title: Friends, not foes: Magnetoencephalography as a tool to uncover brain dynamics during transcranial alternating current stimulation.
abstract: Brain oscillations are supposedly crucial for normal cognitive functioning and alterations are associated with cognitive dysfunctions. To demonstrate their causal role on behavior, entrainment approaches in particular aim at driving endogenous oscillations via rhythmic stimulation. Within this context, transcranial electrical stimulation, especially transcranial alternating current stimulation (tACS), has received renewed attention. This is likely due to the possibility of defining oscillatory stimulation properties precisely. Also, measurements comparing pre-tACS with post-tACS electroencephalography (EEG) have shown impressive modulations. However, the period during tACS has remained a blackbox until now, due to the enormous stimulation artifact. By means of application of beamforming to magnetoencephalography (MEG) data, we successfully recovered modulations of the amplitude of brain oscillations during weak and strong tACS. Additionally, we demonstrate that also evoked responses to visual and auditory stimuli can be recovered during tACS. The main contribution of the present study is to provide critical evidence that during ongoing tACS, subtle modulations of oscillatory brain activity can be reconstructed even at the stimulation frequency. Future tACS experiments will be able to deliver direct physiological insights in order to further the understanding of the contribution of brain oscillations to cognition and behavior.
authors.affiliation: Center for Mind/Brain Sciences, University of Trento, Via Delle Regole 101, 38123 Mattarello (Trento), Italy. Electronic address: toralf.neuling@unitn.it.
authors.forename: Toralf
authors.initials: T
authors.lastname: Neuling
authors.affiliation: Center for Mind/Brain Sciences, University of Trento, Via Delle Regole 101, 38123 Mattarello (Trento), Italy.
authors.forename: Philipp
authors.initials: P
authors.lastname: Ruhnau
authors.affiliation: Center for Mind/Brain Sciences, University of Trento, Via Delle Regole 101, 38123 Mattarello (Trento), Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Fuscà
authors.affiliation: Center for Mind/Brain Sciences, University of Trento, Via Delle Regole 101, 38123 Mattarello (Trento), Italy.
authors.forename: Gianpaolo
authors.initials: G
authors.lastname: Demarchi
authors.affiliation: Experimental Psychology Lab, Center for Excellence "Hearing4all," European Medical School, University of Oldenburg, 26111 Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, Carl-von-Ossietzky-Strasse 9-11, 26129 Oldenburg, Germany.
authors.forename: Christoph S
authors.initials: CS
authors.lastname: Herrmann
authors.affiliation: Center for Mind/Brain Sciences, University of Trento, Via Delle Regole 101, 38123 Mattarello (Trento), Italy.
authors.forename: Nathan
authors.initials: N
authors.lastname: Weisz
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D001307:Auditory Perception / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D005072:Evoked Potentials, Auditory; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D012815:Signal Processing, Computer-Assisted; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D014796:Visual Perception / Q000502:physiology; D055815:Young Adult
keywords: Artifact rejection; Entrainment; MEG; Magnetoencephalography; Transcranial alternating current stimulation; tACS