Here are two of the many things that scare me: having to change a tire all by myself (because I’ve never done it) and camping in bear country (because I have). Here are two of the few things that don’t scare me: taking pop quizzes and getting poked with needles. These slim categories of fearlessness make me a natural volunteer for Alzheimer’s research. My mother grew up in Montana and nothing much scared her. She not only changed tires, she put chains on tires by herself, tying them together with shoelaces if they didn’t fit right, lying under the car in a snow storm. As for camping, after a twenty-year hiatus, she decided to try it again—solo, with four children in tow. We didn’t see any bears. The worst thing that happened was that we forgot spoons for our cereal. The best thing was being with Mom, far away from all of her city responsibilities, laughing along with the rest of us as we slurped our Raisin Bran and milk from our cups. Mom was the kind of person you would put last on your list of People Likely to Get Alzheimer’s disease. She was smart and lively and fit; she taught high school English and read like crazy; she weathered two divorces and the loss of her third husband and raised six kids alone. But somehow, Alzheimer’s found her, and it found her early. She was in her late fifties when she suspected something was wrong, was finally diagnosed at 66 and dead at 74. [...]