Functional brain connectivity measures extracted from resting-state functional magnetic resonance imaging (fMRI) scans have generated wide interest as potential noninvasive biomarkers. In this context, performing global signal regression (GSR) as a preprocessing step remains controversial. Specifically, while it has been shown that a considerable fraction of global signal variations is associated with physiological and motion sources, GSR may also result in removing neural activity. Here, we address this question by examining the fundamental sources of resting global signal fluctuations using simultaneous electroencephalography (EEG)-fMRI data combined with cardiac and breathing recordings. Our results suggest that systemic physiological fluctuations account for a significantly larger fraction of global signal variability compared to electrophysiological fluctuations. Furthermore, we show that GSR reduces artifactual connectivity due to heart rate and breathing fluctuations, but preserves connectivity patterns associated with electrophysiological activity within the alpha and beta frequency ranges. Overall, these results provide evidence that the neural component of resting-state fMRI-based connectivity is preserved after the global signal is regressed out.

中文翻译：

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全局信号回归是否会改变与脑电图活动相关的功能磁共振成像连接模式？人类脑电图-功能磁共振成像研究

从静息态功能磁共振成像（fMRI）扫描中提取的功能性大脑连接测量作为潜在的非侵入性生物标志物引起了广泛的兴趣。在这种情况下，执行全局信号回归（GSR）作为预处理步骤仍然存在争议。具体来说，虽然已经表明全局信号变化的相当一部分与生理和运动源相关，但 GSR 也可能导致消除神经活动。在这里，我们通过使用同步脑电图 (EEG)-fMRI 数据结合心脏和呼吸记录检查静息全局信号波动的基本来源来解决这个问题。我们的结果表明，与电生理波动相比，全身生理波动在全局信号变异中所占的比例要大得多。此外，我们表明 GSR 减少了由于心率和呼吸波动而导致的人为连接，但保留了与 α 和 β 频率范围内的电生理活动相关的连接模式。总体而言，这些结果提供了证据，表明在全局信号回归后，基于静息态功能磁共振成像的连接的神经成分得以保留。