We found that mice learned to press a lever that delivered photostimulation exciting the terminals of mPFC neurons within the anteromedial thalamic nucleus (mPFC-to-AM neurons). Mice also learned to deliver photostimulation exciting AM neurons or exciting the terminals of AM neurons in the mPFC (AM-to-mPFC neurons). These results suggest that the activation of mPFC-to-AM or AM-to-mPFC neurons elicits reward that triggers anticipatory behavior. Ex-vivo electrophysiology revealed that photostimulation of mPFC-to-AM neurons excited AM-to-mPFC neurons and that photostimulation of AM-to-mPFC neurons excited mPFC-to-AM neurons, suggesting that mPFC neurons organize a positive feedback loop with AM neurons. Together, these results suggest that AM neurons are reciprocally connected with mPFC neurons, forming a functional loop for regulating motivation of anticipatory behavior.
