Department of Psychology and Neuroscience,
Center for Cognitive Neuroscience.
J Neurosci. 2019 Jan 9;39(2):321-332. doi: 10.1523/JNEUROSCI.1984-18.2018. Epub 2018 Nov 16.
Some people are more willing to make immediate, risky, or costly reward-focused choices than others, which has been hypothesized to be associated with individual differences in dopamine (DA) function. In two studies using PET imaging, one empirical (Study 1: = 144 males and females across 3 samples) and one meta-analytic (Study 2: = 307 across 12 samples), we sought to characterize associations between individual differences in DA and time, probability, and physical effort discounting in human adults. Study 1 demonstrated that individual differences in DA D2-like receptors were not associated with time or probability discounting of monetary rewards in healthy humans, and associations with physical effort discounting were inconsistent across adults of different ages. Meta-analytic results for temporal discounting corroborated our empirical finding for minimal effect of DA measures on discounting in healthy individuals but suggested that associations between individual differences in DA and reward discounting depend on clinical features. Addictions were characterized by negative correlations between DA and discounting, but other clinical conditions, such as Parkinson's disease, obesity, and attention-deficit/hyperactivity disorder, were characterized by positive correlations between DA and discounting. Together, the results suggest that trait differences in discounting in healthy adults do not appear to be strongly associated with individual differences in D2-like receptors. The difference in meta-analytic correlation effects between healthy controls and individuals with psychopathology suggests that individual difference findings related to DA and reward discounting in clinical samples may not be reliably generalized to healthy controls, and vice versa. Decisions to forgo large rewards for smaller ones due to increasing time delays, uncertainty, or physical effort have been linked to differences in dopamine (DA) function, which is disrupted in some forms of psychopathology. It remains unclear whether alterations in DA function associated with psychopathology also extend to explaining associations between DA function and decision making in healthy individuals. We show that individual differences in DA D2 receptor availability are not consistently related to monetary discounting of time, probability, or physical effort in healthy individuals across a broad age range. By contrast, we suggest that psychopathology accounts for observed inconsistencies in the relationship between measures of DA function and reward discounting behavior.
有些人比其他人更愿意做出即时、冒险或高成本的以奖励为导向的选择，这被假设与多巴胺（DA）功能的个体差异有关。在两项使用 PET 成像的研究中，一项是实证研究（研究 1：来自 3 个样本的 144 名男性和女性），一项是元分析研究（研究 2：来自 12 个样本的 307 名参与者），我们试图描述人类成年人中多巴胺个体差异与时间、概率和体力努力折扣之间的关联。研究 1 表明，DA D2 样受体的个体差异与健康人类对金钱奖励的时间或概率折扣无关，并且与体力努力折扣的关联在不同年龄的成年人中不一致。关于时间折扣的元分析结果证实了我们在健康个体中 DA 测量对折扣影响较小的实证发现，但表明 DA 个体差异与奖励折扣之间的关联取决于临床特征。成瘾者的特征是 DA 与折扣之间存在负相关，而其他临床情况，如帕金森病、肥胖和注意力缺陷多动障碍，的特征是 DA 与折扣之间存在正相关。总的来说，这些结果表明，健康成年人的折扣特质差异似乎与 D2 样受体的个体差异没有很强的相关性。元分析相关性效应在健康对照组和精神病理学个体之间的差异表明，与临床样本中 DA 和奖励折扣相关的个体差异发现可能无法可靠地推广到健康对照组，反之亦然。由于时间延迟、不确定性或体力消耗的增加而放弃大奖励以获得小奖励的决策与多巴胺（DA）功能的差异有关，而一些形式的精神病理学则会破坏这种功能。目前尚不清楚与精神病理学相关的 DA 功能改变是否也扩展到解释健康个体中 DA 功能与决策之间的关联。我们表明，在广泛的年龄范围内，DA D2 受体可用性的个体差异与健康个体的时间、概率或体力努力的货币折扣并不一致。相比之下，我们认为精神病理学解释了 DA 功能测量与奖励折扣行为之间关系的不一致。
