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Independent representations of ipsilateral and contralateral limbs in primary motor cortex

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Cite this article as: eLife 2019;8:e48190 doi: 10.7554/eLife.48190

Abstract

Several lines of research demonstrate that primary motor cortex (M1) is principally involved in controlling the contralateral side of the body. However, M1 activity has been correlated with both contralateral and ipsilateral limb movements. Why does ipsilaterally-related activity not cause contralateral motor output? To address this question, we trained monkeys to counter mechanical loads applied to their right and left limbs. We found >50% of M1 neurons had load-related activity for both limbs. Contralateral loads evoked changes in activity ~10ms sooner than ipsilateral loads. We also found corresponding population activities were distinct, with contralateral activity residing in a subspace that was orthogonal to the ipsilateral activity. Thus, neural responses for the contralateral limb can be extracted without interference from the activity for the ipsilateral limb, and vice versa. Our results show that M1 activity unrelated to downstream motor targets can be segregated from activity related to the downstream motor output.

Data availability

Neural and kinematic data have been submitted to the Dryad repository and can be accessed at https://dx.doi.org/10.5061/dryad.06nr12f

The following data sets were generated

Article and author information

Author details

  1. Ethan A Heming

    Centre for Neuroscience Studies, Queen's University, Kingston, Canada
    Competing interests
    No competing interests declared.
  2. Kevin P Cross

    Centre for Neuroscience Studies, Queen's University, Kingston, Canada
    For correspondence
    13kc18@queensu.ca
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-9820-1043
  3. Tomohiko Takei

    Centre for Neuroscience Studies, Queen's University, Kingston, Canada
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6429-5798
  4. Douglas J Cook

    Centre for Neuroscience Studies, Queen's University, Kingston, Canada
    Competing interests
    No competing interests declared.
  5. Stephen H Scott

    Centre for Neuroscience Studies, Queen's University, Kingston, Canada
    Competing interests
    Stephen H Scott, Co-founder and chief scientific officer of Kinarm which commercializes the robot used in the study.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8821-1843

Funding

Canadian Institutes of Health Research (CIHR MOP 84403)

  • Stephen H Scott

Canadian Institutes of Health Research (CIHR PJT 153445)

  • Stephen H Scott

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: Studies were approved by the Queen's University Research Ethics Board and Animal Care Committee (#Scott-2010-035).

Reviewing Editor

  1. Jörn Diedrichsen, University of Western Ontario, Canada

Publication history

  1. Received: May 3, 2019
  2. Accepted: October 17, 2019
  3. Accepted Manuscript published: October 18, 2019 (version 1)
  4. Version of Record published: November 1, 2019 (version 2)

Copyright

© 2019, Heming et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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