The figure presents the location of the main white matter tracts with a lateral trajectory. (A) The key cortical regions that need to be identified are the precentral cortex (blue), pars opercularis of the IFG (pink), pars triangularis (burgundy) and pars orbitalis (green). (B) The most superficial layer of the fibers, which are identified just under the cortex, is composed of the short association u-fibers that connect the neighboring gyri of the frontal lobe. Here, u-fibers within the premotor area are present after removal of the cortex just anterior to the precentral gyrus. (C) The most superficial bundle of long association fibers is formed by the AF/SLF complex (yellow) running around and superficial to the insular limiting sulcus. Within the frontal lobe, anterior to the precentral gyrus, this bundle can be identified at the level of the middle frontal gyrus, aiming for the pars triangularis of the IFG. The most superficial layer from the lateral perspective is formed by the second segment of the superior longitudinal fasciculus (SLF II), which connects the middle frontal gyrus to the inferior parietal lobule. The SLF III and AF terminate within the posterior parts of the inferior frontal gyrus. (D) Removing the AF/SLF complex in front of the precentral sulcus exposes the vertical short association white matter tract, the frontal aslant tract (FAT) (light blue), which connects the SMA complex with the pars opercularis of the IFG. The mesial part of the FAT, which connects the SMA complex with the caudate nucleus, forms the frontal striatal tract (FST)—not seen here (Fig. 3D). (E) The ventral long association bundle is formed by the IFOF/UF complex, terminating within the basal part of the frontal lobe. The frontal lobe is connected with the temporal pole through the UF (red) and with the parietal and occipital lobes through the IFOF (purple). This layer of white matter forms the external and extreme capsule. (F) From this perspective, the frontal horn of the lateral ventricle (white circle) is identified just posterior to the pars triangularis and below the AF/SLF complex.