Our goal is to introduce a novel method for representing, generalising, and comparing gaits; particularly, walking gait. Human walking gaits are a result of complex, interdependent factors that include variations resulting from embodiments, environment and tasks, making techniques that use average template frameworks suboptimal for systematic analysis or corrective interventions. The proposed work aims to devise methodologies for being able to represent gaits and gait transitions such that optimal policies that eliminate the inter-personal variations from tasks and embodiment may be recovered. Our approach is built upon (i) work in the domain of null-space policy recovery and (ii) previous work in generalisation for point-to-point movements. The problem is formalised using a walking phase model, and the null-space learning method is used to generalise a consistent policy from multiple observations with rich variations. Once recovered, the underlying policies (mapped to different gait phases) can serve as reference guideline to quantify and identify pathological gaits while being robust against interpersonal and task variations. To validate our methods, we have demonstrated robustness of our method with simulated sagittal 2-link gait data with multiple ground truth constraints and policies. Pathological gait identification was then tested on real-world human gait data with induced gait abnormality, with the proposed method showing significant robustness to variations in speed and embodiment compared to template based methods. Future work will extend this to kinetic features and higher degree-of-freedom.

No description available.

Certaines observations suggèrent que les afférences méchano-sensorielles peuvent moduler l’activité des générateurs centraux du rythme locomoteur (ou Central Pattern Generators, CPGs). Cependant, il est impossible d’explorer les circuits neuronaux sous-jacents chez l’animal en mouvement à l’aide d’enregistrements électrophysiologiques lors d’expériences de locomotion dite « fictive ». Dans cette étude, nous avons enregistré de façon sélective et non-invasive les neurones moteurs et sensoriels dans la moelle épinière pendant la locomotion active en ciblant génétiquement le senseur bioluminescent GFP-Aequorin chez la larve de poisson zèbre. En utilisant l’imagerie calcique à l’échelle des neurones individuels, nous confirmons que les signaux de bioluminescence reflètent bien le recrutement différentiel des groupes de motoneurones spinaux durant la locomotion active. La diminution importante de ces signaux chez des animaux paralysés ou des mutants immobiles démontre que le retour méchano-sensoriel augmente le recrutement des motoneurones spinaux pendant la locomotion active. En accord avec cette observation, nous montrons que les neurones méchano-sensoriels spinaux sont en effet recrutés chez les animaux en mouvement, et que leur inhibition affecte les réflexes d’échappement chez des larves nageant librement. L’ensemble de ces résultats met en lumière la contribution du retour méchano-sensoriel sur la production locomotrice et les différences qui en résultent entre les locomotions active et fictive. / There is converging evidence that mechanosensory feedback modulates the activity of spinal central pattern generators underlying vertebrate locomotion. However, probing the underlying circuits in behaving animals is not possible in “fictive” locomotion electrophysiological recordings. Here, we achieve selective and non-invasive monitoring of spinal motor and sensory neurons during active locomotion by genetically targeting the bioluminescent sensor GFP-Aequorin in larval zebrafish. Using GCaMP imaging of individual neurons, we confirm that bioluminescence signals reflect the differential recruitment of motor pools during motion. Their significant reduction in paralyzed animals and immotile mutants demonstrates that mechanosensory feedback enhances the recruitment of spinal motor neurons during active locomotion. Accordingly, we show that spinal mechanosensory neurons are recruited in moving animals and that their silencing impairs escapes in freely behaving larvae. Altogether, these results shed light on the contribution of mechanosensory feedback to motor output and the resulting differences between active and fictive locomotion.

