The grid code for ordered experience

Nat Rev Neurosci. 2021 Oct;22(10):637-649. doi: 10.1038/s41583-021-00499-9. Epub 2021 Aug 27.

Abstract

Entorhinal cortical grid cells fire in a periodic pattern that tiles space, which is suggestive of a spatial coordinate system. However, irregularities in the grid pattern as well as responses of grid cells in contexts other than spatial navigation have presented a challenge to existing models of entorhinal function. In this Perspective, we propose that hippocampal input provides a key informative drive to the grid network in both spatial and non-spatial circumstances, particularly around salient events. We build on previous models in which neural activity propagates through the entorhinal-hippocampal network in time. This temporal contiguity in network activity points to temporal order as a necessary characteristic of representations generated by the hippocampal formation. We advocate that interactions in the entorhinal-hippocampal loop build a topological representation that is rooted in the temporal order of experience. In this way, the structure of grid cell firing supports a learned topology rather than a rigid coordinate frame that is bound to measurements of the physical world.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Animals
  • Entorhinal Cortex / cytology
  • Entorhinal Cortex / physiology*
  • Grid Cells / physiology*
  • Hippocampus / cytology
  • Hippocampus / physiology*
  • Humans
  • Learning / physiology*
  • Models, Neurological
  • Nerve Net / cytology
  • Nerve Net / physiology*
  • Space Perception / physiology*