title: Modulation of GABA and resting state functional connectivity by transcranial direct current stimulation.
abstract: We previously demonstrated that network level functional connectivity in the human brain could be related to levels of inhibition in a major network node at baseline (Stagg et al., 2014). In this study, we build upon this finding to directly investigate the effects of perturbing M1 GABA and resting state functional connectivity using transcranial direct current stimulation (tDCS), a neuromodulatory approach that has previously been demonstrated to modulate both metrics. FMRI data and GABA levels, as assessed by Magnetic Resonance Spectroscopy, were measured before and after 20 min of 1 mA anodal or sham tDCS. In line with previous studies, baseline GABA levels were negatively correlated with the strength of functional connectivity within the resting motor network. However, although we confirm the previously reported findings that anodal tDCS reduces GABA concentration and increases functional connectivity in the stimulated motor cortex; these changes are not correlated, suggesting they may be driven by distinct underlying mechanisms.
authors.affiliation: Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Velicia
authors.initials: V
authors.lastname: Bachtiar
authors.affiliation: Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montreal, Canada.
authors.forename: Jamie
authors.initials: J
authors.lastname: Near
authors.affiliation: Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Heidi
authors.initials: H
authors.lastname: Johansen-Berg
authors.affiliation: Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors.forename: Charlotte J
authors.initials: CJ
authors.lastname: Stagg
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
chemical_list: D005680:gamma-Aminobutyric Acid
keywords: GABA; brain stimulation; functional connectivity; human; neuroscience; plasticity; resting state networks; tDCS