title: Functional connectivity in the neuromuscular system underlying bimanual coordination.
abstract: Neural synchrony has been suggested as a mechanism for integrating distributed sensorimotor systems involved in coordinated movement. To test the role of corticomuscular and intermuscular coherence in bimanual coordination, we experimentally manipulated the degree of coordination between hand muscles by varying the sensitivity of the visual feedback to differences in bilateral force. In 16 healthy participants, cortical activity was measured using EEG and muscle activity of the flexor pollicis brevis of both hands using high-density electromyography (HDsEMG). Using the uncontrolled manifold framework, coordination between bilateral forces was quantified by the synergy index RVin the time and frequency domain. Functional connectivity was assessed using corticomuscular coherence between muscle activity and cortical source activity and intermuscular coherence between bilateral EMG activity. The synergy index increased in the high coordination condition. RVwas higher in the high coordination condition in frequencies between 0 and 0.5 Hz; for the 0.5- to 2-Hz frequency band, this pattern was inverted. Corticomuscular coherence in the beta band (16-30 Hz) was maximal in the contralateral motor cortex and was reduced in the high coordination condition. In contrast, intermuscular coherence was observed at 5-12 Hz and increased with bimanual coordination. Within-subject comparisons revealed a negative correlation between RVand corticomuscular coherence and a positive correlation between RVand intermuscular coherence. Our findings suggest two distinct neural pathways: 1) corticomuscular coherence reflects direct corticospinal projections involved in controlling individual muscles; and 2) intermuscular coherence reflects diverging pathways involved in the coordination of multiple muscles.
authors.affiliation: Faculty of Behavioural and Movement Sciences, VU University, Amsterdam, The Netherlands.
authors.forename: Ingmar E J
authors.initials: IE
authors.lastname: de Vries
authors.affiliation: Faculty of Behavioural and Movement Sciences, VU University, Amsterdam, The Netherlands.
authors.forename: Andreas
authors.initials: A
authors.lastname: Daffertshofer
authors.affiliation: Faculty of Behavioural and Movement Sciences, VU University, Amsterdam, The Netherlands.|Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, The Netherlands.
authors.forename: Dick F
authors.initials: DF
authors.lastname: Stegeman
authors.affiliation: Faculty of Behavioural and Movement Sciences, VU University, Amsterdam, The Netherlands; t.boonstra@unsw.edu.au.|Black Dog Institute, University of New South Wales, Sydney, Australia; and.|Systems Neuroscience Group, QIMR Berghofer Medical Research Institute, Brisbane, Australia.
authors.forename: Tjeerd W
authors.identifier: 0000-0002-6969-7243
authors.initials: TW
authors.lastname: Boonstra
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000000981:diagnostic imaging / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult
keywords: corticomuscular coherence; intermuscular coherence; motor coordination; neural synchrony; uncontrolled manifold