Prometheus 6

...Modafinil is not a traditional stimulant; rather than bombarding various parts of the brain with arousal signals, it apparently nudges the brain toward wakefulness through specific pathways, perhaps by increasing serotonin levels in the brain stem. The precise mechanism is still not well understood.

The temptation for healthy people to use such a drug is tremendous; some individuals report that a dose leaves them as refreshed as a short nap....

Nothing better than a mood-modifying drug that we have no idea how it works.

Juicing the Brain
Research to limit mental fatigue among soldiers may foster controversial ways to enhance any person's brain
By Jonathan D. Moreno

Physicians have long tinkered with ways to "improve" the human brain, but as our understanding of that organ's inner workings quickly grows, artificial enhancement is becoming more feasible. Military research is at the forefront of this work, much of it focused on drugs. The goal is to produce a better soldier, but the emerging techniques could just as easily be applied to any individual.