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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

小頭症ラットの海馬神経回路の生後発達異常

中村, 江里, Nakamura, Eri, 井上, 稔, Inouye, MInoru, 伊藤, 義美, Ito, Yoshimi 25 March 2001 (has links)
No description available.
12

Connectomics of extrasynaptic signalling : applications to the nervous system of Caenorhabditis elegans

Bentley, Barry January 2017 (has links)
Connectomics – the study of neural connectivity – is primarily concerned with the mapping and characterisation of wired synaptic links; however, it is well established that long-distance chemical signalling via extrasynaptic volume transmission is also critical to brain function. As these interactions are not visible in the physical structure of the nervous system, current approaches to connectomics are unable to capture them. This work addresses the problem of missing extrasynaptic interactions by demonstrating for the first time that whole-animal volume transmission networks can be mapped from gene expression and ligand-receptor interaction data, and analysed as part of the connectome. Complete networks are presented for the monoamine systems of Caenorhabditis elegans, along with a representative sample of selected neuropeptide systems. A network analysis of the synaptic (wired) and extrasynaptic (wireless) connectomes is presented which reveals complex topological properties, including extrasynaptic rich-club organisation with interconnected hubs distinct from those in the synaptic and gap junction networks, and highly significant multilink motifs pinpointing locations in the network where aminergic and neuropeptide signalling is likely to modulate synaptic activity. Thus, the neuronal connectome can be modelled as a multiplex network with synaptic, gap junction, and neuromodulatory layers representing inter-neuronal interactions with different dynamics and polarity. This represents a prototype for understanding how extrasynaptic signalling can be integrated into connectomics research, and provides a novel dataset for the development of multilayer network algorithms.
13

Recent and remote episodic-like memory : characteristics and circuits : approach via multi-site recordings of oscillatory activity in rat hippocampal and cortical brain regions / Mémoire épisodique récente et ancienne : caractéristiques et circuits

