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1
Pontani, Léa-Laetitia. „Etude biomimétique du cortex cellulaire et ses applications“. Paris 6, 2009. https://tel.archives-ouvertes.fr/tel-00922820.
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Le cytosquelette des cellules est une structure composite et versatile qui leur confère des propriétés mécaniques extrêmement complexes. En particulier, le cortex d’actine qui s'assemble de manière dynamique sous la membrane cellulaire fournit la force nécessaire aux déformations et au mouvement de la cellule : la polymérisation de l'actine permet aux filaments en formation de pousser la membrane et les moteurs moléculaires génèrent des forces contractiles. L’utilisation de systèmes biomimétiques permet d’isoler des modules particuliers du cytosquelette pour les étudier indépendamment de façon simplifiée. Une expérience de reconstitution du cortex d’actine in vitro a été mise au point dans ce but. Les protéines et métabolites nécessaires pour la polymérisation de l’actine sont ainsi introduits dans un liposome et la réaction est localisée à la membrane, en y greffant l'activateur de la polymérisation de l'actine, sur le modèle du cortex cellulaire. Une fois la polymérisation déclenchée, nous sommes arrivés à reproduire un gel d’actine à la membrane, formant une coque. Les propriétés mécaniques de ce système simplifié sont alors étudiées par des expériences qui caractérisent leur dynamique d’étalement sur des surfaces. Les résultats sont comparés à ceux obtenus sur des cellules, et reproduisent une bonne partie des comportements cellulaires. On utilise également ces liposomes dans une situation physiologique: l’internalisation de la toxine de Shiga dans les cellules et nous montrons que la toxine est internalisée dans un système aussi épuré que des liposomes comportant un cortex reconstitué, prouvant le rôle important de l'actine dans ce processus.
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Salbreux, Guillaume. „Modélisation des instabilités du cortex d'actine“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00382577.
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Le cortex d'actine est une fine couche de gel d'une épaisseur de l'ordre du micron, attaché à la membrane lipidique de la cellule. Il est constitué d'un réseau de filaments d'actine qui sont constamment polymérisés à la membrane puis dépolymérisés, dans un mouvement de « tapis roulant ». Des moteurs moléculaires, les myosines, génèrent des contraintes internes dans le gel.Le cortex contrôle ainsi les variations de forme de la cellule. Dans cette thèse nous utilisons le modèle des gels actifs pour explorer certaines propriétés du cortex d'actine. Le gel est décrit a l'échelle mésoscopique comme un matériau viscoélastique nématique dans lequel les myosines utilisent l'énergie fournie par l'hydrolyse de l'ATP pour produire des contraintes actives, c'est à dire plaçant le système hors d'équilibre thermodynamique. Dans un premier temps nous étudions de quelle façon l'épaisseur du cortex peut être régulée, et nous discutons l'apparition d'instabilités actives dans la couche. Nous utilisons l'instabilité du gel ainsi décrite pour interpréter l'observation expérimentale d'oscillations de formes de fibroblastes induites par des canaux calciques mecanosensibles. En incluant un paramètre d'ordre nématique dans notre description, nous montrons que soumettre le cortex à une concentration inhomogène de myosines doit conduire à l'apparition d'un flux de filaments et à la formation d'un anneau, ainsi qu'observé dans plusieurs systèmes expérimentaux, en particulier lors de la cytocinèse. Nous terminons ce travail par une analyse de la mécanique de formation d'un bleb unique induit par une rupture artificielle du cortex par ablation laser.
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Pontani, Lea-Laetitia. „Etude Biomimétique du cortex cellulaire et ses applications“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00922820.
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Le cytosquelette des cellules est une structure composite et versatile qui leur confère des propriétés mécaniques extrêmement complexes. En particulier, le cortex d'actine qui s'assemble de manière dynamique sous la membrane cellulaire fournit la force nécessaire aux déformations et au mouvement de la cellule : la polymérisation de l'actine permet aux filaments en formation de pousser la membrane et les moteurs moléculaires génèrent des forces contractiles. L'utilisation de systèmes biomimétiques permet d'isoler des modules particuliers du cytosquelette pour les étudier indépendamment de façon simplifiée. Une expérience de reconstitution du cortex d'actine in vitro a été mise au point dans ce but. Les protéines et métabolites nécessaires pour la polymérisation de l'actine sont ainsi introduits dans un liposome et la réaction est localisée à la membrane, en y greffant l'activateur de la polymérisation de l'actine, sur le modèle du cortex cellulaire. Une fois la polymérisation déclenchée, nous sommes arrivés à reproduire un gel d'actine à la membrane, formant une coque. Les propriétés mécaniques de ce système simplifié sont alors étudiées par des expériences qui caractérisent leur dynamique d'étalement sur des surfaces. Les résultats sont comparés à ceux obtenus sur des cellules, et reproduisent une bonne partie des comportements cellulaires. On utilise également ces liposomes dans une situation physiologique: l'internalisation de la toxine de Shiga dans les cellules et nous montrons que la toxine est internalisée dans un système aussi épuré que des liposomes comportant un cortex reconstitué, prouvant le rôle important de l'actine dans ce processus.
4
Foussard, Hélène. „Les protéines LRCH : premières études chez la Drosophile“. Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1096/.
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Les protéines Ezrin, Radixin, et Moesin (ERM) permettent de réguler la liaison des protéines membranaires aux filaments d'actine. De nombreuses études ont montré l'implication des protéines ERM dans diverses tumeurs caractérisées par un fort pouvoir métastatique. L'équipe a récemment démontré que la dMoesin, l'unique protéine ERM de Drosophile, est requise pour l'organisation du cortex cellulaire et du fuseau mitotique pour la division cellulaire. Pour mieux comprendre les fonctions de la dMoesin, l'équipe a recherché ses partenaires fonctionnels. Un crible génétique a été réalisé et, parmi les interacteurs génétiques de la dMoesin ainsi identifiés, nous nous sommes concentrés sur la protéine dLRCH, identifiée indépendamment comme partenaire physique de la dMoesin dans un crible double hybride. DLRCH est une protéine pionnière caractérisée par la présence simultanée de domaines LRR (Leucin Rich Repeat) et CH (Calponin Homology). Nous montrons que dLRCH définit une famille de protéines évolutivement conservée de fonction encore inconnue et avons identifié 4 gènes codant pour des protéines LRCH (hLRCH) chez l'Homme. Mon projet de thèse a consisté en l'étude de la fonction éventuelle de cette nouvelle famille de protéines, les protéines LRCH, au cours de la division cellulaire. Au cours de cette étude, nous montrons que dLRCH colocalise avec la dMoesin au sillon de clivage au cours de la division cellulaire chez la Drosophile, ainsi que les protéines hLRCH avec les protéines ERM dans les cellules humaines. Grâce à une analyse fonctionnelle de dLRCH, nous mettons en évidence que son absence perturbe l'organisation du cortex mitotique, sans toutefois bloquer la division cellulaire. Pour étudier les conséquences de l'absence de dLRCH sur la physiologie de l'organisme, nous avons généré un allèle nul de ce gène chez la Drosophile. Nous montrons que le gène dlrch est exprimé dans de nombreux tissus au cours du développement, plus fortement dans certains tissus comme par exemple les gonades. Bien que nous ayons établi que dLRCH n'est pas essentiel à la division cellulaire in vivo, l'absence de dLRCH ne perturbe pas le développement ni la viabilité de la Drosophile, mais entraîne une stérilité complète, ce uniquement chez les femelles. Les individus mutants présentent également une moindre résistance aux conditions extrêmes. Ces travaux constituent donc la première étude fonctionnelle des protéines LRCH chez la DrosophileComparative genomics has revealed an unexpected level of conservation for gene products across the evolution of animal species. However, the molecular function of only a few proteins has been investigated experimentally, and the role of many animal proteins still remains unknown. Here we report the characterization of a novel family of evolutionary conserved proteins, which display specific features of cytoskeletal scaffolding proteins, referred to as LRCHs. Taking advantage of the existence of a single lrch gene in flies, dlrch, we explored its function in cultured cells, and show that dLRCH act to stabilize the cell cortex during cell division. DLRCH depletion leads to ectopic cortical blebs and alters positioning of the mitotic spindle. We further examined the consequences of dLRCH deletion throughout development and adult life. Although dlrch is not essential for cell division in vivo, flies lacking dlrch display a reduced fertility and fitness, particularly when raised at extreme temperatures. These results support the idea that some cytoskeletal regulators are important to buffer environmental variations and ensure the proper execution of basic cellular processes, such as the control of cell shape, under environmental variations
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Rosfelter, Anne. „Le positionnement du fuseau mitotique chez le zygote d'ascidie et son rôle dans la répartition des organelles“. Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS063.
