moderate exercise – in this case walking at one's own pace for 40 minutes three times a week – can enhance the connectivity of important brain circuits, combat declines in brain function associated with aging and increase performance on cognitive tasks.
The higher the connectivity, the better the performance on cognitive tasks, especially the ones we call executive control tasks – things like planning, scheduling, dealing with ambiguity, working memory and multitasking," Kramer said. These are the very skills that tend to decline with aging, he said.
There is more in the report here and the full study (pdf) is available from the link below:
Plasticity of brain networks in a randomized intervention trial of exercise training in older adults