Saypol J M, Roth B J, Cohen L G, Hallett M
Biomedical Engineering and Instrumentation Program, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Ann Biomed Eng. 1991;19(3):317-28. doi: 10.1007/BF02584306.
We present a theoretical comparison of the electric field produced in the brain by three modalities of transcranial stimulation of the cortex: magnetic stimulation, bifocal electric stimulation, and unifocal electric stimulation. The primary focus of this comparison is the focality and direction of the electric fields produced. A three-sphere model is used to represent the scalp, skull, and brain. All electric fields are calculated numerically. For magnetic stimulation we consider only a figure-of-eight coil. We find that magnetic stimulation produces the most focal field, while unifocal electric produces the least. Fields produced during magnetic stimulation are parallel to the head surface, while fields produced during electric stimulation have components both parallel and perpendicular to the head surface. The electric field produced by magnetic stimulation is shown to be insensitive to the skull conductivity, while that produced by electric stimulation is very sensitive to it.
磁刺激、双焦点电刺激和单焦点电刺激。该比较的主要关注点是所产生电场的聚焦性和方向。使用三球体模型来表示头皮、颅骨和大脑。所有电场均通过数值计算得出。对于磁刺激，我们仅考虑一个8字形线圈。我们发现磁刺激产生的电场最聚焦，而单焦点电刺激产生的电场聚焦性最差。磁刺激期间产生的电场与头部表面平行，而电刺激期间产生的电场既有平行于头部表面的分量，也有垂直于头部表面的分量。结果表明，磁刺激产生的电场对颅骨电导率不敏感，而电刺激产生的电场对其非常敏感。
