For the MRI, the subject lies on a table that slides inside a donut's machine containing a magnetic field. MRI coils-special padded sensors that improve image quality-are placed around the head and neck. A pressure cuff placed around the arm measures blood pressure. The subject wears earplugs to muffle loud thumping noises that occur during electrical switching of the magnetic fields. The subject is in constant visual contact with the researchers and MR technologist and may request to stop the study at any time.