Dynamic Nigrostriatal Dopamine Biases Action Selection

Dopamine is thought to play a critical role in reinforcement learning and goal-directed behavior, but its function in action selection remains largely unknown. Here we demonstrate that nigrostriatal dopamine biases ongoing action selection. When mice were trained to dynamically switch the action selected at different time points, changes in firing rate of nigrostriatal dopamine neurons, as well as dopamine signaling in the dorsal striatum, were found to be associated with action selection. This dopamine profile is specific to behavioral choice, scalable with interval duration, and doesn’t reflect reward prediction error, timing, or value as single factors alone. Genetic deletion of NMDA receptors on dopamine or striatal neurons or optogenetic manipulation of dopamine concentration alters dopamine signaling and biases action selection. These results unveil a crucial role of nigrostriatal dopamine in integrating diverse information for regulating upcoming actions, and they have important implications for neurological disorders, including Parkinson’s disease and substance dependence. •Nigrostriatal dopamine signaling is associated with ongoing action selection•Dopamine signaling is necessary for appropriate action selection•Optogenetic manipulations can bidirectionally modulate online action selection•Modeling suggests dopamine could bias choice by modifying striatal activity Howard et al. recorded nigrostriatal dopamine signaling while animals dynamically altered their actions to retrieve rewards. They found that dopamine signaling is associated with action selection and that modulating dopamine biases the online action selection processes.