Bagshaw E V, Evans M H
Exp Brain Res. 1976 Jun 30;25(4):391-400. doi: 10.1007/BF00241729.
Tungsten stimulating microelectrodes have been tested in monopolar, bipolar and concentric configurations for the extent to which unwanted current spread occurred. Current spread from monopolar electrodes in close conformity with the predictions of the inverse square law, both in vitro in vivo. The bipolar and concentric configurations, tested only in vitro, had current-spread characteristics which did not follow the inverse square law so closely. The bipolar configuration gave little reduction in spread, compared wpith a monopolar electrode, but the concentric configuration did reduce the extent of stimulus spread. The extent of spread depends greatly upon a number of experimental variables, including the dimensions of the microelectrode tip. For studies requiring precise localization with low stimulus currents, it is advisable to determine the inverse square law constant for each experimental situation. For more generalized stimulation purposes within the mammalian C.N.S., employing monopolar microelectrodes of moderate tip size, brief pulses of 10 muA can be expected to stimulate myelinated axons with about 0.15 mm of the tip, and 100 muA WILL Stimulate with a radius of about 0.5 mm.
钨刺激微电极已在单极、双极和同心配置下进行了测试，以确定不需要的电流扩散程度。单极电极的电流扩散在体外和体内都与平方反比定律的预测高度一致。双极和同心配置仅在体外进行了测试，其电流扩散特性并不那么严格地遵循平方反比定律。与单极电极相比，双极配置在扩散减少方面效果不佳，但同心配置确实减少了刺激扩散的程度。扩散程度在很大程度上取决于许多实验变量，包括微电极尖端的尺寸。对于需要在低刺激电流下进行精确定位的研究，建议针对每种实验情况确定平方反比定律常数。对于哺乳动物中枢神经系统内更广泛的刺激目的，使用中等尖端尺寸的单极微电极，预计10微安的短脉冲可刺激尖端约0.15毫米范围内的有髓轴突，100微安将刺激半径约为0.5毫米范围内的轴突。
