A reassessment of the role of activity in the formation of eye-specific retinogeniculate projections.

In all mammalian species the projections from the two eyes to the dorsal lateral geniculate nucleus of the thalamus terminate in separate layers or territories. This mature projection pattern is refined early in development from an initial state where the inputs of the two eyes are overlapping. Here I discuss the results of studies showing that the formation of segregated eye-specific retinogeniculate projections involves activity-mediated binocular competition. I conclude that while retinal activity undoubtedly is involved in this process, the results of recent studies cast doubt on the prevalent notion that retinal waves of activity play an instructional role in the formation of segregated retinal projections.