The research was conducted at the MNI's McConnell Brain Imaging Centre, where subjects were scanned using fMRI (functional Magnetic Resonance Imaging). Twenty healthy smokers were recruited for the study and were randomly divided into one of two groups: "expectant" (they could smoke right after the test) or "non-expectant" (they could only smoke four hours after the test). The researchers scanned the brains of each subject to pinpoint the areas that were active while the subjects were exposed to visual smoking cues through videotaped footage of people lighting cigarettes, smoking while socializing or blowing smoke rings. In the group who expected to smoke immediately after the test, areas of the brain implicated in arousal, attention, and cognitive control were activated. In the subjects who could only smoke four hours after the test, there was almost no neural response to smoking cues, even if the subject reported an equivalent craving level.
"Although the effect of exposure to drug-associated cues has been studied with various drugs of abuse, this is the first study to show the link between expectancy levels and smoking cues," explained Dr. Alain Dagher, a neurologist who specializes in functional brain imaging. "Our findings confirm the importance of expectancy in the neural response to these cues, and lend support to the theory that these cues act on brain areas involved in arousal and attention, particularly the dorsolateral prefrontal cortex, which is involved in the regulation and planning of drug-seeking or drug-avoiding behaviour."
While smokers were scanned in both an abstinent and non-abstinent state, this factor had less of an effect on brain activation levels when compared to expectancy. Aside from revealing this important characteristic of craving, Dr. Dagher says that "this study also has an impact on the treatment of nicotine addiction, as our research sheds light on the differences in people who can and can't control their will to smoke. People who quit smoking can expect to be exposed to other smokers, or to situations in which they previously smoked cigarettes. These exposures have an activating effect on the brain, which can lead to relapse. The prefrontal cortex plays a role in resisting such automatic behaviours. Not only did we find that expectant smokers are more susceptible to visual cues, but these findings also suggest that stress, alcohol or anything else that disrupts the pre-frontal cortex can predispose people to relapse."
Since exposure to drug-associated cues induces both subjective (ie craving) and behavioural (ie drug seeking) responses, and is thought to play a significant role in the maintenance of drug habits, this research may influence the development drug addiction therapy in the future.
This research is funded through the strategic initiative Advancing the Science to Reduce Tobacco Abuse and Nicotine Addiction in a partnership with Canadian Institutes of Health Research, Institutes of: Neurosciences, Mental Health and Addiction, Cancer Research, Aboriginal Peoples' Health, Circulatory and Respiratory Health, Gender and Health, Human Development Child and Youth Health; Canadian Cancer Society; National Cancer Institute of Canada; Heart and Stroke Foundation; Health Canada; Canadian Lung Association in partnership with l'Association pulmonaire du Québec. Co-ordination of the strategic initiative is provided by the Canadian Tobacco Control Research Initiative (CTCRI).