New research supports the idea that the brains of older adults who maintain physical fitness by engaging in regular strenuous exercise more closely resemble those of younger adults. The researchers used functional MRI to measure fluctuations in blood oxygen level-dependent signals as the 52 study participants performed tasks involving several varieties of cognitive control. The fMRI scans indicated that young adults primarily used the dorsolateral prefrontal cortex—a classical working memory, cognitive control center of the brain that is activated more as tasks became more demanding. In general, the brain calls upon its resources like firefighters respond to a multi-alarm fire:...