The role of serotonin in human brain function remains elusive due, at least in part, to our inability to measure rapidly the local concentration of this neurotransmitter. We used fast-scan cyclic voltammetry to infer serotonergic signaling from the striatum of 14 brains of human patients with Parkinson's disease. Here we report these novel measurements and show that they correlate with outcomes and decisions in a sequential investment game. We find that serotonergic concentrations transiently increase as a whole following negative reward prediction errors, while reversing when counterfactual losses predominate. This provides initial evidence that the serotonergic system acts as an opponent to dopamine signaling, as anticipated by theoretical models. Serotonin transients on one trial were also associated with actions on the next trial in a manner that correlated with decreased exposure to poor outcomes. Thus, the fluctuations observed for serotonin appear to correlate with the inhibition of over-reactions and promote persistence of ongoing strategies in the face of short-term environmental changes. Together these findings elucidate a role for serotonin in the striatum, suggesting it encodes a protective action strategy that mitigates risk and modulates choice selection particularly following negative environmental events.

中文翻译：

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5-羟色胺瞬态在人脑中的保护作用编码。

血清素在人脑功能中的作用仍然难以捉摸，至少部分是由于我们无法快速测量这种神经递质的局部浓度。我们使用快速扫描循环伏安法从帕金森氏病患者的14个大脑纹状体推断血清素能信号。在这里，我们报告这些新颖的度量，并显示它们与顺序投资博弈中的结果和决策相关。我们发现，继阴性奖励预测误差后，血清素能浓度总体上会暂时增加，而反事实性损失占主导时则逆转。如理论模型所预期的，这提供了血清素能系统充当多巴胺信号传导的对手的初步证据。一项试验中的5-羟色胺瞬态也与下一项试验中的行动相关联，其方式与减少不良结果的暴露相关。因此，针对5-羟色胺观察到的波动似乎与过度反应的抑制相关，并在面对短期环境变化时促进正在进行的策略的持久性。这些发现共同阐明了5-羟色胺在纹状体中的作用，表明它编码了一种保护作用策略，可以减轻风险并调节选择的选择，尤其是在负面环境事件之后。