The primary feature that distinguishes the human brain from that of other species is the enormous expansion of the neocortex relative to total brain volume. Our extensive profiling allowed us to ask directly how transcription varies across the neocortex. Surprisingly, we find a remarkable degree of transcriptional uniformity compared to other brain regions, apparently reflecting the similarity in laminar architecture across the entire neocortex28. However, there is significant, albeit less robust, variation in gene expression across cortical areas with two hallmark features. First, individual cortical samples showed such strong transcriptional similarities to neighbouring samples that the topography of the neocortex as a whole can, in part, be reconstructed based on their molecular profiles. One possible explanation is that these proximity relationships mirror lineage relationships of neocortical neurons generated from proximal parts of the developing neuroepithelium. Second, some primary sensory and motor regions do have distinct whole-transcriptome signatures, probably related to their specialized cellular and functional architecture. It is also likely that other more subtle features of cortical parcellation may not have been detected in the current analysis, including those identified
