DISTINCT NEURAL CODING STRATEGIES FOR VALUE IN ENTORHINAL CORTEX AND HIPPOCAMPAL CA1

Recent studies have shown that the hippocampal CA1 region encodes value-related information in addition to its established roles in spatial and episodic memory. Because CA1 receives its major cortical input from the entorhinal cortex (EC), a key unresolved question is whether value information is also represented in the EC and how such signals relate to value processing in CA1. To address this, we targeted dopamine receptor–enriched layer II island cells of the medial entorhinal cortex (MEC), which project to the lacunosum-moleculare region of CA1, using Wfs1-Cre mice. We performed in vivo microendoscopic calcium imaging of CA1 pyramidal neurons and MEC layer II pyramidal (L2P) neurons during a probabilistic odor–reward association task. Both regions exhibited significant value-related activity, but with markedly distinct coding properties. Population activity in CA1 increased monotonically with value, whereas MEC L2P activity decreased. Moreover, value signals emerged earlier and were stronger in CA1 than in MEC. Although population-level value representations were preserved across odor contexts in both regions, this stability arose from different sources: individual MEC L2P neurons maintained consistent value tuning across contexts, whereas CA1 neurons did not. Finally, chemogenetic suppression of MEC L2P neurons altered CA1 population dynamics but had minimal effects on CA1 value signals. Together, these results suggest that MEC and CA1 employ distinct and partially independent neural coding strategies to represent value.