Extended Data Figure 15. Summary Schematic of Proposed Model of Arealization.

In this study, we find that in addition to their neuronal progeny, radial glia from distinct cortical areas are already distinct from each other (A). At early second trimester timepoints, the strongest contrast is seen radial glia at the frontal and occipital poles of the neocortex (B). The gene expression signatures of cells at different cortical areas are highly dynamic across developmental time (C) and across the differentiation axis (RG → IPC → excitatory neuron) (D). As differentiation progresses, these dynamic gene signatures give rise to other major cortical areas, and further refinement occurs, likely as sensory input to the cortex begins to take place.