Component of the orbtial frontal cortex The rostral boundary is the first slice where the lateral orbital gyrus is apparent with the frontomarginal sulcus whereas the caudal boundary is the disappearance of the lateral orbital gyrus. The medial and lateral boundaries are the midpoint of the olfactory sulcus and the lateral bank of the lateral orbital sulcus and/or the circular insular sulcus respectively (Christine Fennema-Notestine). [ BIRNLEX:1244 ]