Nikulin V V, Brismar T
Department of Clinical Neuroscience, Karolinska Institutet, Clinical Neurophysiology, Karolinska Hospital R2:01, S-17176, Stockholm, Sweden.
Neuroscience. 2006;137(2):647-57. doi: 10.1016/j.neuroscience.2005.10.031. Epub 2005 Dec 9.
Coordination of neuronal oscillations generated at different frequencies has been hypothesized to be an important feature of integrative brain functions. The present study aimed at the evaluation of the cross-frequency phase synchronization between electroencephalographic alpha and beta oscillations. The amplitude and phase information were extracted from electroencephalograms recorded in 176 healthy human subjects using an analytic signal approach based on the Hilbert transform. The results reliably demonstrated the presence of phase synchronization between alpha and beta oscillations, with a maximum in the occipito-parietal areas. The phase difference between alpha and beta oscillations showed characteristic peaks at about 2 and -1 radians, which were common for many subjects and electrodes. A specific phase difference might reflect similarity in the organization and interconnections of the networks generating alpha and beta oscillations across the entire cortex. Beta oscillations, which are phase-locked to alpha oscillations--alpha-synchronous beta oscillations--were largest in the occipito-parietal area with a second smaller maximum in the frontal area, thus demonstrating a topography, which was different from the conventional alpha and beta oscillations. The strength of the alpha-synchronous beta oscillations was not exclusively defined by the amplitude of the alpha rhythm indicating that they represent a distinct feature of the spontaneous electroencephalogram, which allows for a refined discrimination of the dynamics of beta oscillations.
不同频率产生的神经元振荡的协调被认为是大脑整合功能的一个重要特征。本研究旨在评估脑电图中α波和β波振荡之间的跨频率相位同步。使用基于希尔伯特变换的解析信号方法，从176名健康人类受试者记录的脑电图中提取幅度和相位信息。结果可靠地证明了α波和β波振荡之间存在相位同步，在枕顶叶区域最为明显。α波和β波振荡之间的相位差在约2弧度和 -1弧度处显示出特征性峰值，这在许多受试者和电极中都很常见。特定的相位差可能反映了在整个皮层中产生α波和β波振荡的网络的组织和互连的相似性。与α波振荡锁相的β波振荡——α同步β波振荡——在枕顶叶区域最大，在额叶区域有第二个较小的峰值，从而显示出一种不同于传统α波和β波振荡的地形图。α同步β波振荡的强度并非完全由α节律的幅度决定，这表明它们代表了自发脑电图的一个独特特征，有助于更精确地区分β波振荡的动态变化。
