I’ll leave it to you to puzzle through the article’s abstract, accepted for publication in the Journal of Neuroscience, but I think the title says it fairly aptly:

Little Exercise, Big Effects: Reversing Aging and Infection-Induced Memory Deficits, and Underlying Processes 

“…this small amount of exercise was sufficient to completely reverse infection-induced impairments in hippocampus-dependent long-term memory compared with sedentary animals”

Translation: Exercise, even a little, repairs your brain.