Cigarette smokers who suffer damage to a particular brain region often lose the urge to smoke, according to a new study. Although brain damage is hardly a recommended treatment for smokers who want to quit, researchers say the findings provide important insight into the biological basis of addictive behaviors.
Previous research on addiction has implicated the insula, a brain region tucked into a deep fold in the cerebral cortex. In brain scans of cocaine addicts, for example, the insula lights up in response to images of drug paraphernalia. Those kinds of images also tend to give addicts an urge to take more drugs. Similarly, videos of people smoking stimulate the insula in smokers' brains. Such work suggests that the insula helps generate addicts' drug-related urges. So what would happen if the insula suddenly went offline?
Antoine Bechara, a neuroscientist at the University Southern California in Los Angeles, and colleagues investigated this question in 19 cigarette smokers who had suffered insula damage as a result of a stroke or other neurological problem. Twelve of these people stopped smoking immediately after their brain injury and reported feeling no urges to smoke and no relapses since they quit. "My body forgot the urge to smoke," one man told the researchers. Before his stroke he was smoking 40 unfiltered cigarettes a day and had no intention of quitting. Among a group of 50 smokers with brain damage that did not include the insula, only four quit the habit with comparable ease, the researchers report in tomorrow's issue of Science.
"This really helps us understand how the brain works in addictive disorders," says Edythe London, a neuropharmacologist at the University of California, Los Angeles. London says the new study bolsters the idea that the insula mediates emotional responses that contribute to addiction. "Gut feelings that are associated with cravings are probably only experienced after the information is processed in the insula," she says.
The findings could have implications for how to beat addiction, Bechara says. Based on the experiences related by the insula-damaged patients, he suspects that the insula is needed create the feeling that smoking is a bodily need. Bechara notes that other research has suggested that the bodily effects of smoking--particularly the effects on the airways--are a crucial part of the satisfaction smokers get from puffing away. If so, he speculates, smoking cessation therapies such as denicotinized cigarettes may ultimately prove more effective than nicotine patches because they provide physical sensations that stimulate the insula and satisfy the smoker.