A couple of recent studies have reinforced the lifelong potential for brain plasticity (the ability of the brain to rewire itself through experience) and the importance of physical exercise for cognitive vitality. One study focused on 1) adults over 50 with mild cognitive impairment, the other one on 2) stroke survivors.

1)  Memory problems: Adults 50-years-old and over with mild cognitive impairment (an advanced form of memory problems, but pre-dementia) were asked to exercise for three 50-minute sessions per week for 24 weeks (a total of 60 hours). Results: there were small, but measurable, cognitive benefits even 18 months after the start of the program (around a year after the supervised exercise activities ended).
Study: Nicola T. Lautenschlager et al. Effect of Physical Activity on Cognitive Function in Older Adults at Risk for Alzheimer Disease. Journal of the American Medical Association, 3 September 2008 [link]

2) Stroke Rehab: the study showed how sustained physical rehabilitation can have a beneficial brain impact for stroke survivors, and that the effect was more clear by walking in a treadmill (as a cardiovascular exercise) than by doing assisted stretching exercises.

The press release for the other study, Treadmill Exercise Retrains Brain And Body Of Stroke Victims, contains this quote:”This is great news for stroke survivors because results clearly demonstrate that long-term stroke damage is not immutable and that with exercise it’s never too late for the brain and body to recover,” says Daniel Hanley, M.D., professor of neurology at the Johns Hopkins University School of Medicine.

Indeed, there is no reason why the process of physical and cognitive rehabilitation (or “enhancement”) should ever stop, either as part of formal therapy or as a lifestyle modification.
This Los Angeles Times article, Brain function gets a boost from walking, provides good commentary on both studies, and includes this nice quote:

“The act of doing a movement over and over can also stimulate the brain’s neurocircuits, he adds, resulting in activity in various regions of the brain. That activity may decrease over time as the body becomes more efficient at the activity. But other stimulation can have an effect — while a person walks outside with a friend, for example, the brain is guiding a number of activities, such as talking and observing.”

Which is why we always emphasize the importance of  novelty and challenge. Doing the same thing over and over and over and over, with the same level of difficulty, brings limited if any cognitive benefits.