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Après la fécondation d’un ovocyte, un aster de microtubules se forme autour de l’ADN mâle. Cet aster spermatique permet d’amener le pro-noyau femelle jusqu’au pro-noyau mâle pour qu’ils puissent fusionner. Il permet aussi de déplacer l’ADN fusionné jusqu’au centre de la cellule pour assurer une division cellulaire équitable. Les mécanismes de centration d’un aster ou d’un fuseau ont donné lieu à de nombreuses recherches, que ce soit par modélisation, expérimentalement chez des espèces telles C. elegans, P. lividus, M.musculus ou in vitro sur des extraits de Xenopus laevis. Trois mécanismes principaux se dégagent : le pushing, le cortical pulling et le cytoplasmic pulling (ou bulk pulling). En étudiant le déplacement de l’aster et du fuseau mitotique chez le zygote de l’ascidie P. mammillata j’ai découvert un système qui combine ces trois mécanismes en s’appuyant sur l’alternance des étapes du cycle cellulaire. En méiose, l’aster utilise la polymérisation des microtubules qui le composent pour pousser contre le cortex d’actine et s’en décoller (pushing). Arrivé en interphase, l’aster retourne contre le cortex grâce à une traction qu’exerce la membrane sur les microtubules (cortical pulling). Enfin à l’entrée en mitose, la traction membranaire cesse et libère les asters du fuseau mitotique, qui cèdent donc aux forces exercées par le transport d’organelles vers le centre de l’aster (cytoplasmic pulling) qui semblent constantes durant le cycle cellulaire. Cela permet de centrer le fuseau. En même temps que l’aster se forme et se déplace, une réorganisation des compartiments intracellulaires se met en place. Pour comprendre de quelle manière l’organisation intracellulaire peut être perturbée par la formation de l’aster, j’ai étudié le cas du vitellus. En effet, le vitellus, qui est présent sous forme de vésicules, est initialement abondant et homogène dans l’ovocyte non fécondé. Cependant, dès que l’aster apparaît, sa répartition change et les vésicules de vitellus sont exclues de la zone contenant l’aster. Cette exclusion générée à la formation de l’aster chez le zygote, est maintenue au cours du développement. Dans mes travaux, j’ai pu observer qu’elle est majoritairement due à l’accumulation à l’aster d’autres organelles comme le réticulum endoplasmique. La fonction de transport des microtubules de l’aster suffit donc à réorganiser complètement la cellule en excluant certaines organelles et en en accumulant d’autres. Les déplacements de l’aster et du fuseau mitotique, leur régulation par le cycle cellulaire, et la réorganisation intracellulaire, identifiés ici chez le zygote d’ascidie, s’appuient sur le fonctionnement d’éléments fondamentaux d’une cellule, à savoir : les microtubules, le cortex d’actine, le réticulum endoplasmique, les protéines du cycle cellulaire, etc. Les découvertes présentées revêtent ainsi une portée universelle, adaptable aux spécificités de différents types cellulairesAfter oocyte fertilization, a microtubule aster forms around the male DNA. The sperm aster brings the female pro-nucleus to the male pro-nucleus so they can fuse, but it also moves the fused nuclei to the cell center to ensure an equitable cell division. Numerous studies performed in vitro, by modeling or experimentally in species such as C. elegans, P. lividus, and M. musculus, addressed the aster and spindle centration mechanisms. Three main mechanisms emerged; pushing, cortical pulling, and cytoplasmic pulling. By studying aster centration in the zygote of the ascidian P. mammillata, I discovered a system that combines these three mechanisms based on the cell cycle stages. In meiosis, the aster uses the polymerization of its microtubules to push against the actin cortex and move away from it (pushing). Once in interphase, the aster returns to the cortex by a pull exerted by the membrane on the microtubules (cortical pulling). At mitosis entry, cortical pulling stops, and releases the mitotic spindle's asters. In consequence, the asters give in to the forces exerted by the transport of organelles to the aster center (cytoplasmic pulling), that appeared constant during the cell cycle. Cytoplasmic pulling hence participate in centering the spindle While the aster forms and moves, the intracellular compartments reorganize. To understand how intracellular organization can be disrupted by aster formation, I studied the case of yolk. The yolk, in the form of vesicles (called granules or platelets), is initially abundant and homogeneous in the unfertilized oocyte. However, as soon as the aster appears, its distribution changes and the yolk platelets are excluded from the region containing the aster. This exclusion generated by the aster formation in the zygote is maintained during development. I observed that yolk exclusion is mainly due to the accumulation at the aster of other organelles such as the endoplasmic reticulum. The transport function of the aster microtubules is therefore sufficient to completely reorganize the cell by excluding some organelles and accumulating others. The movements of the aster and the spindle, their regulation by cell cycle, and the intracellular reorganization, identified here in the ascidian zygote, rely on basic elements of a cell, namely: the microtubules, the actin cortex, the endoplasmic reticulum, the proteins of the cell cycle, etc. Thus, the discoveries presented here cover a broad scope, and seem adaptable to the specificities of different cell types
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Paluch, Ewa. „Motilité cellulaire sur des systèmes simplifiés : de l' oscillation au mouvement dirigé“. Paris 7, 2005. http://www.theses.fr/2005PA077075.
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Lieleg, Oliver. „Model systems of the actin cortex“. kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/672641/672641.pdf.
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Yonis, Amina Yahya. „Molecular control of actin cortex organisation and dynamics“. Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10043285/.
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The cortex is a ~100nm thick layer of F-actin located under the cell membrane, rich in myosin II and actin-binding proteins. It is essential for cytokinesis, cell locomotion, and tissue morphogenesis. Despite its importance, our knowledge of the cortex is poor. Two actin nucleators, Diaph1 and the Arp2/3 complex, have been shown to generate actin filaments in the cortex. The actin networks generated by these nucleators display clear differences in their organisation and the actin-binding proteins they recruit. Therefore, cells may be able to rapidly control their cortical mechanical properties by regulating the activity of each nucleator. When I searched for regulators of mDia1 and Arp2/3 in a proteomic analysis of the cortex, I found four candidate nucleation promotion factors (NPFs): IQGAP1, NCKIPSD, Fli-I and the WAVE complex. Interestingly, IQGAP1 and NCKIPSD interact with both Diaph1 and the Arp2/3 complex, suggesting they may participate in crosstalk. I examined the role of each NPF in the generation and maintenance of cortical actin. After examining the localisation of each NPF, I determined their impact on cortical assembly by examining how their depletion affected bleb size. Indeed, reduction in Arp2/3 activity leads to smaller blebs, while large blebs result from a decrease in Diaph1 activity. IQGAP1 and NCKIPSD depletion yielded large bleb phenotypes, WAVE gave a small bleb phenotype consistent with its role in regulating Arp2/3, and Fli-I depletion had no phenotype. Next, I examined changes in F-actin network organisation after NPF depletion with scanning electron microscopy. The density and interconnection of the network were altered, further suggesting the importance of IQGAP1, NCKIPSD and WAVE in controlling the organisation of the actin cortex. I showed that NPF depletion significantly affected successful completion of mitosis in HeLa cells. Finally, in collaboration with other students, I examined how NPFs controlled properties of cell mechanics.
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Bovellan, M. K. „Assembly and composition of the cellular actin cortex“. Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1357426/.
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The actin cortex is a thin layer of F-actin, actin regulating proteins, and myosin under the cell membrane. It has a fundamental role in cell morphogenesis, motility, mitosis, cytokinesis, and cell shape maintenance. Yet, how the cell cortex forms as well as the protein composition of the cortex remain unknown. In this study using M2 melanoma cell blebs and metaphase HeLa cells I describe proteins needed for cortex reassembly and reveal the protein composition of the actin cortex. Blebs represent a natural situation in which the membrane is transiently devoid of an actin cortex. Thus the formation of a new actin cortex in the bleb can be studied. Blebs also provide a cell fraction enriched in F-actin cortex, making them an ideal model to study cortex proteomics. After having shown that no nucleation independent mechanism participate in cortex reassembly in membrane blebs, I discovered by localisation and silencing studies, that formin Diaph1 and the Arp2/3 complex are needed for the cortex nucleation, as both localised to the cortex and depletion of either led to cortical defects. Simultaneous depletion of Diaph1 and the Arp2/3 complex led to disappearance of the cellular cortex, suggesting that together they provide the majority of the F-actin in the cortex. Cortex composition studies of blebs isolated from blebbing cells revealed the presence of many actin binding proteins at the cortex. Localisation and depletion studies revealed that capping, and effective actin turnover are essential for cortical stability and that flightless-I may regulate cortex nucleation together with Rho GTPases. These findings have important implications for our understanding of cortical properties, which are not only important for cell morphogenesis and shape maintenance, but facilitate tumour growth and dissemination.
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Bohec, Pierre. „Etude du comportement hors-équilibre du cortex cellulaire“. Paris 7, 2012. http://www.theses.fr/2012PA077039.
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La cellule est capable, en consommant l'énergie issue de l'hydrolyse de l’ATP, d'exercer des forces qui prennent leurs origines dans des réactions biochimiques. Un élément important de la cellule est le cytosquelette, composé principalement de microtubules et de filaments d'actine, il en constitue l'architecture et lui. Donne l'essentiel de ses propriétés mécaniques. Il est composé de polymères réticulés et, du point de vue de la rhéologie, a un comportement viscoélastique. Au sein du cytosquelette, des processus tels que la polymérisation de l'actine ou des microtubules permettent d'exercer des forces. Des protéines, de la famille des moteurs moléculaires, ont pour rôle spécifique de convertir l'énergie stockée sous forme chimique en énergie mécanique. L'activité mécanique hors-équilibre de la cellule est donc directement reliée à ces forces d'origine biochimique. Dans ce travail, nous avons étudié la distribution statistique des forces d'origine biochimique s'exerçant sur une bille de taille micrométrique attachée au cortex d'actine par l'intermédiaire des récepteurs de l'adhésion cellulaire : les intégrines. L'étude des forces d'origine biologique est inséparable de la connaissance des forces d'origine thermique car à cette échelle micrométrique la contribution des forces thermiques n'est pas négligeable. Les forces s'exerçant sur la sonde ont donc deux origines possibles : biologique ou thermique. Notre approche expérimentale est basée sur la combinaison de deux techniques de microrhéologie, active et passive, ce qui nous permet de calculer la fonction d'autocorrélation temporelle des forces exercées sur une sonde accrochée à J'actine corticale et de la comparer à la fonction d'autocorrélation des forces thermiques estimée via le théorème de fluctuation-dissipation. La différence entre ces deux spectres nous donne une idée de la contribution des forces d'origine biologique au mouvement de la bille et une mesure de l'écart du système à l'équilibre thermodynamique. Afin d'étudier plus en détail ce système de bille subissant des forces de la part de l'actine corticale, nous avons étudié l'effet de la variation de la densité de ligand recouvrant la bille. La question qui nous a animés tout au long de ce travail est l'origine de ces forces biologiques ou plus exactement la nature du composant du cytosquelette qui exerce ces forces athermiques. Dans un premier temps, nous avons étudié l'influence de la température sur ces forces biologiques. Nous avons ensuite étudié l'effet de la déplétion de l'ATP dans la cellule, de la dépolymérisation de l'actine et de l'inhibition des moteurs moléculaires de la famille des myosinesBy consuming energy from the hydrolysis of ATP, cells are able to exert forces that stem from biochemical reactions. A central element of cells is the cytoskeleton, which is mainly composed of microtubules and actin filaments and accounts for the architecture and most of the mechanical properties of the cells. It is made of crosslinked polymers and, in terms of rheology, has a viscoelastic behavior. Within the cytoskeleton, processes such as actin or microtubule polymerization can exert forces. Proteins from the molecular motor family have the specific role of conveiting the energy stored in chemical form into mechanical energy. The out-of-equilibrium mechanical activity of thé cell is directly related to these forces of biochemical origin. In this work, we studied the statistical distribution of biochemical forces exerted on a micrometer-sized bead attached to the actin cortex through cell adhesion receptors: integrins. The study of the forces of biological on gin is inseparable from knowledge of the forces of thermal origin because, at this microscopic scale, the contribution of thermal forces is not negligible. The forces actin g on the probe have two possible origins: biological or thermal. Our experimental approach is based on the combination of two microrheology techniques, active and passive, which allows us to calculate the temporal autocorrelation function of the forces exerted on a probe attached to the cortical actin and compare it to the autocorrelation function of the estimated thermal forces via the fluctuation-dissipation theorem. The difference between these two spectra gives us an idea of the contribution of the forces of biological origin to the movement of the bead and a measure of the deviation of the System from thermodynamic equilibrium. To further investigate this System, i. E. A bead undergoing forces from the cortical actin, we studied the effect of varying the ligand coating density on the bead. The question that has driven us throughout this work is the origin of these biological forces or, more precisely the nature of the component of the cytoskeleton that exerts these athermal forces. Initially, we studied the influence of temperature on these biological forces. We then studied the effect of depletion of ATP in the cell, of the depolymerization of actin and of the inhibition of molecular motors of the myosin family
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Lyall, Evan Harrison. „Surround Integration During Active Sensation in the Mouse Barrel Cortex“. Thesis, University of California, Berkeley, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13422798.