Allerborn, Marina 04 November 2016 (has links)
La mémoire épisodique, notre capacité de se rappeler des épisodes particuliers de notre vie, a été initialement définie chez l'homme en termes de l'information qu'elle contient, quel événement a eu lieu, où et dans quel contexte /quand s'est-il produit? La démonstration de l'existence de cette forme de mémoire chez l'animal a été réalisée chez le geais buissonnier. En effet, cet oiseau cacheur est capable de former une représentation mentale complexe du type de nourriture qu'il a caché, où et quand. Cette forme de mémoire qualifiée d' « episodic-like » a depuis une dizaine d'année été établie chez le rongeur. Au cours de ma thèse, j'ai suivi deux objectifs: valider un nouveau paradigme de mémoire épisodique chez le rat et l'utiliser pour étudier les circuits neuronaux qui sous-tendent cette forme particulière de mémoire. La première partie du manuscrit présente le développement et la validation d'un protocole original destiné à l'étude de la mémoire épisodique chez le rat. Lors de la conception de cette tâche, nous avons essayé de réduire au minimum la procédure d'entrainement des animaux afin de préserver l'essence même de la mémoire épisodique qui est la mémoire d'épisodes uniques. Pendant la tâche les rats ont été exposés à deux épisodes différents, au cours desquels des combinaisons uniques odeurs-place (information « quoi et où ») ont été présentées dans des contextes différents enrichis et multi-sensoriels (information « dans quel contexte »). Nous avons démontré que certains rats («ww») étaient capables de former des associations de mémoire (« episodic-like ») qui leur permettent de se souvenir de l'intégralité de l'épisode présenté après des délais courts (24h) et longs (24 jours) et dans différentes situations de rappel, tandis que d'autres («rest») ne se souvenaient que partiellement des informations présentes lors de l'épisode. Une approche pharmacologique réalisée lors de la validation de la tâche nous a permis de confirmer que l'hippocampe dorsal était nécessaire au rappel épisodique complet. Dans une version étendue du protocole dans laquelle des rats ont été exposés à deux épisodes supplémentaires, nous avons trouvé que l'expérience des épisodes préalablement acquis par les rats facilite l'encodage de nouveaux épisodes et que la mémoire de ces épisodes est plus stable. La deuxième partie de la thèse présente une première approche de l'étude des circuits neuronaux sous tendant la formation et la récupération de la mémoire épisodique. L'approche méthodologique utilisée est l'enregistrement multi-site de potentiels de champs locaux chez l'animal vigile. Le réseau de structures enregistrées inclut les aires sensorielles olfactives, des régions du cortex préfrontal médian et latéral ainsi que les régions dorsales et ventrales de l'hippocampe. Après avoir extrait des signaux le contenu fréquentiel dans deux bandes de fréquences (béta et théta), nous avons analysé les variations de puissance de l'activité oscillatoire dans ces bandes en utilisant des analyses en transformées de Hilbert et ondelette de Morlet. La période d'analyse est centrée sur l'échantillonnage de l'odeur, dernière information traitée avant que l'animal produise sa réponse comportementale. Les changements de puissance dans les deux bandes en réponse à l'odeur ont été comparés dans les différentes situations expérimentales pour les rats «ww» et les rats «rest». Les résultats obtenus montrent que le réseau de structures activées dans la bande béta en réponse à l'odeur est différent en fonction du profil de rappel des animaux (les rats du profil «ww» versus les rats «rest») à la fois en encodage et en situation de rappel. L'activité dans le réseau est également différente en fonction du type de réponse (hit versus rejet correct) / Episodic memory, our capacity to recollect particular life episodes, has been initially defined in terms of the information it contains, what kind of event, where and in which context/when did it take place. Pioneering studies on food-caching birds have demonstrated that animals are also able to form such complex memories, referred to as episodic-like memories in animals, however its modelling in rodents has proved challenging. The aim of this thesis was twofold: further development and validation in rats of a new episodic-like memory paradigm and study of neural circuits involved in formation and retrieval of this particular memory. The first part of the thesis presents the original behavioral paradigm developed in our group. In our task we tried to minimize training procedure in order to preserve the nature of episodic memory which is the memory for unique life episodes. Hereby rats were exposed to two different episodes, during which unique odor-place combinations (“what and where” information) were presented in different enriched multisensory contexts (“in which context” information). We found that some rats (“ww” group) were indeed able to form episodic-like memory associations which can be recalled after short (24 h) and long delays (24 days) in different experimental situations, while other animals (“rest” group) remembered only parts of the information contained in the initial episodes. Using pharmacological inactivation of dorsal hippocampus we have demonstrated that hippocampus is required specifically for retrieval of associated episodic-like memory information, but not for retrieval of single elements of the presented episodes in our task. In an extended version of the protocol in which rats were exposed to two additional episodes we found that previously acquired experience of the rats facilitates the encoding of new episodes and that the memory of these new episodes is more stable. The second part of the manuscript presents the first approach to study neural circuits involved in episodic-like memory encoding and retrieval in our task. Electrophysiological methodology was based on local field potential recordings obtained in parallel in several brain regions in behaving animals. The network of structures investigated included olfactory neocortical brain areas, brain regions in lateral and medial prefrontal cortex and the dorsal and ventral part of the hippocampus. The analysis was based on the estimation of magnitude of the oscillatory activity (described as power changes) in theta and beta frequency bands using Hilbert and Morlet wavelet transform for the analyses. The power analysis evolved around odor sampling event which constituted the last piece of information required for recollection of the whole episodic-like memory association. The odor-induced changes in power were compared between “ww” and “rest” animals in different experimental situations. We found that the network of activated brain regions in beta frequency band differed as a function of the memory profile of the rats (complete episodic-like memory recollection versus remembering partial information of the episodes) during both memory encoding as well as retrieval. We have also demonstrated that this active network changes when memory becomes consolidated (recent versus remote memory). Additionally we have shown that the activity in the network depends on the type of the response (hit versus correct rejection) given by the rat during memory encoding and retrieval. The network of brain regions that showed changes in theta power during memory formation and retrieval differed strongly from beta band network. In contrast to beta, the memory profile effect was much less prominent for theta band. However similarly to beta, there were also significant changes in network depending on the encoding session and the age of memory at test
14

