that the 10 dB bandwidth (BW10dB) of the non-Foster circuit-augmented EAD antenna is more than 6 times the original BW10dB value of the corresponding passive EAD antenna.
Borkowski, M. (Maciej). "Digital Δ-Σ Modulation:variable modulus and tonal behaviour in a fixed-point digital environment". Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514289101.
Texto completo da fonteBerg, Junker Maria Constance. "Neural correlates of romantic love and romantic attachment". Thesis, Högskolan i Skövde, Institutionen för biovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-16055.
Texto completo da fonteJebari, Salha. "The inelastic Cooper pair tunneling amplifier (ICTA)". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY036/document.
Texto completo da fonteJosephson parametric amplifiers (JPA), have proven to be an indispensable tool for awide range of experiments on quantum devices in the microwave frequency regime, becausethey provide the lowest possible noise. However, JPAs remain much more difficult to use andoptimize than conventional microwave amplifiers. Recent experiments with superconductingcircuits consisting of a DC voltage-biased Josephson junction in series with a resonator,showed that a tunneling Cooper pair can emit one or several photons with a total energyof 2e times the applied voltage. In this thesis we show that such q circuit can be used toimplement a new type of phase preserving microwave amplifier, which we call InelasticCooper pair Tunneling Amplifier (ICTA). It is powered by a simple DC bias and offers nearquantum-limited noise performance.We start this work by presenting a brief and simple picture of the basic ICTA operatingprinciples. In analogy with the quantum theory of JPAs, we calculate the performances ofthis amplifier such as the gain, bandwidth and noise. Then, we present the first experimentalproof that amplification close to the quantum limit is possible without microwave drive inan extremely simple setup. These measurements are made on a first generation of samplesbased on aluminium junctions. According to our theoretical and experimental results, wehave designed microwave circuits presenting specific frequency-dependent impedances tothe junction in order to optimize the performances of our amplifier. This second generationof ICTA samples is fabricated from niobium nitride and provide significantly lower noiseand higher gain.We expect that once fully optimized, such an amplifier, powered by simple DC voltagescould then make measuring microwave signals at the single photon level much easier andallow to deploy many amplifiers on a chip. It could therefore be an important ingredient forqubit readout in large-scale quantum processors
Nevřivý, Tomáš. "Kompaktní měnič pro BLDC motor". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-219927.
Texto completo da fonteCarvalho, Ana Raquel Franky Gomes. "Modulation of limbic noradrenergic circuits by cannabinoids". Doctoral thesis, 2010. http://hdl.handle.net/1822/11751.
Texto completo da fonteThe endocannabinoid system has been implicated in the regulation of several physiological functions. The widespread distribution of the endocannabinoid system in the central nervous system (CNS) accounts for many effects attributed to cannabinoids. Importantly, cannabinoids have been shown to modulate mood, cognition and memory. There is growing evidence suggesting that cannabinoids can interact with the noradrenergic system. Noradrenergic transmission in the CNS has also been implicated in the regulation of mood, cognition and memory. In the present work, the hypothesis that cannabinoids can impact noradrenergic transmission in the limbic system was examined. Firstly, localization of the cannabinoid receptor type 1 (CB1r) was performed in the nucleus accumbens (Acb) and in the nucleus of the solitary tract (NTS), using immunohistochemical techniques, to clarify the anatomical substrates underlying potential interactions. It was shown that CB1r is present in noradrenergic neurons of the NTS. In addition, CB1r was found in the Acb but rarely in noradrenergic terminals. Furthermore, the effects of cannabinoid administration on adrenergic receptor (AR) expression in the Acb were studied. Western blot analysis of accumbal tissue revealed that exogenous administration of the synthetic cannabinoid WIN 55,212-2 decreases α2A- and β1-AR expression. Finally, the importance of norepinephrine (NE) in cannabinoid-induced behaviors was tested. Using the place conditioning paradigm and the elevated zero maze (EZM), the effects of cannabinoids on aversion and anxiety, respectively, were tested following depletion or blockade of noradrenergic transmission in the Acb or in the bed nucleus of the stria terminalis (BNST). Using an immunotoxin approach, NE depletion restricted to the Acb, but not BNST, blocked the expression of aversion to WIN 55,212-2. Depletion of NE had no effect on WIN 55,212-2-induced anxiety. Moreover, the fact that blockade of β1-AR in the Acb prevents WIN 55,212-2-induced aversion suggests that noradrenergic transmission via β1-AR is critical for eliciting this behavior. In conclusion, the present work provides new evidence supporting the idea that cannabinoids can impact noradrenergic transmission in the limbic system. In addition, cannabinoid-induced aversion is dependent on intact noradrenergic transmission in the Acb. Taken together, the studies provide herein clarify the anatomical and neurochemical substrates for cannabinoid actions in the CNS.
