Development of Higher-Level Vision: A Network Perspective

Schematic overview over the two developmental models contrasted in the review. A, In the hierarchical development model, the adult network slowly emerges from lower to higher stages in a feedforward sweep. Areas of the same hierarchical level develop at the same time, as “add-on” to the existing hierarchy, so that at each age the network essentially resembles a partial version of the adult network. In this model, V1 would be a major bottleneck for the development of the entire system. B, In the dynamic network model, the visual system instead steps through a sequence of unique networks that are not partial versions of the adult network but can differ in fundamental ways. Connectivity at young ages does not necessarily match the adult, and areas that ultimately occupy similar hierarchical levels develop at different times. In the model, alternative starting points for development exist beyond V1. Note that for clarity only the network components most relevant for the review are shown in this summary (Thal: thalamus, both first- and second-order nuclei. The dashed versus solid line in B indicates a change in strength of a connection).