Neurophysiological correlates of force control improvement induced by sinusoidal vibrotactile stimulation

Author(s)

Germer, Carina Marconi ^[1] ; Del Vecchio, Alessandro ^[2] ; Negro, Francesco ^[3] ; Farina, Dario ^[2] ; Elias, Leonardo Abdala ^{[4, 1]}

Affiliation

^[1] Univ Estadual Campinas, Sch Elect & Comp Engn, Dept Biomed Engn, Neural Engn Res Lab, Campinas - Brazil

^[2] Imperial Coll London, Neuromech & Rehabil Technol Grp, Dept Bioengn, Fac Engn, London - England

^[3] Univ Brescia, Dept Clin & Expt Sci, Res Ctr Neuromuscular Funct & Adapted Phys Act Te, Brescia - Italy

^[4] Univ Estadual Campinas, Ctr Biomed Engn, Campinas - Brazil

• Document type: Journal article
• Source: JOURNAL OF NEURAL ENGINEERING; v. 17, n. 1 FEB 2020.
• Web of Science Citations: 0

Abstract

Objective. An optimal level of vibrotactile stimulation has been shown to improve sensorimotor control in healthy and diseased individuals. However, the underlying neurophysiological mechanisms behind the enhanced motor performance caused by vibrotactile stimulation are yet to be fully understood. Therefore, here we aim to evaluate the effect of a cutaneous vibration on the firing behavior of motor units in a condition of improved force steadiness. Approach. Participants performed a visuomotor task, which consisted of low-intensity isometric contractions of the first dorsal interosseous (FDI) muscle, while sinusoidal (175 Hz) vibrotactile stimuli with different intensities were applied to the index finger. High-density surface electromyogram was recorded from the FDI muscle, and a decomposition algorithm was used to extract the motor unit spike trains. Additionally, computer simulations were performed using a multiscale neuromuscular model to provide a potential explanation for the experimental findings. Main results. Experimental outcomes showed that an optimal level of vibration significantly improved force steadiness (estimated as the coefficient of variation of force). The decreased force variability was accompanied by a reduction in the variability of the smoothed cumulative spike train (as an estimation of the neural drive to the muscle), and the proportion of common inputs to the FDI motor nucleus. However, the interspike interval variability did not change significantly with the vibration. A mathematical approach, together with computer simulation results suggested that vibrotactile stimulation would reduce the variance of the common synaptic input to the motor neuron pool, thereby decreasing the low frequency fluctuations of the neural drive to the muscle and force steadiness. Significance. Our results demonstrate that the decreased variability in common input accounts for the enhancement in force control induced by vibrotactile stimulation. (AU)

• FAPESP's process: 17/22191-3 - Effects of sensory and biomechanical manipulations on the neurophysiological control of muscle force: experiments and computer simulations
• Grantee: Leonardo Abdala Elias
• Support Opportunities: Regular Research Grants