Exploring the effects of Ia reciprocal inhibition on neuromodulatory commands in the human lower limb
Bibliographic record
Abstract
The control of normal motor behaviors involves sublime interactions between excitatory, inhibitory and neuromodulatory commands to motoneurons. The effects of altered inhibition on neuromodulatory commands has not received much attention in humans. Yet, motoneuron firing patterns can be readily measured from the muscle fibers they innervate, collectively known as motor units (MUs), due to their one‐to‐one spike ratio. Persistent inward currents (PICs) are reduced with activation of Ia fibers from the antagonist muscle in the decerebrate cat. Here, we set out to explore whether estimated PICs are affected by a tonic vibratory input to antagonist tendons in humans. MU firing patterns of the tibialis anterior (TA), soleus (SOL) and medial gastrocnemius (MG) were discriminated using high‐density surface electromyography array electrodes and a convolutive blind source separation algorithm. PICs were estimated using the paired MU analysis technique, which quantifies discharge rate hysteresis (ΔF) by comparing the onset and offset of a high‐threshold MU with respect to a low‐threshold MU, providing an estimate of neuromodulatory drive to the MU. Participants performed isometric plantarflexion and dorsiflexion triangular ramp contractions to 30% of maximal voluntary contraction with 10 s ascending and descending phases. In half of the trials, we applied vibration (128 Hz) to the distal TA tendon (plantarflexion) or Achilles tendon (dorsiflexion) with a constant force of 15 ± 2 N. There were large decreases in ΔF for both the SOL (31.3 ± 7.94%, p = 0.006, d = 0.81) and MG (31.4 ± 10.36%, p = 0.008, d = 0.9) during plantarflexion contractions with vibration applied to the distal TA tendon, and there was a moderate decrease in ΔF for the TA (10.9 ± 8.79%, p = 0.009, d = 0.63) during dorsiflexion with vibration to the Achilles tendon. These findings suggest that Ia reciprocal inhibition from the antagonist muscle can reduce the discharge rate hysteresis, providing insights about the interactions that occur to produce normal human motor behaviors. Support or Funding Information This work was supported by National Institute of Health (NIH) grants R01NS098509‐01 and T32HD007418‐23, and a Natural Sciences and Engineering Research Council of Canada (NSERC) Postdoctoral Fellowship.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".