The central sulcus: an observer-independent characterization of sulcal landmarks and depth asymmetry.

Studies of the central sulcus (CS) often use observer-dependent procedures to assess CS morphology and sulcal landmarks. Here, we applied a novel method combining automated sulcus reconstruction, surface parameterization, and an observer-independent depth measurement to study the CS. This facilitated the quantitative assessment of the spatial position and intersubject variability of several sulcal landmarks. Sulcal depth profiles also allowed us to develop an algorithm for the clear identification of several landmarks, including the pli de passage fronto-pariétal moyen (PPFM), first described by Broca. Using this algorithm, the PPFM was identified in the majority of sulci, but exhibited limited spatial variability. This appears to support Cunningham's theory that this landmark may be a developmental remnant, and may argue against its role as a guide to the more variable somatotopic hand area. Sulcal depth profiles were also utilized to assess the influence of sex, handedness, and age on CS morphology. These profiles revealed leftward depth asymmetry in the superior extent of the CS of male subjects and near the midpoint of the CS in female subjects. Age correlations were performed for these asymmetries, and a significant correlation was seen only in the male subgroup.