The combination or integration of locomotion modes, is analyzed through the design, development, and verification of a miniature integrated jumping and gliding robot, the MultiMo-Bat, which is inspired by the locomotion strategies of vampire bats, locusts, and pelicans. This robot has a mass of between 100 and 162 grams and exhibits high jumping and gliding performance, reaching heights of over 4.5 meters, to overcome obstacles in the environment. Integration results in a smaller, lighter robot with high cooperation between the modes. This thesis presents a previously unstudied robot design concept and highlights the understudied evolutionary concept within organism mobility of integration of locomotion modes. High performance locomotion modes also require high energy density actuators. To this end, a design methodology is developed for tailoring magnetic springs to the characteristics of shape memory alloy-actuated mechanisms, which allow the MultiMo-Bat to reach jumping heights of 3.5 m with active wing deployment and full controller. Through a combinations of permanent magnets, a magnetic spring can be customized to desired characteristics; theoretically any welldefined function of force vs. displacement can be created. The methodology is not limited to SMA but can be adapted to any smart actuator, joint, or situation which requires a fixed complex force-displacement relationship with extension other interactions and magnetic field design. Robotic locomotion is also much more idealized than that of their biological counter parts. This thesis serves to highlight just how non-ideal, yet robust, biological locomotion can inspire concepts for enhancing the robustness of robot locomotion. We studied the desert locust (Schistocerca gregaria), which is adapted for jumping at the extreme limits of its surface friction, as evident by its morphological adaptations for not only jumping, but slipping. Analysis of both foot morphology and jumping behavior are used to understand how the feet interact with different surfaces, including hydrophobic glass, hydrophilic glass, wood, sandstone, and mesh. The results demonstrate a complex interplay of embodied mechanical intelligence, allowing the foot to interact and adapt passively to different surfaces without burdening the organism with additional tasks. The key morphological and dynamical features are extracted to create a concept for developing multi-Surface Locust Inspired Passively-adaptable (SLIP) feet. A simple interpretation of the concepts are then used to construct a SLIP foot for the MultiMo-Bat. These feet allow the MultiMo-Bat to reach jumping heights of well over 4 m, greater than any other electrically powered robot, and this is achieved on a 45 degree angled surface while slipping. The SLIP foot concept can be directly applied to a wide range of robot size scales, thus enhancing their dynamic terrestrial locomotion on variable surfaces.

In the amphibious fish Polypterus senegalus, focussing on lateral line, vision and electrosensation, we investigated sensory abilities, their interactions, and changes in their effects on locomotor behaviour between aquatic and terrestrial environments. First, we blocked lateral line, vision, or both, and examined effects on locomotion in both environments. Both senses affected both types of locomotion. When fish could see but not feel, variation in several kinematic variables increased, suggesting that sensory integration may affect locomotor control. Next, we assessed response to optokinetic stimuli of varying size and speed. Temporal and spatial visual acuity were both low, as expected in a nocturnal ambush predator. Visual ability in air was much reduced. Finally, we attempted to record electrogenesis in Polypterus, but did not observe the electric discharges reported in a previous study. Future studies might examine changes in sensory function, interaction and importance in behaviour in Polypterus raised in a terrestrial environment.

