On a separate day, participants will also undergo magnetic resonance imaging (MRI), a diagnostic test that uses a magnetic field and radio waves to produce images of the brain. For this procedure, the subject lies still on a stretcher that is moved into the scanner (a narrow cylinder containing the magnet). Earplugs are worn to muffle loud noises caused by electrical switching of radio frequency circuits used in the scanning process. The scan lasts about 45 to 60 minutes.