Raz J, Biggins C A, Turetsky B, Fein G
Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor 48109.
IEEE Trans Biomed Eng. 1993 Sep;40(9):909-18. doi: 10.1109/10.245612.
We describe a statistical frequency domain approach to localizing equivalent dipole generators of human brain evoked potentials. The frequency domain representation allows considerable data reduction, constrains the magnitude function of the dipoles to be smooth, and accounts for the statistical properties of the background EEG. A previous paper described a restrictive model in which the dipole orientations were assumed to be fixed over time, and only one dipole was allowed. In this paper, we consider the more general model in which the orientation can vary over time, and which includes multiple dipole generators. The varying orientation model has the practical advantage of being more nearly linear and more flexible than the fixed orientation model, which facilitates convergence of the iterative fitting algorithm. We suggest a measure of goodness-of-fit that compares the likelihood of the dipole model with the likelihoods of saturated and null models. We report the results of fitting the model to recorded auditory and visual evoked potentials. A single dipole with fixed orientation seems to be an adequate model of the auditory midlatency response, while two dipoles with varying orientation are needed to fit the later P200 component. Analysis of the visual P100 response to unilateral stimulation localized a generator in the contralateral occipital cortex, as expected from anatomical considerations. A two-dipole model fit the visual P100 response of bilateral stimulations, and the locations of the two dipoles were similar to the locations obtained by single-dipole fits to the responses to left and right unilateral stimuli.
我们描述了一种用于定位人类脑诱发电位等效偶极子发生器的统计频域方法。频域表示允许大量的数据简化，限制偶极子的幅度函数为平滑的，并考虑背景脑电图的统计特性。先前的一篇论文描述了一个受限模型，其中假设偶极子方向随时间固定，并且只允许有一个偶极子。在本文中，我们考虑更一般的模型，其中方向可以随时间变化，并且该模型包括多个偶极子发生器。与固定方向模型相比，变化方向模型具有更接近线性和更灵活的实际优势，这有利于迭代拟合算法的收敛。我们提出了一种拟合优度度量，它将偶极子模型的似然性与饱和模型和零模型的似然性进行比较。我们报告了将该模型拟合到记录的听觉和视觉诱发电位的结果。具有固定方向的单个偶极子似乎是听觉中潜伏期反应的一个充分模型，而拟合后期的P200成分则需要两个具有变化方向的偶极子。对单侧刺激的视觉P100反应的分析将一个发生器定位在对侧枕叶皮层，这与解剖学考虑所预期的一致。一个双偶极子模型拟合了双侧刺激的视觉P100反应，并且这两个偶极子的位置类似于通过对左右单侧刺激的反应进行单偶极子拟合所获得的位置。
