Neural Regeneration Research ›› 2015, Vol. 10 ›› Issue (11): 1735-1736.doi: 10.4103/1673-5374.165318

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Who is who after spinal cord injury and repair? Can the brain stem descending motor pathways take control of skilled hand motor function?

Guillermo García-Alías*, V. Reggie Edgerton   

  1. Department of Integrative Biology and Physiology, University of California, Los Angeles, CA, USA
  • Received:2015-07-18 Online:2015-12-07 Published:2015-12-07
  • Contact: Guillermo Garcia-Alias, Ph.D.,guillermo284@gmail.com.
  • Supported by:

    This work was supported by a grant from Wings for Life, Spinal Cord Foundation (WFL-US-004/11) to GGA, the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health under Award Number U01EB015521 and the Christopher & Dana Reeve Foundation.
    The authors thank Mr. Anthony Yeung for his reviewing the paper.
    VRE holds a shareholder interest in NeuroRecovery Technologies. VRE is also President and Chair of the company’s Board of Directors. VRE, hold certain inventorship rights on intellectual property licensed by The Regents of the University of California to NeuroRecovery Technologies
    and it’s subsidiaries.

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Abstract:

Anatomical, electrophysiological and genetic studies have carefully dissected the pathways connecting the brain and the spinal cord. Lawrence and Kuypers described the organization of the descending motor pathways in the non human primate spinal cord. In spite of the differences between species regarding the precise anatomical location of each spinal pathway and the selective connectivity onto spinal interneurons and motoneurons, the pattern of organization described is conserved among the mammalian spinal cord. Based on their description, the major descending motor pathways are grouped depending on their anatomical origin and their terminal distribution pattern in the spinal grey matter. The motor cortex projects corticospinal axons to the spinal cord, which mostly run in the contralateral cord and innervate the mid and dorsal grey matter neurons. On the other hand, the spinal pathways originated in the brain stem are subdivided in the lateral and ventromedial systems. Whereas, the ventromedial system fibers are originated in the reticular formation and the vestibular complex, and terminate in the ventral and medial parts of the ventral horn grey matter, the lateral system fibers have their origin in red nucleus and preferentially terminate in the dorsal and lateral parts of the dorsal and medial grey matter. Together with the corticospinal fibres, the lateral brain-stem system contact interneurons related to motoneurons of distal muscles, whereas, ventromedial system pathways contact interneurons related to motoneurons of proximal muscles. Functionally, the corticospinal and lateral brain stem pathway are involved in the control of distal arm and hand muscles involved in skilled limb movements, the ventral brain stem pathways are mostly involved in the control the most proximal musculature of the trunk and limbs involved in posture and locomotion. Behavioral and electrophysiological studies, mostly performed in cats and non human primates corroborated these anatomical findings. Furthermore, rodents with injuries indiscrete areas of the spinal cord selectively impair specific motor functions, evidencing the functional specificity of each spinal pathways and the spinal networks innervated.