Putative neurodevelopmental mechanisms underlying the observed preferential connectivity between cytoarchitectonically similar cortical areas.

(A) The cytoarchitecture of areas in the adult cerebral cortex might reflect their distinct time courses in neurogenesis. Heterochronous and spatially ordered neurogenetic gradients indicate distinct time windows in neurogenesis in the mouse, with arrows denoting the direction of propagation of neuron release and accumulation [53]. Hence, similar cytoarchitecture might entail a similar time course of neurogenesis, thus biasing the cortical connections to form primarily between areas with similar overlapping time windows, since they host more neurons functioning as probable “connection partners.” (B) The duration of neurogenesis is shorter in mice compared to macaque monkeys [54]. Overall, a shorter neurogenetic period and less distinct time windows of neurogenesis may result in the observed species-specific relation of the existence of connections and the cytoarchitecture of the cerebral cortex.