Loss of Depotentiation in Focal Dystonia

Background Focal dystonia is a brain disorder. It affects a muscle or muscles in a specific part of the body. Researchers think it may be related to excessive training or practice. They want to know more about how much training might trigger focal dystonia. Objectives: To study why people develop focal dystonia. To study how brain plasticity changes with focal dystonia. Eligibility: People at least 18 years of age with focal dystonia. Healthy volunteers the same age are also needed. Design: Participants will be screened with a physical exam and questions. They may have blood and urine tests. Participants will have up to 3 testing visits. Participants will have small electrodes stuck on the skin on the hands or arms. Muscle activity will be recorded. Participants will have transcranial magnetic stimulation (TMS). A wire coil will be placed onto the scalp. A brief electrical current will pass through the coil. The current will create a magnetic field that affects brain activity. Participants may be asked to tense certain muscles or do simple actions during TMS. A nerve at the wrist will get weak electrical stimulation. The stimulation may be paired with TMS for very short times. Participants will receive repeated magnetic pulses. Participants will receive a total of 150 pulses during a 10-second period. An entire testing visit will last about 3 hours. ...