SINGLE NEURONS IN RAT MEDIAL PREFRONTAL CORTEX ENCODE DECISION VARIABLES FOR TIME INVESTMENT

The question “How long should I wait?” is a fundamental decision problem in everyday life. To answer it, we must consider the subjective value of time and the uncertainty about both positive and negative outcomes. How neural circuits construct such time value estimates is not well understood. The medial prefrontal cortex (mPFC) represents decision variables relevant for temporal cognition and is thus a prime candidate for encoding time value.
Here, we investigated how mPFC represents time value to guide decision-making. We established a novel behavioral task in rats, which combines elements of perceptual and value-based decision-making, allowing us to study how decision variables are integrated to construct time value. Rats discriminated between auditory binaural click trains and invested time into their decisions to obtain randomly delayed rewards of varying size. They invested more time in proportion to statistical decision confidence, as well as in proportion to expected reward size, thus constructing integrated time value estimates to guide investment behavior.
We then recorded single neurons in the mPFC prelimbic area during task performance using Neuropixels probes. We found that the task-related activity of single neurons fell into distinct clusters, defined by characteristic dynamical patterns. Neurons encoded key decision variables such as decision confidence, reward size, and the integrated value of both. We further observed neurons with a ramping activity during waiting, with neural activity predictive of the rat’s trial-by-trial time investment.
These findings suggest that mPFC integrates diverse information to represent time value and thereby optimize time investment decisions.