Abstract Despite near-identical genetics, humans and chimpanzees display striking cognitive differences, thought to emerge from overall brain size variation and subtle divergences in brain connectivity. We present a comparative analysis of deep white matter bundle (DWMB) morphology in 39 in vivo chimpanzees and 39 humans, using diffusion MRI and a novel isomap-based shape analysis pipeline. After mapping DWMBs into a shared anatomical space via sulcus-informed diffeomorphic registration, we identified robust species-specific differences across key frontal tracts. We focused on four frontal tracts due to their roles in fronto-parietal and fronto-temporal connectivity supporting language, executive function, and socio-emotional processing, with the arcuate fasciculus serving as an internal control given its well-established species differences. Notably, the arcuate fasciculus in humans exhibited greater curvature, volume, and temporal extension—traits absent in chimpanzees and consistent with its role in language. Humans also showed less variability and greater lateralization in the frontal aslant tract, while the uncinate and inferior fronto-occipital fasciculus revealed distinct cross-species expansions. These results provide the first high-dimensional morphological mapping of DWMBs across species, uncovering evolutionary adaptations in frontal connectivity and lateralization that likely underlie human-specific cognitive abilities.
Chauvel et al. (Thu,) studied this question.
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