Grid cells in the MEC (media entorhinal cortex) of rats show repetitive hexagon firing pattern while moving through the environment. In the deeper layer of the MEC, a kind of interneurons have both the head-directing (HD) and grid-like firing properties. The predecessors’ observations indicate the grid cells have ubiquitous intracellular rhythmic oscillating. Moreover, the grid cells’ firing frequencies have interesting approximate proportion relationship with the animal’s moving velocity. Howev