Redundant Input Cancellation by a Bursting Neural Network

Bol, Kieran G. 20 June 2011 (has links)
One of the most powerful and important applications that the brain accomplishes is solving the sensory "cocktail party problem:" to adaptively suppress extraneous signals in an environment. Theoretical studies suggest that the solution to the problem involves an adaptive filter, which learns to remove the redundant noise. However, neural learning is also in its infancy and there are still many questions about the stability and application of synaptic learning rules for neural computation. In this thesis, the implementation of an adaptive filter in the brain of a weakly electric fish, A. Leptorhynchus, was studied. It was found to require a cerebellar architecture that could supply independent frequency channels of delayed feedback and multiple burst learning rules that could shape this feedback. This unifies two ideas about the function of the cerebellum that were previously separate: the cerebellum as an adaptive filter and as a generator of precise temporal inputs.
15

Redundant Input Cancellation by a Bursting Neural Network

Bol, Kieran G. 20 June 2011 (has links)
One of the most powerful and important applications that the brain accomplishes is solving the sensory "cocktail party problem:" to adaptively suppress extraneous signals in an environment. Theoretical studies suggest that the solution to the problem involves an adaptive filter, which learns to remove the redundant noise. However, neural learning is also in its infancy and there are still many questions about the stability and application of synaptic learning rules for neural computation. In this thesis, the implementation of an adaptive filter in the brain of a weakly electric fish, A. Leptorhynchus, was studied. It was found to require a cerebellar architecture that could supply independent frequency channels of delayed feedback and multiple burst learning rules that could shape this feedback. This unifies two ideas about the function of the cerebellum that were previously separate: the cerebellum as an adaptive filter and as a generator of precise temporal inputs.
16

Redundant Input Cancellation by a Bursting Neural Network

Bol, Kieran G. 20 June 2011 (has links)
One of the most powerful and important applications that the brain accomplishes is solving the sensory "cocktail party problem:" to adaptively suppress extraneous signals in an environment. Theoretical studies suggest that the solution to the problem involves an adaptive filter, which learns to remove the redundant noise. However, neural learning is also in its infancy and there are still many questions about the stability and application of synaptic learning rules for neural computation. In this thesis, the implementation of an adaptive filter in the brain of a weakly electric fish, A. Leptorhynchus, was studied. It was found to require a cerebellar architecture that could supply independent frequency channels of delayed feedback and multiple burst learning rules that could shape this feedback. This unifies two ideas about the function of the cerebellum that were previously separate: the cerebellum as an adaptive filter and as a generator of precise temporal inputs.
17

Developmental Emergence of Sparse Coding: A Dynamic Systems Approach

Rahmati, Vahid, Kirmse, Knut, Holthoff, Knut, Schwabe, Lars, Kiebel, Stefan 04 June 2018 (has links) (PDF)
During neocortical development, network activity undergoes a dramatic transition from largely synchronized, so-called cluster activity, to a relatively sparse pattern around the time of eye-opening in rodents. Biophysical mechanisms underlying this sparsification phenomenon remain poorly understood. Here, we present a dynamic systems modeling study of a developing neural network that provides the first mechanistic insights into sparsification. We find that the rest state of immature networks is strongly affected by the dynamics of a transient, unstable state hidden in their firing activities, allowing these networks to either be silent or generate large cluster activity. We address how, and which, specific developmental changes in neuronal and synaptic parameters drive sparsification. We also reveal how these changes refine the information processing capabilities of an in vivo developing network, mainly by showing a developmental reduction in the instability of network’s firing activity, an effective availability of inhibition-stabilized states, and an emergence of spontaneous attractors and state transition mechanisms. Furthermore, we demonstrate the key role of GABAergic transmission and depressing glutamatergic synapses in governing the spatiotemporal evolution of cluster activity. These results, by providing a strong link between experimental observations and model behavior, suggest how adult sparse coding networks may emerge developmentally.
18

