Mice who exercised did better on memory tests, say researchers at the University of Cambridge and the National Institute on Aging in Baltimore. Active test subjects grew more new cells in parts of the brain linked to memory than those who didn’t exercise. Authors say these new cells helped boost cognitive performance, BBC News reports. To determine this, scientists looked at two groups of mice over a period of 105 days, training them to touch a box on a computer screen to get food pellets. One group was then allowed unlimited exercise, running over 20 km a day. The control group didn’t exercise. Both groups were then shown two boxes on a screen, one of which released a treat when touched. After they learned which box impacted the treat, the boxes were moved around. Exercising mice were more successful in locating the box again than their counterparts.