Assessing locomotion in cats trained on a flat treadmill and on a ladder treadmill before and after spinal cord injury (SCI)

Les effets des lésions de la moelle épinière sur la locomotion sont souvent évalués sur un tapis roulant avec une surface plane, ce qui demande peu d’implication active des structures supraspinales. L’objectif du présent travail est d’évaluer si un type d’entraînement nécessitant une plus grande part de contrôle volontaire (c.-à-d. supraspinal) pourrait améliorer la récupération de la marche chez le chat après une hémilésion unilatérale spinale au niveau thoracique (T10). Pour ce faire, pendant 6 semaines les chats ont été entrainés sur un tapis roulant conventionnel ou sur un tapis-échelle roulante, tâche requérant un placement des pattes plus précis. Les paramètres de la marche ont été évalués par cinématique et électromyographie (EMG) avant et une fois par semaine pendant 6 semaines après lésion. Nos résultats comparant la marche sur tapis conventionnel à celle sur échelle roulante montrent des différences dans les excursions angulaires et les couplages entre les membres. On observe aussi des différences dans l’amplitude des EMG notamment une augmentation de la deuxième bouffée du muscle Semitendineux (St) sur l’échelle roulante. Après l’hémilésion spinale cette bouffée disparait du côté de la lésion tandis qu’elle est maintenue du côté intact. Après l’entrainement sur échelle roulante, on observe des changements de trajectoire de la patte et une disparition du pied tombant (foot drag) qui suggèrent une amélioration du contrôle de la musculature distale. Nos résultats montrent que le patron locomoteur observé sur tapis conventionnel est influencé par le type d’entraînement procuré. De plus, certains paramètres de la locomotion suggèrent que l’entraînement sur échelle roulante, qui requiert plus de contrôle supraspinal, favorise une meilleure récupération de la marche après lésion spinale.The effects of spinal cord lesions on locomotion in animals is often assessed on a flat surface which requires minimal supraspinal demands. Here we investigated whether locomotor training requiring more voluntary commands could improve recovery in cats after a unilateral hemisection on the left side (Thoracic 10). Cats were trained for 6 weeks on a conventional flat treadmill (FTM) or on a ‘ladder treadmill’ (LTM) requiring precise foot positioning. Locomotor parameters such as kinematics and electromyographic activity (EMG) were evaluated before and once a week for 6 weeks after spinal hemisection. There were differences in angular excursions and limb couplings when comparing walking on FTM and LTM and important changes occurred in the amplitude of EMGs such as an increased second burst in Semitendinosus (St) during LTM stepping. After the left hemisection, this burst disappeared on the left side while it was maintained on the right (non lesioned) side. With LTM training, we observed changes in limb trajectories and disappearance of foot drag of the left foot during FTM stepping suggesting a better control of distal musculature. Our results show that locomotor patterns observed during FTM stepping are influenced by different training modalities and also that training on the LTM after a spinal hemisection, demanding more supraspinal control, leads to a better stepping pattern

Cognición y representación interna de entornos dinámicos en el cerebro de los mamíferos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Biológicas, leída el 07/05/2021El tiempo es una de las dimensiones fundamentales de la realidad. Paradójicamente, los fenómenos temporales del mundo natural contienen ingentes cantidades de información redundante, y a pesar de ello, codificar internamente el tiempo en el cerebro es imprescindible para anticiparse a peligros en ambientes dinámicos. No obstante, dedicar grandes cantidades de recursos cognitivos a procesar las características espacio-temporales de entornos complejos debería ser incompatible con la supervivencia, que requiere respuestas rápidas. Aun así, los animales son capaces de tomar decisiones en intervalos de tiempo muy estrechos. ¿Cómo consigue hacer esto el cerebro? Como respuesta al balance entre complejidad y velocidad, la hipótesis de la compactación del tiempo propone que el cerebro no codifica el tiempo explícitamente, sino que lo integra en el espacio. En teoría, la compactación del tiempo simplifica las representaciones internas del entorno, reduciendo significativamente la carga de trabajo dedicada a la planificación y la toma de decisiones. La compactación del tiempo proporciona un marco operativo que pretende explicar cómo las situaciones dinámicas, percibidas o producidas, se representan cognitivamente en forma de predicciones espaciales o representaciones internas compactas (CIR), que pueden almacenarse en la memoria y recuperarse más adelante para generar respuestas. Aunque la compactación del tiempo ya ha sido implementada en robots, hasta ahora no se había comprobado su existencia como mecanismo biológico y cognitivo en el cerebro...Time is one of the most prominent dimensions that organize reality. Paradoxically, there are loads of redundant information contained within the temporal features of the natural world, and yet internal coding of time in the brain seems to be crucial for anticipating time-changing, dynamic hazards. Allocating such significant brain resources to process spatiotemporal aspects of complex environments should apparently be incompatible with survival, which requires fast and accurate responses. Nonetheless, animals make decisions under pressure and in narrow time windows. How does the brain achieve this? An effort to resolve the complexity-velocity trade-off led to a hypothesis called time compaction, which states the brain does not encode time explicitly but embeds it into space. Theoretically, time compaction can significantly simplify internal representations of the environment and hence ease the brain workload devoted to planning and decision-making. Time compaction also provides an operational framework that aims to explain how perceived and produced dynamic situations are cognitively represented, in the form of spatial predictions or compact internal representations (CIRs) that can be stored in memory and be used later on to guide behaviour and generate action. Although successfully implemented in robots, time compaction still lacked assessment of its biological soundness as an actual cognitive mechanism in the brain...Fac. de Ciencias BiológicasTRUEunpu

