Secondary motor cortex tracks decision value and supports behavioral flexibility during non-instructed choice

Optimal decision-making relies on interconnected frontal brain regions, which permit animals to adapt their decisions based on their internal state, experience, and environmental context. Among them, the secondary motor cortex (M2) shows earlier decision-related activity required for sensory-guided action selection. However, the role of M2 in adaptive decision-making in the absence of instructive sensory cues remains unclear. Under such conditions, action-selection relies on abstract representations of actions and their values. Using in vivo microscopy and modeling, we showed that M2 neurons in mice exhibited persistent activity encoding decision values (DV) predicting the probability of action-selection during a non-cue-guided lever task. This was confirmed by the reduced reversal performance upon M2 optogenetic inhibition prior to action-selection. Furthermore, updates in DV determined the rate at which learning is reversed. Together, these results provide strong evidence of the use of DV by M2 to adapt choice in the absence of instructive sensory cues.