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.show moreshow less

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Metadaten
Author:Christopher M. Laine, Eduardo Martinez-Valdes, Deborah Falla, Frank MayerORCiDGND, Dario Farina
DOI:https://doi.org/10.1523/JNEUROSCI.0240-15.2015
ISSN:0270-6474 (print)
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=26338331
Parent Title (English):The journal of neuroscience
Publisher:Society for Neuroscience
Place of publication:Washington
Document Type:Article
Language:English
Year of first Publication:2015
Year of Completion:2015
Release Date:2017/03/27
Tag:EMG; motor units; muscle synergy; partial coherence; quadriceps
Volume:35
Issue:35
Pagenumber:10
First Page:12207
Last Page:12216
Funder: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 / Institut für Sportmedizin und Prävention
Peer Review:Referiert