Event:

Layer 2 of medial entorhinal cortex (MEC) contains “grid cells” - neurons which discharge with strong theta-rhythmicity and in hexagonal grid patterns (Hafting et al., 2005) - and “border cells” – neurons which fire in relation to geometric boundaries of the environment (Solstad et al., 2008). To date however, we still know little about how principal cell heterogeneity (pyramidal versus stellate neurons) and cell-type specific microcircuits relate to spatial representations. To address these issues, we take advantage of improved methodologies for juxtacellular identification of single neurons recorded in freely-moving animals. Our results show that, while stellate cells were uniformly distributed in the cortical plane, pyramidal neurons formed patches which were aligned to layer 1 axons, the parasubiculum and cholinergic inputs. Theta-rhythmicity of spiking was two-fold stronger in pyramidal than in stellate cells. By cell identification and theta-locking-based classification of unidentified recordings, we provide evidence that grid cells might be preferentially recruited from the pyramidal cell population. Border cells on the other hand were almost exclusively observed in stellate neurons. These data point towards the existence of strong structure-function relationships in layer 2 of MEC.