A UNIFORM CODING STRUCTURE IN THE NEOCORTEX.

Prefrontal neurons simultaneously encode multiple task variables. While many studies reported that various groupings of task features could be detected at the population level, the combination of features encoded by individual neurons seemed random. Here, based on unit recordings with Neuropixel probes in behaving rats, we report that far from being random, the representation of information is highly structured. Specifically, the prefrontal network exhibits multiple coding gradients orthogonal to each other in a multidimensional representational space. In this coding structure, neurons have correlated absolute firing rate modulations by different variables, but the polarity of the modulation by one variable is not predictive of that by others. Moreover, this coding structure is manifest in tasks that probe different behavioral processes, ranging from defensive behaviors to sensory discrimination. Last, we find that the same structured representation is apparent in other neocortical regions, including associative and primary sensory areas.