Unraveling the Role of Neuronal Activity in the Formation of Eye-Specific Connections

Abstract

Since the pioneering studies of Wiesel and Hubel on the development and plasticity of ocular dominance columns in the visual cortex, it has been widely thought that correlated discharges of neighboring retinal ganglion cells play an instructive role in the formation of segregated eye-specific domains in the mammalian visual system. Here we review the relevant evidence and conclude that while correlated retinal discharges are required for the formation of segregated eye-specific projections in the visual cortex, there is reason to doubt that this is also the case at the level of the dorsal lateral geniculate. More likely, molecular cues play a key role in the stereotypic pattern of segregated retinogeniculate projections that characterize different species. As yet, the role of activity and the identity of the molecular cues involved in this process remain to be firmly established.