Representational Dynamics in the Hippocampus and Medial Prefrontal Cortex during Learning and Task Mastery

Abstract The hippocampus and the prefrontal cortex interact across a range of cognitive functions, yet how these regions represent space and how these representations evolve across learning remains poorly understood. We recorded large-scale neural activity from the hippocampus (CA1) and the medial prefrontal cortex (mPFC) as rats acquired proficiency in radial maze tasks over weeks. We identified a form of trial-by-trial flickering in which one hippocampal place field gradually overtook the other across successive trials, whereas mPFC firing fields switched randomly. While hippocampal flickering decreased as the task was mastered, mPFC flickering remained random and persisted throughout learning. Population-level UMAP embeddings revealed that mPFC states transitioned smoothly across trials, with the within-session representational drift stabilizing only after a two-week period. These findings suggest that while the hippocampus stabilizes its spatial maps during learning, the mPFC maintains a flexible, flickering representation that facilitates the extraction of abstract task structure and the rapid adaptation required for behavioral flexibility.