title: Amygdala and Ventral Striatum Make Distinct Contributions to Reinforcement Learning.
abstract: Reinforcement learning (RL) theories posit that dopaminergic signals are integrated within the striatum to associate choices with outcomes. Often overlooked is that the amygdala also receives dopaminergic input and is involved in Pavlovian processes that influence choice behavior. To determine the relative contributions of the ventral striatum (VS) and amygdala to appetitive RL, we tested rhesus macaques with VS or amygdala lesions on deterministic and stochastic versions of a two-arm bandit reversal learning task. When learning was characterized with an RL model relative to controls, amygdala lesions caused general decreases in learning from positive feedback and choice consistency. By comparison, VS lesions only affected learning in the stochastic task. Moreover, the VS lesions hastened the monkeys' choice reaction times, which emphasized a speed-accuracy trade-off that accounted for errors in deterministic learning. These results update standard accounts of RL by emphasizing distinct contributions of the amygdala and VS to RL.
authors.affiliation: Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-4415, USA. Electronic address: vincent.costa@nih.gov.
authors.forename: Vincent D
authors.initials: VD
authors.lastname: Costa
authors.affiliation: Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-4415, USA.
authors.forename: Olga
authors.initials: O
authors.lastname: Dal Monte
authors.affiliation: Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-4415, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Lucas
authors.affiliation: Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-4415, USA.
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Murray
authors.affiliation: Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-4415, USA.
authors.forename: Bruno B
authors.initials: BB
authors.lastname: Averbeck
mesh_terms: D000679:Amygdala / Q000502:physiology*; D000818:Animals; D001499:Bayes Theorem; D002755:Choice Behavior / Q000502:physiology*; D003657:Decision Making / Q000502:physiology; D000068156:Formative Feedback; D007858:Learning / Q000502:physiology; D016015:Logistic Models; D008253:Macaca mulatta; D008297:Male; D011930:Reaction Time; D012054:Reinforcement, Psychology; D012193:Reversal Learning / Q000502:physiology*; D012201:Reward; D066328:Ventral Striatum / Q000502:physiology*
keywords: Bayesian; Pearce-Hall; Rescorla-Wagner; amygdala; associability; decision making; lesion; reinforcement learning; speed-accuracy trade-off; ventral striatum