O sistema endocanabinóide tem sido implicado na regulação de várias funções fisiológicas. A dispersa distribuição do sistema endocanabinóide no sistema nervoso central (SNC) explica os muitos efeitos atribuídos aos canabinóides. De realçar que tem sido demonstrado que os canabinóides modelam o humor, cognição e memória. Existe uma crescente evidência sugerindo uma interacção entre o sistema endocanabinóide e o sistema noradrenérgico. Por seu lado, transmissão noradrenérgica no SNC tem sido implicada na regulação do humor, cognição e memória. No presente trabalho, a hipótese de que os canabinóides podem afectar a transmissão noradrenérgica no sistema límbico foi examinada. Inicialmente, a localização do receptor dos canabinóides tipo 1 (CB1r) no núcleo accumbens (Acb) e no núcleo do tracto solitário (NTS) foi efectuada utilizando técnicas de imunohistoquímica, de forma a clarificar os substratos anatómicos subjacente a potenciais interacções. Foi demonstrado que CB1r está presente em neurónios noradrenérgicos do NTS. Para além disso, CB1r foi encontrado no Acb mas raramente em terminais noradrenérgicos. Adicionalmente, os efeitos da administração de canabinóides na expressão de receptores adrenérgicos no Acb foram estudados. Análise por western blot de tecido do Acb revelou que administração exógenea do canabinóide sintético WIN 55,212-2 diminui a expressão dos receptores adrenérgicos α2A e β1. Finalmente, a importância da noradrenalina (NA) nos comportamentos induzidos pelos canabinóides foi testada. Utilizando o paradigma de “place conditioning” e o teste “elevated zero maze” (EZM), os efeitos dos canabinóides na aversão e anxiedade foram testados após depleção ou bloqueio da transmissão noradrenérgica no Acb ou no núcleo da estria terminalis (BNST). Utilizando uma imunotoxina, a depleção restrita de NA no Acb, mas não no BNST, bloqueou a aversão ao WIN 55,212-2. Enquanto que depleção de NA não teve nenhum efeito na anxiedade provocada por WIN 55,212- 2. Mais, o facto de o bloqueio do receptor adrenérgico β1 no Acb prevenir a aversão induzida por WIN 55,212-2 sugere que a transmissão noradrenérgica via este receptor é fundamental para a expressão deste comportamento. Em conclusão, o presente trabalho fornece nova evidência suportando a ideia de que os canabinóides podem afectar a transmissão noradrenérgica no sistema límbico. Mais, a aversão induzida por canabinóides é dependente da transmissão noradrenérgica no Acb. Em conjunto, os estudos apresentados neste trabalho esclarecem os substratos anatómicos e neuroquímicos das acções dos canabinóides no SNC.
Wang, Chi-Han, e 王咨涵. "Altered regulation of neural circuits in limbic structures prior to status epilepticus". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/08471755795329547964.
