What metaphor for the aging brain?

Most of us do not often think about how we think, and that's probably just as well. Our language can circle around itself, often taking us up blind alleys, or into a complexity that is as irredeemable as it is irrelevant to daily practice. But sometimes we must give mind to our metaphors. For a long time we have thought of the brain in old age as an innocent bystander. It sometimes gets bruised and sometimes beaten up, but it's not as though it can do a lot about it. Other metaphors have competed, including the brain as repository, coming to old age with assets that inexorably dwindle, until they meet a threshold, after which disease occurs.

In this issue, Wilson and colleagues¹ report that people who habitually engage in high levels of cognitive activity showed less cognitive decline—and less often had Alzheimer disease (AD)—than did people with less cognitively activating routines. The Rush Memory and Aging Project is a prospective clinicopathologic study, whose 931 participants have agreed to annual examinations and brain autopsy. Its high retention rate (93.5% of people enrolled for more than 1 year average were followed 3.5 times on average) and detailed evaluations provide insights into the …