Temporal dynamics of spontaneous MEG activity in brain networks

TLDR

Functional MRI shows low‑frequency spontaneous BOLD fluctuations coherent within large‑scale cortical and subcortical networks during rest, yet the neuronal mechanisms underlying these resting‑state networks remain poorly understood. This study aims to identify magnetoencephalographic counterparts of the dorsal attention and default mode networks. Seed‑based correlation mapping of time‑dependent MEG power reconstructed at each voxel was used to delineate these networks. MEG‑derived RSNs matched fMRI topography over 5‑minute epochs but were initially confined to the seed hemisphere, while nonstationary analysis revealed transient, more complete networks including contralateral nodes, and spectral analysis showed that these networks manifest as synchronous modulation of theta, alpha, and beta band power—slower than event‑related BOLD correlates.

Abstract

Functional MRI (fMRI) studies have shown that low-frequency (<0.1 Hz) spontaneous fluctuations of the blood oxygenation level dependent (BOLD) signal during restful wakefulness are coherent within distributed large-scale cortical and subcortical networks (resting state networks, RSNs). The neuronal mechanisms underlying RSNs remain poorly understood. Here, we describe magnetoencephalographic correspondents of two well-characterized RSNs: the dorsal attention and the default mode networks. Seed-based correlation mapping was performed using time-dependent MEG power reconstructed at each voxel within the brain. The topography of RSNs computed on the basis of extended (5 min) epochs was similar to that observed with fMRI but confined to the same hemisphere as the seed region. Analyses taking into account the nonstationarity of MEG activity showed transient formation of more complete RSNs, including nodes in the contralateral hemisphere. Spectral analysis indicated that RSNs manifest in MEG as synchronous modulation of band-limited power primarily within the theta, alpha, and beta bands—that is, in frequencies slower than those associated with the local electrophysiological correlates of event-related BOLD responses.