It’s more likely to lose brain cells due to lack of use than overuse, this article explains. Mark Rosenzweig of U. of C. Berkeley and Michael Mersenich of U. of C. San Francisco and others found that with activity and exercise, that pathways in the brain actually changed. They found that the brain is “fluid” and can change by what we do. Both mental and physical exercise can lower the dementia risk. Vigorous daily exercise can lower the chances of getting dementia by 60% they say.