Phasic Responses of Mesolimbic Dopamine Neurons are Recruited in Parallel to Sensorimotor Pathways Mediating Cued Approach

Abstract

Sensory cues that predict the availability of a reward acquire predictive (expected value) and incentive (drive reward-seeking action) properties. Midbrain dopaminergic (mDA) neurons respond to sensory cues with a that correlates with both expected value and reward-seeking action. This has led to the proposal that phasic mDA responses to cues may inform value-based decisions, elicit actions, and/or induce motivational states; however, causal tests of these possibilities are incomplete and it remains unclear whether these diverse effects are functionally dissociable. Here, we found that direct mDA neuron stimulation, both calibrated to physiological responses and at greater intensity/duration, can be sufficient to reinforce action while not being sufficient to elicit reward-seeking in trained mice. mDA neuron stimulation fails to be efficiently acquired as a reward-predictive nor discriminative cue. In contrast, the same stimulation of descending neocortical inputs to mDA neurons is both reinforcing and sufficient to act as a predictive cue. These data argue that physiological activation of mDA neurons by reward-predictive cues is recruited in parallel to descending sensorimotor pathways that couple sensory cues to reward-seeking action.