You need a brain fitness program if you want to keep your mind in top shape and dramatically slow the effects of age-related cognitive decline. If you don’t do anything to protect your existing neurons and add new ones, you will lose them. If neurons are used, they remain active and healthy and create functional connections with other neurons, increasing their activity and health. Exerting your brain may even lead to the birth of new neurons, and it rescues the neurons you already have from decay, the “use it or lose it” phenomenon.