Patients will undergo a magnetic resonance imaging (MRI) scan. Before the scan, they will complete a safety questionnaire about the presence of any metal in their bodies. Patients are at risk for injury from the MRI magnet if they have pacemakers, dental implants or other devices. Female patients will undergo a pregnancy test. The technique MRI uses includes a strong magnetic field and radio waves to obtain images of body organs and tissues. During the initial MRI scan, patients will lie still on a table that will slide into the enclosed tunnel of the scanner. They will be in the scanner for about an hour. During the procedure, they may be asked to lie as still as possible for up to 20 minutes at a time. As the scanner takes pictures, patients will hear knocking or beeping sounds. Each participant will wear earplugs to reduce this noise. They will be able to communicate with the MRI staff at all times during the scan, and they may ask to be removed from the machine at any time. The functional MRI (fMRI) scan will involve taking pictures of the brain while patients are performing tasks. All the tasks will be explained, and patients will have the chance to practice them before entering the scanner. During the fMRI, patients will view short film segments of people making gestures. Before and after the scan, patients will be asked to complete several short questionnaires. The testing sessions will take a total of about 2 hours.