Reseach has shown that a little bit of caffine has been shown to help mental activity. However since caffine dehyrates one of the side effects when doing a lot of brain work is headaches and tiredness. Generally drinking plenty of water helps keep the brain hydrated. Note it is a little bit of caffine less than a standard cup of coffee seems to be enough.
The studies that show caffiene improves performance, also show that you get an improvement if you start from a zero base of caffiene. If you have a regular daily usage of caffiene you get NO benefit, from that dosage you have to increase it.
It is a stimulant and your body adjusts to regular usage.
I'd disagree on the basis of countless articles such as the link at the bottom. There are countless ways to improve clarity of thought that're ultimately far more beneficial ;-) http://www.sunfood.net/jeaa/coffee.html
I heard from someone that the only thing they actually know about the brain is that it needs water. If you've got a water purifier then I spose it would help out more... maybe..