Cette thèse étudie la modulation des circuits neuronaux spinaux impliqués dans les fonctions motrices et leur contrôle corticospinal lors de la locomotion chez l’Homme sain et après accident vasculaire cérébral (AVC). Dans ce contexte, la stratégie utilisée a consisté à moduler les comportements de ces circuits en modifiant soit les volées afférentes d’origine suprasegmentaire ou les volées afférentes d’origine périphérique et d’étudier le retentissement de ces modifications sur le comportement des circuits neuronaux spinaux au cours de différentes tâches motrices dont la marche.Trois grands thèmes émergent de ce projet :« L’influence combinée des entrées corticospinales et de l’inhibition réciproque sur l’activité des motoneurones des fléchisseurs plantaires de la cheville » a été étudiée en station debout et lors de la marche stabilisée. Les résultats ont suggéré que l'interaction entre les motoneurones spinaux, les interneurones inhibiteurs Ia et les volées motrices corticospinales descendantes ainsi que leur contribution relative à l'activité des motoneurones des fléchisseurs plantaires de la cheville dépendent de la tâche motrice. Plus d’interaction entre les entrées descendantes et les interneurones Ia pendant la station debout était présente, probablement pour renforcer l’activation tonique des motoneurones du soléaire.« La modulation liée à la tâche de l’inhibition spinale croisée entre les membres inférieurs chez l’Homme » a été étudiée au niveau des muscles soléaires en position assise, debout et lors de la marche stabilisée. Nos résultats suggèrent que la transmission neurale croisée, via les interneurones commissuraux des groupes I et II, est déprimée par les entrées descendantes bilatérales du cortex moteur ou pendant le mouvement volontaire. La modulation spécifique de l’inhibition croisée du groupe II au cours de la locomotion suggère un contrôle des structures mésencéphaliques monoaminergiques et son rôle dans la coordination des jambes pendant la locomotion. « L’influence de la musique sur les automatismes locomoteurs après un Accident Vasculaire Cérébral » a été étudiée durant la marche stabilisée chez les patients atteints d’AVC. Nos résultats préliminaires suggèrent que l’écoute musicale modulerait les réseaux neuronaux médullaires impliqués dans les automatismes locomoteurs. / This thesis investigates the modulation of spinal neuronal circuits involved in motor function and their corticospinal control during locomotion in healthy humans and after stroke. In this context, the strategy was to modulate the behavior of these circuits by modifying either the afferent volleys from suprasegmental origin or from peripheral origin and to study the impact of these changes on the behavior of spinal neuronal circuits during different motor tasks such as walking.Three major themes emerge from this project:« Combined influence of corticospinal inputs and reciprocal inhibition on ankle plantar flexor motoneuron activity during walking » was investigated during standing and during stabilized walking. The results suggested that the interaction between spinal motoneurons, Ia inhibitory interneurones and motor corticospinal descending volleys and their relative contribution to the activity of plantar flexor motoneurons of the ankle depend on the motor task. More interaction between descending inputs and Ia interneurones during standing was present, presumably to strengthen the tonic activation of the soleus motoneurons.« Task-related modulation of crossed spinal inhibition between human lower limbs» has been studied at the soleus muscles in sitting, standing and during stabilized walking. Our results suggest that crossed neural transmission via commissural interneurones of groups I and II, is depressed by bilateral descending inputs of motor cortex during voluntary movement. Specific modulation of the crossed inhibition by group II afferents during locomotion suggests a control from monoaminergic mesencephalic structures and its role in legs coordination during locomotion.« The influence of music on locomotor automatisms after stroke» was investigated during stabilized locomotion in stroke patients. Our preliminary results suggest that music modulate the spinal neuronal networks involved in locomotor automatisms.

