This is how memory loss begins, Sophie tells me: You show up at work, forgetting that you are supposed to be at a breakfast meeting with a client. You blank on the names of your neighbors. Soon enough you walk into a room without any clue as to why you are there. Sophie, a lawyer in her early 50s, who asked to go by a pseudonym, had been suffering from frequent hot flashes and night sweats, both associated with menopause, but the forgetfulness seemed to be in another league. What was happening to her mind?