title: Simultaneous transcranial direct current stimulation (tDCS) and whole-head magnetoencephalography (MEG): assessing the impact of tDCS on slow cortical magnetic fields.
abstract: Transcranial direct current stimulation (tDCS) can influence cognitive, affective or motor brain functions. Whereas previous imaging studies demonstrated widespread tDCS effects on brain metabolism, direct impact of tDCS on electric or magnetic source activity in task-related brain areas could not be confirmed due to the difficulty to record such activity simultaneously during tDCS. The aim of this proof-of-principal study was to demonstrate the feasibility of whole-head source localization and reconstruction of neuromagnetic brain activity during tDCS and to confirm the direct effect of tDCS on ongoing neuromagnetic activity in task-related brain areas. Here we show for the first time that tDCS has an immediate impact on slow cortical magnetic fields (SCF, 0-4Hz) of task-related areas that are identical with brain regions previously described in metabolic neuroimaging studies. 14 healthy volunteers performed a choice reaction time (RT) task while whole-head magnetoencephalography (MEG) was recorded. Task-related source-activity of SCFs was calculated using synthetic aperture magnetometry (SAM) in absence of stimulation and while anodal, cathodal or sham tDCS was delivered over the right primary motor cortex (M1). Source reconstruction revealed task-related SCF modulations in brain regions that precisely matched prior metabolic neuroimaging studies. Anodal and cathodal tDCS had a polarity-dependent impact on RT and SCF in primary sensorimotor and medial centro-parietal cortices. Combining tDCS and whole-head MEG is a powerful approach to investigate the direct effects of transcranial electric currents on ongoing neuromagnetic source activity, brain function and behavior.
authors.affiliation: Institute of Medical Psychology and Behavioral Neurobiology and MEG Center, University of Tübingen, 72076 Tübingen, Germany; Applied Neurotechnology Lab, Department of Psychiatry and Psychotherapy, University of Tübingen, 72076 Tübingen, Germany; Donders Centre for Brain, Cognition and Behavior, Department of Artificial Intelligence, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: Eliana
authors.initials: E
authors.lastname: Garcia-Cossio
authors.affiliation: Institute of Medical Psychology and Behavioral Neurobiology and MEG Center, University of Tübingen, 72076 Tübingen, Germany; Applied Neurotechnology Lab, Department of Psychiatry and Psychotherapy, University of Tübingen, 72076 Tübingen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Witkowski
authors.affiliation: MEG Core Facility, National Institute of Mental Health (NIMH), NIH, Bethesda, MD 20892, USA.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Robinson
authors.affiliation: Human Cortical Physiology and Stroke Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke (NINDS), NIH, Bethesda, MD 20892, USA.
authors.forename: Leonardo G
authors.initials: LG
authors.lastname: Cohen
authors.affiliation: Institute of Medical Psychology and Behavioral Neurobiology and MEG Center, University of Tübingen, 72076 Tübingen, Germany; Ospedale San Camillo, Istituto di Ricovero e Cura a Carattere Scientifico, 30126 Venezia, Italy.
authors.forename: Niels
authors.initials: N
authors.lastname: Birbaumer
authors.affiliation: Institute of Medical Psychology and Behavioral Neurobiology and MEG Center, University of Tübingen, 72076 Tübingen, Germany; Applied Neurotechnology Lab, Department of Psychiatry and Psychotherapy, University of Tübingen, 72076 Tübingen, Germany. Electronic address: surjo.soekadar@uni-tuebingen.de.
authors.forename: Surjo R
authors.initials: SR
authors.lastname: Soekadar
mesh_terms: D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D060526:Magnetic Fields; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D012542:Scattering, Radiation; D065908:Transcranial Direct Current Stimulation / Q000379:methods*
keywords: Magnetoencephalography; Slow cortical fields; Source-reconstruction; Transcranial direct current stimulation