This image made from video released by the Syrian Civil Defense White Helmets, which has been authenticated based on its contents and other AP reporting, shows a toddler given oxygen through respirators foll... . FILE- In this May 19, 2015, file photo, R. Scott Turner, Professor of Neurology and Director of the Memory Disorder Center at Georgetown University Hospital, points to PET scan results that are part of a study on Alzheimer'... Scientists propose new way to define Alzheimer's disease using biological signs, such as brain changes, not just memory loss and other symptoms.