Abstract
Grid and head direction codes in the medial entorhinal cortex represent cognitive spaces for navigation and memory 1,2. In grid cells the expression of the grid code is thought to be independent of head direction, whereas in conjunctive cells the grid code is tuned to a single head direction 3. This distinction between non-directional grid cells and unidirectional conjunctive cells is also present in models and proposed functions for grid codes 4–11. However, while grid cells are not tuned to a single direction, whether their firing is independent of direction is less clear. Here we demonstrate location-dependent modulation of grid cell firing by head direction. Individual firing fields recorded from mouse and rat grid cells have multiple and different preferred directions. This local directionality of grid firing is accounted for by models in which grid cells integrate inputs from conjunctive cells with co-aligned, spatially non-uniform firing fields. Thus, the firing of grid cells is consistent with their integration of upstream grid codes. For downstream neurons in the dentate gyrus that receive input from grid cells, integration of rich directional information within the grid code may contribute to pattern separation computations by decorrelating different points of view from the same spatial location 12–14.