(M15+) ***

Director: Neil Burger.

Cast: Bradley Cooper, Abbie Cornish, Robert De Niro.

THERE'S a popular myth that we humans only use a small percentage of our brains.

While that myth might be total rubbish, this film is not.

Based on the book The Dark Fields, Limitless explores that myth in stylised but engrossing fashion, with Cooper playing the hapless writer Eddie who manages to unlock the "unused 80 per cent" of his mind.

The trigger is a drug called NZT that Eddie secures from his ex-brother-in-law, and with the NZT kicking through his system suddenly Eddie is finishing that unfinished novel of his in a matter of days, charming women, learning languages and making a killing on the stock market.

But, as with all drugs, there is a comedown - and this one might involve murder.

The premise - even if Mythbusters has already busted it - is a ripper, and the film really pushes the potential of it. What would such a drug do? What would you do while on it? What would happen if you stopped taking it? What if you couldn't get more of it? What if other people took it? What if incredibly dangerous people took it?

The film revels in the differences between Eddie being on the drug and off it, switching from the dull blue-gray of Eddie's world without NZT to the shiny, rapidly moving, drug-fuelled existence that comes when he takes the drug. And while Limitless has the substance to match the style, it does seem to go over-the-top with its camera wizardry and CG tweaks to Eddie's hyper-reality, as well as his narration.

Eddie's an interesting character but not one we ever really like, and it's probably only Cooper's sheer force of personality that makes him engaging. His journey and increasing paranoia remain fascinating enough to follow him though, and the film does offer a certain "what if" voyeurism.

There are plenty of thrills, a good sense of momentum, and the script is pretty tight but Limitless really succeeds on the strength of its idea. While it's not that the film-makers do an amazingly stunning job with that idea, it's perhaps more that they don't fumble it at all.