DISTORTION OF MAGNETIC EVOKED FIELDS AND SURFACE-POTENTIALS BY CONDUCTIVITY DIFFERENCES AT BOUNDARIES IN BRAIN-TISSUE
DISTORTION OF MAGNETIC EVOKED FIELDS AND SURFACE-POTENTIALS BY CONDUCTIVITY DIFFERENCES AT BOUNDARIES IN BRAIN-TISSUE
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DOI：
10.1016/s0006-3495(90)82635-7
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发表时间：
1990-06-01
影响因子：
3.4
通讯作者：
OKADA, YC
中科院分区：
文献类型：
--
作者：
HUANG, JC;NICHOLSON, C;OKADA, YC
我们研究了在什么条件下，电导率的不均匀可能显著改变由于大脑中的初级电流(即神经元电流)而引起的磁场(MEF)。在一个孤立的海龟小脑浸泡在一个大的生理盐水浴缸的情况下，我们的理论分析显示，由于初级电流，对于实验确定的小脑组织和生理盐水的电导值，小脑表面显著提高了MEF，提高了两倍。对电导效应的进一步参数研究表明，由于位于电导边界1 mm内的神经元电流，电导边界可能显著改变MEF，就像在水肿区、中风期间可能出现的缺氧边缘或人头脑室附近的活跃神经元的情况一样。对于固定的神经源，电导边界可以改变其MEF的大小，而不影响其时间波形。然而，这种边界效应被发现对于局部接近沟或裂隙中皮质源的模型几何图形来说是很小的，其中来自相邻沟壁的边界效应往往相互抵消。
We investigated the conditions under which inhomogeneity in electrical conductivity may significantly modify the magnetic evoked field (MEF) due to primary currents (i.e., neuronal currents) in the brain. In the case of an isolated turtle cerebellum immersed in a large bath of physiological saline, our theoretical analysis showed the cerebellar surface to significantly enhance the MEF due to a primary current, by a factor of as much as two, for experimentally determined values of the conductivities of the cerebellar tissues and saline. A further parametric investigation of the conductivity effect revealed that conductivity boundaries may significantly modify the MEF due to neuronal currents located within 1 mm of a conductivity boundary, as would be the case for active neurons near an edema, an anoxic fringe such as might occur during stroke, or a ventricle in the human head. For a stationary neural source, conductivity boundaries may modify the magnitude of its MEF without affecting its temporal waveform. However, this boundary effect was found to be small for a model geometry locally approximating cortical sources in a sulcus or a fissure, where the boundary effects from adjacent sulcal walls tend to cancel each other.