This research compares motor cortex lateralization and microstructure in chimpanzees and humans, suggesting key evolutionary insights.
Motivation: To understand the evolutionary development of hand motor cortex specialization and lateralization related to handedness in great apes. Goal(s): To investigate the cortical motor hand-knob area microstructure, as well as its hemispheric laterality, between chimpanzee and human brains. Approach: Myelin and iron accumulation were analyzed in hand foot and face cortical regions using high-resolution qMRI brain maps (R2* and MTsat) from 16 chimpanzees post-mortem and 54 humans in vivo. Results: In both species, qMRI values were higher in the hand field suggesting higher myelin and iron content compared to foot and face fields. Lateralization of measures was only observed in humans. Impact: The evolution of hand motor skills involves significant changes in cortical microstructure. Our findings provide valuable insights into the anatomical underpinnings of distinct motor behaviors, such as extensive tool use observed in hominids
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Chauvel et al. (2025) studied this question.
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