Texto completo da fonte國立陽明大學
生理學研究所
101
The generation of epilepsy depends on the circuit transition from normal state to abnormal state, and this transition is involved in the changes of brain activities including neuronal firing patterns, coordination of neural populations, and correlation between single neurons and neural populations. However, the determinants and regulators prior to status epilepticus (SE) are not well understood. In this dissertation, different approaches to spatio-temporal dynamics of brain were used to study the transition factors from normal state to epileptic state. Firstly, to understand the transition of epilepsy, the neural activities in the hippocampus were measured by neuronal ensemble recording in Sprague Dawley rats treated with pilocarpine. According to the analysis of firing coincident from neuronal ensembles, a decrease of hippocampal coincidence was correlated with the development of SE. The hippocampal desynchronization might be a predicting factor of SE. However, we found a very heterogeneous change in the firing rate across putative hippocampal neurons. Secondly, the neural activities prior to SE in pilocarpine-treated rats were recorded in multiple regions of the limbic system including the CA1, CA3, dentate gyrus, anterior nucleus of thalamus, amygdala, entorhinal cortex, subiculum, and medial septum. The synchronization between different brain regions was computed by inter-structure coherence to assess the brain connection prior to SE. According to neural network analysis, we identified the enhanced beta synchrony in the limbic system prior to the occurrence of SE. Specifically, a significant beta synchrony between the amygdala and the anterior nucleus of thalamus was found. Therefore, the neural connection between the amygdala and the thalamus might involve in the development of SE. Thirdly, an imbalance between neural excitation and inhibition in the brain may underlie the transition from normal state to epileptic state. For example, a change in GABAergic transmission might participate in this transition process in pilocarpine model. To evaluate the involvement of GABAergic transmission, a pharmaceutical approach was used. In rats treated with diazepam, a GABAA receptor agonist, we found a decrease in the firing rate of high-spiking neurons in association with a lower rate of SE induction. This finding suggests that the GABAergic transmission plays an important role in generation of SE. In conclusion, these results suggest that hippocampal desynchronization is a key electrophysiological change prior to the occurrence of SE. The limbic hyper-synchronization at beta oscillation is a characteristic feature in rats with SE. Moreover, a blockade of GABAA receptors might prevent the development of SE by decreasing the firing rate of high-spiking neurons. Further studies are warranted to determine the exact biomarkers prior to SE and their underlying mechanisms in pilocarpine-treated rats.
Fang, Ben, e 房仲彬. "Design of a modulation circuit for high detection limit system". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/08209702342524846381.
Texto completo da fonteHong-YuHuang e 黃弘宇. "Study and Application of IGBT Switch Circuit with Current-limit Protection". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/07401862631895690207.
Texto completo da fonte國立成功大學
電機工程學系
104
Abstract This thesis mainly studies on a switch circuit with current limitation. When short circuit fault occurs, high short circuit current may damage devices and system. According to output characteristic of IGBT, collector current is proportional to its saturation voltage, and can be limited at a safe value while IGBT operating in active region, and it is related gate-to-emitter voltage. Integrate these characteristics to driver circuit of IGBT, a novel protection switch circuit is proposed. This protection switch circuit can inhibit fault current by operating IGBT in active region. Comparing with the conventional mechanical protection, it has a shorter response time, and can clear fault before fault current increases to maximum value. Eliminating difficulty of arc suppression of short current in a DC system. In a AC system, there is no delay to shut off the fault current. Standard of fault current withstanding for devices will be lower. Thus, cost can be reduced and reliability can be enhanced. In this thesis, this short circuit protection switch will be implemented to DC and AC applications. One is a digital control inverter, and the other is grid-connected solid state circuit breaker. These circuits can achieve short circuit protection, short circuit current limiting, and auto restarting.
Su, Chung-tao, e 蘇鈞陶. "Limbic Circuits Involved in Hypothalamic Regulation of Stress Responses: Amygdala and Bed Nucleus of the Stria Terminalis". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/76003227272345806130.
