مکانیزم اثر پیش پالسهای زیرآستانه دیپلاریزه کننده برای تحریک انتخابی فیبرهای عصبی

various approaches have been proposed to provide special selective capabilities in electrical stimulation of nerve fibers. Waveform-based approach benefits from nonlinear properties of the nerve fibers by applying specially designed stimulus waveforms to the electrode. Under-threshold depolarizing prepulses followed by the stimulus pulse have been used for selective stimulation of fibers far from the electrode without activation of close fibers. Although it is shown that depolarizing prepulses increase the excitation threshold of the membrane, the mechanisms underlying their effect on the activation threshold of nerve fibers have not been completely clarified. In this simulation study we showed that the depolarizing prepulse affects not only the excitation threshold but also the block threshold of nerve fibers. Based on these phenomena we explained how these prepulses inhibit fibers around the electrode from activation, allowing the stimulus pulse to selectively stimulate more distant ones. We showed that the same mechanisms exist when a depolarizing prepulse is used for selective stimulation of small nerve fibers by inhibiting the larger ones. The insight into these mechanisms is necessary in effective use of the prepulse technique for selective stimulation of .target fibers in a certain distance range and with a certain diameter range