Smoking and brain laterality: Identification of nicotine´s effects on functional brain asymmetry and stress reduction

Although cigarette smoking is a well established risk factor for several serious diseases, most people find it difficult to quit. There may be individual differences in motives for smoking and in the situational cues that elicit smoking, but cessation seems to be especially difficult for those who tend to smoke for nicotine`s physiological effects in the management of stress and negative mood. In order to understand nicotine`s potential of addiction and to help highly nicotine-dependent smokers quit, it is essential to investigate both the psychologically relevant neurophysiological effects of smoking and the activation patterns in the brain which are associated with unpleasant emotional states or an individual`s vulnerability to certain types of emotions. There is evidence in the literature that a biopsychological link between these two aspects might be provided by laterality research. Following this new approach, the relevance of functional hemispheric asymmetries and specific asymmetrical activation patterns in the brain to smoking and it`s reinforcing effects will be investigated. Since nicotine seems to have the potential to produce various, partly antagonistic psychological effects, it seems important to determine those neurophysiological effects that help to maintain the habit in a certain individual. At present, appropriate and standardized instruments for assessing smoker-types do not exist. A first aim, therefore, will be to reliably type smokers using psychologically and neurophysiologically relevant categories. Differences between different types of smokers and between smokers and non-smokers in trait characteristics of cerebral laterality will then be investigated. For assessing laterality both behavioural and electrophysiological measures (EEG) will be applied. In addition to that, changes of laterality patterns that will be induced by smoking and smoking-abstinence will be investigated. Finally, specific changes of laterality patterns will be identified in different types of smokers and in non-smokers that will be induced by stress. The linkage of findings about laterality patterns related to smoking and abstinence on the one hand and emotions/stress on the other hand may provide an essential impulse for the understanding of nicotine`s reinforcing effects, at least in smoker-types smoking for the anxiety-reducing or calming effects of nicotine.

Although cigarette smoking is a well established risk factor for several serious diseases, most people find it difficult to quit. There may be individual differences in motives for smoking and in the situational cues that elicit smoking, but most smokers tend to smoke for nicotine`s physiological effects in the management of stress and negative mood. These mood enhancing and relaxing effects of nicotine are probably essential for its potential of addiction. One goal of the research project was to investigate to which changes in the brain the improvement of mood and, therefore, nicotine`s potential of addiction, can be attributed. Special attention was focused on differences in the activity of the left and right halves of the brain. An important part of the findings demonstrates that spontaneously occurring changes of left-right asymmetry in the most anterior (i.e., frontopolar) regions of the cerebral cortex are related to state-dependent changes of mood. Positive and relaxed mood was found to increase when frontopolar activation asymmetry shifted to the right. When frontopolar activation asymmetry shifted to the left, mood was worse. One of the main findings of the research project is that when smokers do not smoke for one hour, the left frontopolar cortex becomes more activated than the right, even after this short period of abstinence. Smoking a cigarette results in an asymmetry shift to the right, that is, in a relatively stronger activation of the right frontopolar cortex. This effect is stronger in heavy smokers than in light smokers. The shift of activity in the frontopolar cortex may explain the mood enhancing and relaxing effects of nicotine. The linkage of findings about specific and characteristic changes of activation patterns in the brain related to smoking and abstinence on the one hand and mood changes on the other hand helps to understand nicotine`s reinforcing and, therefore, addictive effects, at least in smokers smoking for the mood enhancing or calming effects of nicotine. In future, this understanding may contribute to the development of successful and innocuous methods to help highly nicotine-dependent smokers quit.