July 27, 2011, 12:01 am, By GRETCHEN REYNOLDS  For those of us hoping to keep our brains fit and healthy well into middle age and beyond, the latest science offers some reassurance. Activity appears to be critical, though scientists have yet to prove that exercise can ward off serious problems like Alzheimer’s disease. But what about the more mundane, creeping memory loss that begins about the time our 30s recede, when car keys and people’s names evaporate? It’s not Alzheimer’s, but it’s worrying. Can activity ameliorate its slow advance — and maintain vocabulary retrieval skills, so that the word “ameliorate” leaps to mind when needed? If you would like to read more of this article please click here to go to the New York Times site