The striatal dopaminergic system has been implicated in reinforcement learning (RL), motor performance, and incentive motivation. Various computational models have been proposed to account for each of these effects individually, but a formal analysis of their interactions is lacking. Here we present a novel algorithmic model expanding the classical actor-critic architecture to include fundamental interactive properties of neural circuit models, incorporating both incentive and learning effects into a single theoretical framework. The standard actor is replaced by a dual opponent actor system representing distinct striatal populations, which come to differentially specialize in discriminating positive and negative action values. Dopamine modulates the degree to which each actor component contributes to both learning and choice discriminations. In contrast to standard frameworks, this model simultaneously captures documented effects of dopamine on both learning and choice incentive-and their interactions-across a variety of studies, including probabilistic RL, effort-based choice, and motor skill learning.Keywords: dopamine, striatum, reinforcement learning, choice incentive, computational model Dopamine plays a crucial role in human and animal cognition, substantially influencing a diversity of processes including reinforcement learning, motivation, incentive, working memory, and effort. Dopaminergic neurons in the substantial nigra and ventral tegmental area project to a very wide set of subcortical and cortical areas, with strongest innervation in the basal ganglia (BG), specifically in the ventral and dorsal striatum. Dysregulation of dopamine is present in a wide array of mental illnesses such as Parkinson's disease, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, and Tourette's syndrome and is a central pharmaceutical target used to treat symptoms across these and numerous other pathologies.Although considerable progress has been made in our understanding of its various distinct roles, there remain fundamental debates concerning its precise mechanisms and functions, especially regarding their integration and interactions. In reward-based decision making in particular, two largely separate traditions have studied the reinforcement learning and the incentive theories of dopamine (Berridge, 2007). Despite solid evidence for both theories, theoretical and empirical studies tend to favor and focus on one or the other interpretation, with little attempt to unify them or to study their interaction. Here we develop an explicit computational analysis of the dual role of striatal dopamine in modulation of incentive motivation (affecting choice), reinforcement learning, and how these processes interact. This endeavor allows us not only to account for both types of findings alone but also those that could not be explained by either theory in isolation.
RL Theory of DopamineOne widely accepted theory of dopamine function relates to its role in model-free reinforcement learning (RL). Specifically, phasic f...