title: Neurophysiological and behavioural effects of dual-hemisphere transcranial direct current stimulation on the proximal upper limb.
abstract: Dual-hemisphere transcranial direct current stimulation over the primary motor cortex (M1-M1 tDCS) is assumed to modulate neural excitability in a polarity-dependent manner and improve motor performance of the hand. In the proximal upper limb, the neurophysiological and behavioural after-effects of M1-M1 tDCS are not well known. This study investigated the after-effects of M1-M1 tDCS on contralateral, ipsilateral and transcallosal excitability to the proximal upper limb muscle biceps brachii (BB). Circle tracing was used to assess motor performance before and after tDCS as this task requires coordination of proximal and distal musculature. Sixteen healthy right-handed adults participated in the study, each receiving M1-M1 tDCS (1 mA, 15 min) or sham tDCS in separate sessions. The anode was positioned over right M1 and cathode over left M1. M1-M1 tDCS suppressed transcallosal inhibition from the M1 under the cathode (P < 0.045). No other neurophysiologic or behavioural effects were observed (P > 0.6). The study provides important information regarding inconsistent neurophysiological and behavioural changes following tDCS that have implications for future tDCS research on the motor system.
authors.affiliation: Movement Neuroscience Laboratory, Department of Exercise Sciences, and Centre for Brain Research, The University of Auckland, Auckland, New Zealand.
authors.forename: Alana B
authors.initials: AB
authors.lastname: McCambridge
authors.affiliation: Movement Neuroscience Laboratory, Department of Exercise Sciences, and Centre for Brain Research, The University of Auckland, Auckland, New Zealand.
authors.forename: James W
authors.initials: JW
authors.lastname: Stinear
authors.affiliation: Movement Neuroscience Laboratory, Department of Exercise Sciences, and Centre for Brain Research, The University of Auckland, Auckland, New Zealand. w.byblow@auckland.ac.nz.
authors.forename: Winston D
authors.initials: WD
authors.lastname: Byblow
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D034941:Upper Extremity / Q000502:physiology*; D055815:Young Adult
keywords: Direct current stimulation; Electrode montage; Ipsilateral; Motor cortex; Proximal; Upper limb