title: High-density surface electromyography improves the identification of oscillatory synaptic inputs to motoneurons.
abstract: Many studies have addressed corticomuscular coherence (CMC), but broad applications are limited by low coherence values and the variability across subjects and recordings. Here, we investigated how the use of high-density surface electromyography (HDsEMG) can improve the detection of CMC. Sixteen healthy subjects performed isometric contractions at six low-force levels using a pinch-grip, while HDsEMG of the adductor pollicis transversus and flexor and abductor pollicis brevis and whole-head magnetoencephalography were recorded. Different configurations were constructed from the HDsEMG grid, such as a bipolar and Laplacian montage, as well as a montage based on principal component analysis (PCA). CMC was estimated for each configuration, and the strength of coherence was compared across configurations. As expected, performance of the precision-grip task resulted in significant CMC in the β-frequency band (16-26 Hz). Compared with a bipolar EMG montage, all multichannel configurations obtained from the HDsEMG grid revealed a significant increase in CMC. The configuration, based on PCA, showed the largest (37%) increase. HDsEMG did not reduce the between-subject variability; rather, many configurations showed an increased coefficient of variation. Increased CMC presumably reflects the ability of HDsEMG to counteract inherent EMG signal factors-such as amplitude cancellation-which impact the detection of oscillatory inputs. In contrast, the between-subject variability of CMC most likely has a cortical origin.
authors.affiliation: MOVE Research Institute, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands;
authors.forename: Chiel van de
authors.initials: Cv
authors.lastname: Steeg
authors.affiliation: MOVE Research Institute, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands;
authors.forename: Andreas
authors.initials: A
authors.lastname: Daffertshofer
authors.affiliation: MOVE Research Institute, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands; Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen Medical Centre, Nijmegen, The Netherlands;
authors.forename: Dick F
authors.initials: DF
authors.lastname: Stegeman
authors.affiliation: MOVE Research Institute, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands; School of Psychiatry, University of New South Wales, Sydney, Australia; and Black Dog Institute, Sydney, Australia t.boonstra@unsw.edu.au.
authors.forename: Tjeerd W
authors.initials: TW
authors.lastname: Boonstra
mesh_terms: D000328:Adult; D000465:Algorithms; D001683:Biological Clocks / Q000502:physiology*; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D009434:Neural Pathways / Q000503:physiopathology; D009991:Oscillometry / Q000379:methods; D017729:Presynaptic Terminals / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D009435:Synaptic Transmission / Q000502:physiology*
keywords: amplitude cancellation; common oscillatory drive; corticomuscular coherence; motor unit; surface EMG