As someone who wakes up, turns on the TV, eats a cookie, and then sits at my desk to write, some might say I'm rather sedentary. That is not the case for my mother and many of her friends at the senior living facility where they reside. In fact, I've never seen such an active group of people in my life—and most of them are in their 80s, 90s, and even 100s. Time and again, experts stress the importance of not only physical exercise and a healthy diet, but also mental stimulation in order to ...