title: Resting state functional connectivity measures correlate with the response to anodal transcranial direct current stimulation.
abstract: Responses to non-invasive brain stimulation are highly variable between subjects. Resting state functional connectivity was investigated as a marker of plasticity induced by anodal transcranial direct current stimulation (tDCS). Twenty-six healthy adults (15 male, 26.4 ± 6.5 years) were tested. Experiment 1 investigated whether functional connectivity could predict modulation of corticospinal excitability following anodal tDCS. Experiment 2 determined test-retest reliability of connectivity measures. Three minutes of electroencephalography was recorded and connectivity was quantified with the debiased weighted phase lag index. Anodal (1 mA, 20 min) or sham tDCS was applied to the left primary motor cortex (M1), with a change in motor evoked potential amplitude recorded from the right first dorsal interosseous used as a marker of tDCS response. Connectivity in the high beta frequency (20-30 Hz) between an electrode approximating the left M1 (C3) and electrodes overlying the left parietal cortex was a strong predictor of tDCS response (cross-validated R2= 0.69). Similar relationships were observed for alpha (8-13 Hz; R2= 0.64), theta (4-7 Hz; R2= 0.53), and low beta (14-19 Hz; R2= 0.58) frequencies, however, test-retest reliability of connectivity measures was strongest for the high beta frequency model (ICC = 0.65; good reliability). Further investigation of the high beta model found that greater connectivity between C3 and a cluster of electrodes approximately overlying the left parietal cortex was associated with stronger responses to anodal (rho = 0.61, P = 0.03), but not sham tDCS (rho = 0.43, P = 0.14). Functional connectivity is a strong predictor of the neuroplastic response to tDCS and may be one important characteristic to assist targeted tDCS application.
authors.affiliation: The Robinson Research Institute, School of Medicine, The University of Adelaide, Adelaide, 5005, SA, Australia.
authors.forename: Brenton
authors.identifier: 0000-0002-7129-6684
authors.initials: B
authors.lastname: Hordacre
authors.affiliation: Computational and Theoretical Neuroscience Laboratory, School of Information Technology and Mathematical Sciences, University of South Australia, Mawson Lakes, SA, Australia.
authors.forename: Bahar
authors.initials: B
authors.lastname: Moezzi
authors.affiliation: The Robinson Research Institute, School of Medicine, The University of Adelaide, Adelaide, 5005, SA, Australia.|Discipline of Psychiatry, School of Medicine, The University of Adelaide, Adelaide, SA, Australia.
authors.forename: Mitchell R
authors.initials: MR
authors.lastname: Goldsworthy
authors.affiliation: Brain and Mental Health Laboratory, School of Psychological Sciences and Monash Biomedical Imaging, Monash Institute of Cognitive and Clinical Neuroscience, Monash University, Melbourne, Vic, Australia.
authors.forename: Nigel C
authors.initials: NC
authors.lastname: Rogasch
authors.affiliation: The Robinson Research Institute, School of Medicine, The University of Adelaide, Adelaide, 5005, SA, Australia.
authors.forename: Lynton J
authors.initials: LJ
authors.lastname: Graetz
authors.affiliation: The Robinson Research Institute, School of Medicine, The University of Adelaide, Adelaide, 5005, SA, Australia.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Ridding
mesh_terms: D000328:Adult; D058256:Brain Waves; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation
keywords: electroencephalography; motor cortex; partial least squares; plasticity; transcranial magnetic stimulation