The term "Peeping Tom" comes from the story of Lady Godiva, who rode through town naked on horseback and asked residents not to look. iStockphoto.com hide caption

itoggle caption iStockphoto.com

A PET scan of the brain of a person with Alzheimer's disease. U.S. National Institute on Aging/Wikimedia Commons hide caption

itoggle caption U.S. National Institute on Aging/Wikimedia Commons

Dr. Amit Etkin and a research assistant help a participant into the bore of the MRI. Courtesy of the Etkin Lab at Stanford University hide caption

itoggle caption Courtesy of the Etkin Lab at Stanford University