Fish is brain food. Several kinds of fish have a fatty acid known as omega-3 which is vital for the development of the outer membrane of brain cells. Omega-3s are believed to contribute to greater alertness and lower the risk of dementia. Also, studies show that women who eat fatty fish during their third trimester of pregnancy have babies who tend to perform better cognitively.
(try salmon or avocado) 
Iron restores cognitive function. New studies revealed that being mildly iron deficient affects attention, learning, and memory.
(eat more spinach and swiss chard) 
Antioxidant rich foods protect neurons from damage. By-products of normal metabolism are known as free radicals. These free radicals are highly active oxygen molecules that lack an electron and can damage healthy tissue. Foods high in antioxidants help correct the problem by donating an electron to the free radicals and neutralizing their reactivity.
(blueberries, chocolate, and nuts are a great source) 
with low GI release glucose slowly into the bloodstream to supply the brain with energy keeping you mentally alert through out the day.
(wheat bran and brown pasta will do the trick) 