Les tests couramment utilisés pour évaluer le déficit sensori-moteur induit par une lésion du cerveau chez le rat posent problèmes en termes de sensibilité, d’objectivité et de quantification. Nous avons émis l'hypothèse selon laquelle l'analyse 3D de la cinématique de la locomotion constitue un paradigme expérimental approprié pour quantifier un tel déficit. Aussi, la locomotion a été étudiée lors d'une course sur tapis roulant (25 cm/s) muni ou pas d'obstacles (deux obstacles de 3cm de haut et 1,2 cm de large) à l'aide du système optoélectronique VICON. Le mouvement des quatre pattes a été simultanément enregistré avant et après induction d'une lésion unilatérale soit du striatum (mort d'origine métabolique des neurones striataux) soit du cortex cérébral (infarctus du cortex moteur) chez le rat adulte. Le laboratoire a précédemment montré que ces deux modèles de lésion conduisaient à une anomalie plus ou moins durable de la traversée d'une poutre étroite et surélevée, test classiquement utilisé pour évaluer la locomotion du rat. La première étude décrit pour la première fois la stratégie utilisée par le rat pour franchir un obstacle. Elle révèle que le franchissement s'accompagne d'une rupture complète du pattern locomoteur de base et que l'élévation des ceintures contribue de façon notable au passage de chacune des pattes au- dessus de l'obstacle. La seconde étude montre que la lésion du striatum s'accompagne d'un déficit locomoteur durable lors des deux modalités de course, l'anomalie portant sélectivement sur les pattes contralatérales à la lésion. Plus précisément, ces pattes présentent une flexion exagérée pendant la phase d'appui dont la durée est augmentée. Par ailleurs, lorsque que la patte antérieure opposée à la lésion conduit la manœuvre de franchissement, elle prend fréquemment appui sur l'obstacle suite à une initiation trop précoce de son élévation. Dans ce cas, la patte postérieure homolatérale franchit ou non correctement l'obstacle. L’ensemble de ces résultats suggère l’implication du striatum dans la programmation des mouvements guidés par la vue. La dernière expérience montre qu'aucune des modalités de locomotion n'est affectée par la lésion corticale, suggérant que le faisceau corticospinal n’est indispensable ni à la locomotion ni à son adaptation à l’environnement. En conclusion, notre travail montre que nos modalités d'enregistrement de la locomotion sont appropriées pour quantifier le déficit fonctionnel induit par une lésion du striatum, mais pas celui induit par une lésion du cortex moteur. Il serait intéressant de répéter les expériences lors d'une course volontaire, de manière à s'affranchir de la stimulation sensitive générée par le déroulement du tapis sous les pattes et d’étudier la réversibilité du déficit en cas de lésion partielle du striatum. / Although the rat has become the favourite animal model in preclinical researches on locomotion, studies designed to assess the strategy used by rats to avoid obstacle avoidance are lacking in rats. Using an optoelectronic 3D motion analysis system, we have, therefore, compared the step pattern, timing and length variables of locomotor cycles, trajectories and joint angles values of limbs when rats stepped between and overcame obstacles (3 cm-height) fixed on a treadmill belt (25 cm/s). Motion of all the four limbs was serially recorded for a 10 weeks long-period in adult animals with an initial age of 11 weeks. The results show that obstacle avoidance results in disruption of the basic step pattern thus resulting in increased stride length of all limbs, increased duration of the swing phase of forelimbs, only, and appearance of quadrupedal stance phases. They also reveal that elevation of limbs above the obstacle not only involved their flexion but also displacement of corresponding girdles. Remarkably, trajectory of the forelimb that was the second to overcome obstacle was the mirror image of that of the leading forelimb. Lastly, all measured parameters remain stable over the observation period during which body weight gain reaches 100 g (one third of the initial body weight). In conclusion, our study may represent a basic work for futures studies aimed at understanding the neural pathways involved in pathologies associated with deficit/recovery of challenged locomotion.

<p>In recent years, large-scale brain recordings in nonhuman primates have been a driving force for both fundamental neuroscience and the field of brain-machine interfaces (BMIs). This required monkey implants connected to external amplifiers and computers with ever increasing number of cables. As shown with our recent demonstration of 2,000 neurons recorded in one monkey, a tethered recording system begins to get bulky and complex, particularly for our BMI and neurophysiological research. To address this problem, we developed a multichannel wireless recording framework. The system was been tested in freely moving rhesus monkey by integrating wireless neural recordings with external computers performing BMI decoding, behavioral manipulanda and optical tracking. This technology can be applied to primate behavior research and, in the near future, wireless, fully implantable human neuroprosthetics, which is of great significance to those suffering from locomotor deficiencies, such as those brought on by spinal cord injury and stroke. Aided with these advances, I was able to study monkeys in unrestrained locomotion while their cortical activity was continuously monitored. I also explored unrestrained behaviors and how they showed distinct transitions in neural dynamics as monkeys engaged in different behavioral activities or learned new motor skills, such as bipedal walking. I was able to decode them many of these behavioral states from cortical activity with neural classifiers. Lastly, monkeys were able to perform BMI tasks continuously for many hours, allowing us to prove the relevance of unrestrained noise in BMI performance. Lastly, I present my role in developing two brain actuated movement platforms, a robotic exoskeleton under the guise of the WalkAgain project, and a microelectrode BMI enabled wheelchair. This body of work should assist those on the path to the next generation of clinical neuroprostheses and neural communication systems.</p> / Dissertation

