Prelimbic neuron assemblies with delayed activation encode the economic decision-making process in a bandit game.

The medial prefrontal cortex (mPFC) is critical to an animal's value-based decision-making process. However, due to heterogeneity of local mPFC neurons, which neuron group and how it contributes to the alteration of the animal's decision is yet to be explored. And the effect of empty reward in this process is often neglected. Here, we adopted a two-port bandit game paradigm for mice and applied synchronized calcium imaging to the prelimbic area of the mPFC. The results showed that neurons recruited in the bandit game exhibit three distinct firing patterns. Specially, neurons with delayed activation (deA neurons1) carried exclusive information on reward type and changes of choice value. We demonstrated that these deA neurons were essential for the construction of choice-outcome correlation and the trial-to-trial modification of decision. Additionally, we found that in a long-term gambling game, members of the deA neuron assembly were dynamically shifting while maintaining the function, and the importance of empty reward feedbacks were gradually elevated to the same level as reward. Together, these results revealed a vital role for prelimbic deA neurons in the gambling tasks and a new perspective on the encoding of economic decision-making.