Differential Joint-Specific Corticospinal Tract Projections within the Cervical Enlargement

摘要: The motor cortex represents muscle and joint control projects to spinal cord interneurons and–in many primates, including humans–motoneurons, via the corticospinal tract (CST). To examine these CST anatomical mechanisms, we determined if sites controlling individual forelimb joints project differentially distinct cervical territories, defined regionally by locations of putative last-order that were transneuronally labeled intramuscular injection pseudorabies virus. Motor joint-specific identified using intracortical-microstimulation. segmental termination fields from sites, anterograde tracers, comprised a high density core terminations was consistent between animals surrounding lower projection more variable. Core shoulder, elbow, wrist overlapped in medial dorsal horn intermediate zone at C5/C6 but separated C7/C8. Shoulder preferentially terminated dorsally, horn; wrist/digit ventrally zone; elbow medially zone. Pseudorabies virus injected or muscles overlapping populations predominantly muscle-specific premotor interneurons, survival time for disynaptic transfer muscle. At C5/C6, projections all zones located regions densely irrespective C7/C8 densest interneuron territory, which lateral In contrast, shoulder dorsally only partially territory. Our findings show surprising fractionation caudal enlargement may be organized engage different circuits distal proximal control.