Rehabilitation Engineering

Population ageing has major consequences and implications in all areas of our daily life as well as other important aspects, such as economic growth, savings, investment and consumption, labour markets, pensions, property and care from one generation to another. Additionally, health and related care, family composition and life-style, housing and migration are also affected. Given the rapid increase in the aging of the population and the further increase that is expected in the coming years, an important problem that has to be faced is the corresponding increase in chronic illness, disabilities, and loss of functional independence endemic to the elderly (WHO 2008). For this reason, novel methods of rehabilitation and care management are urgently needed. This book covers many rehabilitation support systems and robots developed for upper limbs, lower limbs as well as visually impaired condition. Other than upper limbs, the lower limb research works are also discussed like motorized foot rest for electric powered wheelchair and standing assistance device

Etude du contrôle postural chez l'homme (analyse des facteurs neurophysiologiques, biomécaniques et cognitifs, impliqués dans les 500 premières millisecondes d'une chute)

La chute chez les seniors constitue un problème de santé publique. Citée comme la seconde cause de décès accidentel dans le monde, elle concerne un tiers des Français de plus de 65 ans. Les séquelles physiques et fonctionnelles qui en résultent, les conséquences psychosociales nuisibles pour la qualité de la vie, la perte d autonomie et son coût de prise en charge justifient l attention qui lui est actuellement portée. Du point de vue du chercheur, les interprétations sous-jacentes à la surexposition des personnes âgées au risque de chute restent controversées, notamment parce que la compréhension de la coordination dynamique corporelle et de l implication corticale lors du contrôle de l équilibre est encore limitée. L étude de la chute et des mécanismes qui y conduisent présente donc un double intérêt, fondamental et sociétal. Une chute survient si deux conditions sont réunies. La première est la perte initiale de l équilibre, un pré-requis qui peut toucher la population entière dans son quotidien. La seconde est un échec des mécanismes de rééquilibration, c est à dire de la stratégie de réponse mise en œuvre pour compenser la déstabilisation : comment s opère la sélection d une stratégie de rattrapage, à partir de quelle appréciation du contexte et des informations sensorielles disponibles est-elle choisie ? qu est ce qui assure son opérationnalité et garantit le rattrapage ou signe au contraire son échec ?...Pour répondre à ces questions, nous nous sommes donc intéressés à ce moment critique où il est encore possible de modifier l issue finale par des ajustements posturaux et des actions motrices rapides et adéquats chez une population de jeunes adultes. La première étude est une analyse globale de la phase précoce d une chute -abrégée par un harnais- (soit quelques centaines de millisecondes après la perturbation), afin d évaluer la capacité du sujet à réagir à une perturbation imprévue et de développer des stratégies garantissant une protection efficace. Cette première étape se propose d identifier les indicateurs discriminants et prédictifs d une chute et d un rattrapage au niveau neurophysiologique et biomécanique. Cette étude a également permis de mettre en évidence la présence d un délai temporel incompressible appelé phase passive , source de contraintes spatio-temporelles à l expression complète d une réponse posturale adaptée. Dans la seconde étude, de modélisation, nous avons élaboré un modèle mécanique personnalisé, construit à partir de radiographies tridimensionnelles non invasives du corps entier. Cette modélisation nous a permis d analyser la contribution relative de propriétés biomécaniques passives et des synergies musculaires actives en jeu pendant les perturbations récupérables de l équilibre ou non en comparant les résultats expérimentaux ( réels ) obtenus à l aide d un dispositif asservi pour provoquer des chutes de plain-pied et la réponse théorique prédite ( simulée ) à l aide du modèle. Les résultats obtenus permettent de confirmer que le comportement du corps est en phase précoce-dicté par ses propriétés mécaniques, et peut être assimilé à un modèle simplifié. Après avoir mis en évidence l existence d une phase inertielle d une durée équivalente à la moitié du temps disponible avant l impact, notre questionnement s est orienté vers le traitement de l information en-cours lors de cette phase