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WASHINGTON - Damage to a silver dollar-sized spot deep in the brain seems to wipe out the urge to smoke, a surprising discovery that may shed important new light on addiction. The research was inspired by a stroke survivor who claimed he simply forgot his two-pack-a-day addiction - no cravings, no nicotine patches, not even a conscious desire to quit.

A customer smokes inside a pub in Washington in this 2006 file photo. [AP]

"The quitting is like a light switch that went off," said Dr. Antoine Bechara of the University of Southern California, who scanned the brains of 69 smokers and ex-smokers to pinpoint the region involved. "This is very striking."

Clearly brain damage isn't a treatment option for people struggling to kick the habit.

But the finding, reported in Friday's edition of the journal Science, does point scientists toward new ways to develop anti-smoking aids by targeting this little-known brain region called the insula. And it sparked excitement among addiction specialists who expect the insula to play a key role in other addictions, too.

"It's a fantastic paper, it's a fantastic finding," said Dr. Nora Volkow, director of the National Institute on Drug Abuse and a longtime investigator of the brain's addiction pathways.

"What this study shows unequivocally is the insula is a key structure in the brain for perceiving the urges to take the drug," urges that are "the backbone of the addiction," Volkow added.

Why? The insula appears to be where the brain turns physical reactions into feelings, such as feeling anxious when your heart speeds up. When those reactions are caused by a particular substance, the insula may act like sort of a headquarters for cravings.

Some 44 million Americans smoke, and the government says more than 400,000 a year die of smoking-related illnesses. Declines in smoking have slowed in recent years, making it unlikely that the nation will reach a public health goal of reducing the rate to 12 percent by 2010.

Nicotine is one of the most addictive substances known, and it's common for smokers to suffer repeated relapses when they try to quit.

So imagine Bechara's surprise at hearing a patient he code-named "Nathan" note nonchalantly that "my body forgot the urge to smoke" right after his stroke.

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