Esta tese objetivou investigar as características biomecânicas da corrida com mínima proteção para a planta do pé, bem como o efeito do treinamento sob estas condições sobre o aparelho locomotor. Para isso, 3 experimentos foram realizados: o experimento 1 caracterizou a realização da corrida e o efeito do treinamento com os pés descalços sobre parâmetros biomecânicos da corrida; o experimento 2 testou o efeito da transição de 4 meses do calçado tradicional para o minimalista, manipulando-se o calçado esportivo; e o experimento 3 comparou indivíduos habituados ao uso do calçado com indivíduos habituados a movimentos em condições de mínima proteção. Uma esteira equipada com plataformas de força (Sistema Gaitway) e um eletromiógrafo (EMG 1000 Sistema Lynx) foram utilizados para a aquisição dos dados biomecânicos. Agudamente, os 3 experimentos mostraram interferência negativa da proteção plantar reduzida sobre parâmetros da força de reação do solo (FRS). Contudo, no experimento 1 observou-se possibilidade de menor ocorrência de primeiro pico da FRS em indivíduos habituados a movimentos com mínima proteção, significando sobrecarga externa reduzida. Os experimentos 1 e 2 evidenciam melhora do controle de sobrecarga externa em função de 4 meses de treinamento com mínima proteção, diminuindo em até 54,4% o choque mecânico. Conclui-se que, forma aguda e em indivíduos não adaptados, as condições de mínima proteção podem interferir negativamente no movimento e no controle das cargas externas, aumentando a sobrecarga imposta ao aparelho locomotor durante a corrida. Contudo, a experiência em mínima proteção, principalmente adotada de forma crônica e específica, influencia positivamente o gerenciamento das cargas mecânicas, melhorando o controle de choque e rendimento / This thesis aimed to investigate the biomechanical characteristics of running with minimal protection for the foot, as well as the training effects upon the human body under this condition. For that, three experiments were performed: experiment 1 compared individuals accustomed to the use of footwear with individuals accustomed to motor tasks in conditions of minimal protection; the second experiment characterized the running barefoot and the effects of 4-month training barefoot upon its biomechanical parameters; and experiment 3 tested the effects of 4-month transition from traditional running shoe to the minimalist shoe, only manipulating the footwear. A treadmill equipped with force platforms (System Gaitway) and an electromyography (EMG 1000 - Lynx System) were used to measure the biomechanical variables. Acutely, the 3 experiments showed negative interference of minimal protection upon parameters of the ground reaction force (GRF). However, the experiment 1 presented the possibility of lower first peak of GRF occurrence in the participants who are adapted to minimal protection condition, what means decreased external load. The experiments 2 and 3 showed improvements in the external forces control as a response to 4 months of adaptation in minimal protection running, what could decrease about 54,4% of mechanical stress. In conclusion, the minimal protection condition can negatively influence the movement and stress control in a acute way and in individuals who are not adapted to minimal protection condition, increasing the overload imposed to human body during running. However, the adaptation to minimal protection condition, mainly in a chronicle and specific way, exert a positive influence upon the management of mechanical loads, improving impact control and performance

The purpose of this thesis was to determine the neuronal circuitry mediating U50,488-induced locomotion in preweanling rats. To this end, preweanling rats received bilateral electrolytic lesions of the ventromedial thalamus or superior colliculus and, two days later, the same rats received a challenge injection of U50,488. It was predicted that bilateral lesions of the ventromedial thalamus or superior colliculus would attenuate the U50,488-induced locomotor activity of 18-day-old rats.