Read this article just now! Great news for everybody! Here’s another reason to start exercising 
Research has found that exercise causes more new neurons to be formed in a critical brain region, and contrary to an earlier study, these new neurons do not cause the individual to forget old memories, according to research by Texas A&M College of Medicine scientists, in the Journal of Neuroscience.
https://www.sciencedaily.com/releases/2016/08/160803124445.htm