Neural mechanisms underlying uninstructed orofacial movements during reward-based learning behaviors.

During reward-based learning tasks, animals make orofacial movements that globally influence brain activity at the timings of reward expectation and acquisition. These orofacial movements are not explicitly instructed and typically appear along with goal-directed behaviors. Here, we show that reinforcing optogenetic stimulation of dopamine neurons in the ventral tegmental area (oDAS) in mice is sufficient to induce orofacial movements in the whiskers and nose without accompanying goal-directed behaviors. Pavlovian conditioning with a sensory cue and oDAS elicited cue-locked and oDAS-aligned orofacial movements, which were distinguishable by a machine-learning model. Inhibition or knockout of dopamine D1 receptors in the nucleus accumbens inhibited oDAS-induced motion but spared cue-locked motion, suggesting differential regulation of these two types of orofacial motions. In contrast, inactivation of the whisker primary motor cortex (wM1) abolished both types of orofacial movements. We found specific neuronal populations in wM1 representing either oDAS-aligned or cue-locked whisker movements. Notably, optogenetic stimulation of wM1 neurons successfully replicated these two types of movements. Our results thus suggest that accumbal D1-receptor-dependent and -independent neuronal signals converge in the wM1 for facilitating distinct uninstructed orofacial movements during a reward-based learning task. [Display omitted] • Optogenetic stimulation of VTA-DA neurons (oDAS) elicits orofacial movement • Cue-oDAS association induces distinct cue-locked and oDAS-aligned orofacial actions • Accumbal D1Rs mediate oDAS-aligned, but not cue-locked, motion • Different neuronal signals converge in wM1, triggering unique orofacial movements Investigating how mice display differential orofacial movements during reward anticipation and acquisition, Li and Nakano et al. highlight the pivotal role of the whisker primary motor cortex. It channels distinct neuronal signals—some via the mesolimbic dopamine pathway, others bypassing it—to facilitate unique orofacial actions. [ABSTRACT FROM AUTHOR]