US-German Collaboration: Testing Muscle Synergies in a Neuromechanical Rat Model for Nominal and Perturbed Locomotion

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This project focuses on the neural and biomechanical principles that result in dynamic stability during locomotion. Medical treatments and diagnosis for neurological conditions that affect balance and coordination (e.g. spinal cord injury, stroke, Parkinson's) can be improved with a better understanding of mammalian spinal cord circuits. Neuromechanical models will also inspire improvements to the design of mechanical systems and controllers for assistive exoskeletons for human stability and mobility. For example, such a neural model could be effective for controlling a person's muscles in tandem with control of an exoskeleton's motors and with the person's intact systems. Control systems derived from this work may also provide autonomous legged robots greater mobility and adaptability for movement in unknown terrain. This project will also involve international collaboration and interdisciplinary education and training at the intersection of neurobiology, zoology, mechanical engineering, and system control.To better understand how the mammalian nervous system processes multi-sensory feedback for dynamic control of the many degrees of freedom in the rear legs, the investigators will: 1) Use simultaneous two-plane X-ray videography, force plates and EMG recordings to measure the kinematics, ground reaction forces, and muscle activations of rats running in various environments (treadmills of different speeds and flexibility, and on substrates with unexpected disturbances such as holes, a trapdoor and a shifting ground condition); 2) Use these data to expand a sagittal plane biomechanical model and conductance-based neural model of the rat to produce self-supporting walking of the hind legs in three dimensions; and 3) Investigate mechanisms for control of synergistic muscle groups by exploring different organizational models and testing the capability of these models for adapting to perturbations and maintaining dynamic control of walking behavior.A companion project is being funded by the Federal Ministry of Education and Research, Germany (BMBF).