Absence of postural muscle synergies for balance after spinal cord transection

Autor: Chvatal, Stacie A.; Macpherson, Jane M.; Torres-Oviedo, Gelsy; Ting, Lena H.
Sprache: Englisch
Veröffentlicht: 2013
Quelle: PubMed Central (PMC)
Online Zugang: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC
http://www.ncbi.nlm.nih.gov/pubmed/23803327
http://dx.doi.org/10.1152/jn.00038.2013
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3763149
https://doi.org/10.1152/jn.00038.2013
Erfassungsnummer: ftpubmed:oai:pubmedcentral.nih.gov:3763149

Zusammenfassung

Although cats that have been spinalized can also be trained to stand and step with full weight support, directionally appropriate long-latency responses to perturbations are impaired, suggesting that these behaviors are mediated by distinct neural mechanisms. However, it remains unclear whether these responses reflect an attenuated postural response using the appropriate muscular coordination patterns for balance or are due to fundamentally different neural mechanisms such as increased muscular cocontraction or short-latency stretch responses. Here we used muscle synergy analysis on previously collected data to identify whether there are changes in the spatial organization of muscle activity for balance within an animal after spinalization. We hypothesized that the modular organization of muscle activity for balance control is disrupted by spinal cord transection. In each of four animals, muscle synergies were extracted from postural muscle activity both before and after spinalization with nonnegative matrix factorization. Muscle synergy number was reduced after spinalization in three animals and increased in one animal. However, muscle synergy structure was greatly altered after spinalization with reduced direction tuning, suggesting little consistent organization of muscle activity. Furthermore, muscle synergy recruitment was correlated to subsequent force production in the intact but not spinalized condition. Our results demonstrate that the modular structure of sensorimotor feedback responses for balance control is severely disrupted after spinalization, suggesting that the muscle synergies for balance control are not accessible by spinal circuits alone. Moreover, we demonstrate that spinal mechanisms underlying weight support are distinct from brain stem mechanisms underlying directional balance control.