CA1-Projecting Subiculum Neurons Facilitate Object-Place Learning

Recent anatomical evidence suggests a functionally significant back-projection pathway from the subiculum to CA1. Here we show that the afferent circuitry of CA1-projecting subicular neurons is biased by inputs from CA1 inhibitory neurons as well as visual cortex, but lacks input from entorhinal cortex. Efferents of the CA1-projecting subiculum neurons also target perirhinal cortex, an area strongly implicated in object-place learning. We identify a critical role for CA1-projecting subicular neurons in object-location learning and memory, and show that this projection modulates place-specific activity of CA1 neurons as well as their responses to displaced objects. Together, these experiments reveal a novel pathway by which cortical inputs, particularly those from visual cortex, reach hippocampal output region CA1, and our findings implicate this circuitry in the formation of complex spatial representations and learning of object-place associations.