Cover and Figure 1. The structures involved in the dorsolateral (pink), anterior cingulate (green), and orbitofrontal (blue) prefrontal-subcortical circuits are color-coded onto the left side of axial magnetic resonance images (A-E). The approximate extent and locations of the classic major long cortical association tracts are color-coded onto the right side of axial magnetic resonance images (A-E) and summarized in cartoon form on a lateral view of the brain (Cover). 1,2Figure 2. Variability (or probability) maps created by transforming the functional anatomy of individual brains into a common anatomic space indicate considerable normal variation.3-8 On the right is a variability map for primary visual cortex (Brodmann's area 17), with the number of individuals (out of 10) which overlapped. On the left is a probability map (30% threshold) of the corpus callosum, color-coded by cortical area of fiber origin. Note the large areas of overlap, indicating differences in functional anatomy across individuals.