Retinal waves coordinate patterned activity throughout the developing visual system

The morphological and functional development of the vertebrate nervous system is initially governed by genetic factors and subsequently refined by neuronal activity. However, fundamental features of the nervous system emerge before sensory experience is possible. Thus, activity-dependent development occurring before the onset of experience must be driven by spontaneous activity, but the origin and nature of activity in vivo remains largely untested. Here we use optical methods to show in live neonatal mice that waves of spontaneous retinal activity are present and propagate throughout the entire visual system before eye opening. This patterned activity encompassed the visual field, relied on cholinergic neurotransmission, preferentially initiated in the binocular retina and exhibited spatiotemporal correlations between the two hemispheres. Retinal waves were the primary source of activity in the midbrain and primary visual cortex, but only modulated ongoing activity in secondary visual areas. Thus, spontaneous retinal activity is transmitted through the entire visual system and carries patterned information capable of guiding the activity-dependent development of complex intra- and inter-hemispheric circuits before the onset of vision. In live neonatal mice, waves of spontaneous retinal activity are present and can propagate patterned information capable of guiding activity-dependent development of complex intra- and inter-hemispheric circuits throughout the visual system before the onset of vision (before eye opening). Spontaneous activity aids pattern formation in fetal retina Previous work on in vitro preparations of developing retina tissue has revealed spontaneous waves of activity, thought to be important in the development of the visual system. Here, Michael Crair and colleagues use optical methods to demonstrate the existence of retinal waves in live neonatal mice, and to show how these waves of activity propagate through the visual system before eye-opening, to drive activity-dependent maturation of the system. This finding suggests that spontaneous neural activity sculpts wiring throughout the brain during fetal development, and that disruptions in this ongoing activity may play an important part in neurological disorders such as autism in humans.