Geniculocortical Input Drives Genetic Distinctions Between Primary and Higher-Order Visual Areas

Studies of area patterning of the neocortex have focused on primary areas, concluding that the primary visual area, V1, is specified by transcription factors (TFs) expressed by progenitors. Mechanisms that determine higher-order visual areas (V-HO) and distinguish them from V1 are unknown. We demonstrated a requirement for thalamocortical axon (TCA) input by genetically deleting geniculocortical TCAs and showed that they drive differentiation of patterned gene expression that distinguishes V1 and V-HO. Our findings suggest a multistage process for area patterning: TFs expressed by progenitors specify an occipital visual cortical field that differentiates into V1 and V-HO; this latter phase requires geniculocortical TCA input to the nascent V1 that determines genetic distinctions between V1 and V-HO for all layers and ultimately determines their area-specific functional properties.