Motor Control After Human SCI Through Activation of Muscle Synergies Under Spinal Cord Stimulation

Spinal cord stimulation (SCS) has enabled motor recovery in paraplegics with motor complete spinal cord injury (SCI). However, the physiological mechanisms underlying this recovery are unknown. This paper analyzes muscle synergies in two motor complete SCI patients under SCS during standing and comp...

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Bibliographic Details
Published inIEEE transactions on neural systems and rehabilitation engineering Vol. 27; no. 6; pp. 1331 - 1340
Main Authors Cheng, Richard, Sui, Yanan, Sayenko, Dimitry, Burdick, Joel W.
Format Journal Article
LanguageEnglish
Published United States IEEE 01.06.2019
Subjects
Animals
Delays
Electromyography
electromyography (EMG)
Feature extraction
Frequency measurement
matrix factorization
Muscle synergy
Muscles
Spinal cord
spinal cord injury (SCI)
spinal cord stimulation (SCI)
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Summary:Spinal cord stimulation (SCS) has enabled motor recovery in paraplegics with motor complete spinal cord injury (SCI). However, the physiological mechanisms underlying this recovery are unknown. This paper analyzes muscle synergies in two motor complete SCI patients under SCS during standing and compares them with muscle synergies in healthy subjects, in order to help elucidate the mechanisms that enable motor control through SCS. One challenge is that standard muscle synergy extraction algorithms, such as non-negative matrix factorization (NMF), fail when applied to SCI patients under SCS. We develop a new algorithm-rShiftNMF-to extract muscle synergies in these cases. We find muscle synergies extracted by rShiftNMF are significantly better at interpreting electromyography (EMG) activity, and resulting synergy features are more physiologically meaningful. By analyzing muscle synergies from SCI patients and healthy subjects, we find that: 1) SCI patients rely significantly on muscle synergy activation to generate motor activity; 2) interleaving SCS can selectively activate an additional muscle synergy that is critical to SCI standing; and 3) muscle synergies extracted from SCI patients under SCS differ substantially from those extracted from healthy subjects. We provide evidence that after spinal cord injury, SCS influences motor function through muscle synergy activation.
ISSN:1534-4320
1558-0210
DOI:10.1109/TNSRE.2019.2914433