Appareil locomoteur

Résumé

L’appareil locomoteur, appelé aussi système musculo-squelettique, est un système d'organes qui confère aux animaux la faculté de se mouvoir physiquement dans un milieu (aérien, terrestre, aquatique), en faisant usage de leurs muscles et de leur squelette. Hormis la locomotion, le squelette procure également un support et une protection aux organes internes. Chez de nombreux organismes, le squelette est également utilisé pour stocker des graisses et des minéraux et pour produire des cellules sanguines. Appareil locomoteur humain L'appareil locomoteur humain se compose du squelette humain, fait d'os attachés aux autres os par des articulations, et de muscles squelettiques attachés au squelette par des tendons. Chez la plupart des animaux à appareil locomoteur solide, la moelle osseuse jaune est utilisée pour stocker de l'énergie pour les muscles et la moelle rouge produit des cellules sanguines dont certaines transportent l'oxygène requis par le corps. Appareil loco

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Reverse engineering the motor control system

Berat Denizdurduran

Mammalian motor control is implemented by a combination of different networks and system, working coherently to plan the movement of the body or a limb and to execute this movement a dynamical environment. While it is believed that complex, voluntary movements are planned in the motor areas of the cortex, the execution of the movement is controlled by a combination of cortical and cerebellar networks together with central pattern generators and reflex circuits in the spinal cord. In this thesis, we propose an abstract model that captures the basic properties of mammalian motor control, using the example of two different movements: arm movements as well as locomotion. Our model consists of three parts: first a high-level network, that learns movements, using a combination of actor-critic based reinforcement learning and Optimal Control theory. The second part corresponds to spinal reflex circuits that execute basic movements of the musculo-skeletal system. They are modeled by a simple neural network, that learns the dynamic properties of the muscoloskeletal system by the mechanism of spontaneous motor activity (muscle twithing) combined with a Hebbian learning rule. We demonstrate that this network can learn the antagonistic control of joint movements. The final part of the model is a cerebellar network, that translates a complex movement trajectory, such as reaching, and activates the spinal reflex circuits to execute the movement. The mapping between the cerebellar neurons and the spinal reflex circuits are trained with artificial neural networks. Using a musculoskeletal arm model, we demonstrate that the proposed neural motor control model can generate the movement to arbitrary goal position.

EPFL2019

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A computational modeling approach to study the neuromechanics of terrestrial locomotion

Shravan Tata Ramalingasetty

The main theme of my thesis will be to use neuro-muscular modeling techniques to study locomotion of terrestrial mammals. Locomotion is the ability of animals to interact with the environment to propel themselves in space. It involves co-ordination and precise timing of tens of muscles and multiple joints to produce rhythmic, efficient and robust gaits. It is now understood that it is a complex interaction of brain, spinal cord, the musculo-skeletal system and the environment. During my thesis I plan to develop models of rodents to non-human primates to humans to study the interactions between these components. I will be carrying out my research at BioRob lab and funded by the Human Brain Project. After spending an year on this subject currently I have developed a neuro-muscular hind limb model of a mouse. I am using this model to study different locomotion theories ranging from reflex based abstraction methods to Central Patter Generator networks and spiking neuron based spinal circuits. The closed loop approach seems promising and I am now able to generate stable locomotion on a forward dynamics model using all the mentioned frameworks. The future plan will be to further improve the rodent model with more degrees of freedom in the forelimb and extend the same modeling approach to develop non-human primate and human models to carry out similar experiments.

EPFL2022

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Robots are increasingly used as scientific tools to investigate animal locomotion. However, designing a robot that properly emulates the kinematic and dynamic properties of an animal is difficult because of the complexity of musculoskeletal systems and the limitations of current robotics technology. Here we propose a design process that combines high-speed cineradiography, optimization, dynamic scaling, 3D printing, high-end servomotors, and a tailored dry-suit to construct Pleurobot: a salamander-like robot that closely mimics its biological counterpart, Pleurodeles waltl. Our previous robots helped us test and confirm hypotheses on the interaction between the locomotor neuronal networks of the limbs and the spine to generate basic swimming and walking gaits. With Pleurobot, we demonstrate a design process that will enable studies of richer motor skills in salamanders. In particular, we are interested in how these richer motor skills can be obtained by extending our spinal cord models with the addition of more descending pathways and more detailed limb central pattern generators (CPG) networks. Pleurobot is a dynamically-scaled amphibious salamander robot with a large number of actuated degrees of freedom (27 in total). Because of our design process, the robot can capture most of the animal’s degrees of freedom and range of motion, especially at the limbs. We demonstrate the robot’s abilities by imposing raw kinematic data, extracted from X-ray videos, to the robot’s joints for basic locomotor behaviors in water and on land. The robot closely matches the behavior of the animal in terms of relative forward speeds and lateral displacements. Ground reaction forces during walking also resemble those of the animal. Based on our results we anticipate that future studies on richer motor skills in salamanders will highly benefit from Pleurobot’s design.

Royal Soc2016

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