Figure 6: Development of symmetric surface-based atlas.
(a) Development of symmetric surface-based atlas. (i) Using MSM, the left and right hemispheres from each week of the non-symmetric spatiotemporal dHCP atlas were co-registered in order to generate left-right vertex correspondence of coarse scale patterns of cortical folding (sulcal depth). Registration was run in left-to-right and right-to-left directions. (ii) Deformation maps of the left-to-right and the inverse of the right-to-left registrations were averaged to generate an intermediate symmetric template space. (iii) Local non-symmetric template metrics and anatomical meshes were resampled into their corresponding symmetric template (dhcpSym). Consecutive registrations between local symmetric templates were then performed to achieve a local to 40-week PMA registration deformation. A further resampling step was performed to get local template metrics and anatomical meshes into 40-week PMA symmetric template space (dhcpSym40). (b) Difference between left and right sulcal depth maps without cross-hemispheric registration, with cross-hemispheric registration, and with cross-hemispheric registration + averaging left and right sulcal depth templates. For the HCP-YA, the difference map without cross-hemispheric registration represents the difference between the left and right sulcal depth templates calculated in FreeSurfer fsaverage space, whereas the difference map with cross-hemispheric registration represents the difference between the left and right sulcal depth templates calculated in HCP fs_LR 32k space.