L'objectif de ce travail est de fournir quelques éléments de compréhension sur les règles d'organisation de l'activité locomotrice chez l'homme. Son originalité réside dans le fait d'analyser la locomotion humaine dans ses composantes (sensori)motrice et cognitive : ainsi la locomotion est considérée et analysée comme l'activité coordonnée des membres inférieurs combinée à des stratégies de planification communes à l'ensemble des mouvements orientés vers un but spatial. Deux niveaux de description de la locomotion sont pris en compte, l'analyse des processus aboutissant à la formation du pas et ceux liés à la génération de la trajectoire locomotrice. Les effets propres et conjoints du mode et de la vitesse de locomotion, ainsi que de la géométrie des trajets, sur la régulation de l'activité locomotrice, sont étudiés au moyen (principalement) de l'analyse cinématique mais également électromyographique et vidéooculographique. Les origines de certains invariants cinématiques de la locomotion humaine sont étudiées pour ces deux niveaux d'analyse et la caractérisation des mouvements du regard et du corps lors des<br />changements de direction de marche est réalisée. Enfin, quelques approches et principes particulièrement intéressants, comme le principe de segmentation et celui d'optimalité, sont discutés dans le cadre général de l'étude expérimentale et de la modélisation des processus de génération et de contrôle des trajectoires locomotrices.

Thèse de doctorat : Sciences et techniques des activités physiques et sportives : Rennes 2 : 2008. / Bibliogr. p.139-162. Table des illustrations et tableaux.

Thèse de doctorat : Physiologie et biologie des organismes et des populations, Ethologie : Strasbourg : 2009. / Thèse soutenue sur un ensemble de travaux. Titre provenant de l'écran-titre. Bibliogr. 20 p.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2009. / Härtill 5 uppsatser.

This thesis covers the study of an actively assisted passive walker with discontinuous and impulsive actuation. The dynamics of the passive and active portions are derived, and a comprehensive mathematical model is proposed. An actuation method is also proposed to study the use of multiple discrete actuation events in a walking gait. Two key cases are considered: actuation at the stance point and at the EA point of a non-kneed walker. An experimental walker was designed that is capable of passive walking and has an experimental implementation of the proposed actuation system. A thorough characterization of the model is then performed, with experimental validation to show that: at high ramp angles, energy injection results in an increase in BOA of ~38% on a stable walking gait at a Ct of 0.086, and at low ramp angles, injection results in a stride length increase of ~29% at a Ct of 0.06.

No description available.

Detailed information on diet and foraging behavior is necessary for understanding predator-prey interactions and food-web dynamics. The primary objective of this dissertation was to gain a more complete understanding of the natural foraging behavior of Weddell seals (Leptonychotes weddellii) in McMurdo Sound, Antarctica using a video data recorder to document the seal's three-dimensional movements and encounters with prey. Seals exhibited a variety of dive types that could be sorted into five groups based on 18 dive descriptors. Three of these groups (deep aerobic, deep anaerobic, and shallow aerobic) were identified as foraging dives, the frequency of which varied with bathymetry. Deep aerobic foraging dives were similar in depth and duration to foraging dives in previous studies and were more common at offshore breathing holes. However, differences occurred between offshore free-ranging and isolated-hole dives in the behaviors involving descent and the frequency of certain behavioral transitions. These differences were responses by the seals to variations in prey abundance, rather than responses to a change in breathing hole availability. Even with an apparently homogenous sample of seals, there was significant individual variability in foraging success, behavior, diet, and foraging tactics. Dive depth, duration, distance, and energetic cost were important for explaining foraging success when seals dove in shallow areas where Antarctic silverfish (Pleuragramma antarcticum) were more difficult to reach and less abundant. However, the relationship between those variables was not the same for all individuals. Diet and foraging tactics also varied significantly among individuals diving near the coastline. Two coastal seals specialized on silverfish, while two others consumed silverfish and benthic prey. Although benthic prey were more accessible along the coastline than offshore, silverfish, which have a high lipid content, required less handling to consume. Thus, it may be energy-efficient for seals to specialize on silverfish at coastal locations despite the additional time and energy required to travel to depths where silverfish are located. These results helped us understand variability within Weddell seal populations and the basis upon which foraging decisions are made in response to changes in bathymetry, access to breathing holes, and prey abundance and availability.

published_or_final_version / Orthopaedic Surgery / Master / Master of Philosophy

Extensive research has documented the stereotypical kinematic and kinetic patterns in healthy human walking, but we have a limited understanding of the neuromechanical control principles that contribute to their execution. Furthermore, the strategies used to adapt human walking to morphological or environmental constraints are poorly understood. After a traumatic injury, like amputation, regaining independent mobility is a primary goal of rehabilitation. Without a clear understanding of the neuromechanical principles governing locomotion, monitoring and quantitatively improving gait rehabilitation outcomes is challenging. The purpose of this doctoral work was to identify controlled variables in able and impaired human walking and to compare the control strategies used to adapt to a novel walking environment both with and without amputation. I apply an uncontrolled manifold (UCM) analysis to test whether likely goal variables of human walking are selectively stabilized through step-to-step variability structure. I found that both able-bodied subjects and subjects with an amputation maintain consistent whole body dynamics and leg power production by exploiting inherent motor abundance. Consistent leg power production is accomplished primarily through step-to-step leg force corrections that are driven by variable timing of ankle torque production. Covariance between ankle and knee torques enable robust motor control in able-bodied individuals, but this stabilizing mechanism is absent in individuals with a transtibial amputation. This coordinated joint torque control also appears to assist able-bodied short-term adaptation, invoked by split-belt treadmill walking. However, loss of ankle motor control and distal sensory feedback due to amputation appears to limit reactive, feedback driven adaptation patterns in subjects with an amputation. Ultimately, this work highlights the role of intact distal sensorimotor function in locomotor control and adaptation. The major findings I present have substantial implications for gait rehabilitation and prosthetic design.

Over the past five decades spatial behavior has been a subject of research interest in psychology and neuroscience, in part based on philosophical theories of mental spatial representations. In order to continue uncovering the facts regarding spatial behavior, the focus of this thesis was on the contribution of entry point and visual inputs to the organization of exploratory locomotion and spatial representation in the rat. Despite the contribution of the hippocampus to spatial abilities, the exploratory locomotion is still visually organized in rats with damage to the hippocampus. On the other hand, recent studies have demonstrated a contribution of visual areas to the spatial ability of the rat. Nevertheless, the contribution of visual cortex to the organization of exploratory locomotion has not been studied in an open field. The experiments in this thesis were designed to characterize the organization of exploratory locomotion to the point of entry and/or visual cues. Rats were started from the edge or center of an open table near or on which a salient object could be placed. The main findings were that rats organized their exploratory locomotion to their point of entry and modified their behavior as they encountered objects. Also, rats with damage to visual cortex displayed an extra-attachment to the visual objects and in contrast to controls did not expand their exploratory locomotion with time. The results are discussed with respect to the centrality of the entry point in the organization of exploratory locomotion and the neural network that control visual exploration in the rat. / xiii, 220 leaves : ill. ; 29 cm. --