Kobiella Andrea, Ripke Stephan, Kroemer Nils B, Vollmert Christian, Vollstädt-Klein Sabine, Ulshöfer Dorothea E, Smolka Michael N
Neuroimaging Center, Department of Psychiatry, Technische Universität Dresden, Dresden, Germany; Department of Addictive Behavior and Addiction Medicine, Central Institute of Mental Health, University of Heidelberg, Mannheim, Germany.
Addict Biol. 2014 Sep;19(5):918-30. doi: 10.1111/adb.12057. Epub 2013 May 16.
Previous studies demonstrated higher discount rates for delayed rewards in smokers than non-smokers. We performed this study to determine whether those differences in intertemporal choice are due to pharmacological effects of nicotine and to track related brain regions. Thirty-three non-smokers and 27 nicotine-dependent smokers underwent functional magnetic resonance imaging while performing an intertemporal choice task consisting of 40 sets of monetary reward options that varied by delay to delivery. Smokers were investigated in a state of nicotine satiation. Non-smokers were investigated twice, receiving nicotine (2 mg) and placebo gums in a double-blinded, randomized cross-over design. Smokers displayed steeper temporal discounting than non-smokers. Those behavioural differences were reflected in the brain response during the decision between two alternative money/time pairs: smokers showed less activation in parietal and occipital areas (e.g. precuneus) than non-smokers under placebo. A single dose of nicotine in non-smokers led to a similar effect on brain activation but did not impact behaviour. Processing of the reward magnitude of money/time pairs differed between smokers and non-smokers: smokers showed decreased reactivity of the ventral striatum. Moreover, there was an acute nicotine effect in non-smokers on processing of the reward magnitude: nicotine increased the correlation of blood oxygen level-dependent response and mean amount in the left hippocampus, amygdala and anterior insula. We conclude that cross-sectional differences between smokers and non-smokers are only, in part, due to the acute pharmacological effects of nicotine. Longitudinal studies are needed to investigate pre-drug group characteristics as well as consequences of smoking on discounting behaviour and its neural correlates.
先前的研究表明，吸烟者对延迟奖励的折扣率高于非吸烟者。我们进行这项研究是为了确定跨期选择中的这些差异是否归因于尼古丁的药理作用，并追踪相关脑区。33名非吸烟者和27名尼古丁依赖吸烟者在进行一项跨期选择任务时接受了功能磁共振成像，该任务由40组货币奖励选项组成，奖励根据交付延迟而有所不同。吸烟者在尼古丁饱和状态下接受调查。非吸烟者接受了两次调查，在双盲、随机交叉设计中分别接受尼古丁（2毫克）和安慰剂口香糖。吸烟者表现出比非吸烟者更陡峭的时间折扣。这些行为差异反映在两种替代金钱/时间对之间的决策过程中的大脑反应中：在安慰剂作用下，吸烟者在顶叶和枕叶区域（如楔前叶）的激活程度低于非吸烟者。非吸烟者单次服用尼古丁对大脑激活产生了类似的影响，但并未影响行为。吸烟者和非吸烟者在处理金钱/时间对的奖励幅度方面存在差异：吸烟者腹侧纹状体的反应性降低。此外，非吸烟者在处理奖励幅度时存在急性尼古丁效应：尼古丁增加了左海马、杏仁核和前岛叶中血氧水平依赖反应与平均金额之间的相关性。我们得出结论，吸烟者和非吸烟者之间的横断面差异仅部分归因于尼古丁的急性药理作用。需要进行纵向研究来调查用药前的组特征以及吸烟对折扣行为及其神经相关性的影响。
