The researchers used functional MRI (Magnetic Resonance Imaging) to perform tasks and record brain activity over time. The tasks were designed to test impulse control, the ability to shift focus away from smoking-related images, and the ability to observe one's own behavior.

The results showed that there were large differences in brain activity during the tasks depending on whether you were a smoker, a former smoker or had never smoked. Smokers had lower activity than non-smokers in the areas in the front of the brain that are responsible for our impulse control. At the same time, smokers had increased activity in deeper brain areas that are linked to the reward effects of, for example, nicotine.

The people who had stopped smoking were distinguished partly by not having any such activity in deeper parts of the brain and partly by high activity in the impulse and behavior control areas. They even had higher activity than the never-smokers in these control areas. The researchers believe that this can be said to reflect, among other things, the willpower of the former smokers. They also emphasize that their results show how important it is that smoking cessation methods include efforts to support and train the abilities needed to take control of the drug craving.

The study has been published online pending print in the scientific journal Neuroimage.