Receptive field center size decreases and firing properties mature in ON and 6 OFF retinal ganglion cells after eye opening in the mouse

35 Development of the mammalian visual system is not complete at birth but continues 36 postnatally well after eye opening. Though numerous studies have revealed changes in 37 development of the thalamus and visual cortex during this time, less is known about the 38 development of response properties of the retinal ganglion cells (RGCs). Here, we mapped 39 functional receptive fields of mouse RGCs using a Gaussian white-noise checkerboard stimulus 40 and a multielectrode array to record from retinas at eye opening, three days later, and four weeks 41 after birth, when visual responses are essentially mature. Over this time, receptive field center 42 size of ON and OFF RGC populations decreased. The average receptive field center size of ON 43 RGCs was larger than that of OFF RGCs at eye opening, but they decreased to the same size in 44 the adult. Firing properties were also immature at eye opening. RGCs had longer latencies, 45 lower frequencies of firing, and lower sensitivity than in the adult. Hence, the dramatic 46 maturation of the visual system during the first weeks of visual experience includes the retina. 47