Redundant Input Cancellation by a Bursting Neural Network

Bol, Kieran G. January 2011 (has links)
One of the most powerful and important applications that the brain accomplishes is solving the sensory "cocktail party problem:" to adaptively suppress extraneous signals in an environment. Theoretical studies suggest that the solution to the problem involves an adaptive filter, which learns to remove the redundant noise. However, neural learning is also in its infancy and there are still many questions about the stability and application of synaptic learning rules for neural computation. In this thesis, the implementation of an adaptive filter in the brain of a weakly electric fish, A. Leptorhynchus, was studied. It was found to require a cerebellar architecture that could supply independent frequency channels of delayed feedback and multiple burst learning rules that could shape this feedback. This unifies two ideas about the function of the cerebellum that were previously separate: the cerebellum as an adaptive filter and as a generator of precise temporal inputs.
19

Developmental Emergence of Sparse Coding: A Dynamic Systems Approach

Rahmati, Vahid, Kirmse, Knut, Holthoff, Knut, Schwabe, Lars, Kiebel, Stefan 04 June 2018 (has links)
During neocortical development, network activity undergoes a dramatic transition from largely synchronized, so-called cluster activity, to a relatively sparse pattern around the time of eye-opening in rodents. Biophysical mechanisms underlying this sparsification phenomenon remain poorly understood. Here, we present a dynamic systems modeling study of a developing neural network that provides the first mechanistic insights into sparsification. We find that the rest state of immature networks is strongly affected by the dynamics of a transient, unstable state hidden in their firing activities, allowing these networks to either be silent or generate large cluster activity. We address how, and which, specific developmental changes in neuronal and synaptic parameters drive sparsification. We also reveal how these changes refine the information processing capabilities of an in vivo developing network, mainly by showing a developmental reduction in the instability of network’s firing activity, an effective availability of inhibition-stabilized states, and an emergence of spontaneous attractors and state transition mechanisms. Furthermore, we demonstrate the key role of GABAergic transmission and depressing glutamatergic synapses in governing the spatiotemporal evolution of cluster activity. These results, by providing a strong link between experimental observations and model behavior, suggest how adult sparse coding networks may emerge developmentally.
20

Neuroendocrine Modulation of Complex Behavior and Physiology in C. elegans

Florman, Jeremy T. 30 September 2020 (has links)
To survive, animals must adapt to a complex and challenging world in a way that is flexible and responsive, while maintaining internal homeostasis. Neuromodulators provide a means to systemically alter behavioral or physiological state based on intrinsic or extrinsic cues, however dysregulated neuroendocrine signaling has negative consequences for fitness and survival. Here I examine neuroendocrine function and dysfunction using the escape response in Caenorhabditis elegans. The RFamide neuropeptide FLP-18 is a co-transmitter with the monoamine tyramine and functions both synergistically and antagonistically to tyramine in coordinating escape behavior. Using behavioral analysis and calcium imaging, I show that FLP-18 functions primarily through the G-protein coupled receptor (GPCR) NPR-5 to increase calcium levels in muscle, enhancing locomotion rate, bending and reversal behavior during the escape response. Furthermore, I examine the relationship between persistent acute stress and resilience using repeated activation of the escape response as a model of neuroendocrine dysregulation. Repeated activation of the escape response shortens lifespan and renders animals more susceptible to thermal, oxidative, and nutritional stress. Tyramine release is necessary and sufficient for this effect and activity of the tyraminergic RIM neurons is differentially regulated by acute versus long-term stressors. Impaired stress resistance requires both the GPCR TYRA-3 in the intestine and intestinal neuropeptide release. Activation of the insulin receptor DAF-2 is downstream of TYRA-3 and inhibits the transcription factors DAF-16/FOXO, SKN-1/Nrf2 and HSF-1, linking monoamine signaling in acute stress to the insulin signaling pathway and impaired resilience to long-term stressors.

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