Interfacing motor units in non-human primates identifies a principal neural component for force control constrained by the size principle
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Motor units convert the last neural code of movement into muscle forces. The classic view of motor unit control is that the central nervous system sends common synaptic inputs to motoneuron pools and that motoneurons respond in an orderly fashion dictated by the size principle. This view however is in contrast with the large number of dimensions observed in motor cortex which may allow individual and flexible control of motor units. Evidence for flexible control of motor units may be obtained by tracking motor units longitudinally during tasks with some level of behavioural variability. Here we identified and tracked populations of motor units in the brachioradialis muscle of two macaque monkeys during ten sessions spanning over one month with a broad range of rate of force development (1.8 - 38.6 N∙m∙s-1). We found a very stable recruitment order and discharge characteristics of the motor units over sessions and contraction trials. The small deviations from orderly recruitment were fully predicted by the motor unit recruitment intervals, so that small shifts in recruitment thresholds happened only during contractions at high rate of force development. Moreover, we also found that one component explained more than ~50% of the motor unit discharge rate variance, and that the remaining components represented a time-shifted version of the first. In conclusion, our results show that motoneurons recruitment is determined by the interplay of the size principle and common input and that this recruitment scheme is not violated over time nor by the speed of the contractions.
Date Issued
2022-09-28
Date Acceptance
2022-07-16
Citation
The Journal of Neuroscience, 2022, 42 (39), pp.7383-7399
ISSN
0270-6474
Publisher
Society for Neuroscience
Start Page
7383
End Page
7399
Journal / Book Title
The Journal of Neuroscience
Volume
42
Issue
39
Copyright Statement
© 2022 the authors
SfN exclusive license (https://www.jneurosci.org/content/licenses).
SfN exclusive license (https://www.jneurosci.org/content/licenses).
Sponsor
Commission of the European Communities
Identifier
https://www.jneurosci.org/content/42/39/7386
Grant Number
810346
Subjects
Neurology & Neurosurgery
11 Medical and Health Sciences
17 Psychology and Cognitive Sciences
Publication Status
Published
Date Publish Online
2022-09-28