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Organisms scan their sensors around their environment to build an internal representation of that environment in a process known as active sensation. The integration of information across time and space is critical to providing context as to what is the organism is perceiving. However, the neural circuits that encode and underlie the integration of incoming sensory information have predominantly been studied in the context of passive sensation. Studying these circuits in the context of active sensation is imperative to generating a better understanding of how the brain naturally encodes sensation. This would have profound impacts on understanding the mechanisms of a number of neural disorders, including autism and attention-deficit/hyperactivity disorder, as well as how to improve the acuity of artificial sensation implanted into disabled individuals. To better understand how the mammalian brain encodes and integrates information during active sensation, my collaborators and I developed several novel paradigms to study surround integration in the mouse barrel cortex during active whisking. In Chapter 1 I establish why this is an important problem, and briefly summarize what is already known about sensory coding in the mouse whisker system. In Chapter 2 my collaborators and I probe how mice represent the location of an object within its whisking field, and how the integration of information across surround whiskers affects this representation. In doing so we discover a novel thalamocortical transformation where surround integration in the cortex suppresses activity in layer 4 of the cortex, ultimately generating a smooth map of scanned space in cortical layer 2/3. In Chapter 3 I utilize a novel tactile display to better understand the logic of multi-whisker integration in two cortical layers. In this unpublished work, I show that contrary to the previous literature in anesthetized mice, cortical neurons in awake, whisking mice powerfully summate specific whisker combinations supralinearly, generating a sparse code representing the entire combinatoric space of whisker touch. In Chapter 4, I conclude with some closing thoughts and propose some future lines of inquiry to further this research.
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Thaler, D. E. „Supplementary motor cortex and the control of action“. Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235063.
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Vaghela, M. B. „Biological control of the mechanical properties of the actin cortex“. Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/10048164/.
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Wittmann, Marco. „From actions to agents : value representation in frontal cortex“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:37387351-cd95-4f24-ad16-1cc67d181a7b.
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In this thesis, I investigated computational and neural mechanisms underlying foraging-related behavior in humans. A consideration of the ecological constraints under which mammalian behavior first evolved guided my investigation of learning and decision-making in frontal cortex. When engaged in foraging, animals have to figure out how profitable their actions are and whether it is better to continue foraging in their current environment or to switch to an alternative. They have to track the reward income of their actions over time and also take into account that the actions of other foraging animals have a direct influence on their reward income (Chapter 1). Based on these observations, I looked at similar types of behavior in humans using computational modeling and functional magnetic resonance imaging. I studied how people evaluate the profitability of their actions over time (Chapter 2). Dorsal anterior cingulate cortex carried a detailed representation of the value of the current foraging action, which was influenced by reward memories with different time constants (Chapter 3). Tracking the reward income of one's actions is not only important in order to learn about the profitability of the environment, it can also inform estimates of one's own and other people's abilities. Ability estimates can be used in a direct way to predict the reward outcome that the actions of one's own self and others will have. I found that people learn about their own and others' abilities in a rational manner but also that ability estimates of self and other were partly confused with each other, depending on whether subjects cooperated or competed with each other (Chapter 4). The confusion effect is reflected in Brodmann area 9 activity indicating that area 9 integrates self and other related information. Perigenual anterior cingulate tracked the ability estimates for oneself, suggesting that it might compute the success expectation of an action independent of particular features of the environment (Chapter 5). In sum, different subregions of medial frontal cortex carried different types of action-related value representations that can guide decision-making.
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Fritzsche, M. „Homeostasis of the cellular actin cortex and its filament length-distribution“. Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1382930/.
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The cell cortex is a thin network of actin, myosin motors, and associated proteins that underlies the plasma membrane in most eukaryotic cells. It enables cells to resist extracellular stresses, perform mechanical work, and change shape. The actin network undergoes constant reorganisation due to molecular turnover. Hence, cortical structural and mechanical properties depend strongly on the relative turnover rates of its constituents and the actin filament length-distribution, but quantitative data on these dynamics remains elusive. I combined single molecule speckle microscopy and photobleaching experiments with microscopic computer simulations to analyse how molecular binding dynamics of G-actin to filaments sets network turnover and consequently the mechanical properties of the cellular actin cortex in living cells. Using photobleaching experiments, I found that two filament families with very different turnover rates composed the actin cortex: one with fast turnover dynamics and polymerisation resulting from addition of monomers to free barbed-ends and one with slow turnover dynamics with polymerisation resulting from formin-mediated filament growth. I show that filaments in the second subpopulation are on average longer than those in the first and that cofilin-mediated severing of formin-capped filaments contributes to replenishing the filament subpopulation with free barbed-ends. Additionally, I measured the molecular association rates and the distribution of travel-distances of single actin monomers and formin dimers in speckle experiments and showed that this travel-distance distribution is consistent with the actin filament length-distribution found from photobleaching experiments and molecular simulations. Furthermore, I compare the steady state cortex of different cell lines and newly formed cortices in cellular blebs and discuss the role of cross-linkers like α-actinin and myosin mini-filaments in the actin cortex. Together, my results provide a quantitative characterisation of essential mechanisms underlying actin cortex homeostasis.
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Dal, Bò Giulia <1983>. „The posterior parietal cortex: a bridge between vision and action“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6756/1/DalBo%27_Giulia_tesi.pdf.
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The present work takes into account three posterior parietal areas, V6, V6A, and PEc, all operating on different subsets of signals (visual, somatic, motor). The work focuses on the study of their functional properties, to better understand their respective contribution in the neuronal circuits that make possible the interactions between subject and external environment. In the caudalmost pole of parietal lobe there is area V6. Functional data suggest that this area is related to the encoding of both objects motion and ego-motion. However, the sensitivity of V6 neurons to optic flow stimulations has been tested only in human fMRI experiments. Here we addressed this issue by applying on monkey the same experimental protocol used in human studies. The visual stimulation obtained with the Flow Fields stimulus was the most effective and powerful to activate area V6 in monkey, further strengthening this homology between the two primates.
The neighboring areas, V6A and PEc, show different cytoarchitecture and connectivity profiles, but are both involved in the control of reaches. We studied the sensory responses present in these areas, and directly compared these.. We also studied the motor related discharges of PEc neurons during reaching movements in 3D space comparing also the direction and depth tuning of PEc cells with those of V6A. The results show that area PEc and V6A share several functional properties. Area PEc, unlike V6A, contains a richer and more complex somatosensory input, and a poorer, although complex visual one. Differences emerged also comparing the motor-related properties for reaches in depth: the incidence of depth modulations in PEc and the temporal pattern of modulation for depth and direction allow to delineate a trend among the two parietal visuomotor areas.
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Dal, Bò Giulia <1983>. „The posterior parietal cortex: a bridge between vision and action“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6756/.
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The present work takes into account three posterior parietal areas, V6, V6A, and PEc, all operating on different subsets of signals (visual, somatic, motor). The work focuses on the study of their functional properties, to better understand their respective contribution in the neuronal circuits that make possible the interactions between subject and external environment. In the caudalmost pole of parietal lobe there is area V6. Functional data suggest that this area is related to the encoding of both objects motion and ego-motion. However, the sensitivity of V6 neurons to optic flow stimulations has been tested only in human fMRI experiments. Here we addressed this issue by applying on monkey the same experimental protocol used in human studies. The visual stimulation obtained with the Flow Fields stimulus was the most effective and powerful to activate area V6 in monkey, further strengthening this homology between the two primates.
The neighboring areas, V6A and PEc, show different cytoarchitecture and connectivity profiles, but are both involved in the control of reaches. We studied the sensory responses present in these areas, and directly compared these.. We also studied the motor related discharges of PEc neurons during reaching movements in 3D space comparing also the direction and depth tuning of PEc cells with those of V6A. The results show that area PEc and V6A share several functional properties. Area PEc, unlike V6A, contains a richer and more complex somatosensory input, and a poorer, although complex visual one. Differences emerged also comparing the motor-related properties for reaches in depth: the incidence of depth modulations in PEc and the temporal pattern of modulation for depth and direction allow to delineate a trend among the two parietal visuomotor areas.
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Coravos, Jonathan S. (Jonathan Stuck). „Molecular organization of the actin cortex in apical constriction and epithelial folding“. Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111230.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 120-139).
Actin and myosin generate contractile forces to change tissue and cell shape. These shape changes are essential for many biological functions, ranging from muscle contraction to tissue morphogenesis in development. While the spatial organization and composition of the actin and myosin contractile force generating machine is well known in muscle, it is less understood in nonmuscle epithelia, which change shape during development and form functional barriers on an organism's inner surfaces. Prevailing models for nonmuscle contractility suggest that the intrinsic ability of mixed polarity actin networks and uniformly distributed myosin to contract into asters drives nonmuscle contractility. Here, I provide insight into the mechanism of nonmuscle contraction by demonstrating that the apical actin cortex and associated proteins are spatially organized in epithelia. In addition, I demonstrate that this spatial organization forms a sarcomere-like actomyosin apparatus, which is essential for epithelial contractility. This updated model is likely to inform our understanding of a wide range of contractile force-generating systems, and may lead to advances in understanding of pathologies that involve defects in contractility, like cardiovascular disease and pulmonary fibrosis.
by Jonathan S. Coravos.
Ph. D.
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Morss, Andrew J. „Optical Trapping Techniques Applied to the Study of Cell Membranes“. The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343686888.
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Hansell, D. J. „Action of ACTH peptides on the adrenal gland“. Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233492.
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Kennerley, Steven W. „The role of the medial frontal cortex in updating action representations“. Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422663.
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Penelope, Kostopoulos. „Active retrieval processes and the mid-ventrolateral prefontal cortex : an event-related fMRI study“. Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32835.
