Olive oil is not good brain food.It is an omega 9 monosaturated oil,it does have SOME benefits but not like the ones found in Omega 3's. You can find omega 3' in small amounts in leafy greens,but you would have to eat alot of them to get a good amount of 3's.
the problem with olives as a preferred fat source,is that you are creating an imbalance of your fat ratios. Yes you can eat nuts and other fare,but where are you going to get your omega 3's?
That is why they are called ESSENTIAL FATTY ACIDS. They are essential for our health and life. They are also called ESSENTIAL because our bodies cannot manufacuture them and they must be consumed.