Pascual-Marqui R D, Valdes-Sosa P A, Alvarez-Amador A
Neurosciences Branch, National Center for Scientific Research, Havana, Cuba.
Int J Neurosci. 1988 May;40(1-2):89-99. doi: 10.3109/00207458808985730.
The EEG is modelled as the superposition of two component processes: the xi and the alpha processes. In the frequency domain, the xi process is always present and appears as a spectral peak with maximum amplitude at very low frequencies, while the alpha process is characterized by a spectral peak with its maximum located in the traditional alpha band (7-13 Hz), and is not necessarily always present. The multivariate properties of EEG spectra are adequately modelled with frequency independent coherence matrices for each process. Multichannel EEG studies reveal interesting properties: (1) the generalized coherence for alpha is much larger than for xi, indicating increased functional coupling for the alpha process; (2) the alpha coherence matrix has reduced dimensionality, possibly related to a small number of generators; (3) xi coherences are zero phase with magnitudes that decrease exponentially with interelectrode distance; and (4) alpha coherences have significant nonzero phase shifts.
脑电图（EEG）被建模为两个组成过程的叠加：ξ过程和α过程。在频域中，ξ过程始终存在，并表现为在极低频率处具有最大振幅的频谱峰值，而α过程的特征是其最大频谱峰值位于传统的α频段（7 - 13赫兹），并且不一定总是存在。EEG频谱的多变量特性通过对每个过程使用频率无关的相干矩阵进行了充分建模。多通道EEG研究揭示了有趣的特性：（1）α的广义相干性比ξ大得多，表明α过程的功能耦合增加；（2）α相干矩阵的维度降低，可能与少量发生器有关；（3）ξ相干性的相位为零，其幅度随电极间距离呈指数下降；（4）α相干性具有显著的非零相移。
