Multimodal Data Demonstrating White Matter Connections Within the Central Sulcus Subserving the Somato-cognitive Action Network

Introduction: The somato-cognitive action network (SCAN) consists of three nodes interspersed within Penfield’s motor effector regions. The configuration of the somato-cognitive action network nodes resembles the one of the ‘plis de passage’ (PDP) of the central sulcus (CS). Thus, we hypothesize that the PDP may provide a structural substrate of the SCAN.

Methods: We performed microdissections in sixteen cadaveric human hemispheres, mapped localizations of PDP into standard stereotactic space, and seeded fMRI connectivity across 9,000 resting-state fMRI scans. We performed direct electrical stimulation (DES) of the anterior bank of the CS in 6 patients undergoing craniotomy for lesion resection and recorded motor evoked potentials (MEP) responses of 33 eloquent sites. Stimulation sites were registered with neuronavigation, cortical surfaces were extracted through patient’s imaging and reconstructed using Freesurfer and Brainstorm/MATLAB toolbox. We performed population-based tractography using data from 1065 healthy individuals to map the trajectories and cortical coverage of the three subdivisions of the superior longitudinal fasciculus (SLF) I, II, and III in relation to the precentral gyrus.

Results: We consistently identified a chain of three distinct PDP with increased underlying white matter, in locations analogous to the SCAN nodes. Our fMRI studies demonstrated the connectivity of these sites with the SCAN. Intraoperative recordings during direct electrical central sulcus stimulation further identified inter-effector regions corresponding to PDP locations. Population-based tractography showed minimal overlap between SLF fiber tracts and SCAN nodes.

Conclusion : Our comprehensive approach utilizing microdissections, resting state MRI connectomes, population-based tractography, and intraoperative mapping studies indicates that the PDP of the CS are subserving the SCAN nodes as a structural, anatomical substrate. This work provides a critical step towards improved understanding of the SCAN in both structural and functional terms. Further, our work may help guide the development of operative resective techniques for complex surgery of the motor cortex.