Coloured arrows: known/hypothesized pathways for sensory information. Purple: the head direction system receives projections from visual area 17 and from retrosplenial cortex (RSC). Head direction potentially gates an egocentric–allocentric transformation (red) between parietal and retrosplenial cortices, necessary to transform egocentric boundary distance (sensory input) to allocentric boundary distance (BVCs). Blue and green: complementary pathways conveying sensory information to grid cells, sources attributed to the dorsal and ventral visual streams (VS), respectively. Black arrows/arrowheads: pathways for idiothetic information, i.e. path integration signals. Abbreviations: BVCs, boundary vector cells; GCs, grid cells; HDCs, head direction cells; lEC, lateral entorhinal cortex; mEC; medial entorhinal cortex; PCs, place cells. Note, some known projections are omitted for clarity, e.g. from retrosplenial cortex to mEC.