Spatial and memory circuits in the medial entorhinal cortex.

The large capacity of episodic memory is thought to be supported by the emergence of distinct hippocampal cell assemblies for unrelated memories, such that interference is minimized. In large-scale population recordings, the orthogonal nature of hippocampal representations across environments is evident in the complete reorganization of the firing locations of hippocampal place cells. Entorhinal grid cells provide inputs to the hippocampus, and their firing patterns shift relative to each other across different environments. Although this suggests that altered grid cell firing could generate distinct hippocampal population codes, it has recently been shown that new and distinct hippocampal place fields emerge while grid cell firing is compromised. We therefore propose that separate circuits within the medial entorhinal cortex are specialized for performing either spatial or memory-related computations.