MILES O’BRIEN:

When you think of the human brain and electricity, there is a good chance you might conjure up this intense image. The treatment powerfully depicted in the 1975 Oscar-winning movie "One Flew Over the Cuckoo's Nest" is called electroconvulsive therapy.

It's delivers big jolts of alternating current to treat severe depression. It is still used as a last resort, but in reality it is painless. So is TDCS, which uses direct current, roughly equivalent to a nine-volt battery.

The basic idea goes back to the Romans, who used electric fish as a headache cure. But in 2000, some German scientists published this paper, which proved weak electrical current can modulate brain activity. Ever since, scientific interest in TDCS has amped up steadily.