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In recent years, although a number of functional neuroimaging studies have demonstrated a relationship between activity in the prefrontal cortex and memory retrieval, it has been difficult to relate specific aspects of retrieval processing to specific regions of the prefrontal cortex. The present event-related fMRI study focuses on the role of the mid-ventrolateral prefrontal cortex in active retrieval processes, leading to the dissociation of different aspects of mnemonic information. Thirteen normal volunteers were scanned with a 1.5-T Siemens Vision Scanner. Functional images sensitive to the blood oxygenation level dependent (BOLD) signal were acquired in an event-related fashion. In the experimental condition one of four different faces was briefly presented at one of four different locations on the screen. This encoding phase was followed by a question phase during which a cue in the center of the screen instructed the subjects to either retrieve the particular face of the initially presented stimulus or its location. After a delay, a test stimulus was presented and the subjects had to decide whether it corresponded to the aspect of the encoded stimulus instructed by the cue (i.e. the particular face or location). In the recognition control condition for the same sequence of events the subjects had simply to recall the encoded stimulus in order to recognize it in the test phase. The subtraction method was used to compare the signal between these two conditions. Correlation maps computed for the group revealed, relative to the recognition condition, selective increases in activity in the mid-ventrolateral prefrontal cortex when subjects were involved in active retrieval processes both for visual spatial (i.e. location) and visual non-spatial (i.e. face) material. These results support the hypothesis that the mid-ventrolateral prefrontal cortical region is selectively involved in active mnemonic retrieval.
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Collette, Sven. „Value-based decision-making of actions and tasks in human prefrontal cortex“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00828227.
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Les mécanismes de décision impliqués dans le switching entre tâches à la base d'un indice a été étudié intensément, p.ex. la suspension de l'exécution d'une tâche pendant la réalisation d'une autre, avec une récompense fixe. Dans ce cas, le cortex frontopolaire (CFP) est impliqué quand les sujets doivent garder en tête un but principal pendant l'exécution de buts parallèles, et le cortex cingulaire antérieur (CCA) associerait les actions à leurs résultats. Pendant ma thèse, j'ai étudié le switching à différents niveaux d'abstraction de l'action dans la prise de décision fondée sur la valeur espérée: choisir librement d'un côté entre deux actions simples, de l'autre côté entre deux structures abstraites, i.e. des tâches. Les signaux BOLD ont été enregistrés en IRMf sur des sujets sains pendant une expérience d'apprentissage inversé probabiliste, avec des probabilités de récompenses stochastiques anti-corrélées. J'ai comparé des modèles d'apprentissage par renforcement et d'inférence bayésienne afin d'en déduire pour chaque sujet les valeurs des options, qui ont été régressées contre la réponse BOLD. Les résultats montrent une implication du cortex préfrontal ventromédian et du striatum au niveau des actions, et en contraste le CFP, le CCA et le cortex préfrontal dorsolatéral au niveau des tâches. Le CFP surveille les preuves en faveur de la tâche alternative, et le CCA témoigne d'un effet tâche, prédisant le switching entre tâches, mais pas entre actions. En outre, j'ai montré un engagement spécifique du réseau préfrontal dans la prise de décision fondée sur la valeur espérée de structures abstraites à travers des analyses de connectivité.
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Cerpa, Gilvonio Juan Carlos. „Cortex préfrontal et flexibilité comportementale : implication de la noradrénaline“. Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0367.
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La survie d’un organisme nécessite qu’il soit capable de prendre des décisions adaptées dans un environnement changeant. Ces décisions dépendent de multiples processus cognitifs qui ont pu être étudiés par l’intermédiaire des apprentissages associatifs. Ainsi, le contrôle de l’action repose sur des processus distribués au sein de larges circuits cérébraux impliquant notamment les régions préfrontales. Ces fonctions du cortex préfrontal sont largement influencées par l’action de neuromodulateurs, parmi lesquels la noradrénaline, qui pourrait jouer un rôle essentiel dans la flexibilité comportementale. Mon travail de thèse a donc cherché à déterminer l’implication de l’innervation noradrénergique du cortex préfrontal dans l’adaptation à des changements des conséquences de l’action. Une première partie a consisté à étudier l’organisation de l’innervation noradrénergique au sein de différentes aires préfrontales par des méthodes de quantification automatisée. Dans une deuxième partie, nous avons utilisé un protocole instrumental nécessitant un apprentissage flexible des relations causales entre actions et conséquences. A l’aide de ce protocole et de toxines induisant une déplétion noradrénergique, nous avons démontré l’implication de la noradrénaline au sein d’une région du cortex préfrontal, le cortex orbitofrontal, pour la flexibilité comportementale nécessaire au contrôle de l’action, en particulier pour prendre en compte des changements dans l’identité et la valeur des récompenses associées à cette action. Une comparaison avec le cortex préfrontal médian d’une part, et avec le rôle de l’innervation dopaminergique d’autre part, suggère que le rôle de la noradrénaline est spécifique de la région et de l’espèce neurochimique. Dans une troisième partie, nous avons développé plusieurs approches pharmacogénétiques visant à préciser les phases de l’apprentissage impliquant la modulation noradrénergique, et observé certaines limites de ces approches. Ces travaux confirment l’importance de l’action neuromodulatrice sur les fonctions préfrontales et surtout étendent nos connaissances des circuits cérébraux impliqués dans le contrôle de l’action permettant l’adaptation à un environnement changeantAn organism depends for its survival on the ability to take adaptive decisions in an ever-changing environment. These decisions involve several cognitive processes that can be revealed by the study of associative learning processes. Thus, action control has been found to rely on processes that distribute across a network of cerebral structures including prefrontal regions. Prefrontal functions are largely influenced by neuromodulators such as noradrenaline, which is thought to be involved in behavioural flexibility. My Ph.D. project therefore aimed at clarifying the role of noradrenergic modulation of prefrontal cortex regions in adapting a subject’s behaviour to changes in action consequences. In the first chapter, we studied the organization of noradrenergic innervation in the various prefrontal areas, by means of an automated quantification method. In the second chapter, we applied a behavioural protocol requiring flexible learning of the causal relationships between actions and their outcomes. Using this protocol and neurotoxins to deplete prefrontal regions from noradrenergic innervation, we showed that noradrenaline in a specific area, the orbitofrontal cortex, was necessary to action control, in particular to mediate changes in the identity and value of expected outcomes. Comparing this contribution to the role of medial prefrontal cortex on one hand, and of dopaminergic modulation on the other hand, suggests that the role of noradrenergic neuromodulation is both region- and mediator-specific. In the third chapter, we developed a series of chemogenetic approaches to identify the temporal involvement of noradrenaline in the various phases of the task, and we identified some of the limits of these approaches. This work confirms the importance of neuromodulation in prefrontal cortical function and furthers our understanding of cerebral circuits involved in action control and adaptation to a changing environment
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Slachevsky-Chonchol, Andrea. „Cortex préfrontal et contrôle de l'action : approche clinique et expérimentale“. Paris 6, 2003. http://www.theses.fr/2003PA066309.
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Hubrich, Hanna. „Active Matter in Confined Geometries - Biophysics of Artificial Minimal Cortices“. Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-152A-5.
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Khoder, Suzana. „Role of the prefrontal-brainstem pathway in mediating avoidance behavior“. Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0256.
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Les mammifères, comme par exemple les rongeurs, soumis à des expériences aversives présentent des réponses comportementales de peur caractéristiques notamment une réponse d'immobilisation (freezing) ou d'évitement. Alors que le rôle du cortex préfrontal dorso-médian (CPFdm) dans l’acquisition ainsi que l’expression du freezing a déjà été expérimentalement établi, son implication dans l’encodage des réponses d’évitement de peur ainsi que l’interaction entre les circuits neuronaux préfrontaux impliqués dans le freezing et/ou l’évitement restent mal compris. Afin de répondre à ces questions, nous avons développé au laboratoire un paradigme expérimental permettant à une souris d’acquérir et d’exprimer le freezing ou l’évitement lors de la présentation d'un même stimulus aversif et ceci en fonction du contexte environnant. Ainsi, nous avons pu déterminer si les mêmes circuits neuronaux dans le cortex préfrontal dorso-médian encodent les deux réponses de peur, le freezing et l’évitement. Nous avons mis en oeuvre au cours de ce travail des approches comportementales, de traçage neuroanatomique, d'immunohistochimie, d'enregistrements extracellulaires in vivo et intracellulaires in vitro ainsi que des approches optogénétiques. Nos résultats indiquent que (i) le CPFdm et les régions dorsales de la substance grise périaqueducale sont activés pendant le comportement d'évitement, (ii) une sous population de neurones du CPFdm encode le comportement d'évitement mais pas le freezing, (iii) cette population neuronale projette sur le dl/lPAG, (iv) l'activation et l'inhibition optogénétique de cette projection induit et bloque l'apprentissage de l'évitement, respectivement et (v) l'apprentissage de l'évitement est associé à la mise en place d'une plasticité des afférences préfrontales sur le dl/lPAG. Dans leur ensemble ces résultats démontrent pour la première fois que la plasticité dépendante de l'activité des neurones du CPFdm projettant sur le dl/lPAG contrôle l'apprentissage de l'évitement de peurMammals, including rodents show a broad range of defensive behaviors as a mean of coping with threatful stimuli including freezing and avoidance behaviors. Several studies emphasized the role of the dorsal medial prefrontal cortex (dmPFC) in encoding the acquisition as well as the expression of freezing behavior. However the role of this structure in processing avoidance behavior and the contribution of distinct prefrontal circuits to both freezing and avoidance responses are largely unknown. To further investigate the role of dmPFC circuits in encoding passive and active fear-coping strategies, we developed in the laboratory a novel behavioral paradigm in which a mouse has the possibility to either passively freeze to an aversive stimulus or to actively avoid it as a function of contextual contingencies. Using this behavioral paradigm we investigated whether the same circuits mediate freezing and avoidance behaviors or if distinct neuronal circuits are involved. To address this question, we used a combination of behavioral, neuronal tracing, immunochemistry, single unit and patch clamp recordings and optogenetic approaches. Our results indicate that (i) dmPFC and dorsolateral and lateral periaqueductal grey (dl/lPAG) sub-regions are activated during avoidance behavior, (ii) a subpopulation of dmPFC neurons encode avoidance but not freezing behavior, (iii) this neuronal population project to the dl/lPAG, (iv) the optogenetic activation or inhibition of this pathway promoted and blocked the acquisition of conditioned avoidance and (v) avoidance learning was associated with the development of plasticity at dmPFC to dl/lPAG synapses. Together, these data demonstrate for the first time that activity-dependent plasticity in a subpopulation of dmPFC cells projecting to the dl/lPAG pathway controls avoidance learning
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Daviaux, Yannick. „Intégration sensorimotrice et contexte somatosensoriel : vers une meilleure compréhension des processus neuronaux impliqués dans le couplage action-perception“. Nantes, 2015. http://www.theses.fr/2015NANT3014.
