Hippocampal and Medial Prefrontal Cortical Maps Represent Episodes and Rules in a Common Task Space

Memory helps us adapt to changing circumstances but needs guidance to retrieve relevant episodes. Episodic memory requires the hippocampus, the prefrontal cortex (PFC) guides memory retrieval, but how their representations interact is unclear. Using state-space analysis of neuronal spiking, we found CA1 and PFC activity within and between rats formed similar, low-dimensional, region-specific "shapes" representing different tasks tested in the same maze. Task shapes were organized by behaviorally salient variables including time and maze start and goal locations. PFC predicted CA1 representations when both regions were needed to solve a spatial memory task, but not in a cue approach task that required neither region. Task demands imposed common dimensions on CA1 and PFC maps whose topologies distinguished episodic and rule-related computations.