Depotentiation in People With Focal Hand Dystonia

Background: \- Focal hand dystonia (FHD) causes muscles to contract, leading to abnormal movements or postures. Musicians, writers, and athletes often get it. Researchers want to study how patients with this condition learn, a process of the brain that depends on a property called plasticity. Objective: \- To study brain plasticity in people with FHD. Eligibility: * Right-handed adults 18 years and older with FHD. * Healthy, right-handed adult volunteers. Design: * Participants will be screened with medical history, physical exam, pregnancy test, and questionnaire about their right-handedness. * Participants will have 2 study visits on 2 different days. * Participants will sit in a chair and have up to 30 Transcranial Magnetic Stimulation (TMS) pulses on the left side of the head. A brief electrical current passes through a wire coil on the scalp. They will hear a click and may feel a pulling on the skin or muscle twitches. They may have to keep their eyes open and remain alert, tense certain muscles, or perform simple finger movements. * Forty more pulses, with 10 seconds between, will be given on the left side of the head. Some will be small, some big. * Researchers will measure muscle response through small electrodes taped to the right hand. * A cloth cap will be put on the participant s head. Researchers will write on tape on the cap. * Participants will have the r-PAS. An electrical stimulator will be placed on the nerve at the right wrist. Repeated magnetic pulses will be delivered in trains or short bursts together with electrical stimulation of nerve. Participants will receive up to 840 pulses. * Participants will be contacted after a few days for a follow-up check.