Integration of value and action in medial prefrontal neural systems

Abstract

The rodent medial prefrontal cortex (mPFC) plays a key role in regulating cognition, emotion, and behavior. mPFC neurons are activated in diverse experimental paradigms, raising the questions of whether there are specific task elements or dimensions encoded by mPFC neurons, and whether these encoded parameters are selective to neurons in particular mPFC subregions or networks. Here, we consider the role of mPFC neurons in processing appetitive and aversive cues, outcomes, and related behaviors. mPFC neurons are strongly activated in tasks probing value and outcome-associated actions, but these responses vary across experimental paradigms. Can we identify specific categories of responses (e.g., positive or negative value), or do mPFC neurons exhibit response properties that are too heterogeneous/complex to cluster into distinct conceptual groups? Based on a review of relevant studies, we consider what has been done and what needs to be further explored in order to address these questions.

Keywords: Cues; Electrophysiology; Ensembles; Frontal; Neurophysiology; Outcome; Punishment; Reward; Single-neuron; Valence.

Fig. 1

What factors may explain apparent heterogeneity in mPFC neuron value signaling? (A) Three example mPFC neurons (from Kaminska and Moorman, in prep.) responsive to both appetitive and aversive outcome-predicting cues (left), only appetitive cues (middle), or only aversive cues (right). (B–F) Schematics of potential explanations for diversity in mPFC value encoding. (B) Subregion differences (e.g., different responses in PL vs IL neurons), (C) Differences in afferent projection target (e.g., different responses in neurons projecting to BLA vs NAc), (D) Differences in actions (e.g., neurons may respond to behaviors such as lever-press vs well-entry instead of or in addition to outcomes), (E) Potential cognitive factors (e.g., neurons may respond to variables associated with decision-making, learning, navigation, etc.), (F) Heterogeneous signaling (e.g., mixed selectivity) whereby individual neurons encode unique combinations of value, action, cognition, etc., at different strengths.