In a finding that could lead to powerful new treatments for smokers unable to quit, scientists have discovered that people who experienced stroke damage to a prune-sized spot deep within the brain suddenly lost the urge to light up.
The research, published today in the journal Science, underscores nicotine's far-reaching grip on a smoker's neural circuitry -- and how much there remains to learn about it. Until now, addiction researchers have largely ignored the brain structure implicated in the study -- a region called the insula.
"It's a really tremendous paper, one that points us in a whole new direction," says Steven Grant, who is chief of the clinical neuroscience branch of the government's National Institute on Drug Abuse and was not involved in the study. "It says: This is a brain area the addiction field needs to focus a lot of attention on."
While intentionally inflicting damage to a smoker's brain is ethically out of the question, scientists said it might be possible to mimic the effect of insula injury with drugs or other therapies. Such treatments could also help people addicted to chemicals other than nicotine, researchers said.
In the study, researchers at the University of Southern California and University of Iowa looked at 69 smokers with various brain injuries, mostly as the result of a stroke. All the participants had smoked at least five cigarettes a day for two years or more.
Of 19 smokers whose insula had been damaged, 13 almost immediately stopped smoking, researchers found. One of the most striking cases was a 38-year-old mathematician, identified as "Patient N."
A smoker since the age of 14, the man typically inhaled more than 40 unfiltered cigarettes a day -- his final one on the evening before his stroke.
But when he woke up in the hospital, his nicotine cravings had disappeared. "My body forgot the urge to smoke," Patient N told researchers.
"His quitting was completely effortless, like a switch going off," says Antoine Bechara, a researcher in USC's Brain and Creativity Institute and senior author of the report.
Patient N even became so disgusted by the smell of his hospital roommate, who frequently left the building to smoke, that he asked to change rooms.
Researchers were at a loss to explain what's going on in the brains of Patient N and the other quitters. Another mystery: why six of the insula-damaged subjects did not quit smoking.
