Stecker Mark M
Department of Neurology, Geisinger Medical Center, Danville, PA 17822, USA.
IEEE Trans Biomed Eng. 2005 Sep;52(9):1619-21. doi: 10.1109/TBME.2009.851495.
The potential recorded by a set of electrodes as an action potential traverses a small axonal segment is proportional to the transmembrane potential produced during stimulation of that axon segment by the same set of recording electrodes, under certain circumstances. First, the membrane must have a constant thickness which is so small that the difference between the surface area of the inner and outer surfaces is minimal. Second, all media must be linear. Third, there must be a monotonically increasing relation between the mean transmembrane potential induced by a stimulus and the maximum transmembrane potential. Fourth, as each axon segment depolarizes, the transmembrane current and change in membrane potential during this time are same. This principle remains true for magnetic stimulation and recording as long as currents generated at the boundaries between regions of differing conductivity outside the axon contribute minimally to the field at the axon. This allows the identification of the point at which an action potential generates a maximal extracellular potential as the point that is stimulated with the lowest threshold.
在某些情况下，当动作电位穿过一小段轴突时，一组电极记录到的电位与同一组记录电极刺激该轴突段时产生的跨膜电位成正比。首先，膜必须具有恒定的厚度，且该厚度要足够小，使得内表面和外表面的表面积差异最小。其次，所有介质必须是线性的。第三，刺激诱导的平均跨膜电位与最大跨膜电位之间必须存在单调递增关系。第四，随着每个轴突段去极化，此时的跨膜电流和膜电位变化是相同的。只要轴突外部不同电导率区域之间的边界处产生的电流对轴突处的场贡献最小，该原理对于磁刺激和记录同样适用。这使得能够将动作电位产生最大细胞外电位的点识别为以最低阈值刺激的点。
