The superior frontal sulcus in the human brain: Morphology and probability maps

The superior frontal sulcus (SFS) is the major sulcus on the dorsolateral frontal cortex that defines the lateral limit of the superior frontal gyrus. Caudally, it originates near the superior precentral sulcus (SPRS) and, rostrally, it terminates near the frontal pole. The advent of structural neuroimaging has demonstrated significant variability in this sulcus that is not captured by the classic sulcal maps. The present investigation examined the morphological variability of the SFS in 50 individual magnetic resonance imaging (MRI) scans of the human brain that were registered to the Montreal Neurological Institute (MNI) standard stereotaxic space. Two primary morphological patterns were identified: (i) the SFS was classified as a continuous sulcus or (ii) the SFS was a complex of sulcal segments. The SFS showed a high probability of merging with neighbouring sulci on the superior and middle frontal gyri and these patterns were documented. In addition, the morphological variability and spatial extent of the SFS were quantified using volumetric and surface spatial probability maps. The results from the current investigation provide an anatomical framework for understanding the morphology of the SFS, which is critical for the interpretation of structural and functional neuroimaging data in the dorsolateral frontal region, as well as for improving the accuracy of neurosurgical interventions. Detailed examinations of sulcal morphology are necessary to improve the localization of functional activity in relation to specific anatomical landmarks and to improve our understanding of intrinsic neuroanatomical landmarks used during neurosurgical interventions. The present investigation characterized the morphological variability of the superior frontal sulcus (SFS) in 50 individual subject magnetic resonance imaging (MRI) volumes (i.e., 100 hemispheres) registered to the Montreal Neurological Institute (MNI) stereotaxic space. The morphological patterns of the posterior (red) and anterior (green) rami of the SFS were quantified using volumetric and surface spatial probability maps, which are made freely available. image