Geva A B, Pratt H, Zeevi Y Y
Evoked Potentials Laboratory, Technion, Israel Institute of Technology, Haifa.
Electroencephalogr Clin Neurophysiol. 1995 May;96(3):278-86. doi: 10.1016/0168-5597(94)00294-o.
Scalp recording of electrical events allows evaluation of human cerebral function, but contributions of the specific brain structures generating the recorded activity are ambiguous. This problem is ill-posed and cannot be solved without auxiliary physiological knowledge about the spatio-temporal characteristics of the generators' activity. In our source localization by model-based wavelet-type decomposition, scalp recorded signals are decomposed into a combination of wavelets, each of which may describe the coherent activity of a population of neurons. We chose the Hermite functions (derived from the Gaussian function to form mono-, bi- and triphasic wave forms) as the mathematical model to describe the temporal pattern of mass neural activity. For each wavelet we solve the inverse problem for two symmetrically positioned and oriented dipoles, one of which attains zero magnitude when a single source is more suitable. We use the wavelet to model the temporal activity pattern of the symmetrical dipoles. By this we reduce the dimension of inverse problem and find a plausible solution. Once the number and the initial parameters of the sources are given, we can apply multiple source localization to correct the solution for generators with overlapping activities. Application of the procedure to subcortical and cortical components of somatosensory evoked potentials demonstrates its feasibility.
对电活动进行头皮记录可用于评估人类大脑功能，但产生所记录活动的特定脑结构的贡献并不明确。这个问题是不适定的，若没有关于发生器活动时空特征的辅助生理学知识就无法解决。在我们基于模型的小波型分解的源定位方法中，头皮记录信号被分解为小波的组合，每个小波可能描述一群神经元的相干活动。我们选择埃尔米特函数（由高斯函数推导而来，形成单、双和三相波形）作为数学模型来描述大量神经活动的时间模式。对于每个小波，我们求解两个对称定位和定向偶极子的逆问题，当单个源更合适时，其中一个偶极子的幅度为零。我们使用小波来模拟对称偶极子的时间活动模式。通过这种方式，我们降低了逆问题的维度并找到一个合理的解决方案。一旦给出源的数量和初始参数，我们就可以应用多源定位来校正具有重叠活动的发生器的解决方案。将该程序应用于体感诱发电位的皮层下和皮层成分证明了其可行性。
