In the language dominant hemisphere, damage to the ventrolateral frontal cortex, including surrounding tissue and underlying white matter, results in the language disorder known as Broca’s aphasia. Moreover, in patients undergoing surgery, stimulation of the posterior ventrolateral frontal cortex of the language dominant hemisphere is sufficient to produce speech arrest. The present study provides an in-depth analysis of the sulcal morphology of this region using magnetic resonance imaging. Morphological patterns of the anterior ascending ramus of the lateral fissure (aalf), the horizontal ramus of the lateral fissure (half), the sulcus diagonalis (ds), and the triangular sulcus (ts) were classified after voxels representing these sulci were labelled in 40 in-vivo MRI volumes (1.5T) that were linearly registered to the Montreal Neurological Institute (MNI) stereotaxic space. The spatial variability and extent of each sulcus was then quantified across subjects using probabilistic mapping. The results demonstrate that the ds, found on the pars opercularis of the inferior frontal gyrus, is a relatively superficial sulcus that can be identified in about 50% of subjects. The aalf and the half, on the other hand, are reliable sulci that extend medially to reach the insula and thus help define the pars triangularis and pars opercularis. Finally, the ts, which divides the pars triangularis into an anterior and a posterior component, often merges with the anterior end of the inferior frontal sulcus. Understanding the details of the sulcal morphology of this region is crucial to the correct anatomical localization of ventrolateral frontal cortex involved in language processing.

Morphological patterns and spatial probability maps of the sulci of the ventrolateral frontal cortex