I watched a great doco, "how to live younger", the first episode examines the effectiveness of exercise on the mind with respect to declining mental cognition and dementia. It probably covers a lot of what you want to know. Basically to remain optimally healthy, they suggest the best exercise is whatever you can actually stick with, but daily, even just walking. Getting the blood flowing increases the blood vessels in the brain, which increases blood flow to the brain. But they go into heaps of detail about individual parts of the brain, what their function is and how exercise helps that region, specifically. They talk about the chemicals your muscles release and what the benefits are, hormones and how they relate to body function etc. If you have a vpn, it's streaming for free on abc iview currently.