- The pre-cuneus is the medial cortex of the superior parietal gyrus. Its anterior boundary is the marginal segment of the cingulate sulcus and its posterior boundary is the parieto-occipital fissure. The inferior boundary is the subparietal sulcus. Because the lateral boundary cannot be defined by any clear sulcus, the boundary is defined by the most superior medial sulcus in the coronal view. (Fig. 1, Fig. 2)
- Masking of the pre-cuneus is done in the coronal view. Locate the parieto-occipital fissure in the sagittal view, click on its superior end, and switch to the corresponding slice in the coronal view (Fig. 3). At this slice, locate the subparietal sulcus, trace it to its internal endpoint, and draw a straight line up to the internal end of the most superior medial sulcus. Fill in everything within these boundaries. (The most superior medial sulcus may change often between slices.) (Fig. 4)
- Moving posteriorly, the marginal segment of the cingulate sulcus will appear. This sulcus can be found easily in the sagittal view as shown in Figure 5. At this point mask from the marginal segment of the cingulate sulcus to its internal endpoint, and draw a straight line to the internal endpoint of the subparietal sulcus. Mask the subparietal sulcus to its medial end, and fill in everything within these boundaries. Continue this step until the subparietal sulcus in no longer visible. (Fig. 5, Fig. 6)