2026-03-12 カリフォルニア大学リバーサイド校(UCR)
＜関連情報＞
- https://news.ucr.edu/articles/2026/03/12/overlooked-brainstem-pathway-controls-human-hands
- https://www.pnas.org/doi/10.1073/pnas.2518217123
哺乳類の前肢運動制御の基礎となる髄質およびC3-C4固有脊髄路 Medullary and C3–C4 propriospinal pathways underlying mammalian forelimb movement control
Vishwas Jindal, Matteo M. Grudny, Daniel W. Wesson, +1 , and Shahabeddin Vahdat
Proceedings of the National Academy of Sciences Published:January 28, 2026
DOI:https://doi.org/10.1073/pnas.2518217123
Significance
Our study identifies a conserved medullary network, comprising the Lat-RM and CauM, underlying forelimb movement control across species, while also revealing cortical differences potentially driven by task demands or interspecies neuroanatomical variations. This network follows an orderly organization of cortical connections along the ventro-medio-dorsal axis of the medulla. We provide functional mapping of the human C3–C4 propriospinal pathway, which exhibits anatomically segregated connectivity with brainstem nuclei, cerebellum, and motor cortex. Together, our findings suggest an indirect motor pathway involving both the reticulospinal tract and the C3–C4 propriospinal system that contributes to fine hand motor control and highlight the central role of the propriospinal system in integrating reticular, cortical, and cerebellar inputs to support this function.
Abstract
Classic models associate goal-directed upper limb movements with cortical motor areas and balance control with the brainstem. However, recent rodent studies suggest that medullary regions and local spinal circuits also contribute to forelimb execution, leaving it uncertain if these findings apply to humans. Critically, the dynamic interactions among medullary motor regions, intersegmental spinal networks, and cortical sensorimotor areas during hand movement control remain poorly understood. Here, through functional MRI (fMRI) studies in humans and mice during forelimb movement tasks, we reveal topographically organized corticomedullary networks, comprising the lateral rostral medulla (Lat-RM) and caudal medulla (CauM), that regulate forelimb movement. In mice, the corticomedullary coupling in both CauM and Lat-RM increased systematically along a ventro-medio-dorsal gradient, with the strongest links to primary motor and premotor cortices. In humans, higher‐order sensorimotor regions drove the strongest connectivity with CauM and Lat-RM, while the more medially located medial rostral medulla remained weakly engaged. Furthermore, simultaneous brain-spinal fMRI revealed distinct functional territories within the human C3–C4 cervical spinal cord, with ventral regions exhibiting strong connectivity to the medulla and dorsal regions to lower cervical segments. Together, our findings identify a conserved corticomedullary network underlying forelimb movement control across species, while also uncovering variation in cortical involvement. They indicate the presence of an indirect pathway involving both the reticulospinal pathway and the C3–C4 propriospinal system, which contributes to fine hand motor control in the mammalian brain.