afin d évaluer la contribution corticale alors que la réponse posturale évolue. La troisième étude consiste principalement à appréhender la charge cognitive impliquée dans le contrôle sensori-moteur, en particulier lors d une chute, à l aide du paradigme de double-tâche. En conclusion, à travers une approche pluridisciplinaire, les résultats obtenus dans cette thèse permettent d émettre des recommandations intéressantes pour une prévention et une rééducation adaptée dans le but de contribuer à l amélioration de la qualité de vie des personnes âgées.A better understanding of what happens during an unintentional fall is relevant in preventing their occurrence. A fall is due to a failure of compensatory reactions to recover from postural perturbations during the descent phase which starts at the subject loss of balance point and lasts no more than 700-1000milliseconds [Hsiao, 1998]. The aim of the first study was to compare the biomechanical and muscular behavior during the pre-impact phase during non-recoverable falls and successful recovery trials. The experimental study aimed to evaluate the subject s ability to distinguish in the first 500 milliseconds following the onset of perturbation a low-threatening perturbation from a high challenging one and can then predict the scenario that will more likely lead to a fall using specific motor strategies. In such a challenging task, we hypothesized that the constraints imposed by the biomechanical properties ultimately determine the ability to trigger efficient muscle activities. Full body 3D kinematics and associated muscle activities were collected in 30 young healthy subjects during fast and slow unpredictable multidirectional support-surface translations. 40 cm support-surface translations were used to evoke the balancing reactions (0,35 vs 0,9 m/s during resp. 1000 vs 500 millisecond The perturbation velocities were selected so that successful recovery should occur in milder trials whereas fast trials were sufficiently challenging to trigger non-recoverable falls. Analyses focused on the spatial and temporal characteristics of the Centre of Mass, angle variations, recovery step characteristics, and EMG activities (onset latencies and amplitudes) across each trial and muscle. Moreover, a 17-segment numerical and personalized model was created, based on stereoradiographic head to feet X-ray images followed by 3D-reconstruction methods to assess subject-specific geometry and inertial parameters. The outputs resulting from simulated falls allowed us to discard the contributions of the passive (inertia-induced) versus the active mechanisms (feedback-controlled and time-delayed neuromuscular components) of the response. The first outcome of that study was that the fall could be divided in distinct phases. For about 200 milliseconds following the onset of platform translation, the head remained stable in space. Similarly, the comparison with the simulated data supported that the CoM displacement matched the subject-dependant mechanical model. During a second phase of the fall, despite the fact that automated muscle postural synergies started at 80 milliseconds after perturbation onset, the trajectory of the body appeared to be exclusively dictated by its biomechanical properties. Later, muscle activities influenced the body trajectories, which consequently differed on a trial-to-trial basis. The simulation was in good agreement with the experimental results. The specificity of the postural response resulting in a strategy chosen to avoid a fall thus appeared in a late-phase, which can be explained because during a fall, the subjects had to prepare to the impact on the basis of sensory information that were not redundant but available in a sequential order: proprioceptive information appearing first while vestibular and visual information continued to signal a stabilized head in space. The sole proprioceptive information would be insufficient to trigger rapid and appropriate postural response. Moreover, in accordance with our results suggesting the importance of the late-phase and on-line controlled responses, a long inertial passive phase in the fast trials does not allow a large spatiotemporal window for compensatory reactions to occur. These could not only depend on the previously described automated postural synergies because the time constraints imposed by biomechanics permit in principle volitional motricity to play an important role very early in the fall. (...)PARIS5-Bibliotheque electronique (751069902) / SudocSudocFranceF

Identification of molecular mechanisms underlying frailty and successful aging in centenarians

