For the fusiform gyrus, it is necessary to have a 3D object model in order to reference its boundaries. The lateral boundary of the fusiform gyrus is the lateral occipito-temporal sulcus which separates the inferior temporal gyrus from the fusiform gyrus. The medial boundary is the collateral sulcus which separates the fusiform from the parahippocampal gyrus (Fig. 1). In the coronal view, the fusiform’s anterior boundary is marked by the emergence of the temporal horn, collateral sulcus and amygdala (Fig. 2, Fig. 3).
Masking in the coronal view, trace the lateral occipitotemporal sulcus to its internal end point mask a straight line to the internal end point of the collateral sulcus. Then, trace the collateral sulcus completely and mask the area between the created boundaries. Continue this step until reaching the posterior end of the fusiform. Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13 demonstrate this step moving posteriorly through coronal slices.
Posterior Border Definition – For each hemisphere, go to the most medial slice in the sagittal view where the parietal-occipital sulcus is clearly visible (clicking on the interhemispheric fissure in the axial plane helps to find the most medial slice). Click on the most anterior point of the parieto-occipital sulcus in the sagittal view and check the corresponding coronal view.
The most anterior point of the parietal-occipital sulcus is the point right above the calacrine sulcus. The corresponding slice in the coronal view is the posterior boundary of the fusiform gyrus. (Fig. 14, Fig. 15)