Texto completo da fonte長庚大學
基礎醫學研究所
91
The hypothalamo-pituitary-adrenal axis (HPA axis) response is the classical response when animals receive stressful challenges. The paraventricular nucleus of the hypothalamus (PVH) plays a key role in HPA axis response. PVH releases corticotrophin-releasing factor (CRF) to the anterior pituitary gland to increase plasma adrenocorticotrophin (ACTH) level, which in turn to raise the plasma corticosterone level. The efferent of PVH are well known, but the afferents of PVH are complicated and abstruse. Limbic system is the central structure involved in memory, learning and emotional regulations. The amygdala is involved in behavioral, autonomic, and neuroendocrine responses to stressful stimuli. Recent studies showed that lesion of the amygdala can attenuate the HPA axis response to stress, and infusion of corticosterone directly into the amygdala results in the opposite effects. On the other hand, the bed nucleus of the stria terminalis (BNST), the integrative center of the limbic system, receives afferents from the amygdala and hippocampus and projects to the PVH. The goal of my study was to determine the anatomical relationship among amygdala, BNST and PVH under stress. Male Sprague-Dawley rats received contexual conditioned fear paradigm of conditioned stimulus (CS) and unconditioned stimulus (US) for one, three, or five days. On the day of sacrifice, rats were exposed to CS only. Immunohistochemical staining of Fos-immunoreactivity (ir) was used to identify activated cells, and in situ hybridization was used to detect CRF mRNA and arginine vasopressin (AVP) mRNA in the hypothalamus. Tract tracing studies were conducted to characterize the anatomical relationship among amygdala, BNST and PVH. My findings showed that conditioned fear elevated Fos-ir expression in the PVH and medial nucleus of the amygdala (MeA), and decreased Fos-ir expression in the central nucleus of the amygdala (CeA) and dorsal lateral nucleus of the BNST. CRF mRNA level was upregulated in the PVH, BNST and CeA in conditioned rats. Conditioned fear also elevates AVP mRNA expression in the PVH. Tract tracing studies demostrated that CeA could project to PVH via the BNST, and MeA could project to the PVH directly. These studies provide evidences that conditioned fear could alter limbic cellular activity which might involved in HPA regulation, and the tract tracing studies further suggest an anatomical framework between limbic system and PVH under stress.
Schäfers, Andrea T. U. [Verfasser]. "Developmental neuroplasticity in the hippocampus : an interplay of prefrontal-limbic circuits / vorgelegt von Andrea T. U. Schäfers". 2009. http://d-nb.info/1004384440/34.
Texto completo da fonteChang, Jonathan. "Computational Framework for the Identification of Neural Circuits Underlying Psychiatric Disorders". Thesis, 2021. https://doi.org/10.7916/d8-chec-c143.
Texto completo da fonteMendelsohn, Alana Irene. "Specifying neurons and circuits for limb motor control". Thesis, 2016. https://doi.org/10.7916/D84749S7.
Texto completo da fonteBartošová, Tereza. "Výskyt symptomů temporo-limbické dysfunkce u pacientů s bolestmi hlavy". Master's thesis, 2014. http://www.nusl.cz/ntk/nusl-337314.
Texto completo da fonte(7025126), Ahmedullah Aziz. "Device-Circuit Co-Design Employing Phase Transition Materials for Low Power Electronics". Thesis, 2019.
