A hormone that is released during exercise may improve brain health and lessen the damage and memory loss that occur during dementia, a new study finds. The study, which was published this month in Nature Medicine, involved mice, but its findings could help to explain how, at a molecular level, exercise protects our brains and possibly preserves memory and thinking skills, even in people whose pasts are fading.

Considerable scientific evidence already demonstrates that exercise remodels brains and affects thinking. Researchers have shown in rats and mice that running ramps up the creation of new brain cells in the hippocampus, a portion of the brain devoted to memory formation and storage. Exercise also can improve the health and function of the synapses between neurons there, allowing brain cells to better communicate.

In people, epidemiological research indicates that being physically active reduces the risk for Alzheimer’s disease and other dementias and may also slow disease progression.

But many questions remain about just how exercise alters the inner workings of the brain and whether the effects are a result of changes elsewhere in the body that also happen to be good for the brain or whether the changes actually occur within the brain itself.