Exercise, researchers have found over the years, appears to help people fight the natural memory loss that comes with aging.
More Vital Signs Columns Now a new study suggests a possible explanation for why this is so. The report, which appears online in The Proceedings of the National Academy of Sciences, says working out may stimulate the growth of neurons in a part of the brain associated with memory loss.

The researchers, led by Dr. Scott A. Small, an associate professor of neurology at the Columbia University Medical Center, looked at changes in the brains of volunteers who worked out on exercise equipment.

The researchers were trying to confirm the findings of earlier research they did involving mice. When the mice exercised, blood flow increased to a part of the brain called the hippocampus, and more specifically to the dentate gyrate. In post-mortems, the researchers found evidence of neuron growth in the dentate gyrate.

The research could not be replicated in people for reasons practical - who would volunteer? - and ethical, to say nothing of legal.

But using 11 volunteers, an M.R.I. machine and equipment like treadmills, the researchers were able to see whether blood flow increased to the same part of the brain in humans as it had in mice. It did, suggesting that working out may help produce neurons in a part of the hippocampus that loses them disproportionately as people age.

The researchers also found that as the volunteers went through a three-month exercise period, their scores on memory tests went up.

‘Our study does suggest that it’s probably aerobic exercise that’s inducing this effect,’ Dr. Small said.