Enhancing Motor Task Training by Action Observation Watching Others Perform the Task

This study will determine how the brain learns a new motor task when the subject practices the task and watches others perform it (action observation) at the same time. Healthy normal volunteers between 18 and 55 years of age may be eligible for this study. Candidates are screened with a medical history, general and neurological exam, and a brain MRI if one has not been done within 12 months of entering the study. Participants undergo one or both of the following experiments: 1. Effect of Transcranial Magnetic Stimulation on Motor Training and Action Observation Subjects participate in at least 12 4-hour test sessions, separated by at least 1 day. Each session includes the following: * Functional MRI (fMRI): MRI scanning uses a magnetic field and radio waves to produce images of the brain. For fMRI, the subject performs tasks during the scan to allow researchers to see brain changes that occur during performance of the activity. * Transcranial magnetic stimulation (TMS): For this test, a wire coil is held on the scalp. A brief electrical current passes through the coil to stimulate the brain. The stimulation may cause a twitch in muscles of the face, arm, or leg, and the subject may hear a click and feel a pulling sensation on the skin under the coil. During the stimulation, the subject is asked to: 1) perform the training task (make brisk thumb movements); 2) watch a video showing the hand of another person performing the same task; and 3) perform the task and watch the video at the same time, synchronizing his or her movements with those observed in the video. * Surface electromyography: Electrodes are filled with a conductive gel and taped to the skin over a hand muscle to measure the electrical activity of the muscle. * Behavioral measurements: Evaluation of learned movement tasks. * Questionnaires to test attention, fatigue and mood before, during and after each test session. 2. Effect of Pharmacological Agents on Motor Training and Action