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La réalisation d'actions motrices efficaces est essentielle aux interactions avec notre environnement. Une des clefs du succès de ces actions réside dans la potentialisation effective du couplage action-perception. La littérature abonde pourtant de circonstances de détérioration comportementale de ce couplage. , i. E. Lorsque l'état somatosensoriel des individus est altéré. Les travaux de cette thèse visent à appréhender les processus neuronaux impliqués dans cette détérioration. Nous évoquerons comment les travaux menés dans la littérature ont guidé notre attention jusqu'aux transformations corticales relatives à la fonction sensorimotrice. Les contraintes expérimentales relatives aux études comportementales seront identifiées et justifieront la mise en place d'une nouvelle procédure, permettant d'appréhender les corrélats corticaux de la détérioration du couplage à partir de mesures de l'activité électroencéphalographique (EEG). Les résultats, obtenus dans une tâche de pointage d'un objet placé à distances variables, seront discutés au regard de la construction de la représentation sensorimotrice du corps. La plasticité de cette représentation expliquera la détérioration du couplage action-perception, dans le cadre spécifique de ce paradigme. Les interprétations seront élargies aux concepts de body-image, de body-schema et d'espace péripersonnelEfficient motor actions are essential in daily life's interaction with our environment. It is well accepted that action-perception coupling plays a major role for such successful visuomotor actions. However, impaired coupling can occur when the somatosensory state of individuals is altered. This work aimed at identifying the cortical correlates of impared action-perception coupling. An enhanced experimental procedure was developed according to the constraints relevant for electroencephalographic measurements (EEG), used to study the sensorimotor coupling-related neural processes. The findings were obtained in a reaching-to-grasp paradigm, in which individuals had to judge whether they were able to reach an object. Results are discussed regarding the construction of the sensorimotor representation of the body. Plasticity of such a representation is discussed from the concepts of body image, body schema and peripersonal space, to account for impaired action-perception coupling
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Lacerda, Rodrigues N. T. „Moesin orchestrates the reorganisation of the actin cortex and shape changes during mitotic progression in an epithelium“. Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1468688/.
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Animal cells endure dramatic actin-dependent changes in shape as they progress through mitosis – they round up at mitotic entry, elongate at anaphase and split into two at cytokinesis. In this thesis I explore the role of Moesin, an actin-membrane crosslinker and the sole ERM protein expressed in Drosophila, in orchestrating rearrangements of the actin cortex and morphological changes in epithelial cells undergoing mitosis. To perform my studies I used the fly notum and sensory organ precursor (SOP) cells therein as a model system. In this thesis I show that Moesin is required for the stabilisation of the actomyosin cortex at metaphase. This mechanism is dependent upon phosphorylation of Moesin by the Slik kinase, which activates the ERM protein. Reduced levels of Moesin or Slik lead to myosin-II-driven cortical instabilities. Cortical stabilisation in mitotic SOP cells ensures the efficient accumulation of fate determinants at the plasma membrane. At mitotic exit, a pool of active, phosphorylated Moesin is lost from the cell poles, thereby triggering polar relaxation and initiating anaphase cell elongation. These two events precede furrow formation, are independent of centrosome or astral microtubules-derived signals, and are induced by proximity of the segregating chromosomes to the cell poles. I show that a pool of kinetochore-localised PP1-87B phosphatase and its regulatory subunit Sds22 inactivate cortical Moesin and elicit the dismantling of the actomyosin cortex at mid-anaphase. Cells with reduced amounts of PP1-87B or Sds22 fail to clear Moesin and actin from the anaphase poles. Importantly, these defects in polar relaxation are mimicked by the expression of a constitutively active form of Moesin in fly tissues. Finally, I demonstrate that delocalisation of PP1/Sds22 from the kinetochores via KNL1 depletion abolishes polar blebbing at anaphase and impairs cell elongation. My work shows how the dynamic regulation of Moesin activation and localisation controls shape changes in cells undergoing mitosis. Moreover, it sheds light on a novel mechanism of polar relaxation at anaphase, in which a kinetochore-derived signal instructs the cell cortex to become polarised, thereby initiating cytokinesis.
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Viellard, Juliette. „Etudes des circuits neuronaux organisant l'évitement actif instrumental et l'évitement contextuel non instrumental“. Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0456.
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Les mammifères, y compris les rongeurs, présentent un large éventail de comportements défensifs actifs, tels que l’évitement, ou passif, tel que l’immobilisation (le freezing), à des fins d’adaptation et de survie. La réponse d'évitement est une réaction apprise dans laquelle un individu prend le contrôle de situations dangereuses pour faire face aux menaces. Une forme d'évitement qui a été étudiée est l'évitement actif signalé, où les individus sont entraînés à éviter une situation et fuient en réponse à un signal précédemment associé à un stimulus aversif. Il a été souligné que le Cortex préfrontal dorso-médian (CPFdm) joue un rôle important dans l’encodage de l’acquisition et de l’expression du freezing ainsi que dans les réponses d’évitement. Cependant, sa contribution à l'acquisition et à l'expression de comportements d'évitement n'est pas claire, et les circuits neuronaux du CPFdm qui gèrent ensemble les stratégies d’adaptation actives et passives, restent à découvrir. Pour répondre à cette question, nous avons développé un nouveau paradigme comportemental dans lequel une souris a la possibilité de se figer ou d’éviter un stimulus aversif en fonctions des contingences contextuelles. Premièrement, nous avons étudié le rôle de la voie entre le CPFdm et la matière grise periaqueducale (PAG) dans l’évitement actif signalé, et sa relation avec le freezing. Nos résultats indiquent que (i) le CPFdm et le dl/lPAG sont activés lors du comportement d'évitement, (ii) et que l'inhibition optogénétique de cette voie bloque l'acquisition de l'évitement conditionné. Une forme d'évitement non instrumental est également étudiée, dans laquelle l'individu apprend à éviter l'environnement aversif en utilisant uniquement des indices contextuels et affichant des comportements d'évaluation des risques à l’encontre de l'environnement dangereux. Il a été précédemment démontré que dans cette situation, un circuit septohippocampale-hyptothalamique-tronc cérébrale est spécialement activé. Cette analyse a aussi révélé que le noyau dorsal pré-mamillaire (PMD) devait être impliqué de manière critique dans l'évitement passif contextuel. Nous avons analysé l'influence de la modulation du PMD et de ses projections au niveau de ses cibles principales, sur le processus d'expression et de reconsolidation de l'évitement passif contextuel. Nos résultats ont montré qu’une (i) voie septohippocampale-hyptothalamique-tronc cérébrale spécifique était impliquée dans notre paradigme d’évitement passif. (ii) De plus, l’inhibition du PMD lors d'une exposition au contexte aversif altère à la fois l'expression des comportements d'évitement et la reconsolidation de la mémoire. (iii) Enfin l’inhibition au niveau des terminaux du PMD altère l'expression et la reconsolidation de la mémoire dans le dlPAG et dans l’AMv. Les expériences de ce projet ont été menées à bien à l’aide d’analyse Fos, d'inhibition pharmacogénétique et optogénétiquesMammals, including rodents show a broad range of defensive behaviors as a mean of coping actively, such as avoidance behaviors, or passively such as freezing behavior. The avoidance response is a learned response in which an individual takes control in dangerous situations to deal with threats. One form of avoidance that has been investigated is the signaled active avoidance, where individuals are trained to avoid an environment, and escape in response to a cue previously associated with an aversive stimulus. It has been emphasized that the dmPFC plays an important role in encoding freezing acquisition and expression as well as active avoidance responses. However the neural circuits of the dmPFC processing the expression and acquisition of both active and passive coping strategies are yet to be discovered. To adress this question, we developed a novel behavioral paradigm in which a mouse has the possibility to either passively freeze to an aversive stimulus or to actively avoid it as a function of contextual contingencies. We first investigated the role of the pathway between the dmPFC and PAG in signaled active avoidance, and its relation with freezing. Our results indicate that (i) dmPFC and dl/lPAG sub-regions are activated during avoidance behavior, (ii) and that the optogenetic inhibition of this pathway blocked the acquisition of active avoidance. A non-instrumental form of avoidance is also investigated where the individual learns to avoid the aversive environment using contextual clues only, and displaying risk assessment behaviors toward the fearful environment. It has been previously shown that in this situation, a circuit involving the septohippocampal-hypothalamic-brainstem pathway is involved. It also revealed that the dorsal premammillary nucleus (PMD) must be critically involved in contextual passive avoidance. We analysed how the manipulation of the PMD and its projections to its main targets influences the expression and reconsolidation processes of contextual passive avoidance. Our results showed that (i) a specific septohippocampal-hypothalamic-braintem pathway is involved in our passive avoidance paradigm. (ii) Silencing the PMD during context exposure impairs both avoidance expression and memory reconsolidation and that (iii) the inhibition at terminal level impairs the expression and memory reconsolidation in both dlPAG and AMv. Both parts of the project assessed these questions using Fos immunochemistry analysis, manipulations of neural circuits using optogenetic, and pharmacogenetic techniques
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Avsaar, Emin. „Actions of adenosine in the rat entorhinal cortex in an in vitro model of epilepsy“. Thesis, Royal Holloway, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420817.
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Devonshire, Ian Mark. „A functional imaging and electrophysiological investigation of cocaine's actions on the rat primary somatosensory cortex“. Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425608.
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Filimon, Flavia. „Multisensory and sensorimotor representations for action in human posterior parietal cortex investigated with functional MRI“. Diss., [La Jolla] : University of California, San Diego, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3320178.
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Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed September 24, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 133-135).
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BONAZZI, Laura. „Complex Movements for Voluntary Actions Evoked by Electrical Stimulation in the Motor Cortex of Rats“. Doctoral thesis, Università degli studi di Ferrara, 2012. http://hdl.handle.net/11392/2389280.
