A Hierarchy of corticospinal plasticity in human hand and forearm muscles

BACKGROUND AND OBJECTIVE The ability of the motor system to show plastic change underlies skill learning, and also permits recovery after injury. METHODS One puzzling observation is that after stroke, upper limb flexor muscles show good recovery but extensors remain weak;this is a major contributor to residual disability. We hypothesised that there might be differences in potential for plasticity across hand and forearm muscles, and investigated this using two protocols based on transcranial magnetic brain stimulation (TMS) in healthy human subjects.