Research Clinic on Gambling Disorders, Aarhus University Hospital, Nørrebrogade 44, Building 30, DK-8000 Aarhus C, Denmark.
Psychiatry Res. 2012 Oct 30;204(1):55-60. doi: 10.1016/j.pscychresns.2012.04.012. Epub 2012 Aug 11.
Two mechanisms of midbrain and striatal dopaminergic projections may be involved in pathological gambling: hypersensitivity to reward and sustained activation toward uncertainty. The midbrain-striatal dopamine system distinctly codes reward and uncertainty, where dopaminergic activation is a linear function of expected reward and an inverse U-shaped function of uncertainty. In this study, we investigated the dopaminergic coding of reward and uncertainty in 18 pathological gambling sufferers and 16 healthy controls. We used positron emission tomography (PET) with the tracer [(11)C]raclopride to measure dopamine release, and we used performance on the Iowa Gambling Task (IGT) to determine overall reward and uncertainty. We hypothesized that we would find a linear function between dopamine release and IGT performance, if dopamine release coded reward in pathological gambling. If, on the other hand, dopamine release coded uncertainty, we would find an inversely U-shaped function. The data supported an inverse U-shaped relation between striatal dopamine release and IGT performance if the pathological gambling group, but not in the healthy control group. These results are consistent with the hypothesis of dopaminergic sensitivity toward uncertainty, and suggest that dopaminergic sensitivity to uncertainty is pronounced in pathological gambling, but not among non-gambling healthy controls. The findings have implications for understanding dopamine dysfunctions in pathological gambling and addictive behaviors.
对奖励的过度敏感和对不确定性的持续激活。中脑-纹状体多巴胺系统明显编码奖励和不确定性，其中多巴胺能激活是预期奖励的线性函数，是不确定性的倒 U 形函数。在这项研究中，我们调查了 18 名病理性赌博患者和 16 名健康对照者的奖励和不确定性的多巴胺编码。我们使用正电子发射断层扫描（PET）和示踪剂[11C]raclopride来测量多巴胺的释放，我们使用爱荷华赌博任务（IGT）来确定整体奖励和不确定性。我们假设，如果多巴胺释放编码病理性赌博中的奖励，我们会发现多巴胺释放和 IGT 表现之间存在线性关系。另一方面，如果多巴胺释放编码不确定性，我们会发现倒 U 形关系。如果是病理性赌博组，而不是健康对照组，那么纹状体多巴胺释放和 IGT 表现之间存在倒 U 形关系。这些结果与多巴胺对不确定性敏感的假设一致，表明病理性赌博者对不确定性的多巴胺敏感性明显增强，而非赌博健康对照组则不然。这些发现对于理解病理性赌博和成瘾行为中的多巴胺功能障碍具有重要意义。
