Abstract
The reliability of magnetoencephalography (MEG) resting-state functional connectivity in schizophrenia (SZ) is unknown as previous research has focused on healthy controls (HC). Here, we examined reliability in 26 participants (13-SZ, 13-HC). Eyes opened and eyes closed resting-state data were collected on 4 separate occasions during 2 visits, 1 week apart. For source modeling, we used minimum norm software to apply dynamic statistical parametric mapping. Source analyses compared the following functional connectivity metrics from each data run: coherence (coh), imaginary coherence (imcoh), pairwise phase consistency (ppc), phase-locking value (plv), phase lag index (pli), weighted phase lag index (wpli), and weighted phase lag index debiased (wpli2). Intraclass correlation coefficients (ICCs) were calculated for whole brain, network, and network pair averages. For reliability, ICCs above 0.75 = excellent, above 0.60 = good, above 0.40 = fair, and below 0.40 = poor reliability. We found the reliability of these metrics varied greatly depending on frequency band, network, network pair, and participant group examined. Broadband (1–58 Hz) whole brain averages in both HC and SZ showed excellent reliability for wpli2, and good to fair reliability for ppc, plv, and coh. Broadband network averages showed excellent to good reliability across 1 hour and 1 week for coh, imcoh, ppc, plv, wpli within default mode, cognitive control, and visual networks in HC, while the same metrics had excellent to fair reliability in SZ. Regional network pair averages showed good to fair reliability for coh, ppc, plv within default mode, cognitive control and visual network pairs in HC and SZ. In general, HC had higher reliability compared to SZ, and the default mode, cognitive control, and visual networks had higher reliability compared to somatosensory and auditory networks. Similar reliability levels occurred for both eyes opened and eyes closed resting-states for most metrics. The functional connectivity metrics of coh, ppc, and plv performed best across 1 hour and 1 week in HC and SZ. We also found that SZ had reduced coh, plv, and ppc in the dmn average and pair values indicating dysconnectivity in SZ. These findings encourage collecting both eyes opened and eyes closed resting-state MEG, while demonstrating that clinical populations may differ in reliability.
Highlights
Magnetoencephalography (MEG) is an advantageous neuroimaging tool to study psychosis due to its safety as a noninvasive test, along with the high dimensional data it provides on neuronal activity, oscillatory dynamics, and connectivity at a millisecond time scale
The results indicate functional connectivity reliability is highly dependent on connectivity metric, frequency band, and region or network size
In healthy controls (HC), we confirmed some patterns of functional connectivity for certain metrics and frequency bands, which were in line with previous research
Summary
Magnetoencephalography (MEG) is an advantageous neuroimaging tool to study psychosis due to its safety as a noninvasive test, along with the high dimensional data it provides on neuronal activity, oscillatory dynamics, and connectivity at a millisecond time scale. Other studies have reported weighted phase-lag index (wpli) and the imaginary part of coherency had excellent to good reliability of global connectivity over 30 trials in alpha and theta bands, but often fair to poor reliability in other frequency bands and in vertex-based connectivity [4]. It is clear given the variability of previous MEG functional connectivity findings that more research is needed to reach a consensus on which functional connectivity metric is best suited for MEG resting-state studies
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