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Electrical intracortical microstimulation (ICMS) has been widely used to study the functional organization of the motor cortex. The ICMS with longer stimulus trains of about 500 ms (long-duration ICMS) evoked complex and coordinated movement, similar to those of natural behaviour. A recent paper (Ramanathan et al., 2006) have reported that long-duration ICMS in rat motor cortex can result in complex, multijoint forelimb movements organized in a roughly topography. We pose the question if different features of motor control (e.g. body map, movement patterns, target location in space) can develop overlapping maps in the forelimb region of the rat’s M1. We performed long-duration ICMS to evoke complex, multijoint forelimb movements and we used 3D motion analysis tools to measure kinematic variables of electrically-evoked movements. The analysis was aimed to define the classes of movement and their topography across the cortical surface. Then, the following kinematic parameters, related to the limb and the paw component, were determined from the analysis: maximal displacement in XYZ, latency, duration, peak velocity, mean velocity, number of peak velocity , trajectory, vector, path index.
According to our methode, the repertoire of the limb movement included: abduction, adduction, extension, retraction and elevation while paw movements included: opening, closure, opening/closure sequence and supination.
To analyze our data, multivariate test for difference in means (MANOVA), one-way ANOVA and Tukey’s test were performed.
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Insel, Nathan. „Physiology of the medial frontal cortex during decision-making in adult and senescent rats“. Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/196140.
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Convergent evidence suggests that the dorsal medial prefrontal cortex (dmPFC) makes an important contribution to goal-directed action selection. The dmPFC is also part of a network of brain regions that becomes compromised in old age. It was hypothesized that during decision-making, some process of comparison takes place in the dmPFC between the representation of available actions and associated values, and that this process is changed with aging. These hypotheses were tested in aged and young adult rats performing a novel 3-choice, 2-cue decision task. Neuron and local field potential activity revealed that the dmPFC experienced different states during decision and outcome phases of the task, with increased local inhibition and oscillatory (gamma and theta) activity during cue presentation, and increased excitatory neuron activity (among regular firing neurons) at goal zones. Although excitatory and inhibitory activity appeared anti-correlated over phases of the decision task, cross-correlations and the prominent gamma oscillation revealed that excitation and inhibition were highly correlated on the millisecond scale. This "micro-scale" coupling between excitation and inhibition was altered in aged rats and the observed changes were correlated with changes in decision and movement speeds of the aged animals, suggesting a putative mechanism for age-related behavioral slowing. With respect to decision-making, both aged and young adult rats learned over multiple days to follow the rewarded cue in the 3-choice, 2-cue task. Support for the hypothesis that the dmPFC simultaneously represents alternative actions was not found; however, neuron activity selective for particular goal zones was observed. Interestingly, goal-selective neural activity during the decision period was more likely to take place on error trials, particularly on high-performing sessions and when rats exhibited a preference for a particular feeder. A possible interpretation of these patterns is that goal representations in the dmPFC might have sometimes overruled learned habits, which are likely to be involved in following the correct cue and which are known to be supported by other brain regions. These results describe fundamental properties of network dynamics and neural coding in the dmPFC, and have important implications for the neural basis of processing speed and goal-directed action.
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Romaniuk, Liana. „Functional neuroanatomy of action selection in schizophrenia“. Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5758.
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Schizophrenia remains an enigmatic disorder with unclear neuropathology. Recent advances in neuroimaging and genetic research suggest alterations in glutamate-dopamine interactions adversely affecting synaptic plasticity both intracortically and subcortically. Relating these changes to the manifestation of symptoms presents a great challenge, requiring a constrained framework to capture the most salient elements. Here, a biologically-grounded computational model of basal ganglia-mediated action selection was used to explore two pathological processes that hypothetically underpin schizophrenia. These were a drop in the efficiency of cortical transmission, reducing both the signal-to-noise ratio (SNR) and overall activity levels; and an excessive compensatory upregulation of subcortical dopamine release. It was proposed that reduced cortical efficiency was the primary process, which led to a secondary disinhibition of subcortical dopamine release within the striatum. This compensation was believed to partly recover lost function, but could then induce disorganised-type symptoms - summarised as selection ”Instability” - if it became too pronounced. This overcompensation was argued to be countered by antipsychotic medication. The model’s validity was tested during an fMRI (functional magnetic resonance imaging) study of 16 healthy volunteers, using a novel perceptual decision-making task, and was found to provide a good account for pallidal activation. Its account for striatum was developed and improved with a small number of principled model modifications: the inclusion of fast spiking interneurons within striatum, and their inhibition by the basal ganglia’s key regulatory nucleus, external globus pallidus. A key final addition was the explicit modelling of dopaminergic midbrain, which is dynamically regulated by both cortex and the basal ganglia. This enabled hypotheses concerning the effects of cortical inefficiency, compensatory dopamine release and medication to be directly tested. The new model was verified with a second set of 12 healthy controls. Its pathological predictions were compared to data from 12 patients with schizophrenia. Model simulations suggested that Instability went hand-in-hand with cortical inefficiency and secondary dopamine upregulation. Patients with high Instability scores showed a loss of SNR within decision-related cortex (consistent with cortical inefficiency); an exaggerated response to task demands within substantia nigra (consistent with dopaminergic upregulation); and had an improved fit to simulated data derived from increasingly cortically-inefficient models. Simulations representing the healthy state provided a good account for patients’ motor putamen, but only cortically-inefficient simulations representing the ill state provided a fit for ventral-anterior striatum. This fit improved as the simulated model became more medicated (increased D2 receptor blockade). The relative improvement of this account correlated with patients’ medication dosage. In summary, by distilling the hypothetical neuropathology of schizophrenia into two simplified umbrella processes, and using a computational model to consider their effects within action selection, this work has successfully related patients’ fMRI activation to particular symptomatology and antipsychotic medication. This approach has the potential to improve patient care by enabling a neurobiological appreciation of their current illness state, and tailoring their medication level appropriately.
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Petroni, Filippo. „A computational analysis of the functional role of timing of action potentials in the cerebral cortex“. Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289105.
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Maffei, Giovanni. „Automatic and deliberate control of action: an embodied perspective of artificial and biological brains“. Doctoral thesis, Universitat Pompeu Fabra, 2018. http://hdl.handle.net/10803/666954.
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Animals evolved to survive in dynamic environments by developing multiple behavioral strategies to adapt and to learn from their interaction with the world. Associative mechanisms and internal representations are at the core brain computation, however, to acquire a complete knowledge of their relevance for behavior it is necessary to take into consideration their embodied nature. In an interdisciplinary effort which integrates methods from computational modeling, robotics, and electrophysiology, this dissertation presents a series of studies that aim at advancing the understanding of the automatic and deliberate processes that regulate embodied control of action in the brain. Through the formulation of a biologically constrained control architecture engaged in a real-world foraging task, we lay the ground for modeling and analyzing complex goal-oriented behavior emerging from the interplay between the automatic cerebro-cerebellar system acquiring sensory-motor associations, and the deliberate fronto-hippocampal system providing goal-oriented navigation and planning. Following the behavioral analysis of the stimulus-response model of cerebellar learning, we later ask how could the cerebellum implement anticipatory control, which is both adaptive and resistant to uncertainty. To answer this question, we explore the properties of the automatic control system and advance a novel hypothesis on the role of the cerebellum, by recasting its computation in the perceptual domain. Finally, we ask how the automatic and deliberate systems interact during unexpected situations that require a sudden change of plans. By analyzing the neural dynamics of the human frontal cortex in the control of deliberate action switch, we support the contribution of low-frequency oscillatory dynamics within this area to orchestrate behavior, based on internal representations of goals and rules. Altogether these results contribute to our understanding of how automatic and deliberate processes control action in the brain and advance novel insights that challenge or extend current theories. Despite the main aim to understand the brain, these insights could also be applied to the development of novel control systems for a new generation of robots.Els animals van evolucionar per sobreviure en entorns dinàmics desenvolupant múltiples estratègies de comportament per adaptar-se i aprendre de la seva interacció amb el món. Els mecanismes associatius i les representacions internes estan en el nucli del càlcul del cervell, però, per adquirir un coneixement complet de la seva rellevància per a la conducta, cal tenir en compte la seva naturalesa incorporada. En un esforç interdisciplinari que integra mètodes de modelització computacional, robòtica i electrofisiologia, aquesta tesi presenta una sèrie d’estudis que pretenen avançar en la comprensió dels processos automàtics i deliberats que regulen el control de l’acció incorporat al cervell. Mitjançant la formulació d’una arquitectura de control biològicament restringida dedicada a una tasca de forjat en el món real, posem el terreny per modelar i analitzar una conducta orientada a objectius complexos que sorgeix de la interacció entre el sistema cerebrovascular cerebral automàtic que adquireix associacions sensorials motores i deliberat sistema fronto-hipocamp que proporciona una navegació i una planificació orientades a objectius. Després de l’anàlisi conductual del model d’estímul-resposta de l’aprenentatge cerebel.lari, ens preguntem més endavant com es pot aplicar el cerebel a un control anticipat que e ́s a la vegada adaptatiu i resistent a la incertesa. Per respondre a aquesta pregunta, explorem les propietats del sistema de control automàtic i avancem una nova hipòtesi sobre el paper del cerebel, tot reformant la seva computacio ́ en el domini perceptiu. Finalment, preguntem com interactuen els sistemes automa`tic i deliberat durant situacions inesperades que requereixen un canvi sobtat de plans. Analitzant la dina`mica neural de l’escorça frontal humana en el control del canvi d’acció deliberada, recolzem l’aportació de dinàmiques oscil.ladores de baixa freqüència en aquesta àrea per orquestrar el comportament, basant-se en representacions internes d’objectius i regles. Tot plegat, aquests resultats contribueixen a la nostra comprensió de com processos automàtics i deliberats controlen l’acció en el cervell i avancen noves idees que desafien o allarguen les teories actuals. Malgrat l’objectiu principal d’entendre el cervell, aquestes idees també es podrien aplicar al desenvolupament de nous sistemes de control per a una nova generació de robots.
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Mikula, Laura. „Intégration multisensorielle pour les mouvements de pointage chez les sujets sains et les patients avec ataxie optique“. Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1117/document.
