Document Type
Journal Article
Publication Title
European Journal of Neuroscience
Volume
58
Issue
9
First Page
4011
Last Page
4033
PubMed ID
37840191
Publisher
Wiley
School
Centre for Human Performance / School of Medical and Health Sciences
RAS ID
64596
Funders
Edith Cowan University / Slovenian Research and Innovation Agency
Abstract
Spinal motoneuron firing depends greatly on persistent inward currents (PICs), which in turn are facilitated by the neuromodulators serotonin and noradrenaline. The aim of this study was to determine whether jaw clenching (JC) and mental stress (MS), which may increase neuromodulator release, facilitate PICs in human motoneurons. The paired motor unit (MU) technique was used to estimate PIC contribution to motoneuron firing. Surface electromyograms were collected using a 32-channel matrix on gastrocnemius medialis (GM) during voluntary, ramp, plantar flexor contractions. MU discharges were identified, and delta frequency ( F), a measure of recruitment–derecruitment hysteresis, was calculated. Additionally, another technique was used (VibStim) that evokes involuntary contractions that persist after cessation of combined Achilles tendon vibration and triceps surae neuromuscular electrical stimulation. VibStim measures of plantar flexor torque and soleus activity may reflect PIC activation. F was not significantly altered by JC (p =.679, n = 18, 9 females) or MS (p =.147, n = 14, 5 females). However, all VibStim variables quantifying involuntary torque and muscle activity during and after vibration cessation were significantly increased in JC (p < .011, n = 20, 10 females) and some, but not all, increased in MS (p =.017–.05, n = 19, 10 females). JC and MS significantly increased the magnitude of involuntary contractions (VibStim) but had no effect on GM F during voluntary contractions. Effects of increased neuromodulator release on PIC contribution to motoneuron firing might differ between synergists or be context dependent. Based on these data, the background level of voluntary contraction and, hence, both neuromodulation and ionotropic inputs could influence neuromodulatory PIC enhancement.
DOI
10.1111/ejn.16158
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Comments
Mesquita, R. N. O., Taylor, J. L., Trajano, G. S., Holobar, A., Gonçalves, B. A. M., & Blazevich, A. J. (2023). Effects of jaw clenching and mental stress on persistent inward currents estimated by two different methods. European Journal of Neuroscience, 58(9), 4011-4033. https://doi.org/10.1111/ejn.16158