Do you know Dr. Maoshing Ni? He is the author of several books on health and longevity and runs the Ask Dr. Mao site.
He has a list of tips on boosting your brain power on the yahoo site. Useful tips include doing some brain exercises like puzzles and memorizing items in a list; getting enough sleep (and grabbing a power nap) and exercise; eating the right foods; brewing your own herbs; and drinking green tea every day (I’ve got mine right here! 
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I would add to the list the fermented foods like natto and miso. What do you do to keep your brain healthy?