Mediodorsal thalamus nucleus–medial prefrontal cortex circuitry regulates cost–benefit decision-making selections

Value-based decision-making involves weighing costs and benefits. The activity of the medial prefrontal cortex reflects cost-benefit assessments, and the mediodorsal thalamus, reciprocally connected with the medial prefrontal cortex, has increasingly been recognized as an active partner in decision-making. However, the specific role of the interaction between the mediodorsal thalamus and the medial prefrontal cortex in regulating the neuronal activity underlying how costs and benefits influence decision-making remains largely unexplored. We investigated this by training the rats to perform a self-determined decision-making task, where longer nose poke durations resulted in correspondingly larger rewards. Our results showed that the inactivation of either the medial prefrontal cortex or the mediodorsal thalamus significantly impaired rat to invest more nose poke duration for larger rewards. Moreover, optogenetic stimulation of the mediodorsal thalamus-medial prefrontal cortex pathway enhanced rats' motivation for larger rewards, whereas inhibition of this pathway resulted in decreased motivation. Notably, we identified a specific population of neurons in the medial prefrontal cortex that exhibited firing patterns correlated with motivation, and these neurons were modulated by the mediodorsal thalamus-medial prefrontal cortex projection. These findings suggest that the motivation during decision-making is encoded primarily by activity of particular neurons in the medial prefrontal cortex and indicate the crucial role of the mediodorsal thalamus-medial prefrontal cortex pathway in maintaining motivation.