Grill W M, Mortimer J T
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106-4912, USA.
IEEE Trans Biomed Eng. 1997 Jan;44(1):1-9. doi: 10.1109/10.553708.
The objective of this research was to develop a technique to excite selectively nerve fibers distant from an electrode without exciting nerve fibers close to the electrode. The shape of the stimulus current waveform was designed based on the nonlinear conductance properties of neuronal sodium channel. Models of mammalian peripheral myelinated axons and experimental measurements on cat sciatic nerve were used to determine the effects of subthreshold polarization on neural excitability and recruitment. Subthreshold membrane depolarization generated a transient decrease in neural excitability and thus an increase in the threshold for stimulation by a subsequent stimulus pulse. The decrease in excitability increased as the duration and amplitude of the subthreshold depolarization were increased, and the increase in threshold was greater for fibers close to the electrode. When a depolarizing stimulus pulse was applied immediately after the subthreshold depolarization, nerve fibers far from the electrode could be stimulated without stimulating fibers close to the electrode. Subthreshold depolarizing prepulses inverted the current-distance relationship and allowed selective stimulation of nerve fibers far from the electrode.
本研究的目的是开发一种技术，能够选择性地激发远离电极的神经纤维，而不激发靠近电极的神经纤维。基于神经元钠通道的非线性电导特性设计了刺激电流波形。利用哺乳动物外周有髓轴突模型和对猫坐骨神经的实验测量，来确定阈下极化对神经兴奋性和募集的影响。阈下膜去极化导致神经兴奋性短暂降低，从而使后续刺激脉冲的刺激阈值升高。兴奋性的降低随着阈下去极化的持续时间和幅度增加而增大，且靠近电极的纤维阈值升高幅度更大。当在阈下去极化后立即施加去极化刺激脉冲时，可以在不刺激靠近电极的纤维的情况下刺激远离电极的神经纤维。阈下去极化预脉冲反转了电流-距离关系，并允许选择性刺激远离电极的神经纤维。