259 p.El envejecimiento es un proceso sistémico, multifactorial y degenerativo caracterizado por el declive y la pérdida de capacidades físicas y mentales. La esperanza media de vida ha aumentado considerablemente en el último siglo, incrementando así el número de personas mayores en la población y, por tanto, las limitaciones funcionales y las enfermedades relacionadas con la edad. En este sentido, la fragilidad representa un nuevo síndrome geriátrico que se caracteriza por una pérdida de la capacidad funcional y una disminución de la capacidad de respuesta al estrés fisiológico, lo que resulta en una mayor vulnerabilidad del individuo y en resultados negativos para la salud. Se trata de una afección dinámica que se está convirtiendo en un importante problema de salud que es necesario detectar e intervenir. Se sabe relativamente poco sobre la fisiopatología de este síndrome y los mecanismos moleculares subyacentes a la fragilidad siguen siendo poco conocidos. Con el fin de abordar esta cuestión, se analizó el perfil transcriptómico de un conjunto de individuos robustos y frágiles residentes en el País Vasco, y se encontraron 35 genes expresados diferencialmente que se asociaron con el estado e fragilidad. Éstos incluían genes asociados a inflamación, respuesta inmune o miRNAs, procesos previamente relacionados con la fragilidad. Entre ellos, 7 candidatos fueron validados en cohortes independientes y también mostraron un patrón de expresión similar en mioblastos y fibroblastos primarios humanos mantenidos en cultivo. Su expresión fue parcialmente restaurada tras diferentes programas de intervención en individuos frágiles. Análisis adicionales revelaron la expresión de un conjunto mínimo de 3 genes (aumento de EGR1 y disminución de DDX11L1 y miR454) fuertemente asociados con el estado de fragilidad y las características clínicas vinculadas a la fragilidad como la multimorbilidad y la polifarmacia. Además, descubrimos su papel en el envejecimiento celular e identificamos su actividad como mediadores de vías asociadas a la senescencia, convirtiéndose en potenciales actores en la fisiopatología de este síndrome geriátrico. En conjunto, nuestros resultados revelan un vínculo entre fragilidad y senescencia.El envejecimiento cerebral consiste en una pérdida progresiva de las capacidades funcionales que se asocia a un deterioro cognitivo progresivo y puede conducir a enfermedades neurodegenerativas.Aunque se han utilizado diferentes enfoques para identificar biomarcadores y vías moleculares subyacentes al envejecimiento cerebral, se mantienen en gran medida desconocidos. Los centenarios,muestran una longevidad extrema que se acompaña de una mejor función cognitiva, menos comorbilidades y una mayor calidad de vida y, por lo tanto, se han propuesto como modelo de envejecimiento saludable. En nuestro estudio, realizamos análisis transcriptómicos en muestras de hipocampo humano de individuos de diferentes edades, incluyendo individuos jóvenes, ancianos y centenarios, con el fin de abordar los mecanismos moleculares subyacentes al envejecimiento cerebral.Identificamos un patrón de expresión génica diferencial en muestras cerebrales de centenarios en comparación con los otros dos grupos. En particular, varios miembros de la familia de genes de las metalotioneínas (MTs) se expresaron en gran medida en el hipocampo de los centenarios. Estos hallazgos se validaron en dos cohortes adicionales e independientes. En particular, las MTs fueron expresadas principalmente por los astrocitos y estudios funcionales in vitro describieron el papel de las MTs en su viabilidad y actividad. De hecho, el silenciamiento de MT1 o MT3 en astrocitos humanos primarios provocó una disminución de la proliferación, un aumento de la apoptosis y la senescencia, junto con un incremento de la expresión de genes inflamatorios. En general, estos resultados muestran que el hipocampo de los centenarios presenta altos niveles de MTs, que se expresan principalmente en los astrocitos convirtiéndose en un mecanismo defensivo que podría proporcionar neuroprotección en el cerebro durante el envejecimiento. Otros análisis adicionales, revelaron un subconjunto de 6 genes cuya expresión se correlacionaba con el envejecimiento cronológico en el hipocampo humano. Entre ellos, el descenso de RAD23B mostró las mayores diferencias a nivel estadístico tanto en humanos como enratones. La validación en cohortes adicionales confirmó la disminución de los niveles de RAD23B con la edad, también a nivel proteico, que se agravaban en condiciones patológicas, ya que sus niveles eran más bajos o totalmente ausentes en pacientes con enfermedad de Alzheimer. Además, experimentos de silenciamiento en cultivos celulares in vitro demostraron que estaba implicado en la viabilidad y actividad de los astrocitos, lo que indica que es un biomarcador putativo y regulador del envejecimiento celular en el cerebro

