Retinal waves and visual system development.

Many pathways in the developing visual system are restructured and become highly organized even before vision occurs. Yet the developmental processes underlying the remodeling of visual connectivity are crucially dependent on retinal activity. Surprisingly, the immature and light-insensitive retina spontaneously generates a pattern of rhythmic bursting activity during the period when the connectivity patterns of retinal ganglion cells are shaped. Spatially, the activity is seen to spread across the retina in the form of waves that bring into synchrony the bursts of neighboring cells. Waves are present in the developing retina of higher and lower vertebrates, which suggests that this form of activity may be a common and fundamental mechanism employed in the activity-dependent refinement of early patterns of visual connections. Unraveling the cues encoded by the waves promises to provide important insights into how interactions driven by specific patterns of activity could lead to the modification of connectivity during development.