If you want to live long and strong, you’ve got to do more than work out your body; you’ve got to exer­cise your brain, insists Dr. Elkhonon Gold­berg, clin­i­cal pro­fes­sor of neu­rol­o­gy at New York Uni­ver­si­ty School of Med­i­cine. While we’ve heard for years that men­tal stim­u­la­tion can stave off demen­tia and Alzheimer’s, Dr. Gold­berg…