Institut National de la Santé et de la Recherche Médicale Unité 975, Centre National de la Recherche Scientifique Unité 7225, Groupe Hospitalier Pitié-Salpêtrière, Université Pierre et Marie Curie-Paris 6, Paris, France.
Biol Psychiatry. 2012 Aug 1;72(3):244-50. doi: 10.1016/j.biopsych.2011.12.028. Epub 2012 Feb 10.
The role of dopamine in reinforcement learning has been extensively studied, but the role of other major neuromodulators, particularly serotonin, remains poorly understood. An influential theory has suggested that dopamine and serotonin represent opponent systems respectively driving reward and punishment learning.
To test this theory, we compared two groups of patients with obsessive-compulsive disorder, one unmedicated (n = 12) and one treated with serotonin reuptake inhibitors (SRI; n = 13). To avoid confounding basic reinforcement learning with strategic conscious reasoning, we used a subliminal conditioning task that involves subjects learning to associate masked cues with gambling outcomes to maximize their payoff. The same task was used in a previous study to demonstrate opposite effects of dopaminergic medication on reward and punishment learning.
Unmedicated obsessive-compulsive disorder patients exhibited an instrumental learning deficit that was fully alleviated under SRI treatment. Contrary to dopaminergic medication, SRIs similarly modulated reward and punishment learning.
Thus, departing from the opponency model, our results support a beneficial role of serotonin in instrumental learning that is independent of outcome valence.
多巴胺在强化学习中的作用已经得到了广泛的研究，但其他主要神经调质的作用，特别是血清素的作用，仍知之甚少。一个有影响力的理论表明，多巴胺和血清素分别代表对立系统，分别驱动奖励和惩罚学习。
为了检验这一理论，我们比较了两组强迫症患者，一组未用药（n = 12），一组用选择性 5-羟色胺再摄取抑制剂（SSRI；n = 13）治疗。为了避免将基本强化学习与策略性有意识推理混淆，我们使用了一个阈下条件作用任务，其中涉及到受试者学习将掩蔽线索与赌博结果联系起来，以最大限度地提高他们的收益。在之前的一项研究中，同样的任务被用来证明多巴胺能药物对奖励和惩罚学习的相反影响。
未经治疗的强迫症患者表现出一种工具性学习缺陷，这种缺陷在 SRI 治疗下得到了完全缓解。与多巴胺能药物不同，SSRIs 同样调节奖励和惩罚学习。
因此，与对立模型相反，我们的结果支持血清素在工具性学习中的有益作用，这种作用与结果的效价无关。
