Holder D S
Department of Physiology, University College, London, UK.
Med Biol Eng Comput. 1992 Mar;30(2):140-6. doi: 10.1007/BF02446122.
Impedance changes were measured during the compound action potential (CAP) in isolated crab nerves with 50 kHz or direct applied current (DC), to suggest an optimal frequency for the imaging of neuronal depolarisation by electrical impedance tomography (EIT). With DC, a predominant apparent impedance decrease of 0.2-0.7 per cent of the resting baseline was observed, which had a time course similar to that of the action potential. Control recordings suggested that these changes could not be attributed to technical errors resulting from the measurement method. A component in some measurements was attributable to effects of the measuring current on the latency of the CAP, but the mechanism underlying the remainder of the changes was unclear. No changes greater than +/- 0.005 per cent were seen with measurement at 50 kHz. This suggests that research into noninvasive rapid imaging of nervous activity in the brain with EIT would be more profitably performed with measurements at frequencies lower than the 50 kHz currently used for safety reasons.
在分离的蟹神经复合动作电位（CAP）期间，使用50 kHz或直流电流（DC）测量阻抗变化，以确定通过电阻抗断层成像（EIT）对神经元去极化进行成像的最佳频率。使用DC时，观察到静息基线的明显阻抗主要下降0.2%-0.7%，其时间进程与动作电位相似。对照记录表明，这些变化不能归因于测量方法导致的技术误差。某些测量中的一个成分可归因于测量电流对CAP潜伏期的影响，但其余变化的潜在机制尚不清楚。在50 kHz测量时，未观察到大于+/-0.005%的变化。这表明，对于使用EIT对大脑神经活动进行无创快速成像的研究，在低于目前出于安全原因使用的50 kHz的频率下进行测量可能更有成效。
