Pascual-Marqui R D, Michel C M, Lehmann D
Department of Neurology, University Hospital, Geneva, Switzerland.
Int J Psychophysiol. 1994 Oct;18(1):49-65. doi: 10.1016/0167-8760(84)90014-x.
This paper presents a new method for localizing the electric activity in the brain based on multichannel surface EEG recordings. In contrast to the models presented up to now the new method does not assume a limited number of dipolar point sources nor a distribution on a given known surface, but directly computes a current distribution throughout the full brain volume. In order to find a unique solution for the 3-dimensional distribution among the infinite set of different possible solutions, the method assumes that neighboring neurons are simultaneously and synchronously activated. The basic assumption rests on evidence from single cell recordings in the brain that demonstrates strong synchronization of adjacent neurons. In view of this physiological consideration the computational task is to select the smoothest of all possible 3-dimensional current distributions, a task that is a common procedure in generalized signal processing. The result is a true 3-dimensional tomography with the characteristic that localization is preserved with a certain amount of dispersion, i.e., it has a relatively low spatial resolution. The new method, which we call Low Resolution Electromagnetic Tomography (LORETA) is illustrated with two different sets of evoked potential data, the first showing the tomography of the P100 component to checkerboard stimulation of the left, right, upper and lower hemiretina, and the second showing the results for the auditory N100 component and the two cognitive components CNV and P300. A direct comparison of the tomography results with those obtained from fitting one and two dipoles illustrates that the new method provides physiologically meaningful results while dipolar solutions fail in many situations. In the case of the cognitive components, the method offers new hypotheses on the location of higher cognitive functions in the brain.
本文提出了一种基于多通道头皮脑电图记录来定位大脑电活动的新方法。与迄今为止提出的模型不同，新方法既不假定有限数量的偶极点源，也不假定给定已知表面上的分布，而是直接计算整个全脑体积中的电流分布。为了在无限组不同可能解中找到三维分布的唯一解，该方法假定相邻神经元同时且同步激活。这一基本假设基于大脑单细胞记录的证据，这些证据表明相邻神经元存在强烈同步性。鉴于这种生理学考虑，计算任务是从所有可能的三维电流分布中选择最平滑的分布，这是广义信号处理中的常见步骤。结果是一种真正的三维断层成像，其特点是定位在一定程度的离散情况下得以保留，即具有相对较低的空间分辨率。我们将这种新方法称为低分辨率电磁断层成像（LORETA），并用两组不同的诱发电位数据进行了说明，第一组展示了对左、右、上、下视网膜半侧棋盘格刺激的P100成分的断层成像，第二组展示了听觉N100成分以及两个认知成分CNV和P300的结果。将断层成像结果与通过拟合一个和两个偶极获得的数据进行直接比较表明，新方法能提供具有生理学意义的结果，而偶极解在许多情况下则无法做到。对于认知成分，该方法为大脑中高级认知功能的位置提供了新的假设。
