Department of Experimental Psychology, University of Cambridge, Cambridge, England.
Neuropsychopharmacology. 2012 Sep;37(10):2244-52. doi: 10.1038/npp.2012.75. Epub 2012 May 30.
Updated theoretical accounts of the role of serotonin (5-HT) in motivation propose that 5-HT operates at the intersection of aversion and inhibition, promoting withdrawal in the face of aversive predictions. However, the specific cognitive mechanisms through which 5-HT modulates withdrawal behavior remain poorly understood. Behavioral inhibition in response to punishments reflects at least two concurrent processes: instrumental aversive predictions linking stimuli, responses, and punishments, and Pavlovian aversive predictions linking stimuli and punishments irrespective of response. In the current study, we examined to what extent 5-HT modulates the impact of instrumental vs Pavlovian aversive predictions on behavioral inhibition. We used acute tryptophan depletion to lower central 5-HT levels in healthy volunteers, and observed behavior in a novel task designed to measure the influence of Pavlovian and instrumental aversive predictions on choice (response bias) and response vigor (response latencies). After placebo treatment, participants were biased against responding on the button that led to punishment, and they were slower to respond in a punished context, relative to a non-punished context. Specifically, participants slowed their responses in the presence of stimuli predictive of punishments. Tryptophan depletion removed the bias against responding on the punished button, and abolished slowing in the presence of punished stimuli, irrespective of response. We suggest that this set of results can be explained by a role for 5-HT in Pavlovian aversive predictions. These findings suggest additional specificity for the influence of 5-HT on aversively motivated behavioral inhibition and extend recent models of the role of 5-HT in aversive predictions.
更新的关于 5-羟色胺（5-HT）在动机中的作用的理论观点提出，5-HT 在厌恶和抑制的交叉点起作用，促进在面临厌恶预测时的撤退。然而，5-HT 调节撤退行为的具体认知机制仍知之甚少。对惩罚的行为抑制至少反映了两个并发过程：将刺激、反应和惩罚联系起来的工具性厌恶预测，以及将刺激和惩罚联系起来而与反应无关的条件性厌恶预测。在当前的研究中，我们研究了 5-HT 在多大程度上调节了工具性与条件性厌恶预测对行为抑制的影响。我们使用急性色氨酸耗竭来降低健康志愿者的中枢 5-HT 水平，并观察了一项新任务中的行为，该任务旨在衡量条件性和工具性厌恶预测对选择（反应偏差）和反应活力（反应潜伏期）的影响。在安慰剂治疗后，参与者对导致惩罚的按钮的反应有偏差，并且在惩罚环境中反应速度较慢，相对于非惩罚环境。具体来说，参与者在有预测惩罚的刺激物存在的情况下减缓了反应。色氨酸耗竭消除了对受惩罚按钮的反应偏差，并消除了在有受惩罚的刺激物存在的情况下的减速，而与反应无关。我们认为，这组结果可以用 5-HT 在条件性厌恶预测中的作用来解释。这些发现表明 5-HT 对厌恶动机行为抑制的影响具有更大的特异性，并扩展了 5-HT 在厌恶预测中的作用的最新模型。
