Abstract
1116
Objectives: We are often attracted by novel visual stimuli, even in the absence of narrative meaning. In order to understand the underlying mechanisms, we examined whether the dopaminergic system is involved in attention to novel visual stimuli in humans. A videotaped depiction of individuals using drug paraphernalia and cocaine served as the novel visual stimulus for drug-naïve subjects. Methods: Fifteen young adults (age: 30.8 ± 9.1) underwent two bolus-injection [11C]raclopride PET scans while viewing videotapes of natural (Scan 1) and drug-usage (Scan 2) scenes. Subjects were cognitively intact and reported no history of drug abuse. Binding potential (BP) maps were constructed using the bolus-plus-infusion transformation method (Kuwabara, et al., 2002). Each BP map was spatially normalized to a standard brain and smoothed with a 10 mm Gaussian kernel using SPM2. BP maps of Scan 1 were contrasted to BP maps of Scan 2 using SPM2 to identify regions showing significant decreases in BP. Results: The SPM analysis revealed one cluster of decreased BP in right anterior putamen at a p<0.05 level with false-discovery-rate (FDR) and requirement of a minimum cluster volume of 0.8 ml (100 voxels). The peak T value was 8.92 (Z = 5.08) at [24, 16, 2], Talairach coordinates, and the cluster volume was 1.0 ml (125 voxels). No clusters were found on the left striatum even at p<0.001, uncorrected level. No subjects reported drug craving during the two PET sessions. Conclusions: This study indicated that viewing the videotaped depiction of novel cocaine-related stimuli induced an increase in endogenous dopamine (DA) in right anterior putamen in healthy, drug-naive subjects without causing craving for the drug. Cocaine abusers who reported drug craving while viewing the same videotape showed a cluster close in space to the current cluster, compared to abusers without craving (Wong, et al., 2006). These two studies suggested the DA release may relate not only to cue-induced craving in abusers but also to attention in non-abusers. Further studies will be required to examine whether non-abusers and craving abusers have distinct mechanisms, or share one mechanism for the increased endogenous DA.
Research Support (if any): AA12839; MH078175; K24 DA00412 (DFW)
- Society of Nuclear Medicine, Inc.