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The dorsolateral corticospinal tract in mice: An alternative route for corticospinal input to caudal segments following dorsal column lesions
Author(s) -
Steward Oswald,
Zheng Binhai,
Ho Carole,
Anderson Kim,
TessierLavigne Marc
Publication year - 2004
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20090
Subject(s) - biotinylated dextran amine , biology , dorsolateral , anatomy , corticospinal tract , neuroscience , dorsal column nuclei , anterograde tracing , axon , pyramidal tracts , dorsum , white matter , retrograde tracing , diffusion mri , prefrontal cortex , magnetic resonance imaging , cognition , radiology , medicine
In rodents, the main contingent of corticospinal tract (CST) axons descends in the ventral part of the dorsal column. There is, however, a contingent of CST axons that descends in the dorsolateral column (the “dorsolateral corticospinal tract,” or DLCST). Here, we define some of the features of the DLCST by tracing CST projections following injections of biotinylated dextran amine into the sensorimotor cortex, assessing the distribution of DLCST axons and terminal arborizations in intact mice and in mice in which the main contingent of CST axons in the dorsal column had been transected. Axons of the DLCST diverge from the main tract at the pyramidal decussation, gather in fascicles in the dorsolateral gray matter below the spinomedullary junction, and project in a gradual trajectory laterally toward the dorsolateral column over the first few cervical segments. DLCST axons then project along the dorsolateral column to sacral levels, giving rise to collaterals that project into the gray matter. Labeled DLCST axons were most abundant in cervical segments, where they were often collected in fascicles, and progressively decreased in number in more caudal segments. Tracing of DLCST axons in mice with selective lesions of the dorsal column revealed that DLCST axons arborize extensively throughout the dorsal and ventral horns and that the overall territory that the DLCST axons invade is similar to the territory innervated by the CST axons in the main tract. Some DLCST axon arbors with varicosities are seen near large neurons in the ventral horn (presumed motoneurons). Substantial numbers of DLCST axons project across the midline to the gray matter on the contralateral side. Thus, the DLCST provides an alternate route for CST input to caudal segments, which is of particular relevance for studies of CST distribution and function following partial spinal cord injuries. J. Comp. Neurol. 472:463–477, 2004. © 2004 Wiley‐Liss, Inc.