Functional architecture of motion direction in the mouse superior colliculus
Motion vision is important in guiding animal behavior. Both the retina and the visual cortex process object motion in largely unbiased fashion: all directions are represented at all locations in the visual field. We investigate motion processing in the superior colliculus of the awake mouse, by optically recording neural responses across both hemispheres. Within the retinotopic map, one finds large regions of [~]500 m size where neurons prefer the same direction of motion. This preference is maintained in depth to [~]350 m. The scale of these patches, [~]30 deg of visual angle, is much coarser than the animals visual resolution. A global map of motion direction shows approximate symmetry between the left and right hemispheres and a net bias for upward-nasal motion in the upper visual field. Unlike other parts of the early visual system, the superior colliculus develops a locally biased representation of object motion.