The causal contributions of medial prefrontal cortex to value-based decisions in mice

Learning from experience is essential to the optimization of behavior. In particular, we learn from past choices and outcomes to infer the predicted values of the actions to be taken. Then based on the values, we may select an informed choice. However, despite the many neural correlates identified, we still do not have a clear picture for how values are computed and translated into informed behavior. Here, we trained head-fixed mice to perform a two-armed bandit task. Animals based their decisions on past choices and reinforcements, consistent with having an internal representation of action values. To determine the causal contributions of the medial prefrontal cortex, we tested the animals before and after an excitotoxic lesion of the medial secondary motor cortex (M2). We found that unilateral M2 lesion led to side-specific effects on the animal’s ability to learn from past choices. To quantify the decision-making process, we fitted the animal’s choice behavior with Q-learning models to extract learning parameters such as learning rate, forgetting rate, and inverse temperature. Altogether, the results provide insights into the causal involvement of mouse mM2 in value-based decision making.