Role of rodent secondary motor cortex in value-based action selection

Despite widespread neural activity related to reward values, signals related to upcoming choice have not been clearly identified in the rodent brain. Here, we examined neuronal activity in the lateral (AGl) and medial (AGm) agranular cortex, corresponding to the primary and secondary motor cortex, respectively, in rats performing a dynamic foraging task. Choice signals arose in the AGm before behavioral manifestation of the animal’s choice earlier than in any other areas of the rat brain previously studied under free-choice conditions. The AGm also conveyed significant neural signals for decision value and chosen value. In contrast, upcoming choice signals arose later and value signals were weaker in the AGl. We also found that AGm lesions made the animal’s choices less dependent on dynamically updated values. These results suggest that rodent secondary motor cortex might be uniquely involved in both representing and reading out value signals for flexible action selection.