Strik W K, Lehmann D
Department of Neurology, University Hospital, Zurich, Switzerland.
Electroencephalogr Clin Neurophysiol. 1993 Oct;87(4):169-74. doi: 10.1016/0013-4694(93)90016-o.
For the segmentation of series of momentary potential distribution maps into epochs of quasi-stable landscape (brain electric microstates), the maps are reduced to extracted landscape descriptors. Changes of the descriptors over time are recognized as segment terminators. The selection of the descriptors' tolerated variance (the window size) determines the result. We present a window-determining function which allows a data-driven determination of the optimal window size, based on equal weight given to the recognition of similarity and dissimilarity between maps. Segmentations based on two map descriptors (locations of extreme potentials and centroids) were used on 211 two-second map epochs from 8 normal subjects for validation of the window-determining function and to establish normative data. Using the data-determined window sizes for segmentation, the mean duration of the obtained microstates across subjects did not differ between descriptors (144 and 143 msec, respectively). Random permutation of the maps in time produced significantly shorter segments, ensuring that the segmentation disclosed real properties of the original data and not artifacts of the procedure.
为了将一系列瞬间电位分布图分割为准稳定态势（脑电微状态）的各个时期，这些地图被简化为提取的态势描述符。描述符随时间的变化被识别为段终止符。描述符容忍方差（窗口大小）的选择决定了结果。我们提出了一个窗口确定函数，该函数基于对地图之间相似性和差异性识别给予同等权重，允许数据驱动地确定最佳窗口大小。基于两个地图描述符（极值电位位置和质心）的分割应用于来自8名正常受试者的211个两秒地图时期，以验证窗口确定函数并建立规范数据。使用数据确定的窗口大小进行分割，各受试者获得的微状态平均持续时间在描述符之间没有差异（分别为144毫秒和143毫秒）。地图在时间上的随机排列产生了明显更短的段，确保分割揭示了原始数据的真实属性而非该过程的伪迹。
