Figure 7.

Summary of activity-dependent AIS maturation in visual cortex. (A) Spontaneous activity in form of retinal waves and intrinsic network activity along the developing visual system is present during the embryonic and early postnatal period (indicated by flashes). AIS length maturation is characterized by a tri-phasic time course of structural remodeling. First, during the early postnatal period, AIS steadily increase in length until a maximum is reached at P15. Coincidentally, between P13–14, mice of this strain open their eyes and receive visual input for the first time (indicated by light bulb). Shortly after eye opening, a striking AIS length shortening occurs. After the peak of the critical period at P28, AIS undergo another phase of length remodeling and increase to maintain mature length throughout adulthood. (B) A 1 week sensory deprivation (P21–28) in mice that have undergone eye opening and therefore AIS shortening did not alter AIS length compared to controls at P28 (far right neuron). However, a 2 week deprivation that began around the time of eye-opening (P14–28) was sufficient to prevent AIS length shortening compared to P28 controls. This effect was even more pronounced in dark reared (birth to P28) animals. Strikingly, this last deprivation group also showed similar AIS length distribution as the juvenile AIS group at P15 during normal development (far left neuron).