GUY McKHANN, M.D., is Professor of Neurology and Neuroscience at the Johns Hopkins School of Medicine and founding Director of the Zanvyl Krieger Mind/Brain Institute at Johns Hopkins. He is the founding Chairman of the Department of Neurology at Johns Hopkins and has appeared on 60 Minutes and in other national media. MARILYN ALBERT, Ph.D., is Professor of Psychiatry and Neurology at Harvard Medical School. She is Director of the Gerontology Research Unit at Massachusetts General Hospital and was recently appointed Director of the Division of Cognitive Neuroscience and the CoDirector of