This study will use magnetic resonance imaging (MRI) to investigate how the brain controls bimanual movements (movements of both hands).

Healthy normal volunteers between 21 and 65 years of age may be eligible for this study.

Participants will have a medical history, physical and neurological examinations, and will complete a questionnaire before and after testing. The study consists of two parts: 1) finger movement training and 2) magnetic resonance imaging, as follows:

Part 1 - Finger movement training

Participants will train to do three different finger movements using the index finger of both hands. The fingers will be taped to a device that measures their movement. The movements are:

• Lifting and dropping the index fingers of each hand repetitively and in synchrony (starting and stopping at the same time). The amplitude of finger movements is the same for both hands.
• Lifting and dropping the index fingers of each hand repetitively and in synchrony, but with a different amplitude for each hand.
• Lifting and dropping of the index finger of each hand repetitively, but each with a different amplitude and not in synchrony.

Part 2 - Magnetic resonance imaging

Participants will perform the trained movements during MRI scanning. This diagnostic procedure uses a magnetic field and radio waves to produce images of brain structure and activity. For MRI, 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.