Prefrontal mechanisms of goal progress inference and monitoring in macaque monkeys

Primates pursue goals over extended periods and over multiple steps. The ability to track progress and its rate is critical for such pursuit, yet the neural mechanisms of this tracking are unclear. We recorded single-unit activity from macaque midcingulate cortex (MCC) and lateral prefrontal cortex (LPFC) whilst animals worked for immediate rewards and checked a gauge showing progress towards a larger reward. MCC expressed a temporally extended progress rate signal linked to the long timescale neurons in the region. LPFC expressed progress rate only when inferences on that property were required. In MCC, independent feedback-valence information was also preserved, enabling both readout of work success and rate-specific progress updating. An RNN trained under the same constraints showed that progress rate representations emerge spontaneously, and are critical for tracking goal progress. These results demonstrate a frontal mechanism for inferring and predicting goal progress by extracting progress rate information.