The famous mathematician Paul Erdos turned to the use of amphetamines to help himself study.
There is a new class of drugs, called nootropics, that may have the potential to improve short-term memory though not general intelligence. They have different mechanisms of actions, many of which rely on increasing levels of the neurotransmitter acetylcholine. Nootropics are usually independent of the dopamine system (there are exceptions such as Selegiline) and are consequently uncontrolled, unlike most of the stimulant based drugs.