human nonsmokers have not yet been reported, and would be important for a more complete understanding of the effects of tobacco on brain activity. While this group of studies demonstrates specific regional activation with nicotine or smoking, they also imply activation of cortico–basal ganglia–thalamic brain circuits (Alexander et al. 1990) that mediate the subjective effects of smoking (see Sect. 4). Zubieta et al. (2005) have conducted a 15O-PET study in 19 smokers using nicotine and denicotinized cigarettes, who were abstinent of smoking for 12 h before PET. In this study, increases in the regional cerebral blood flow (rCBF) in visual cortex and cerebellum, and reductions in rCBF in the anterior cingulate, the right hippocampus, and ventral striatum were found. Cigarette craving in chronic smokers also was correlated with rCBF in the right hippocampus, which is a region involved in associating environmental cues with drugs, and in the left dorsal anterior cingulate, an area implicated in drug craving and relapse to drug-seeking behavior.
