title: Selective modulation of interhemispheric functional connectivity by HD-tACS shapes perception.
abstract: Oscillatory neuronal synchronization between cortical areas has been suggested to constitute a flexible mechanism to coordinate information flow in the human cerebral cortex. However, it remains unclear whether synchronized neuronal activity merely represents an epiphenomenon or whether it is causally involved in the selective gating of information. Here, we combined bilateral high-density transcranial alternating current stimulation (HD-tACS) at 40 Hz with simultaneous electroencephalographic (EEG) recordings to study immediate electrophysiological effects during the selective entrainment of oscillatory gamma-band signatures. We found that interhemispheric functional connectivity was modulated in a predictable, phase-specific way: In-phase stimulation enhanced synchronization, anti-phase stimulation impaired functional coupling. Perceptual correlates of these connectivity changes were found in an ambiguous motion task, which strongly support the functional relevance of long-range neuronal coupling. Additionally, our results revealed a decrease in oscillatory alpha power in response to the entrainment of gamma band signatures. This finding provides causal evidence for the antagonistic role of alpha and gamma oscillations in the parieto-occipital cortex and confirms that the observed gamma band modulations were physiological in nature. Our results demonstrate that synchronized cortical network activity across several spatiotemporal scales is essential for conscious perception and cognition.
authors.affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Randolph F
authors.initials: RF
authors.lastname: Helfrich
authors.affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Hannah
authors.initials: H
authors.lastname: Knepper
authors.affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Guido
authors.initials: G
authors.lastname: Nolte
authors.affiliation: Experimental Psychology Lab, Center for Excellence 'Hearing4all', European Medical School, University of Oldenburg, Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Strüber
authors.affiliation: Experimental Psychology Lab, Center for Excellence 'Hearing4all', European Medical School, University of Oldenburg, Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany; Department of Epidemiological Methods and Etiologic Research, Leibniz Institute for Prevention Research and Epidemiology - BIPS, Bremen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rach
authors.affiliation: Experimental Psychology Lab, Center for Excellence 'Hearing4all', European Medical School, University of Oldenburg, Oldenburg, Germany; Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany.
authors.forename: Christoph S
authors.initials: CS
authors.lastname: Herrmann
authors.affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Till R
authors.initials: TR
authors.lastname: Schneider
authors.affiliation: Department of Neurophysiology and Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Engel
mesh_terms: D000328:Adult; D001519:Behavior; D054022:Cerebrum / Q000502:physiology*; D003344:Cortical Synchronization; D004566:Electrodes; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology*; D049489:Stroboscopy; D065908:Transcranial Direct Current Stimulation