Propriospinal cutaneous-induced EMG suppression is unaltered by anodal tDCS of healthy motor cortex

Alana B McCambridge; James W Stinear; Sarah Peek; Winston D Byblow

doi:10.1016/j.clinph.2017.06.035

Propriospinal cutaneous-induced EMG suppression is unaltered by anodal tDCS of healthy motor cortex

Clin Neurophysiol. 2017 Sep;128(9):1608-1616. doi: 10.1016/j.clinph.2017.06.035. Epub 2017 Jun 28.

Authors

Alana B McCambridge¹, James W Stinear², Sarah Peek², Winston D Byblow³

Affiliations

¹ Movement Neuroscience Laboratory, Department of Exercise Sciences, and Centre for Brain Research, The University of Auckland, Auckland, New Zealand; Clinical Neurostimulation Laboratory, Graduate School of Health, University of Technology Sydney, Australia.
² Movement Neuroscience Laboratory, Department of Exercise Sciences, and Centre for Brain Research, The University of Auckland, Auckland, New Zealand.
³ Movement Neuroscience Laboratory, Department of Exercise Sciences, and Centre for Brain Research, The University of Auckland, Auckland, New Zealand. Electronic address: w.byblow@auckland.ac.nz.

PMID: 28715712
DOI: 10.1016/j.clinph.2017.06.035

Abstract

Objective: Cervical propriospinal premotoneurons (PN) relay descending motor commands and integrate peripheral afferent feedback. Effects of anodal transcranial direct current stimulation (a-tDCS) on propriospinal excitability in the upper limbs are unknown.

Methods: Healthy right-handed adults received a-tDCS or sham tDCS over primary motor cortex (M1) at 1mA (Experiment 1, n=18) or 2mA current intensity (Experiment 2, n=15). Propriospinal excitability was assessed by suppression of background electromyography (EMG) in extensor carpi radialis (ECR) from electrical stimulation of the superficial radial nerve during bilateral (Experiment 1 and 2) or unilateral (Experiment 2 only) activation of the left and/or right ECR. EMG suppression could be attributed to an early propriospinal component and late cortical component. Motor evoked potentials (MEP) were obtained as a manipulation check.

Results: Before tDCS, propriospinal-mediated cutaneous-induced suppression was present in each arm for early and late components. ECR MEP amplitude increased after 1mA, but not 2mA, a-tDCS. Neither 1mA nor 2mA a-tDCS modulated either component of ipsilateral or contralateral propriospinal excitability during bilateral or unilateral tasks.

Conclusions: Propriospinal-mediated cutaneous-induced suppression was not modulated by a-tDCS in healthy adults.

Significance: Reporting non-significant findings is paramount for the development of clinically-relevant tDCS protocols.

Keywords: Bilateral; Propriospinal; Unilateral; Upper limb; tDCS.

Publication types

Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Aged
Double-Blind Method
Electromyography / methods*
Evoked Potentials, Motor / physiology*
Female
Humans
Male
Middle Aged
Motor Cortex / physiology*
Motor Neurons / physiology*
Radial Nerve / physiology*
Spinal Cord / physiology
Spinal Nerves / physiology*
Transcranial Direct Current Stimulation / methods*
Young Adult