Encontre o texto completo da fontePhase transition materials (PTM) have garnered immense interest in concurrent post-CMOS electronics, due to their unique properties such as - electrically driven abrupt resistance switching, hysteresis, and high selectivity. The phase transitions can be attributed to diverse material-specific phenomena, including- correlated electrons, filamentary ion diffusion, and dimerization. In this research, we explore the application space for these materials through extensive device-circuit co-design and propose new ideas harnessing their unique electrical properties. The abrupt transitions and high selectivity of PTMs enable steep (< 60 mV/decade) switching characteristics in Hyper-FET, a promising post-CMOS transistor. We explore device-circuit co-design methodology for Hyper-FET and identify the criterion for material down-selection. We evaluate the achievable voltage swing, energy-delay trade-off, and noise response for this novel device. In addition to the application in low power logic device, PTMs can actively facilitate non-volatile memory design. We propose a PTM augmented Spin Transfer Torque (STT) MRAM that utilizes selective phase transitions to boost the sense margin and stability of stored data, simultaneously. We show that such selective transitions can also be used to improve other MRAM designs with separate read/write paths, avoiding the possibility of read-write conflicts. Further, we analyze the application of PTMs as selectors in cross-point memories. We establish a general simulation framework for cross-point memory array with PTM based selector. We explore the biasing constraints, develop detailed design methodology, and deduce figures of merit for PTM selectors. We also develop a computationally efficient compact model to estimate the leakage through the sneak paths in a cross-point array. Subsequently, we present a new sense amplifier design utilizing PTM, which offers built-in tunable reference with low power and area demand. Finally, we show that the hysteretic characteristics of unipolar PTMs can be utilized to achieve highly efficient rectification. We validate the idea by demonstrating significant design improvements in a Cockcroft-Walton Multiplier, implemented with TS based rectifiers. We emphasize the need to explore other PTMs with high endurance, thermal stability, and faster switching to enable many more innovative applications in the future.
Dyer, Joseph-Omer. "Mécanismes neuronaux médullaires, coordination musculaire et fonction motrice chez les sujets hémiparétiques". Thèse, 2010. http://hdl.handle.net/1866/4917.
Texto completo da fonteIn stroke individuals, an abnormal coactivation of knee and ankle extensors is often observed when the paretic leg is voluntarily moved and during gait. The mechanisms underlying this abnormal coactivation are not well understood. Although, stroke is the result of a supraspinal lesion, studies have shown that spinal pathways might also be affected in hemiparesis. This doctoral project aims: 1) to assess intersegmental pathways projecting from knee extensors to ankle extensors in hemiparetic patients and 2) to evaluate whether a potential malfunction in these pathways after stroke is associated with an abnormal coactivation of leg extensors during static contractions and during gait. The first study of this project compares the effects of femoral nerve (FN) stimulation on soleus reflex activity in hemiparetic patients and healthy individuals. An increase of the early short-latency heteronymous facilitation and a decrease of the later inhibition of soleus H reflex induced by FN stimulation were observed in stroke patients. These results demonstrate the malfunction of intersegmental short propriospinal pathways linking quadriceps to soleus after stroke. The second study shows that these changes in the heteronymous modulation assessed with the complex method using soleus H reflex are similar to those found using a simpler method based on the modulation of soleus voluntary EMG. Moreover, changes in the propriospinal modulation observed with both methods were correlated with motor impairments of the paretic leg. The third study has quantified an increased coactivation of knee and ankle extensors during static contractions in stroke patients compared to healthy controls. Furthermore, the increased coactivation of ankle extensors during the voluntary contraction of knee extensors was related to the modified heteronymous modulation in the paretic leg. The fourth study has quantified an increased coactivation of knee and ankle extensors in hemiparetic gait using a temporal coactivation index, that was the peak activation interval (PAI) and a coactivation amplitude index (CAI). In some muscles, these indexes were correlated to the modified intersegmental modulation of soleus voluntary activity on the paretic side of stroke patients. Finally, preliminary results have shown that vibration of the patellar tendon (80 Hz) can reduce the enhanced heteronymous facilitation observed in the paretic leg. This doctoral project demonstrates the malfunction of intersegmental pathways linking quadriceps to soleus in hemiparesis following stroke. The neurophysiological alterations at the spinal level are correlated with functional changes. This malfunction could contribute to the abnormal involuntary coactivation of knee and ankle extensors often observed in the paretic leg while the person attempts to move or during gait. Finally, a preliminary study indicates that mechanical vibration could be a promising sensory modality in the regulation of the hyperexcitability of spinal reflex pathways, which is thought to participate in motor impairments after stroke.