Laureate Institute for Brain Research, Tulsa, Oklahoma, USA.
School of Electrical and Computer Engineering, University of Oklahoma, Tulsa, Oklahoma, USA.
Brain Connect. 2020 Dec;10(10):535-546. doi: 10.1089/brain.2019.0731. Epub 2020 Oct 28.
Concurrent electroencephalography and resting-state functional magnetic resonance imaging (rsfMRI) have been widely used for studying the (presumably) awake and alert human brain with high temporal/spatial resolution. Although rsfMRI scans are typically collected while individuals are instructed to focus their eyes on a fixated cross, objective and verified experimental measures to quantify degree of vigilance are not readily available. Electroencephalography (EEG) is the modality extensively used for estimating vigilance, especially during eyes-closed resting state. However, pupil size measured using an eye-tracker device could provide an indirect index of vigilance. Three 12-min resting scans (eyes open, fixating on the cross) were collected from 10 healthy control participants. We simultaneously collected EEG, fMRI, physiological, and eye-tracker data and investigated the correlation between EEG features, pupil size, and heart rate. Furthermore, we used pupil size and EEG features as regressors to find their correlations with blood-oxygen-level-dependent fMRI measures. EEG frontal and occipital beta power (FOBP) correlates with pupil size changes, an indirect index for locus coeruleus activity implicated in vigilance regulation ( = 0.306, < 0.001). Moreover, FOBP also correlated with heart rate ( = 0.255, < 0.001), as well as several brain regions in the anticorrelated network, including the bilateral insula and inferior parietal lobule. In this study, we investigated whether simultaneous EEG-fMRI combined with eye-tracker measurements can be used to determine EEG signal feature associated with vigilance measures during eyes-open rsfMRI. Our results support the conclusion that FOBP is an objective measure of vigilance in healthy human subjects. Impact statement We revealed an association between electroencephalography frontal and occipital beta power (FOBP) and pupil size changes during an eyes-open resting state, which supports the conclusion that FOBP could serve as an objective measure of vigilance in healthy human subjects. The results were validated by using simultaneously recorded heart rate and functional magnetic resonance imaging (fMRI). Interestingly, independently verified heart rate changes can also provide an easy-to-determine measure of vigilance during resting-state fMRI. These findings have important implications for an analysis and interpretation of dynamic resting-state fMRI connectivity studies in health and disease.
同步脑电图和静息态功能磁共振成像 (rsfMRI) 已广泛用于研究具有高时间/空间分辨率的（推测）清醒和警觉的人类大脑。虽然 rsfMRI 扫描通常是在被试者被指示注视固定十字的情况下采集的，但量化警觉程度的客观和经过验证的实验测量方法并不容易获得。脑电图 (EEG) 是用于估计警觉度的广泛使用的模态，尤其是在闭眼静息状态下。然而，使用眼动追踪设备测量的瞳孔大小可以提供警觉度的间接指标。10 名健康对照参与者进行了 3 次 12 分钟的静息扫描（睁眼，注视十字）。我们同时采集了 EEG、fMRI、生理和眼动追踪数据，并研究了 EEG 特征、瞳孔大小和心率之间的相关性。此外，我们使用瞳孔大小和 EEG 特征作为回归变量，以发现它们与血氧水平依赖 fMRI 测量值的相关性。EEG 额叶和枕叶β功率（FOBP）与瞳孔大小变化相关，这是与警觉调节有关的蓝斑活动的间接指标（ = 0.306， < 0.001）。此外，FOBP 还与心率相关（ = 0.255， < 0.001），以及负相关网络中的几个脑区，包括双侧岛叶和下顶叶。在这项研究中，我们调查了 EEG-fMRI 与眼动追踪测量相结合是否可用于确定睁眼 rsfMRI 期间与警觉度测量相关的 EEG 信号特征。我们的结果支持 FOBP 是健康人体被试警觉度的客观测量指标的结论。研究意义我们揭示了脑电图额叶和枕叶β功率（FOBP）与睁眼静息状态下瞳孔大小变化之间的关联，这支持了 FOBP 可作为健康人体被试警觉度的客观测量指标的结论。该结果通过同时记录的心率和功能磁共振成像（fMRI）得到了验证。有趣的是，独立验证的心率变化也可以提供静息状态 fMRI 期间警觉度的易于确定的测量方法。这些发现对健康和疾病状态下动态静息状态 fMRI 连接研究的分析和解释具有重要意义。
