Moderate exercise can enhance the connectivity of important brain circuits, combat declines in brain function associated with aging and increase performance on cognitive tasks, according to a new study.

The study, led by the University of Illinois and published in Frontiers in Aging Neuroscience, followed 65 adults, aged 59 to 80, who joined a walking group or stretching and toning group for a year.

All of the participants were sedentary before the study, reporting less than two episodes of physical activity lasting 30 minutes or more in the previous six months. The researchers also measured brain activity in 32 younger (18- to 35-year-old) adults.

Neuroscientists have identified several distinct brain circuits, including the default mode network (DMN), which dominates brain activity when a person is least engaged with the outside world - either passively observing something or simply daydreaming.

The new study used functional magnetic resonance imaging to determine whether aerobic activity increased connectivity in the DMN or other brain networks. The researchers measured participants' brain connectivity and performance on cognitive tasks at the beginning of the study, at six months and after a year of either walking or toning and stretching.

At the end of the year, DMN connectivity was significantly improved in the brains of the older walkers - who walked at their own pace for 40 minutes three times a week - but not in the stretching and toning group, the researchers report.