Quantifying the variation of sulcal patterns in extant human endocasts: a probabilistic approach.

International audienceOur knowledge of human brain evolution primarily relies on the interpretation of palaeoneurological evidence. Endocasts (i.e., replica of the internal table of the bony brain case) constitute a proxy for reconstructing a timeline and mode of cerebral changes in the fossil record. The identification of cerebral imprints is critical for assessing the topographic extension and structural organisation of cortical areas. Describing these crucial landmarks in fossil endocasts is challenging due to the fragmentary nature of fossil specimens. Recent introduction of high-resolution imaging techniques in (palaeo)neurology offers new opportunities for tracking detailed endocranial neural characteristics. In this context, this study aims to provide an atlas that documents variation in the extant human endocranial sulcal patterns for subsequent use as a comparative platform for the study of the fossil record. Dry human crania from the Pretoria Bone Collection were scanned using micro-CT at Necsa, Pelindaba (South Africa). Endocasts were virtually extracted using Endex software. Sulci were automatically detected and manually labelled using a programme created with MATLAB. Finally, a probability map was created by projecting all the labelled sulci on an average endocast and calculating the average displacement of each identified sulcus. In providing an innovative, non-invasive, observer-independent method to investigate human endocranial structural organisation, our analytical protocol introduces a promising perspective for discussing long-standing questions in palaeoneurology