RecruitingInfluence of Brain Oscillation-Dependent TMS on Motor FunctionBackground: When people have a stroke, they often have difficulty moving their arms and hands. Transcranial magnetic stimulation (TMS) can improve how well people with and without stroke can move their arms and hands. But the effects of TMS are minor, and it doesn t work for everyone. Researchers want to study how to time brain stimulation so that the effects are more consistent. Objective: To understand how the brain responds to transcranial magnetic stimulation so that treatments for people with stroke can be improved. Eligibility: Adults ages 18 and older who had a stroke at least 6 months ago Healthy volunteers ages 50 and older Design: Participants will have up to 5 visits. At visit 1, participants will be screened with medical history and physical exam. Participants with stroke will also have TMS and surface electromyography (sEMG). For TMS, a brief electrical current will pass through a wire coil on the scalp. Participants may hear a click and feel a pull. Muscles may twitch. Participants may be asked to do simple movements during TMS. For sEMG, small electrodes will be attached to the skin and muscle activity will be recorded. At visit 2, participants will have magnetic resonance imaging (MRI). They will lie on a table that slides into a metal cylinder in a strong magnetic field. They will get earplugs for the loud noise. At visit 3, participants will have TMS, sEMG, and electroencephalography (EEG). For EEG, small electrodes on the scalp will record brainwaves. Participants will sit still, watch a movie, or do TMS. Participants may be asked to have 2 extra visits to redo procedures.