IF YOU are an ageing couch potato, you should seriously consider putting this article aside, getting off your backside and doing something more energetic instead. It seems that taking up exercise can rejuvenate your brain even in old age 鈥� if research on mice is anything to go by.
There is no shortage of evidence that lifelong exercise is good for the brain. For instance, habitual exercisers suffer less brain-tissue loss when they grow old than less active folks, and seniors who are physically fit do better on cognitive tests than those who aren鈥檛. A few years ago, it was shown that younger mice that exercised grew new neurons and had superior cognitive performance to their more lazy kin.
But now a new study suggests it is never too late for lifelong sloths to reap the mental rewards of exercise. Fred Gage and his colleagues at the Salk Institute in La Jolla, California, have found that old sedentary mice begin to grow new neurons and perform better on cognitive tests after they start using a running wheel.
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Gage鈥檚 team studied 15 young mice and 18 mice that were the equivalent of 70-years-old in human terms. About half of each group had running wheels placed in their cages; the others had to do without. Just over a month later, all the animals were subjected to a few days of cognitive tests in the form of the Morris water maze, in which the mouse has to remember the position of a platform submerged in cloudy water.
Old runners found the platform just as quickly as the young mice. But old non-runners took twice as long, as they were worse at remembering where the platform was. Later, new neurons were found growing in the brains of the old mice that had been exercising whereas virtually no neurogenesis was happening in the brains of their slothful peers (The Journal of Neuroscience, vol 25, p 8680).
鈥淣ew neurons were found growing in the brains of the old mice that had been exercising, but not in their slothful peers鈥�
It is thought that exercise might kick-start the growth of new neurons, which is in turn responsible for enhancing the mice鈥檚 cognitive abilities. 鈥淭he light is shining on neurogenesis,鈥� says Gage. But the only way to be absolutely sure is to block ageing animals鈥� ability to generate new neurons while they run, and see if the cognitive effects disappear as well 鈥� not an easy task.
Jim Sallis, a psychologist at San Diego State University in California who studies the effects of the built environment on physical activity, says the study underscores yet again the importance of physical activity. 鈥淭he irony is that we rely more and more on cars, use more labour-saving devices, and continue to build sprawling communities that prevent people from walking even to local shopping areas.鈥�
