The motor cortex is the region of the brain responsible for controlling voluntary motor movements. It contains somewhat fluid maps of the body that change in response to the learning of skilled behavior (ie. playing piano). As these skills are learned, the motor cortex refines the patterns of neuronal activity required for performing these complex tasks. Release of the neurotransmitter acetylcholine into the motor cortex regulates both the refinement of these motor maps and the learning of motor skills. It does so by changing the connections between neurons in the motor cortex. Spinal cord injury that affects output from the motor cortex disrupts these maps, while targeted rehabilitation from spinal cord injury leads to improved recovery of motor skill and maps. I propose to test the role that acetylcholine signaling plays in rehabilitation-mediated recovery from spinal cord injury. These findings will provide new opportunities for pharmacological modulation and for combinatorial treatments that support the recovery of corticospinal circuit function after injury. Additionally, acetylcholine synthesis decreases with age, so these studies could potentially have broad implications in rehabilitation for an aging US population that has shown a parallel increase in age at time of spinal cord injury.