The volitional control of individual motor units is constrained within low-dimensional neural manifolds by common inputs
File(s)
Published version
Author(s)
Rossato, Julien
Avrillon, Simon
Tucker, Kylie
Farina, Dario
Hug, Francois
Type
Journal Article
Abstract
The implementation of low-dimensional movement control by the central nervous system has been debated for decades. In this study, we investigated the dimensionality of the control signals received by spinal motor neurons when controlling either the ankle or knee joint torque. We first identified the low-dimensional latent factors underlying motor unit activity during torque-matched isometric contractions in male participants. Subsequently, we evaluated the extent to which motor units could be independently controlled. To this aim, we used an online control paradigm in which participants received the corresponding motor unit firing rates as visual feedback. We identified two main latent factors, regardless of the muscle group (vastus lateralis-medialis and gastrocnemius lateralis-medialis). The motor units of the gastrocnemius lateralis could be controlled largely independently from those of the gastrocnemius medialis during ankle plantarflexion. This dissociation of motor unit activity imposed similar behavior to the motor units that were not displayed in the feedback. Conversely, it was not possible to dissociate the activity of the motor units between the vastus lateralis and medialis muscles during the knee extension tasks. These results demonstrate that the number of latent factors estimated from linear dimensionality reduction algorithms does not necessarily reflect the dimensionality of volitional control of motor units. Overall, individual motor units were never controlled independently of all others but rather belonged to synergistic groups. Together, these findings provide evidence for a low-dimensional control of motor units constrained by common inputs, with notable differences between muscle groups.
Date Issued
2024-08-21
Date Acceptance
2024-06-21
Citation
Journal of Neuroscience, 2024, 44 (34)
ISSN
0270-6474
Publisher
Society for Neuroscience
Journal / Book Title
Journal of Neuroscience
Volume
44
Issue
34
Copyright Statement
Copyright © 2024 the authors. SfN exclusive license: https://www.jneurosci.org/content/licenses
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/38951036
PII: JNEUROSCI.0702-24.2024
Subjects
COMPARTMENTS
DRIVE
electromyography
Life Sciences & Biomedicine
module
motor neuron
MUSCLE SYNERGIES
NEURONS
Neurosciences
Neurosciences & Neurology
ORGANIZATION
POOLS
QUADRICEPS
real-time feedback
Science & Technology
SHARE
SYNAPTIC INPUT
SYNCHRONY
synergy
Publication Status
Published
Coverage Spatial
United States
Article Number
e0702242024
Date Publish Online
2024-07-01