Fig. 6: Probability maps of lateral prefrontal tertiary sulci.

a Maximum probability maps were generated across all participants with at least one identifiable pimfs component in both hemispheres (N = 58). To generate the maps, each label was transformed from each individual to the common fsaverage space. For each vertex, we calculated the proportion of participants for whom that vertex is labeled as the given sulcus (the warmer the color, the higher the overlap in each image). In the case of multiple labels for one vertex, the sulcus with the highest overlap across participants was assigned to a given vertex. To reduce spatial overlap, these maps can be thresholded to only include vertices with a minimum percent overlap across participants (e.g., 33% (left) or 20% (middle) overlap). The maps of tertiary sulci within the middle frontal gyrus (MFG) in the present study (right, unthresholded) can be used in future studies to guide the definition of tertiary sulci within the MFG. b Maps can be projected to individual participants to guide the definition of tertiary sulci in lateral prefrontal cortex (LPFC). Here, the thresholded maps (20%) for the tertiary sulci are projected back to example (randomly chosen) hemispheres from a 17 year-old (left) and a 6 year-old (right). Outlines of the spatial probability maps (black) are overlaid on the manual sulcal definitions (orange) for visualization purposes. 9: pmfs-p; 10: pmfs-i; 11: pmfs-a; 12: pimfs. While there is not a perfect correspondence between the maps and the tertiary sulci, the maps can guide manual definitions performed by researchers interested in examining LPFC tertiary sulci in future studies. These maps can be applied to other samples and are available for download¹⁰⁹.