Hippocampal neurons construct a map of an abstract value space

The hippocampus is thought to encode a ‘cognitive map’, a structural organization of knowledge about relationships in the world. Place cells, spatially selective hippocampal neurons that have been extensively studied in rodents, are one component of this map, describing the relative position of environmental features. However, whether this map extends to abstract, cognitive information remains unknown. Using the relative reward value of cues to define continuous ‘paths’ through an abstract value space, we show that single neurons in primate hippocampus encode this space through value place fields, much like a rodent’s place neurons encode paths through physical space. Value place fields remapped when cues changed, but also became increasingly correlated across contexts, allowing maps to become generalized. Our findings help explain the critical contribution of the hippocampus to value-based decision-making, providing a mechanism by which knowledge of relationships in the world can be incorporated into reward predictions for guiding decisions.