Abstract
Previous studies have shown that sprouting of corticospinal tract (CST) fibers after spinal cord injury (SCI) contributes to recovery of motor functions. However, the neuroanatomical mechanism underlying the functional recovery through sprouting CST fibers remains unclear. Here we investigated the pattern of reorganization of CST fibers below the lesion site after SCI in adult macaques. Unilateral lesions were made at the level between the C7 and the C8 segment. The extent of spontaneous recovery of manual dexterity was assessed with a reaching/grasping task. The impaired dexterous manual movements were gradually recovered after SCI. When anterograde tract tracing with biotinylated dextran amine was performed to identify the intraspinal reinnervation of sprouting CST fibers, it was found that the laminar distribution of CST fibers was changed. The sprouting CST fibers extended preferentially into lamia IX where the spinal motor neuron pool was located, to innervate the motor neurons directly. Instead, few, if any, CST fibers were distributed in the dorsal laminae. The present results indicate that CST fibers below the lesion site after SCI in macaques are reorganized in conjunction with the recovery of dexterous manual movements.
Highlights
Previous studies have shown that sprouting of corticospinal tract (CST) fibers after spinal cord injury (SCI) contributes to recovery of motor functions
Results of anterograde tract tracing with biotinylated dextran amine (BDA) indicated that CST fibers travelling through the dorsolateral funiculus were not observed at all below the lesion site in any of the four monkeys
It has been considered that axonal sprouting is crucial to spontaneous recovery of motor functions after SCI12, the neuroanatomical mechanism underlying the functional recovery still remains to be known in primates
Summary
Previous studies have shown that sprouting of corticospinal tract (CST) fibers after spinal cord injury (SCI) contributes to recovery of motor functions. Previous studies have shown that after unilateral SCI in primates, at least part of CST fibers extend beyond the lesion site with restoration of manual dexterity[2,3,4,5] It has been reported in rodents that sprouting CST fibers after SCI extend frequently into the medial gray matter where spinal interneurons are located, given that only a few number of CST fibers normally connect with spinal motor neurons directly[6,7,8]. To explore the neuroanatomical mechanism that underlies the functional recovery after SCI in primates, adult macaques underwent spinal cord lesions at the cervical cord level in the present study Employing this primate SCI model, we provide evidence that the sprouting CST fibers are reorganized in conjunction with the restoration of dexterous manual movements
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call