title: Large-scale network-level processes during entrainment.
abstract: Visual rhythmic stimulation evokes a robust power increase exactly at the stimulation frequency, the so-called steady-state response (SSR). Localization of visual SSRs normally shows a very focal modulation of power in visual cortex and led to the treatment and interpretation of SSRs as a local phenomenon. Given the brain network dynamics, we hypothesized that SSRs have additional large-scale effects on the brain functional network that can be revealed by means of graph theory. We used rhythmic visual stimulation at a range of frequencies (4-30 Hz), recorded MEG and investigated source level connectivity across the whole brain. Using graph theoretical measures we observed a frequency-unspecific reduction of global density in the alpha band "disconnecting" visual cortex from the rest of the network. Also, a frequency-specific increase of connectivity between occipital cortex and precuneus was found at the stimulation frequency that exhibited the highest resonance (30 Hz). In conclusion, we showed that SSRs dynamically re-organized the brain functional network. These large-scale effects should be taken into account not only when attempting to explain the nature of SSRs, but also when used in various experimental designs.
authors.affiliation: Center for Mind/Brain Sciences, CIMeC, University of Trento, via delle Regole 101, Mattarello 38122, Italy; Center for Cognitive Neuroscience, University of Salzburg, Hellbrunnerstraße 34/II, Salzburg 5020, Austria. Electronic address: chrysoula.lithari@sbg.ac.at.
authors.forename: Chrysa
authors.initials: C
authors.lastname: Lithari
authors.affiliation: Center for Mind/Brain Sciences, CIMeC, University of Trento, via delle Regole 101, Mattarello 38122, Italy. Electronic address: carolina.sanchez@unit.it.
authors.forename: Carolina
authors.initials: C
authors.lastname: Sánchez-García
authors.affiliation: Center for Cognitive Neuroscience, University of Salzburg, Hellbrunnerstraße 34/II, Salzburg 5020, Austria. Electronic address: philipp.ruhnau@sbg.ac.at.
authors.forename: Philipp
authors.initials: P
authors.lastname: Ruhnau
authors.affiliation: Center for Mind/Brain Sciences, CIMeC, University of Trento, via delle Regole 101, Mattarello 38122, Italy; Center for Cognitive Neuroscience, University of Salzburg, Hellbrunnerstraße 34/II, Salzburg 5020, Austria. Electronic address: nathan.weisz@sbg.ac.at.
authors.forename: Nathan
authors.initials: N
authors.lastname: Weisz
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D001921:Brain / Q000502:physiology*; D058256:Brain Waves; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D012815:Signal Processing, Computer-Assisted; D014793:Visual Cortex / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Entrainment; Functional connectivity; Global density; Graph theory; Node degree; Seeded connectivity; Visual steady-state
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