Plis de passage in the superior temporal sulcus: Morphology and local connectivity

C Bodin,A Pron,M Le Mao,J Régis,P Belin,O Coulon

doi:10.1016/j.neuroimage.2020.117513

Abstract

While there is a profusion of functional investigations involving the superior temporal sulcus (STS), our knowledge of the anatomy of this sulcus is still limited by a large individual variability. In particular, an accurate characterization of the “plis de passage” (PPs), annectant gyri inside the fold, is lacking to explain this variability. Performed on 90 subjects of the HCP database, our study revealed that PPs constitute landmarks that can be identified from the geometry of the STS walls. They were found associated with a specific U-shape white-matter connectivity between the two banks of the sulcus, the amount of connectivity being related to the depth of the PPs. These findings raise new hypotheses regarding the spatial organization of PPs, the relation between cortical anatomy and structural connectivity, as well as the possible role of PPs in the regional functional organization.

Highlights

Neuroanatomists of the 19th century were closely interested in the origin and the individual variability of cortical folding
This study showed that morphological criteria identifiable from individual cortical surfaces can be used to detect and characterize the plis de passage
This lead us to suggest that the previously described asymmetry in the number of plis de passage” (PPs) between the left and right superior temporal sulcus (STS) might be an asymmetry of their depth but that their number is similar between both hemispheres

Summary

Introduction

Neuroanatomists of the 19th century were closely interested in the origin and the individual variability of cortical folding. Later on, Broca (1888) re-used this term and reported the existence of three transverse gyri along the central sulcus (CS) connecting the pre- and postcentral gyri: the PPs frontal superior, middle and inferior Such subdivision of sulci into several pieces was made clearer by Cunningham’s pioneering work on cortical development: he described how folds appear first as distinct segments that merge at a later stage in parallel with cortical expansion (Cunningham, 1890, 1890c, 1897). The central sulcus, in particular, would originate from two pieces separated by what he called a “deep annectant gyrus” (Cunningham, 1897) characterized either by a clear elevation of the fundus or a thickening of its two interlocking extremities which can unite at the bottom (Cunningham, 1892; White et al, 1997) This landmark, that would correspond to Broca’s “PPs fronto-parietal moyen” (PPFM), can persist until adulthood leading to a segmented aspect of the sulcus (Cunningham, 1897; Cykowski et al., 2008; Régis et al, 2005). It was shown to reflect the position of the hand motor area (Boling et al, 1999; Cykowski et al, 2008; Mangin et al, 2019) co-localized with the omega-shaped bending of the surface or “hand knob” (Yousry et al, 1997)

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