Elsevier

Brain Research

Volume 1635, 15 March 2016, Pages 143-152
Brain Research

Research Report
Large-scale network-level processes during entrainment

https://doi.org/10.1016/j.brainres.2016.01.043Get rights and content
Under a Creative Commons license
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Highlights

  • Visual entrainment is considered mostly to modulate cortical power locally.

  • Instead, we hypothesized large-scale effects in the brain functional network.

  • Graph theoretical analysis combined with MEG source localization.

  • Visual entrainment indeed yielded network-level effects.

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.

Keywords

Visual steady-state
Graph theory
Global density
Node degree
Seeded connectivity
Functional connectivity
Entrainment

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