YOUR BRAIN IS IN YOUR HANDS—meaning that in a Canadian study (New York Times, January 26), women 65 to 75 who did an hour or two of weight work (machines or hand-held weights) per week were cognitively sharper and more decisive (by a substantial margin, 10-12 percent!) than those who did only toning and balance exercises. I already dabble on the weight machine, but I fear that I will have to up my weekly total in order to keep the intellect well fed. Right now I’m trying to do a few minutes every day. Heavy!