Comparison of Externally and Self-Initiated Movements

This study will use magnetic resonance imaging (MRI) to investigate how the brain controls voluntary movements triggered by an external stimulus or self-initiated. Registered HCMS healthy normal volunteers may participate. They will complete a questionnaire and will have a medical history and brief physical examination. The study consists of two parts: 1) body movement training and 2) magnetic resonance imaging, as follows: Part 1 - Body movement training Participants will train to do three different body movements involving the hands and feet. The movements will either be self-initiated or in response to a stimulus, such as a visual or auditory trigger. Part 2 - Magnetic resonance imaging Participants will do one or more of the trained movements, with or without a triggering stimulus, during MRI scanning. MRI is a diagnostic procedure that uses a magnetic field and radio waves to produce images of brain structure and activity. For the procedure, the subject lies on a stretcher that is moved into the scanner-a cylinder containing a strong magnet. Earplugs are worn to protect the ears from loud thumping noises that occur with electrical switching of radio frequency circuits. Scanning time varies from 20 minutes to 2 hours, with most examinations lasting 1 to 1-1/2 hours. The subject can communicate with the staff person conducting the test at all times during the scan. A device compatible with magnetic resonance will be used to record the participant\'s body movements. The participant may be asked to push buttons of the device during the tasks.