Right off the bat I can come up only with meldonium, or better known as mildronate. The monthly use of it will cost you like 20 USD, and it is a really good medicine for that. In fact, it was created for the recovery of people with strokes, to recover their brain functions. In any case, it is a very safe compound to use, as it has no side effects, and it has other additional benefits, so you will not lose anything by giving it a try. Also, ghinko biloma is good for brain activity.