Schack B, Vath N, Petsche H, Geissler H-G, Möller E
Institute of Medical Statistics, Computer Science and Documentation, University of Jena, Jahnstr. 3, D-07740, Jena, Germany.
Int J Psychophysiol. 2002 May;44(2):143-63. doi: 10.1016/s0167-8760(01)00199-4.
Because of the importance of oscillations as a general phenomenon of neuronal activity the use of EEG spectral analysis is among the most important approaches for studying human information processing. Usually, oscillations at different frequencies occur simultaneously during information processing. Thus, the question for synchronisation of different frequencies by phase coupling and its possible functional significance is of primary importance. An answer may be given by bispectral analysis. Estimation of the (cross-) bispectrum allows to identify synchronised frequencies and possibly, the existence of non-linear phase coupling of different oscillators. Previous studies have demonstrated the simultaneous occurrence of slow (4-7 Hz) and fast (20-30 Hz) oscillations at frontal and prefrontal electrode positions during memory processing. However, interrelations between these rhythms have not been investigated up to now. In order to test short-term memory, the Sternberg task with random figures and number words was carried out on 10 female subjects. During the task EEG was recorded. Power and bispectral analyses from frontal, prefrontal and frontopolar regions were performed off-line. Increased power was found in both the theta and the gamma bands. Strong phase-coupling between theta at Fz and gamma at F3 and at Fp1, respectively, was shown for memorising number words by means of cross-bicoherence. A possible reason for this is an amplitude modulation of gamma frequencies by slow oscillations. The correspondent coherence analysis between the envelope of gamma frequencies at Fp1 and the raw EEG at Fz supports this presumption. This finding is interpreted as an EEG aspect of the functional linking between the prefrontal areas and the G.cinguli (as part of the limbic system), which are both extremely important for memory functions.
由于振荡作为神经元活动的一种普遍现象具有重要意义，脑电图频谱分析的应用是研究人类信息处理的最重要方法之一。通常，在信息处理过程中，不同频率的振荡会同时出现。因此，通过相位耦合实现不同频率同步及其可能的功能意义这一问题至关重要。双谱分析或许能给出答案。（交叉）双谱的估计有助于识别同步频率，还可能识别不同振荡器的非线性相位耦合的存在。先前的研究表明，在记忆处理过程中，额叶和前额叶电极位置会同时出现慢振荡（4 - 7赫兹）和快振荡（20 - 30赫兹）。然而，到目前为止，尚未对这些节律之间的相互关系进行研究。为了测试短期记忆，对10名女性受试者进行了带有随机数字和数字单词的斯特恩伯格任务。在任务过程中记录脑电图。离线对额叶、前额叶和额极区域进行功率和双谱分析。在θ波和γ波段均发现功率增加。通过交叉双相干性表明，在记忆数字单词时，Fz处的θ波与F3和Fp1处的γ波之间存在强相位耦合。其可能的原因是慢振荡对γ频率进行了幅度调制。Fp1处γ频率的包络与Fz处的原始脑电图之间的相应相干分析支持了这一推测。这一发现被解释为前额叶区域与扣带回（作为边缘系统的一部分）之间功能联系的脑电图表现，这两者对记忆功能都极为重要。
