Remapping revisited: how the hippocampus represents different spaces

Abstract

The representation of distinct spaces by hippocampal place cells has been linked to changes in their place fields (the locations in the environment where the place cells discharge strongly), a phenomenon that has been termed ‘remapping’. Remapping has been assumed to be accompanied by the reorganization of subsecond cofiring relationships among the place cells, potentially maximizing hippocampal information coding capacity. However, several observations challenge this standard view. For example, place cells exhibit mixed selectivity, encode non-positional variables, can have multiple place fields and exhibit unreliable discharge in fixed environments. Furthermore, recent evidence suggests that, when measured at subsecond timescales, the moment-to-moment cofiring of a pair of cells in one environment is remarkably similar in another environment, despite remapping. Here, I propose that remapping is a misnomer for the changes in place fields across environments and suggest instead that internally organized manifold representations of hippocampal activity are actively registered to different environments to enable navigation, promote memory and organize knowledge. The location-specific firing of hippocampal place cells changes when an animal enters a new environment, a phenomenon known as ‘remapping’. In this Perspective, André A. Fenton challenges standard models of place cell remapping and proposes a key role for the ‘re-registration’ of internally organized place cell population dynamics in the encoding of distinct environments.