The answer, according to some, is by using tDCS.
Transcranial direct current stimulation (tDCS) is a form of neurostimulation which uses constant, low current delivered directly to the brain area of interest via small electrodes. It was originally developed to help patients with brain injuries such as strokes. Tests on healthy adults demonstrated that tDCS can increase cognitive performance on a variety of tasks, depending on the area of the brain being stimulated.
Radiolab has an interesting feature on it, from their June 26 podcast, entitled “9-volt Nirvana“, in which the process is described as the attaching of an electrode to your head, and another to your arm. To complete the circuit, use a 9-volt battery, and the result is an electric charge through whichever vague area of the brain you happen to have stuck the electrode.
The treatment itself has its roots in the more arcane uses of electotherapy, but its been shown (people believe) to have positive effects on already healthy humans.
In 9-volt Nirvana, Helen Thomson from New Scientist talks about being hooked up to a source of electricity, and the effect that it had on her.