Feige Bernd, Scheffler Klaus, Esposito Fabrizio, Di Salle Francesco, Hennig Jürgen, Seifritz Erich
Department of Psychiatry and Psychotherapy, University of Freiburg, Germany.
J Neurophysiol. 2005 May;93(5):2864-72. doi: 10.1152/jn.00721.2004. Epub 2004 Dec 15.
Neural correlates of electroencephalographic (EEG) alpha rhythm are poorly understood. Here, we related EEG alpha rhythm in awake humans to blood-oxygen-level-dependent (BOLD) signal change determined by functional magnetic resonance imaging (fMRI). Topographical EEG was recorded simultaneously with fMRI during an open versus closed eyes and an auditory stimulation versus silence condition. EEG was separated into spatial components of maximal temporal independence using independent component analysis. Alpha component amplitudes and stimulus conditions served as general linear model regressors of the fMRI signal time course. In both paradigms, EEG alpha component amplitudes were associated with BOLD signal decreases in occipital areas, but not in thalamus, when a standard BOLD response curve (maximum effect at approximately 6 s) was assumed. The part of the alpha regressor independent of the protocol condition, however, revealed significant positive thalamic and mesencephalic correlations with a mean time delay of approximately 2.5 s between EEG and BOLD signals. The inverse relationship between EEG alpha amplitude and BOLD signals in primary and secondary visual areas suggests that widespread thalamocortical synchronization is associated with decreased brain metabolism. While the temporal relationship of this association is consistent with metabolic changes occurring simultaneously with changes in the alpha rhythm, sites in the medial thalamus and in the anterior midbrain were found to correlate with short time lag. Assuming a canonical hemodynamic response function, this finding is indicative of activity preceding the actual EEG change by some seconds.
脑电图（EEG）α节律的神经相关性目前还知之甚少。在此，我们将清醒人类的EEGα节律与功能磁共振成像（fMRI）所确定的血氧水平依赖（BOLD）信号变化联系起来。在睁眼与闭眼以及听觉刺激与安静状态下，同步记录fMRI期间的头皮脑电图。使用独立成分分析将EEG分离为具有最大时间独立性的空间成分。α成分振幅和刺激条件作为fMRI信号时间过程的一般线性模型回归变量。在这两种范式中，当假设标准BOLD反应曲线（在约6秒时达到最大效应）时，EEGα成分振幅与枕叶区域的BOLD信号降低相关，但与丘脑无关。然而，α回归变量中与实验条件无关的部分显示，丘脑和中脑与EEG和BOLD信号之间存在显著的正相关，平均时间延迟约为2.5秒。初级和次级视觉区域中EEGα振幅与BOLD信号之间的负相关关系表明，广泛的丘脑皮质同步与脑代谢降低有关。虽然这种关联的时间关系与α节律变化同时发生的代谢变化一致，但在内侧丘脑和中脑前部发现的部位与短时间延迟相关。假设典型的血液动力学反应函数，这一发现表明在实际EEG变化前几秒就有活动发生。