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Afin d’effectuer un mouvement de la main, le système nerveux doit mettre en commun des informations issues de plusieurs sens : c’est l’intégration multisensorielle. Le cortex pariétal postérieur est une interface sensorimotrice qui est impliquée dans le processus d’intégration multisensorielle. Si cette région est endommagée, les patients présentent un trouble visuomoteur dénommé ataxie optique qui se caractérise par une difficulté à réaliser des mouvements visuellement guidés de la main. À ce jour, les mécanismes qui sous-tendent l’intégration multisensorielle pour l’action ne sont pas encore totalement connus. Le premier axe de ma thèse consiste à définir, chez les sujets sains, comment les informations visuelles et somatosensorielles sont intégrées pendant la planification d’un mouvement de pointage. Le deuxième axe s’intéresse aux troubles sensorimoteurs associés à l’ataxie optique qui permettent une meilleure compréhension des fonctions du cortex pariétal postérieur dans la planification motrice et le contrôle du mouvementTo execute reach movements, the central nervous system needs to combine informationfrom different sensory modalities, a process knows as multisensory integration. Theposterior parietal cortex is a sensorimotor interface implicated in multisensory integrationprocesses. Patients with a damage to this region exhibit a visuomotor deficit called opticataxia. Patients with optic ataxia present difficulties in performing hand visually-guidedmovements. To date, the mechanisms underlying multisensory integration are still notfully understood. The first aime of my thesis is to determine how visual and somatosensoryinformation are integrated in healthy participants, during the planning of pointingmovements. I will then focus on the sensorimotor deficits observed in optic ataxia whichenable a better understanding of the functions of the posterior parietal cortex in motorplanning and online control
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Hart, Sarah Belger Aysenil. „Function and dysfunction of the prefrontal cortex effects of distraction on active maintenance in healthy controls and individuals with schizophrenia /“. Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,808.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Dec. 18, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Psychology." Discipline: Psychology; Department/School: Psychology.
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Fedorov, Leonid [Verfasser], und Martin [Akademischer Betreuer] Giese. „Experimental Manipulation of Action Perception Based on Modeling Computations in Visual Cortex / Leonid Fedorov ; Betreuer: Martin Giese“. Tübingen : Universitätsbibliothek Tübingen, 2018. http://d-nb.info/1199268518/34.
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GIORDANO, Nadia Concetta. „Early, sustained and broadly-tuned discharge of fast-spiking interneurons in the premotor cortex during action planning“. Doctoral thesis, Scuola Normale Superiore, 2021. http://hdl.handle.net/11384/106386.
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Preparatory neural activity in premotor areas is critical for planning and execution of voluntary movements. Previous studies in monkeys and mice have revealed how the discharges of pyramidal, excitatory neurons (PNs) encode a motor plan for an upcoming movement (Afshar et al., 2011; Chen et al., 2017; Li et al., 2015). However, the contribution of GABAergic interneurons, specifically fast-spiking interneurons (FSNs), to voluntary movements remains poorly understood.
Putative premotor areas involved in action planning have been demonstrated in rodents. In particular, in mice, a premotor area controlling voluntary licking has been identified in the anterior-lateral motor cortex (ALM) (Komiyama et al., 2010). Also, ALM partially overlaps with the rostral forelimb area (RFA), the previously defined premotor region involved in the control of paw movement in rats and mice (Rouiller et al., 1993; Tennant et al., 2011).
To understand the excitatory-inhibitory microcircuit involved in action planning, here I compare directly the response properties of PNs and FSNs during licking behaviour and forelimb retraction in the mouse. Recordings are carried out with both acute electrodes and chronic microelectrode arrays from both the two premotor areas, i.e. the ALM – responsible for licking –, and RFA – involved in paw movement.
Specifically, in a first set of experiments, I used head-restrained mice that spontaneously lick a reward delivered at random intervals from a drinking spout. Mice voluntary performed either single isolated or a burst of consecutive licks, which I categorized, a posteriori, in single (= 1 lick) and multiple licks (≥ 3 licks). During the task, I extracellularly recorded single units’ activity from ALM, using acute in vivo electrophysiology. I identified putative PNs and FSNs, based on well-established features of their waveforms, and investigated their functional properties during the movement.
Unexpectedly, I report that optogenetically-verified FSNs showed an earlier and more sustained activation than PNs. In particular, most of the neurons’ activity anticipated the licking onset, consistently with an involvement of the ALM in movement planning. The majority of the neurons (~90%) increased their firing frequency in correspondence with the movement, but suppressive modulations were also observed in a subset of units. For both PNs and FSNs, I found significantly greater discharge during multiple than single licks and the peak discharge was significantly delayed for both subclasses during multiple licking events. However, FSNs modulated their activity about 100ms earlier than PNs. Furthermore, almost all FSNs showed a peak in their response before the beginning of the sequence of licks. Analysis of mean information content confirms that FSNs predict licking onset not only significantly better, but even earlier, than PNs.
Chronic electrode arrays covering both the ALM and RFA were next used to simultaneously probe neural responses during (i) licking and (ii) forelimb pulling in a robotic device (Spalletti et al., 2017). I report that most of the FSNs respond with a stereotyped increase in their firing rates during both licking and pulling. In stark contrast, PNs show a variety of behaviours, dependent on movement type. At least for a minority of them, licking behaviour and forelimb retraction are represented as two different motor acts, reaching significant levels in the PNs. Accordingly, computational analysis shows that PNs carry more independent information than FSNs.
Altogether, these data indicate that a global rise of GABAergic inhibition mediated by FSNs firing contributes to early action planning.
Next, encouraged by the deeper understanding of the cortical microcircuits underlying movement planning in mice, I exploited this knowledge to explore more complex mechanisms, as action understanding. The neural circuits that integrate performed and observed actions have been found in the premotor cortex of monkeys and named as ‘mirror neurons system’ (di Pellegrino et al., 1992). Recently, the presence of mirror neurons have been demonstrated in rodents in the anterior cingulate cortex (Carrillo et al., 2019), but whether they could contribute to action understanding in the premotor cortex is still unclear.
At behavioural level, the observation of actions can actually lead, in some cases, to the repetition of those same actions. This phenomenon has been named social facilitation, and the underlying motor program has been attributed to the mirror system (Ferrari et al., 2005). Here, I set up a behavioural task similar to the one exploited in monkeys to explore social facilitation in mice. I took advantage of licking behaviour to set up the social facilitation experiment. Therefore, head-restrained mice were allowed to lick water from a feeding needle. I found that mice can actually facilitated to lick more when another individual was engaged in the same action, supporting the hypothesis of a social facilitation in mouse.
Altogether these results indicate that the observers’ behaviour was actually influenced by the demonstrators’ one, laying the groundwork for the study of mirror neurons in mice at cellular level.
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Bohec, Pierre. „Étude du comportement hors-équilibre du cortex cellulaire“. Phd thesis, Université Paris-Diderot - Paris VII, 2012. http://tel.archives-ouvertes.fr/tel-00870466.
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La cellule est capable, en consommant l'énergie issue de l'hydrolyse de l'ATP, d'exercer des forces qui prennent leurs origines dans des réactions biochimiques. Un élément important de la cellule est le cytosquelette, composé principalement de microtubules et de filaments d'actine, il en constitue l'architecture et lui donne l'essentiel de ses propriétés mécaniques. Il est composé de polymères réticulés et, du point de vue de la rhéologie, a un comportement viscoélastique. Au sein du cytosquelette, des processus tels que la polymérisation de l'actine ou des microtubules permettent d'exercer des forces. Des protéines, de la famille des moteurs moléculaires, ont pour rôle spécifique de convertir l'énergie stockée sous forme chimique en énergie mécanique. L'activité mécanique hors-équilibre de la cellule est donc directement reliée à ces forces d'origine biochimique. Dans ce travail, nous avons étudié la distribution statistique des forces d'origine biochimique s'exerçant sur une bille de taille micrométrique attachée au cortex d'actine par l'intermédiaire de récepteurs de l'adhésion cellulaire : les intégrines. L'étude des forces d'origine biologique est inséparable de la connaissance des forces d'origine thermique car à cette échelle microscopique la contribution des forces thermiques n'est pas négligeable. Les forces s'exerçant sur la sonde ont deux origines possibles : biologique ou thermique. Notre approche expérimentale est basée sur la combinaison de deux techniques de microrhéologie, active et passive, ce qui nous permet de calculer la fonction d'autocorrélation temporelle des forces exercées sur une sonde accrochée à l'actine corticale et de la comparer à la fonction d'autocorrélation des forces thermiques estimée via le théorème de fluctuation-dissipation. La différence entre ces deux spectres nous donne une idée de la contribution des forces d'origine biologique au mouvement de la bille et une mesure de l'écart du système à l'équilibre thermodynamique. Afin d'étudier plus en détail ce système de bille subissant des forces de la part de l'actine corticale, nous avons étudié l'effet de la variation de la densité de ligand recouvrant la bille. La question qui nous a animés tout au long de ce travail est l'origine de ces forces biologiques ou plus exactement la nature du composant du cytosquelette qui exerce ces forces athermiques. Dans un premier temps, nous avons étudié l'influence de la température sur ces forces biologiques. Nous avons ensuite étudié l'effet de la déplétion de l'ATP dans la cellule, de la dépolymérisation de l'actine et de l'inhibition des moteurs moléculaires de la famille des myosines.
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Hallin, Nathalie. „Cognitive Dissonance : Neural Correlates and New Theoretical Approaches“. Thesis, Högskolan i Skövde, Institutionen för kommunikation och information, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-7173.
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Cognitive dissonance has traditionally been defined as the negative affective state which accompanies inconsistent cognitions and motivates one to make the cognitions consistent. This thesis critically evaluates two theories about cognitive dissonance. The action-based model of dissonance argues that inconsistent cognitions have the potential to interfere with effective and unconflicted action. The new look model of dissonance, contradicting the traditional definition of dissonance, argues that it is aversive consequences rather than inconsistent cognitions that cause dissonance. Recent studies investigating the neural correlates of dissonance show that parts of anterior cingulate cortex and prefrontal cortex seem to be involved in the dissonance process. One of the major predictions of the new look model of dissonance has been undermined by recent evidence. In contrast, the action-based model of dissonance is supported by recent studies.
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Nöding, Helen [Verfasser], Andreas [Akademischer Betreuer] Janshoff, Andreas [Gutachter] Janshoff, Florian [Gutachter] Rehfeldt, Sarah [Gutachter] Köster, Jörg [Gutachter] Enderlein, Michael [Gutachter] Meinecke und Silvio O. [Gutachter] Rizzoli. „Active and Passive Microrheology of F-Actin Membrane Composites : From Minimal Cortex Model Systems to Living Cells / Helen Nöding ; Gutachter: Andreas Janshoff, Florian Rehfeldt, Sarah Köster, Jörg Enderlein, Michael Meinecke, Silvio O. Rizzoli ; Betreuer: Andreas Janshoff“. Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://d-nb.info/1163109061/34.
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Venturini, Guilherme Costa [UNESP]. „Associações genéticas com o marcador alfa actina 1, e variabilidade genética de características de importância econômica de frangos de corte“. Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/102772.
