THE MEDIAL ENTORHINAL SPATIAL MAP IS BUILT ON EXCITATORY-INHIBITORY MOTIFS DEFINED BY THEIR FUNCTIONAL CELL TYPE AND THETA AFFINITY

Functionally specialized cell types, such as grid, head direction, border, cue and spatially tuned cells, constitute the core elements of the medial entorhinal cortex (mEC) spatial map. Collectively, these cells integrate diverse information about landmarks, distances, and the direction of travel to build a cohesive spatial map. However, it remains unclear how much information is necessary to construct even the most primitive map and how distinct functional cell types coordinate to form a coherent map. Critically, entorhinal excitatory cells are connected via a rich inhibitory cell network, with distinct inhibitory cell classes having differential effects on functionally distinct principal neurons.
Here, we characterised how the propensity to form fields varied with the availability of proximal visual cues across a range of functionally defined cell types in the medial entorhinal cortex while mice were navigating in virtual reality (VR) environments. We used Neuropixels 2.0 silicon probes^​ to record from hundreds of cells simultaneously to infer their putative connectivity patterns. We revealed vastly different principles governing the formation of cue representations in the medial entorhinal cortex compared to the hippocampus, and the key role theta affinity plays in supporting the communication between different functional neural groups.