Figure 2.

Plots of axonal water fraction ƒ across the corpus callosum in 6 representative subjects (A) plotted as fractional distance of callosal length. Substantial variation is present across individuals though the major contour features are preserved and, of interest, the number of partitions based on changes in ƒ concavity is the same in all subjects. Seven callosal subregions based on ƒ reflect microstructural properties such as axon density and size and are specific for each individual subject (B). The results (black arrowheads) show considerable individual variability not accounted for using methods based on fixed ratios (white bar; the Hofer and Frahm parcellation scheme). See Figure S1 for all 30 subjects.