Evidence for a hijacked brain reward system but no desensitized threat system in quitting motivated smokers: An fMRI study.

Abstract

BACKGROUND AND AIMS\nSeveral aspects of how quitting motivated tobacco use disorder (TUD) subjects and never-smokers differ in terms of reward and threat processing remain unresolved. We aimed to examine aberrant reward and threat processes in TUD and the association with smoking characteristics.\n\n\nDESIGN\nA between- and within-subjects fMRI experiment with a 2 (groups) x 4 (stimulus type) factorial design. The experimental paradigm had four conditions: pictures of 1) cigarettes served as drug-related positive cues, 2) food as alternative reward cues, 3) long-term consequences of smoking as drug-related negative cues, and 4) neutral pictures as control.\n\n\nSETTING/PARTICIPANTS\nAdult participants (n = 38 TUD subjects & n = 42 never-smokers) were recruited in Berlin, Germany.\n\n\nMEASUREMENTS\nAs contrasts of primary interest, the interactions of group-by-stimulus-type were assessed. Significance threshold correction for multiple testing was carried out with the family wise error method. Correlation analyses were used to test the association with smoking characteristics.\n\n\nFINDINGS\nThe 2x2 interaction of smoking status and stimulus type revealed activations in the brain reward system to drug-related positive cues in TUD subjects (between-subjects effect: P-values ≤ 0.036). As response to drug-related negative cues, TUD subjects showed no reduced activation of the aversive brain network. Within the TUD group, a significant negative association was found between response of the aversive brain system to drug-related negative cues (within-subjects effect: P-values ≤ 0.021) and the number of cigarettes smoked per day (right insula r = -0.386, p = 0.024; left insula r = -0.351, p = 0.042; right ACC r = -0.359, p = 0.037).\n\n\nCONCLUSIONS\nModerate smokers with tobacco use disorder appear to have altered brain reward processing of drug-related positive (but not negative) cues compared with never smokers.