The deep winding at the brain surface: replicating a historical report associating the 'bridged' central sulcus with the pli de passage fronto-parietal moyen

In 1876, the anatomist Heschl surveyed 1,087 brains identifying six cases of a unilateral bridged central sulcus (CS) at the brain surface. He also measured the height of a minor deep winding at the same location within the CS in the remaining 1,081 brains, reporting a distribution skewed towards significantly increased heights. These observations supported his hypothesis that the bridged CS represents an extreme form of the deep winding within the CS. In this replication we examined structural MRI data from an equally large dataset of 1,112 participants of the Human Connectome Project young adult (HCP-YA) dataset. Through visual inspection, we identified nine cases of a bridged CS, confirming its prevalence of less than 1%. The height of the deep winding, referred to in the HCP-YA dataset as the pli de passage fronto-parietal moyen (PPfpm), was extracted from 1,983 MRI-based hemispheric depth profiles. The resulting PPfpm height distribution, although wider, still mirrored Heschls findings, showing a similar skew towards larger heights. Further analyses of the twin data within the HCP-YA dataset indicated a slightly increased prevalence of the bridged CS in monozygotic and dizygotic twins compared to non-twin individuals, though no concordance of bridged CS was observed in monozygotic twin pairs. This replication study validates both of Heschls observations, describes additional factors that might influence the prevalence of the bridged CS, and refines the characterization of the deep winding height distribution. Together, these findings reaffirm and expand historical insights into the intricate anatomical organization of the CS.