Muscle synergies obtained from comprehensive mapping of the cortical forelimb representation using stimulus triggered averaging of EMG activity

Sommer L.Amundsen Huffmaster, Gustaf M. Van Acker, Carl W. Luchies, Paul D. Cheney

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Neuromuscular control of voluntary movement may be simplified using muscle synergies similar to those found using non-negative matrix factorization. We recently identified synergies in electromyography (EMG) recordings associated with both voluntary movement and movement evoked by high-frequency long-duration intracortical microstimulation applied to the forelimb representation of the primary motor cortex (M1). The goal of this study was to use stimulus-triggered averaging (StTA) of EMG activity to investigate the synergy profiles and weighting coefficients associated with poststimulus facilitation, as synergies may be hard-wired into elemental cortical output modules and revealed by StTA. We applied StTA at low (LOW, ~15 μA) and high intensities (HIGH, ~110 μA) to 247 cortical locations of the M1 forelimb region in two male rhesus macaques while recording the EMG of 24 forelimb muscles. Our results show that 10 –11 synergies accounted for 90% of the variation in poststimulus EMG facilitation peaks from the LOW-intensity StTA dataset while only 4 –5 synergies were needed for the HIGH-intensity dataset. Synergies were similar across monkeys and current intensities. Most synergy profiles strongly activated only one or two muscles; all joints were represented and most, but not all, joint directions of motion were represented. Cortical maps of the synergy weighting coefficients suggest only a weak organization. StTA of M1 resulted in highly diverse muscle activations, suggestive of the limiting condition of requiring a synergy for each muscle to account for the patterns observed.

Original languageEnglish (US)
Pages (from-to)8759-8771
Number of pages13
JournalJournal of Neuroscience
Volume38
Issue number41
DOIs
StatePublished - Oct 10 2018
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by National Institutes of Health (NIH) Grants NS-051825 and NS-064054, NIH Center GrantHD-02528,theUniversityofKansasMedicalCenterBiomedicalResearchTrainingProgram,andtheUniversity of Kansas Madison and Lila Self Graduate Fellowship. We thank Ian Edwards, University of Kansas Medical Center; MollyMcVey,PhD,UniversityofKansasMechanicalEngineeringDepartment;andAnnariaBarnds,PhD,Universityof KansasBioengineeringDepartmentfortheirtechnicalassistance,alongwithDr.ColumD.MacKinnonandtherestof the Movement Disorders Laboratory team at the University of Minnesota for their support. We also acknowledge

Funding Information:
funding from S. Amundsen Huffmaster’s current institution, the University of Minnesota, including the MnDRIVE Postdoctoral Fellowship, NIH Grants R01 NS085188 and R01 NS088679-02, and the UMN Udall Center: National Institute of Neurological Disorders and Stroke Grant 1P50NS098573-01. The authors declare no competing financial interests. CorrespondenceshouldbeaddressedtoDr.PaulD.Cheney,DepartmentofMolecularandIntegrativePhysiology, University of Kansas Medical Center, Kansas City, KS 66160-7336. E-mail: pcheney@kumc.edu. S.L.AmundsenHuffmaster’spresentaddress:DepartmentofNeurology,UniversityofMinnesota,717Delaware Street S.E., Room 516E, Minneapolis, MN 55414. E-mail: slamunds@umn.edu. DOI:10.1523/JNEUROSCI.2519-17.2018 Copyright © 2018 the authors 0270-6474/18/388759-13$15.00/0

Funding Information:
This work was supported by National Institutes of Health (NIH) Grants NS-051825 and NS-064054, NIH Center Grant HD-02528, the University of Kansas Medical Center Biomedical Research Training Program, and the University of Kansas Madison and Lila Self Graduate Fellowship. We thank Ian Edwards, University of Kansas Medical Center; Molly McVey, PhD, University of Kansas Mechanical Engineering Department; and Annaria Barnds, PhD, University of Kansas Bioengineering Department for their technical assistance, along with Dr. ColumD. MacKinnon and the rest of the Movement Disorders Laboratory team at the University of Minnesota for their support. We also acknowledge funding from S. Amundsen Huffmaster’s current institution, the University of Minnesota, including the MnDRIVE Postdoctoral Fellowship, NIH Grants R01 NS085188 and R01 NS088679-02, and the UMN Udall Center: National Institute of Neurological Disorders and Stroke Grant 1P50NS098573-01.

Publisher Copyright:
© 2018 the authors.

Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.

Keywords

  • EMG
  • ICMS
  • Motor cortex
  • Muscle synergies
  • Nonnegative matrix factorization

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