Automated MRI-based parcellation of a putative core auditory region in individual human Heschl's gyrus

The human auditory cortex exhibits substantial anatomical variability, making precise individual-level delineation challenging. Although recent advances in imaging and machine learning techniques have enabled the delineation of approximate boundaries of the human primary auditory cortex, existing approaches often fail to adequately capture individual anatomical variability. Here, we propose an openly accessible, fully automated MRI-based pipeline for identifying a putative core auditory region within Heschl's gyrus by integrating intracortical myelin estimates with cortical curvature. A data-driven clustering algorithm was used to identify highly myelinated regions, and curvature-based constraints were subsequently applied to refine their anatomical boundaries. The resulting parcellations exhibited high myelin-related contrast and accommodated duplicated Heschl's gyri in the examined examples, illustrating their application to complex individual anatomical configurations. Comparative analyses of myelin-only and curvature-constrained definitions demonstrated that the curvature-constrained parcellation showed greater overlap with atlas-defined A1 and TE1.0 and stronger structural connectivity with the medial geniculate body of the thalamus as well as medial and lateral belt areas. Seed-based functional connectivity analyses further revealed connectivity patterns associated with auditory and multisensory functions that were consistent with previous literature. These findings support the parcellated region as an anatomically informed, MRI-based operational definition of a putative core auditory region. Although tonotopic validation remains necessary to establish the correspondence between parcellated boundaries and functionally defined auditory core areas, the proposed approach provides a reproducible framework for investigating the structural and functional organization of Heschl's gyrus at the individual level.