Chávez Mario, Le Van Quyen Michel, Navarro Vincent, Baulac Michel, Martinerie Jacques
Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), CNRS-UPR 640 (Hôpital de la Salpêtrière), Paris, 76651 Cedex 13, France.
IEEE Trans Biomed Eng. 2003 May;50(5):571-83. doi: 10.1109/TBME.2003.810696.
The mechanisms underlying the transition of brain activity toward epileptic seizures remain unclear. Based on nonlinear analysis of both intracranial and scalp electroencephalographic (EEG) recordings, different research groups have recently reported dynamical smooth changes in epileptic brain activity several minutes before seizure onset. Such preictal states have been detected in populations of patients with mesial temporal lobe epilepsy (MTLE) and, more recently, with different neocortical partial epilepsies (NPEs). In this paper, we are particularly interested in the spatio-temporal organization of epileptogenic networks prior to seizures in neocortical epilepsies. For this, we characterize the network of two patients with NPE by means of two nonlinear measures of interdependencies. Since the synchronization of neuronal activity is an essential feature of the generation and propagation of epileptic activity, we have analyzed changes in phase synchrony between EEG time series. In order to compare the phase and amplitude dynamics, we have also studied the degree of association between pairs of signals by means of a nonlinear correlation coefficient. Recent findings have suggested changes prior to seizures in a wideband frequency range. Instead, for the examples of this study, we report a significant decrease of synchrony in the focal area several minutes before seizures (>>30 min in both patients) in the frequency band of 10-25 Hz mainly. Furthermore, the spatio-temporal organization of this preictal activity seems to be specifically related to this frequency band. Measures of both amplitude and phase coupling yielded similar results in narrow-band analysis. These results may open new perspectives on the mechanisms of seizure emergence as well as the organization of neocortical epileptogenic networks. The possibility of forecasting the onset of seizures has important implications for a better understanding, diagnosis and a potential treatment of the epilepsy.
大脑活动向癫痫发作转变的潜在机制仍不清楚。基于对颅内和头皮脑电图（EEG）记录的非线性分析，不同研究小组最近报告称，在癫痫发作开始前几分钟，癫痫脑活动会出现动态平稳变化。这种发作前期状态已在颞叶内侧癫痫（MTLE）患者群体中被检测到，最近在不同的新皮质局灶性癫痫（NPE）患者中也被检测到。在本文中，我们特别关注新皮质癫痫发作前致痫网络的时空组织。为此，我们通过两种相互依赖的非线性测量方法，对两名NPE患者的网络进行了特征描述。由于神经元活动的同步是癫痫活动产生和传播的一个基本特征，我们分析了EEG时间序列之间相位同步的变化。为了比较相位和幅度动态，我们还通过非线性相关系数研究了信号对之间的关联程度。最近的研究结果表明，在癫痫发作前宽带频率范围内会发生变化。相反，对于本研究的实例，我们报告在癫痫发作前几分钟（两名患者均>>30分钟），主要在10 - 25Hz频段，病灶区域的同步性显著降低。此外，这种发作前期活动的时空组织似乎与该频段有特定关系。在窄带分析中，幅度和相位耦合测量产生了相似的结果。这些结果可能为癫痫发作的机制以及新皮质致痫网络的组织开辟新的视角。预测癫痫发作开始的可能性对于更好地理解、诊断和潜在治疗癫痫具有重要意义。
