two things have helped in a way that i definitely noticed: one, gingko biloba. two, zinc.
i think the zinc was more fundamentally helpful and that the gingko biloba acted as a temporary band-aid solution.
there's literature out there on the role of zinc and blood flow.
here's one interesting abstract:
http://sciencelinks.jp/j-east/article/2 ... 211932.php
there are other nutrients out there that are meant to be good for cognition. b-complex is one example. i did have low b vitamins initially, and i do supplement them now, but compared to gingko or zinc, i've never felt the same way after taking b-complex in terms of really getting a noticeable effect.