How Exercise Affects Our Memory

Even a single workout may make our brain’s memory centers, like our muscles, more fit.

A single, moderate workout may immediately change how our brains function and how well we recognize common names and similar information, according to a promising new study of exercise, memory and aging. The study adds to growing evidence that exercise can have rapid effects on brain function and also that these effects could accumulate and lead to long-term improvements in how our brains operate and we remember.

Until recently, scientists thought that by adulthood, human brains were relatively fixed in their structure and function, especially compared to malleable tissues, like muscle, that continually grow and shrivel in direct response to how we live our lives. But multiple, newer experiments have shown that adult brains, in fact, can be quite plastic, rewiring and reshaping themselves in various ways, depending on our lifestyles.

Exercise, for instance, is known to affect our brains. In animal experiments, exercise increases the production of neurochemicals and the numbers of newborn neurons in mature brains and improves the animals’ thinking abilities. Similarly, in people, studies show that regular exercise over time increases the volume of the hippocampus, a key part of the brain’s memory networks. It also improves many aspects of people’s thinking.

But substantial questions remain about exercise and the brain, including the time course of any changes and whether they are short-term or, with continued training, become lasting.

They recruited 26 healthy men and women aged between 55 and 85, who had no serious memory problems and asked them to visit the exercise lab twice. There, they rested quietly or rode an exercise bike for 30 minutes, a workout the scientists hoped would stimulate but not exhaust them.

Afterward, the volunteers lay inside an M.R.I. brain scanner and watched names flash across a computer screen overhead.

The volunteers were asked to press one key onscreen when they recognized celebrities’ names and a different key when the name was unfamiliar. Meanwhile, the researchers tracked their brain activity over all, as well as in the portions involved in semantic-memory processing.

The scientists had expected that the areas needed for semantic memory work would be quieter after the exercise, just as they were after weeks of working out.

But that is not what happened. Instead, those parts of the brains most involved in semantic memory fizzed with far more activity after people had exercised than when they had rested.

At first, the researchers were surprised and puzzled by the results, Doctors says. But then they began to surmise that they were watching the start of a training response.

“There is an analogy to what happens with muscles,” Doctors says.

When people first begin exercising, he points out, their muscles strain and burn through energy. But as they become fitter, those same muscles respond more efficiently, using less energy for the same work.

The scientists’ suspect that, in the same way, the spike in brain activity after a first session of biking is the prelude to tissue remodeling that, with continued exercise, improves the function of those areas.

Our brain’s memory centers become, in other words, more fit.

This study is short-term, though, and does not show the intervening steps involved in changing the brain with regular exercise. It also does not explain how activity alters the brain, although Doctors believes that a surge in certain neurotransmitters and other biochemical after workouts must play a role.

He and his colleagues are hoping to examine those issues in future studies and also zero in on the best types and amounts of exercise to help us maintain our memories of that genial Beatles drummer and all the other touchstones of our pasts.

Lara Khouli.