To examine molecular relationships between different cortical regions, we applied multi-dimensional scaling (MDS; Supplementary Methods 3) to the samples of Brain 1 to visualize their genetic correlations along the directions of the first two (2D) or three (3D) principal components. Remarkably, the transcriptional relationships between samples recapitulate the spatial topography of the neocortex, as qualitatively illustrated after sample mapping in 2D (Fig. 6e). The relative positions of samples in the MDS plot mirror the actual positions of the gyri in the physical brain, shown in Fig. 6d on the MRI of the brain from which the samples were derived. Not only do samples from each lobe group together, but the relative positions of the lobes are anatomically correct. Furthermore, the relative position of each lobe’s samples reflects the cortical topography, with the frontal pole and occipital striate cortex at opposite ends, precentral gyrus near postcentral gyrus, and so on. To provide a quantitative measure of this result we then applied the MDS method in 3D. As the positions of the samples were mapped back into MRI coordinate space, the correlation
