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

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

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

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

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

TimeSlips is a program based on the idea that storytelling can be therapeutic for people with dementia. Dick Blau/TimeSlips hide caption

itoggle caption Dick Blau/TimeSlips

PET scans of the brains of a person with normal memory ability and someone diagnosed with Alzheimer's Image courtesy of the National Institute on Aging/National Institutes of Health hide caption

itoggle caption Image courtesy of the National Institute on Aging/National Institutes of Health

Tennessee women's basketball coach Pat Summitt sits with her dog at her home in Knoxville, Tenn. Summitt plans to coach "as long as the good Lord is willing" despite recently being diagnosed with early onset dementia. Debby Jennings/AP/University of Tennessee hide caption

itoggle caption Debby Jennings/AP/University of Tennessee

A woman with Alzheimer's disease walks in a corridor at a retirement house in Angervilliers, France, last month. Sebastien Bozon/AFP/Getty Images hide caption

itoggle caption Sebastien Bozon/AFP/Getty Images