The development of direction selectivity in the mouse retina

Whether capturing prey or evading predators, an animal's ability to detect movement in the world is critical for its survival. The first cells in the visual pathway that are tuned to detect motion are a subset of retinal ganglion cells called direction-selective ganglion cells (DSGCs). DSGCs respond strongly to motion in the "preferred" direction and weakly to motion in the opposite, or "null" direction. The circuitry underlying this computation consists of precise wiring between inhibitory interneurons, called amacrine cells, and the DSGCs. The role of neural activity in guiding this wiring is not known. We performed a series of experiments to examine whether DSGCs require activity for normal development. First, we tested whether visual experience was required for the establishment of direction selectivity in the retina. We recorded from the retinas of dark-reared mice using large-scale multi-electrode arrays, which allow for the recording from hundreds of neurons simultaneously. We found that DSGCs develop independent of visual experience, and are present as early as eye-opening. Second, to target recordings from DSGCs before eye-opening, we characterized a mouse line where a class of DSGCs expresses a fluorescent reporter. These experiments also allowed for the first complete description of the projection patterns for this cell. Finally, using this transgenic mouse with labeled DSGCs, we showed that DSGCs participate in spontaneous retinal activity before the eyes open, suggesting a possible role for early, spontaneous activity in their developmen