Neural mechanisms underlying the adaptive plasticity of human locomotion

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When we walk, we do not have to think about the detailed movements that our legs are making. All we have to worry about is where we want to go and how fast. It can be so because part of our nervous system that operates autonomously generates the detailed walking movement for us. Such a movement controller is fast and efficient in every day life, as it reduces the amount of attention we have to dedicate to walking.However, when walking movements have to be changed, such as after disease, injury or new environmental needs (for example walking on a boat or, in the future, on Mars), we can't always adapt to the new situation. Sometimes training will help, and sometimes it is inefficient. To adapt, the nervous system must reorganize the way it commands muscles during walking, a phenomenon called locomotor plasticity. At the moment, we have no way to predict when plasticity will occur or not. Understanding how locomotor plasticity occurs is extremely important if we want one day to be able to train effectively astronauts to walk safely on Mars, and people with walking problems to recover their mobility.The present research program proposes an original way to study locomotor plasticity. Using a simple and effective means (walking with an external force applied to the leg by a robotic boot), we can reproduce in the laboratory all the conditions required to adapt walking. Combining this method of adaptation to modern kinematic and neurophysiological testing, we will, over the next 5 years, address 3 fundamental questions on how the nervous system is reorganized during adaptation: 1) what are the important feedback signals needed to adapt? 2) what is the extent/limit of locomotor plasticity? and 3) if training is provided, what are the long-term effects on the nervous system?This is an important research program that opens the study of mechanisms of locomotor plasticity, an aspect of locomotion that is poorly understood at the moment. Results obtained here will have a major impact both in basic science and health applications.