UC Berkeley

To make informed decisions, one needs to understand the world in which those decisions are being made: the current task state. Both the orbitofrontal cortex (OFC) and the hippocampus (HPC) have been implicated in representing task state, but the nature of these representations, and what role each region plays, remains unclear. Recent work from our lab showed that HPC-driven neural oscillations in OFC are critical for value-guided decision making, and that value states in OFC oscillate during the deliberation process. We hypothesized that (1) both HPC and OFC robustly and flexibly represent task state while primates learn and make decisions, and (2) value state dynamics in OFC are shaped by theta oscillations originating from HPC.

We simultaneously recorded large populations of neurons from OFC and HPC while two monkeys performed a probabilistic reversal learning task, where reward contingencies could be captured by two task states. Using population-level decoding, we found neural representations of task state in both OFC and HPC that remained stable within each trial but strengthened with learning as monkeys adapted to reversals. Subjects also appeared to use their understanding of task structure to anticipate reversals, evidenced by anticipatory neural representations of the upcoming task state. We then decoded representations of option values from OFC neurons recorded from two other monkeys performing a value-based decision-making task. Relating decoded state dynamics to theta-filtered LFP signals in OFC, we found that value states switched independent from theta cycles, suggesting that a mechanism other than HPC-driven theta oscillations shapes the dynamics of deliberation.