The identification of extensive samples of motor units in human muscles reveals diverse effects of neuromodulatory inputs on the rate coding
- Department of Bioengineering, Faculty of Engineering, Imperial College London, United Kingdom
- Nantes Université, Laboratory 'Movement, Interactions, Performance', France
- Université Côte d'Azur, LAMHESS, France
- The University of Queensland, School of Biomedical Sciences, Australia
- Department of Integrative Physiology, University of Colorado Boulder, United States
Figures
Figure 1 with 2 supplements
Identification of motor units in two human muscles.
(A) We used a blind-source-separation (BSS) algorithm to decompose the overlapping activity of motor units (MU) into spike trains during a force-matching trapezoidal task (red trace). (B) We …
Figure 1—figure supplement 1
Validation of electromyographic decomposition and motor unit tracking.
We used two approaches to validate the electromyographic decomposition. First, we simulated a pool of 150 motor units producing forces from 10% to 80% of the maximal excitation. Electromyographic …
Figure 1—figure supplement 2
Recruitment thresholds of motor units tracked across contractions.
We tracked motor units across contractions using their unique distribution of action potentials within the grid of 256 electrodes. Then, we estimated their recruitment thresholds as the average of …
Figure 2 with 1 supplement
Non-linear rate coding of motor units.
(A) The relation between firing rate (pulses per second, pps) and the applied force during the ramp-up phase of the contraction was determined by concatenating the instantaneous firing rates for …
Figure 2—figure supplement 1
Relations between force and firing rates fitted with a natural logarithm.
We reported the relations between instantaneous motor units firing rates and the applied force. Then, we fitted these relations for each motor unit using a natural logarithm function (left panels). …
Figure 3
Motor unit firing rates across contraction levels.
The left column shows average firing rate (pulses per second, pps) during the force plateaus for each tracked motor unit across contraction levels for all participants from tibialis anterior (TA) …
Figure 4
Hysteresis between recruitment and derecruitment thresholds.
The left column depicts the relations between the recruitment and derecruitment thresholds of each motor unit from tibialis anterior (TA) (A) and vastus lateralis (VL) (B). These relations were …
Author response image 1
Tables
Table 1
Mean ± standard deviation (range) for the number of motor units across the eight target forces and two muscles.
| 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | |
|---|---|---|---|---|---|---|---|---|
| TA | 38 ± 25 (1–73) | 45 ± 24 (21–83) | 50 ± 27 (24–95) | 49 ± 26 (24–93) | 45 ± 27 (15–93) | 40 ± 25 (14–80) | 37 ± 26 (14–84) | 34 ± 19 (9–60) |
| VL | 44 ± 17 (17–63) | 46 ± 20 (19–71) | 42 ± 20 (10–67) | 34 ± 18 (3–56) | 32 ± 15 (5–53) | 26 ± 13 (3–38) | 26 ± 14 (1–38) | 20 ± 13 (1–37) |
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TA, tibialis anterior; VL, vastus lateralis.
