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Facts, faces, experiences: Our brain’s capacity to learn new things, store the memories and summon them up on demand is a marvel. Yet we take it all for granted until the skills start to crumble in those we love, or in ourselves. What goes awry in the brain to make this happen? (Dance, 5/18)

Given time, any brain can succumb to dementia — memories fade, thoughts scatter, basic abilities wither on the vine. Brains don’t come with lifetime guarantees, but there is one major step you can take to protect yourself from Alzheimer’s or other causes of mental decline: exercise your body. Nothing protects the brain quite like regular exercise, says Jennifer Heisz, a cognitive neuroscientist at McMaster University in Ontario, Canada. Not crossword puzzles, not supplements, not prescription medications. Exercise seems to beat them all, reducing the risk of Alzheimer’s disease or cognitive decline by about 35% to 45%, according to the latest evidence. (Woolston, 5/18)

It’s a safe bet that you’d like to avoid getting Alzheimer’s. But you probably haven’t done the one thing that could make you five times more likely to reach the age of 85 without getting the disease and 7.5 times more likely to have suffered no memory loss or other major cognitive decline. Don’t kick yourself. The only way you could have achieved this spectacular risk reduction was to be born with a genetic variant that’s been found in fewer than 0.5% of people studied. (Ravn, 5/18)