Context-invariant encoding of reward location in a distinct hippocampal population

Abstract

The hippocampus plays a critical role in goal-directed navigation. Across different environments, however, the hippocampal map seems to be randomized, making it unclear how goal locations might be encoded. To address this question, we trained mice to seek reward at several locations on virtual linear tracks, and optical recordings of calcium activity were made at cellular resolution from two major hippocampal output structures, CA1 and the subiculum. These experiments revealed a population of neurons that were consistently active near reward locations. Their pattern of activity sharply contrasted with simultaneously-recorded place cells and even persisted across environments, when other cells remapped randomly. Their timing was closely correlated with reward anticipation behaviors, yet could not be explained by the behaviors themselves, raising the possibility that reward-associated cell signals were used by mice to identify the reward location. These results demonstrate that the hippocampus employs a context-invariant marker of goal locations, and reveal a novel target for studying how the hippocampus contributes to navigation.