An opponent striatal circuit for distributional reinforcement learning

• 成果类型: Article
• 署名作者: Lowet, Adam S.; Zheng, Qiao; Meng, Melissa; Matias, Sara; Drugowitsch, Jan; Uchida, Naoshige
• 署名单位: Harvard University; Harvard University; Harvard University; Harvard University; Harvard Medical School
• 刊物名称: Nature
• ISSN/ISSBN: 0028-2570
• DOI: 10.1038/s41586-024-08488-5
• 发表日期: 2025-03-20
• 关键词: neural variability; nucleus-accumbens; dopamine release; cre-recombinase; distinct roles; neurons; reward; pathways; RISK; CLASSIFICATION

摘要

Machine learning research has achieved large performance gains on a wide range of tasks by expanding the learning target from mean rewards to entire probability distributions of rewards-an approach known as distributional reinforcement learning (RL)1. The mesolimbic dopamine system is thought to underlie RL in the mammalian brain by updating a representation of mean value in the striatum2, but little is known about whether, where and how neurons in this circuit encode information about higher-order moments of reward distributions3. Here, to fill this gap, we used high-density probes (Neuropixels) to record striatal activity from mice performing a classical conditioning task in which reward mean, reward variance and stimulus identity were independently manipulated. In contrast to traditional RL accounts, we found robust evidence for abstract encoding of variance in the striatum. Chronic ablation of dopamine inputs disorganized these distributional representations in the striatum without interfering with mean value coding. Two-photon calcium imaging and optogenetics revealed that the two major classes of striatal medium spiny neurons-D1 and D2-contributed to this code by preferentially encoding the right and left tails of the reward distribution, respectively. We synthesize these findings into a new model of the striatum and mesolimbic dopamine that harnesses the opponency between D1 and D2 medium spiny neurons4, 5, 6, 7, 8-9 to reap the computational benefits of distributional RL.