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Em linhagens de frangos de corte, pesquisas têm sido realizadas para identificar marcadores moleculares responsáveis pela variação fenotípica de características de interesse econômico para auxiliar os procedimentos de seleção. Neste trabalho, o objetivo foi estudar a associação do gene ALFA ACTINA1 com 68 características de desempenho, carcaça e órgãos e estimar parâmetros genéticos para peso corporal aos 42 dias de idade (PV42), órgãos e partes da carcaça para fornecer subsídios ao programa de melhoramento genético de uma linhagem paterna de frangos de corte, selecionada principalmente para PV42. Os dados utilizados foram provenientes da Embrapa Suínos e Aves, Concórdia, SC. As análises de associação genética entre as características estudadas e a ALFA ACTINA1 foram conduzidas pelo método de máxima verossimilhança, considerando quatro modelos de análise. A análise de validação foi realizada por meio de um modelo misto que incluiu o efeito aleatório de animal (poligenes), os efeitos fixos de sexo (2 níveis), incubação (5 níveis) e do SNP (3 níveis), além do erro aleatório. A estimação de parâmetros genéticos foi realizada pelo método da máxima verossimilhança restrita, sob modelo animal multicaracterística para PV42 com características que foram significativamente (p<0,05) associadas com o marcador molecular e com um segundo conjunto de dados que incluiu pesos de carcaça resfriada, de fígado, de coração, de moela e os pesos da asa, das carnes da coxa, da sobrecoxa e do peito, peso do dorso e do filé do peito. O modelo geral utilizado para estimar os parâmetros genéticos incluiu o efeito fixo de grupo incubação-sexo e efeitos aleatórios aditivo e residual. Efeitos aditivos verificados pela substituição alélica do gene ALFA ACTINA1 estão associados com rendimentos da carne do peito (RCPT), do...
In broilers strains, research has been conducted to identify molecular markers responsible for phenotypic variation in traits of economic interest to help the selection procedures. In this work, the aim was to study the association of ALPHA ACTIN1 gene with 68 traits of performance, carcass and organs and to estimate genetic parameters for body weight at 42 days of age (BW42), organs and parts of the carcass to provide tools for the poultry breeding program of a paternal broiler strain and it has been selected mainly for BW42. The data used were from Embrapa Swine and Poultry, Concordia, SC. The analysis of genetic association between traits studied and ALPHA ACTIN1 were conducted by the method of maximum likelihood, considering four models of analysis. The validation analysis was performed using a mixed model that includes the random effect of animal (polygenes), fixed effects of sex (2 levels), incubation (5 levels) and SNP (3 levels) in addition to random errors. The estimation of genetic parameters was obtained by the method of restricted maximum likelihood under animal model multitrait for BW42 with traits significant affected (p<0.05) by the genetic marker and with a second dataset that included cold carcass weight (CW), live (LW), heart (HW), gizzard (GW) and wing (WW), thigh meat (TMW), drumstick (DW) and meat breast muscle (BMW), back (BW) and breast fillet (BFW) weights. The general model used for genetic parameters estimation included the fixed effect of group sex-incubation and effects random additive and residual. Additive effects verified by allelic replacement of ALPHA ACTIN1 gene associated with breast meat yield (BMY), liver yield (LY) and weights at 35 days of age (BW35), skin of drumstick (SDW), DW and BMW. Heritability estimates for these traits beyond BW42 ranged from 0.24 ± 0.06 (LY) to 0.45 ± 0.08... (Complete abstract click electronic access below)
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Venturini, Guilherme Costa. „Associações genéticas com o marcador alfa actina 1, e variabilidade genética de características de importância econômica de frangos de corte /“. Jaboticabal, 2012. http://hdl.handle.net/11449/102772.
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Orientador: Danísio Prado MunariCoorientador: Mônica Corrêa Ledur
Coorientador: Lenira El Faro
Banca: João Ademir de Oliveira
Banca: Jane de Oliveira Peixoto
Banca: Fernando Sebastian Baldi Rey
Banca: Claudia Cristina Paro de Paz
Resumo: Em linhagens de frangos de corte, pesquisas têm sido realizadas para identificar marcadores moleculares responsáveis pela variação fenotípica de características de interesse econômico para auxiliar os procedimentos de seleção. Neste trabalho, o objetivo foi estudar a associação do gene ALFA ACTINA1 com 68 características de desempenho, carcaça e órgãos e estimar parâmetros genéticos para peso corporal aos 42 dias de idade (PV42), órgãos e partes da carcaça para fornecer subsídios ao programa de melhoramento genético de uma linhagem paterna de frangos de corte, selecionada principalmente para PV42. Os dados utilizados foram provenientes da Embrapa Suínos e Aves, Concórdia, SC. As análises de associação genética entre as características estudadas e a ALFA ACTINA1 foram conduzidas pelo método de máxima verossimilhança, considerando quatro modelos de análise. A análise de validação foi realizada por meio de um modelo misto que incluiu o efeito aleatório de animal (poligenes), os efeitos fixos de sexo (2 níveis), incubação (5 níveis) e do SNP (3 níveis), além do erro aleatório. A estimação de parâmetros genéticos foi realizada pelo método da máxima verossimilhança restrita, sob modelo animal multicaracterística para PV42 com características que foram significativamente (p<0,05) associadas com o marcador molecular e com um segundo conjunto de dados que incluiu pesos de carcaça resfriada, de fígado, de coração, de moela e os pesos da asa, das carnes da coxa, da sobrecoxa e do peito, peso do dorso e do filé do peito. O modelo geral utilizado para estimar os parâmetros genéticos incluiu o efeito fixo de grupo incubação-sexo e efeitos aleatórios aditivo e residual. Efeitos aditivos verificados pela substituição alélica do gene ALFA ACTINA1 estão associados com rendimentos da carne do peito (RCPT), do... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In broilers strains, research has been conducted to identify molecular markers responsible for phenotypic variation in traits of economic interest to help the selection procedures. In this work, the aim was to study the association of ALPHA ACTIN1 gene with 68 traits of performance, carcass and organs and to estimate genetic parameters for body weight at 42 days of age (BW42), organs and parts of the carcass to provide tools for the poultry breeding program of a paternal broiler strain and it has been selected mainly for BW42. The data used were from Embrapa Swine and Poultry, Concordia, SC. The analysis of genetic association between traits studied and ALPHA ACTIN1 were conducted by the method of maximum likelihood, considering four models of analysis. The validation analysis was performed using a mixed model that includes the random effect of animal (polygenes), fixed effects of sex (2 levels), incubation (5 levels) and SNP (3 levels) in addition to random errors. The estimation of genetic parameters was obtained by the method of restricted maximum likelihood under animal model multitrait for BW42 with traits significant affected (p<0.05) by the genetic marker and with a second dataset that included cold carcass weight (CW), live (LW), heart (HW), gizzard (GW) and wing (WW), thigh meat (TMW), drumstick (DW) and meat breast muscle (BMW), back (BW) and breast fillet (BFW) weights. The general model used for genetic parameters estimation included the fixed effect of group sex-incubation and effects random additive and residual. Additive effects verified by allelic replacement of ALPHA ACTIN1 gene associated with breast meat yield (BMY), liver yield (LY) and weights at 35 days of age (BW35), skin of drumstick (SDW), DW and BMW. Heritability estimates for these traits beyond BW42 ranged from 0.24 ± 0.06 (LY) to 0.45 ± 0.08... (Complete abstract click electronic access below)
Doutor
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Marcus, Monica M. „Mechanism of action of antipsychotic drugs: focus on the nucleus accumbens and the prefrontal cortex : an experimental study /“. Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-284-5/.
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Blum, Christoph Verfasser], Eberhard [Akademischer Betreuer] [Bodenschatz und Jörg [Akademischer Betreuer] Enderlein. „Curvotaxis and Pattern Formation in the Actin Cortex of Motile Cells / Christoph Blum. Betreuer: Eberhard Bodenschatz. Gutachter: Eberhard Bodenschatz ; Jörg Enderlein“. Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1080030379/34.
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Topalidou, Meropi. „Neuroscience of decision making : from goal-directed actions to habits“. Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0174/document.
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Les processus de type “action-conséquence” (orienté vers un but) et stimulus-réponse sont deux composants importants du comportement. Le premier évalue le bénéfice d’une action pour choisir la meilleure parmi celles disponibles (sélection d’action) alors que le deuxième est responsable du comportement automatique, suscitant une réponse dès qu’un stimulus connu est présent. De telles habitudes sont généralement associées (et surtout opposées) aux actions orientées vers un but qui nécessitent un processus délibératif pour évaluer la meilleure option à prendre pour atteindre un objectif donné. En utilisant un modèle computationnel, nous avons étudié l’hypothèse classique de la formation et de l’expression des habitudes au niveau des ganglions de la base et nous avons formulé une nouvelle hypothèse quant aux rôles respectifs des ganglions de la base et du cortex. Inspiré par les travaux théoriques et expérimentaux de Leblois et al. (2006) et Guthrie et al. (2013), nous avons conçu un modèle computationnel des ganglions de la base, du thalamus et du cortex qui utilise des boucles distinctes (moteur, cognitif et associatif) ce qui nous a permis de poser l’hypothèse selon laquelle les ganglions de la base ne sont nécessaires que pour l’acquisition d’habitudes alors que l’expression de telles habitudes peut être faite par le cortex seul. En outre, ce modèle a permis de prédire l’existence d’un apprentissage latent dans les ganglions de la base lorsque leurs sorties (GPi) sont inhibées. En utilisant une tâche de bandit manchot à 2 choix, cette hypothèse a été expérimentalement testée et confirmée chez le singe; suggérant au final de rejeter l’idée classique selon laquelle l’automatisme est un trait subcorticalAction-outcome and stimulus-response processes are two important components of behavior. The former evaluates the benefit of an action in order to choose the best action among those available (action selection) while the latter is responsible for automatic behavior, eliciting a response as soon as a known stimulus is present. Such habits are generally associated (and mostly opposed) to goal-directed actions that require a deliberative process to evaluate the best option to take in order to reach a given goal. Using a computational model, we investigated the classic hypothesis of habits formation and expression in the basal ganglia and proposed a new hypothesis concerning the respective role for both the basal ganglia and the cortex. Inspired by previous theoretical and experimental works (Leblois et al., 2006; Guthrie et al., 2013), we designed a computational model of the basal ganglia-thalamus-cortex that uses segregated loops (motor, cognitive and associative) and makes the hypothesis that basal ganglia are only necessary for the acquisition of habits while the expression of such habits can be mediated through the cortex. Furthermore, this model predicts the existence of covert learning within the basal ganglia ganglia when their output is inhibited. Using a two-armed bandit task, this hypothesis has been experimentally tested and confirmed in monkey. Finally, this works suggest to revise the classical idea that automatism is a subcortical feature