In the Motor Recovery Laboratory, we study movement in health and after injury to the central nervous system. Our focus is the corticospinal system, which connects motor cortex to the spinal cord because this system is key for skilled movement in health. In addition, injury to the corticospinal system is largely responsible for loss of function after paralyzing injury. We attempt to repair brain-spinal cord connections using activity-based therapies, including electrical stimulation and motor training. The approach capitalizes on the fact that most brain and spinal cord injuries preserve some corticospinal connections. Also, corticospinal connections are highly activity-dependent and can be strengthened with endogenous activity (practice) or exogenous activity (electrical stimulation). We use a combination of anatomical, behavioral, and electrophysiological techniques to address the roles of injury and activity in promoting plasticity and recovery. We also study how plasticity of the motor systems changes with age and how developmental plasticity can be leveraged to promote recovery after injury. The animal models of disease we employ are used to improve our understanding of injury and therapy. Our ultimate goal is to improve motor function in people with brain and spinal cord injury.