Lontis Eugen R, Nielsen Karsten, Struijk Johannes J
Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg 9220, Denmark.
IEEE Trans Biomed Eng. 2009 Feb;56(2):500-12. doi: 10.1109/TBME.2008.2009929. Epub 2008 Dec 2.
The induced electric field transverse to peripheral nerve trunks has been shown to lead to stimulation, contrary to predictions of the cable equation. Two possible mechanisms of activation have been documented in literature: the change in the transmembrane voltage due to an electric field transverse to the membrane of a cylindrical fiber and the transverse field projection on the undulating fiber path within the fascicle. To distinguish between these alternatives, an analysis of the stimulation site was performed in vitro along 15 phrenic nerves from pigs, with a 5-cm-diameter round coil. Stimulation with induced electric field having longitudinal and attenuated transverse components resulted in stimulation sites in the vicinity of the negative peak of the spatial derivative of the longitudinal electric field and threshold variations with coil positions along the nerve trunk. Stimulation with a transverse field yielded patterns of one, two, or three stimulation sites, scattered or uniformly distributed around the location of the two field maxima. A nerve structure analysis outlined the fiber undulation within the fascicle and a network of wavy fascicles. The presence of this network and the variations of the stimulation site, and of the threshold suggest that the path of the fiber has a major undulation due to the undulation of the fascicles within the nerve trunk, which may be responsible for the stimulation with an electric field transverse to the nerve trunk.
与电缆方程的预测相反，已证明横向于周围神经干的感应电场会导致刺激。文献中记录了两种可能的激活机制：由于横向于圆柱形纤维膜的电场导致跨膜电压的变化，以及横向场在束内起伏的纤维路径上的投影。为了区分这些可能性，使用直径为5厘米的圆形线圈，对来自猪的15条膈神经进行了体外刺激位点分析。用具有纵向和衰减横向分量的感应电场进行刺激，会在纵向电场空间导数的负峰附近产生刺激位点，并且阈值会随着线圈沿神经干的位置而变化。用横向场刺激会产生一个、两个或三个刺激位点的模式，这些位点在两个场最大值的位置周围分散或均匀分布。神经结构分析勾勒出束内的纤维起伏以及波浪状束的网络。这种网络的存在以及刺激位点和阈值的变化表明，由于神经干内束的起伏，纤维路径存在主要起伏，这可能是横向于神经干的电场产生刺激的原因。
