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Physiological Recordings of High and Low Output NMJs on the Crayfish Leg Extensor Muscle
Published on: November 17, 2010
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Muscle contractile properties directly influence shared synaptic inputs to spinal motor neurons.
Hélio V Cabral1, J Greig Inglis1, Alessandro Cudicio1
1Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy.
The Journal of Physiology
|May 6, 2024
Summary
Changing muscle length alters neural oscillations, reducing alpha band activity in synaptic inputs and force output. This suggests muscle length impacts neural control and force steadiness.
Area of Science:
- Neuroscience
- Motor Control
- Biomechanics
Background:
- Shared synaptic inputs to alpha motor neurons generate oscillations that can act as noise, impairing voluntary force production.
- Understanding how physiological factors like muscle length influence these oscillations is crucial for comprehending motor control.
Purpose of the Study:
- To investigate the effect of changing muscle length on common synaptic oscillations in spinal motor neurons, specifically within the physiological tremor band (5-15 Hz).
- To determine if alterations in muscle length influence the transmission of neural oscillations into muscle force output.
Main Methods:
- High-density surface electromyography (HDsEMG) was recorded from the tibialis anterior muscle during low-level dorsiflexion at two ankle joint angles (90° and 130°).
- HDsEMG signals were decomposed into motor unit spike trains to analyze coherence in delta, alpha, and beta frequency bands.
- Force steadiness and spectral power within the tremor band were quantified; evoked twitches were recorded to assess muscle contractile properties.
Main Results:
- Alpha band oscillations in both synaptic inputs and force output were significantly reduced when muscle length increased (from 90° to 130° ankle angle).
- No significant changes were observed in delta or beta band oscillations, nor in force steadiness between the two muscle lengths.
- Evoked twitches showed longer durations at longer muscle lengths, indicating enhanced low-pass filtering properties of the muscle.
Conclusions:
- Increasing muscle length enhances the muscle's low-pass filtering capabilities, modulating oscillations from the Ia afferent feedback loop.
- Changes in peripheral contractile properties due to muscle length significantly affect how shared synaptic inputs are translated into muscle force.
- This study highlights the interplay between muscle biomechanics and neural oscillations in motor control.
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