Contemporary Robotics

This book book is a collection of 18 chapters written by internationally recognized experts and well-known professionals of the field. Chapters contribute to diverse facets of contemporary robotics and autonomous systems. The volume is organized in four thematic parts according to the main subjects, regarding the recent advances in the contemporary robotics. The first thematic topics of the book are devoted to the theoretical issues. This includes development of algorithms for automatic trajectory generation using redudancy resolution scheme, intelligent algorithms for robotic grasping, modelling approach for reactive mode handling of flexible manufacturing and design of an advanced controller for robot manipulators. The second part of the book deals with different aspects of robot calibration and sensing. This includes a geometric and treshold calibration of a multiple robotic line-vision system, robot-based inline 2D/3D quality monitoring using picture-giving and laser triangulation, and a study on prospective polymer composite materials for flexible tactile sensors. The third part addresses issues of mobile robots and multi-agent systems, including SLAM of mobile robots based on fusion of odometry and visual data, configuration of a localization system by a team of mobile robots, development of generic real-time motion controller for differential mobile robots, control of fuel cells of mobile robots, modelling of omni-directional wheeled-based robots, building of hunter- hybrid tracking environment, as well as design of a cooperative control in distributed population-based multi-agent approach. The fourth part presents recent approaches and results in humanoid and bioinspirative robotics. It deals with design of adaptive control of anthropomorphic biped gait, building of dynamic-based simulation for humanoid robot walking, building controller for perceptual motor control dynamics of humans and biomimetic approach to control mechatronic structure using smart materials

Deconstructing appearances in the eighteenth-century English novel

Appearances are one of the main concerns in eighteenth-century novels, but most studies relegate them to a subordinate role, in relation to other issues. Following Slavoj Žižek’s understanding of ideology, Alain Badiou’s concept of logics of appearances and Jacques Derrida’s deconstruction, this thesis offers a sustained analysis of a series of issues of appearances in the eighteenth-century novel, through an exploration of sixteen defining traits, based on Samuel Johnson’s definitions of ‘appearance’, ‘appear’ and ‘apparition’. The concept of appearances allows for an interrogation of ideas, beliefs and positions about most things, including appearances themselves, as they remain open, in their structure and logic, destabilising and deconstructing the ways of thinking that try to contain them. This thesis argues that eighteenth-century novels reproduce, resist and deconstruct the eighteenth-century ideology based on a desire to neutralise the effects of appearances. Through a wide range of eighteenth-century novels, from Robinson Crusoe to Evelina, it argues that novels destabilise the relationship between appearance and being, proposing the multiple appearances of beings and becomings. William Godwin’s Caleb Williams is taken as a paradigm, shown to contain most of the issues of appearances in the eighteenth-century novel, revealing that whatever there is, it must be supplemented by appearances in order to appear as reality. This thesis argues that novels came to grasp such a truth of appearances from the beginning of eighteenth-century, by locating appearances subjectively, making more evident the multiplicity and extent of fictions, allowing readers an increased degree of awareness of the fictionality of reality. Thus, this thesis makes a significant contribution to the study of issues of appearance and ideology within literature studies by establishing the genre of the novel as the event of appearances in the eighteenth century

"Within and Without": Exploring the Mind in the Novels of George MacDonald

George MacDonald‟s first published novel, Phantastes, is the story of a young man who enters and must negotiate his way through a fantasy landscape. This landscape, it is suggested, is one of the mind, and Anodos‟ journey through it one of self-exploration and discovery. The sustained metaphor of the mind as a territory to be actively explored through the medium of the physical world, furthermore, is argued to be the basis of several of MacDonald‟s novels. While for Anodos the mind is all, forming as it does the basis of the entire fantasy world of Fairy Land, in the author‟s numerous realist texts the interest emerges in more varied ways, including for example, portrayals of depression, madness, and drug (ab)use. While this significant and unifying feature of MacDonald‟s novels has been at times observed by critics with regard to some individual texts, it has not been directly confronted in terms of an inclusive study of his oeuvre. What this thesis demonstrates is firstly the overwhelming significance of the mind as a focal point for MacDonald‟s novels, as represented by six central texts: Phantastes, Adela Cathcart, Wilfrid Cumbermede, Malcolm, Donal Grant, and The Flight of the Shadow. It is suggested that such a consistent prioritising of the mind over the physical body lies in the author‟s own experience of ongoing physical illness and resulting confrontation with mortality. The mind becomes, for MacDonald, a means of negotiating the relationship between the realms of the physical and the spiritual. In Phantastes, for example, Anodos‟ physical experience (achieved through the genre of fantasy) of his own mind in Fairy Land, concludes with reference to the afterlife. The mind in this (and MacDonald‟s other novels) provides the means by which transcendence is achieved