Figure 3. A model of compression effects that occur in grid cells from modules that map to the ventral visual field but not in grid cells from modules that map to the dorsal visual field .

A, the visual cortex processes optic flow and visual features. Optic flow is strongly present on the ground plane in the ventral visual field whereas distal visual features in the dorsal visual field make good landmarks. B, via multiple processing stages, optic flow and visual features influence hippocampal activity, giving rise to a place‐specific firing in a 2D environment. C, in the entorhinal cortex this 2D place information is translated into the firing of grid cells. Our model has two modules, one that estimates location from optic flow on the ground plane and one that estimates location from static visual features on the walls through triangulation. The anatomical projections from visual cortex to entorhinal cortex are not currently used in our model as shown by the dashed line. D, E, G and H, in configuration A the box is square (D and G) and in configuration B the box is rectangular (E and H) after pushing two opponent walls closer together (when the rat is outside of the box). For the moving feature system responding to the ground plane in the ventral visual field this compression of walls left the firing pattern of a simulated dorsal entorhinal cell unchanged (see D vs. E), while for the static feature system responding to distal features in the dorsal visual field this led to a compression of the firing pattern of a simulated ventral entorhinal cell (see G vs. H). F, for the firing pattern of the simulated dorsal entorhinal cell correlation values for different compressions of B relative to A, there is a peak correlation at ∼3.1% compression. I, for the firing pattern of the simulated ventral entorhinal cell, correlation values peak at ∼95.5% (or about 50 cm) compression of B relative to A.