Motor Neuron Pools of Synergistic Thigh Muscles Share Most of Their Synaptic Input
- Neural control of synergist muscles is not well understood. Presumably, each muscle in a synergistic group receives some unique neural drive and some drive that is also shared in common with other muscles in the group. In this investigation, we sought to characterize the strength, frequency spectrum, and force dependence of the neural drive to the human vastus lateralis and vastus medialis muscles during the production of isometric knee extension forces at 10 and 30% of maximum voluntary effort. High-density surface electromyography recordings were decomposed into motor unit action potentials to examine the neural drive to each muscle. Motor unit coherence analysis was used to characterize the total neural drive to each muscle and the drive shared between muscles. Using a novel approach based on partial coherence analysis, we were also able to study specifically the neural drive unique to each muscle (not shared). The results showed that the majority of neural drive to the vasti muscles was a cross-muscle drive characterized by aNeural control of synergist muscles is not well understood. Presumably, each muscle in a synergistic group receives some unique neural drive and some drive that is also shared in common with other muscles in the group. In this investigation, we sought to characterize the strength, frequency spectrum, and force dependence of the neural drive to the human vastus lateralis and vastus medialis muscles during the production of isometric knee extension forces at 10 and 30% of maximum voluntary effort. High-density surface electromyography recordings were decomposed into motor unit action potentials to examine the neural drive to each muscle. Motor unit coherence analysis was used to characterize the total neural drive to each muscle and the drive shared between muscles. Using a novel approach based on partial coherence analysis, we were also able to study specifically the neural drive unique to each muscle (not shared). The results showed that the majority of neural drive to the vasti muscles was a cross-muscle drive characterized by a force-dependent strength and bandwidth. Muscle-specific neural drive was at low frequencies (<5 Hz) and relatively weak. Frequencies of neural drive associated with afferent feedback (6 - 12 Hz) and with descending cortical input (similar to 20 Hz) were almost entirely shared by the two muscles, whereas low-frequency (<5 Hz) drive comprised shared (primary) and muscle-specific (secondary) components. This study is the first to directly investigate the extent of shared versus independent control of synergist muscles at the motor neuron level.…
Author details: | Christopher M. Laine, Eduardo Andrés Martinez-ValdesORCiDGND, Deborah Falla, Frank MayerORCiDGND, Dario Farina |
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DOI: | https://doi.org/10.1523/JNEUROSCI.0240-15.2015 |
ISSN: | 0270-6474 |
Pubmed ID: | https://pubmed.ncbi.nlm.nih.gov/26338331 |
Title of parent work (English): | The journal of neuroscience |
Publisher: | Society for Neuroscience |
Place of publishing: | Washington |
Publication type: | Article |
Language: | English |
Year of first publication: | 2015 |
Publication year: | 2015 |
Release date: | 2017/03/27 |
Tag: | EMG; motor units; muscle synergy; partial coherence; quadriceps |
Volume: | 35 |
Issue: | 35 |
Number of pages: | 10 |
First page: | 12207 |
Last Page: | 12216 |
Funding institution: | European Research Council Advanced Grant DEMOVE (Decoding the Neural Code of Human Movements for a New Generation of Man-Machine Interfaces) [267888]; University of Potsdam |
Organizational units: | Humanwissenschaftliche Fakultät / Strukturbereich Kognitionswissenschaften / Department Sport- und Gesundheitswissenschaften |
Peer review: | Referiert |
Institution name at the time of the publication: | Humanwissenschaftliche Fakultät / Institut für Sportmedizin und Prävention |