Noninvasive electrical stimulation targeting the posterior lumbosacral roots has been applied recently in reflexes studies and as a neuromodulation intervention for modifying spinal cord circuitry after an injury. Here, we characterized short-latency responses evoked by four bipolar electrode configurations placed longitudinally over the spinal column at different vertebral levels from L1 to T9. They were compared to the responses evoked by the standard unipolar (aka monopolar) electrode configuration (cathode at T11/12, anode over the abdominal wall).Short-latency responses were recorded in the rectus femoris, medial hamstrings, tibialis anterior, and soleus muscles, bilaterally, in eleven neurologically intact participants. The response recruitment characteristics (maximal amplitude, motor threshold) and amplitude-matched onset latencies and paired-pulse suppression (35-ms inter-stimulus interval) were assessed with 1-ms current-controlled pulses at intensities up to 100 mA.The results showed that short-latency responses can be elicited with all bipolar electrode configurations. However, only with the cathode at T11/12 and the anode 10 cm cranially (~T9), the maximum response amplitudes were statistical equivalent (p < .05) in the medial hamstrings, tibialis anterior, and soleus but not the rectus femoris, whereas motor thresholds were not significantly different across all muscles. The onset latency and paired-pulse suppression were also not significantly different across the tested electrode configurations, thereby confirming the reflex nature of the bipolar short-latency responses.We conclude that the bipolar configuration (cathode T11/12, anode ~T9) produces reflex responses which characteristics are ostensibly similar to those evoked by the standard unipolar configuration. This provides an alternative approach for neuromodulation intervention.

中文翻译：

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双极经皮脊柱刺激与标准单极电极配置一样，在人类下肢中唤起短潜伏期反射反应。

针对后腰骶神经根的无创电刺激最近已应用于反射研究，并作为一种神经调节干预措施，用于在受伤后修改脊髓电路。在这里，我们描述了由四个双极电极配置引起的短延迟反应，这些电极配置纵向放置在从 L1 到 T9 的不同椎骨水平的脊柱上。将它们与标准单极（又名单极）电极配置（T11/12 处的阴极，腹壁上的阳极）诱发的反应进行比较。在股直肌、内侧腘绳肌、胫前肌和比目鱼肌中记录了短延迟反应11 名神经系统完好的参与者的双侧肌肉。反应募集特征（最大振幅，运动阈值）和幅度匹配的起始延迟和配对脉冲抑制（35 毫秒的刺激间隔）用 1 毫秒的电流控制脉冲在强度高达 100 毫安时进行评估。结果表明，短延迟响应可以由所有双极电极配置引起。然而，只有在 T11/12 处的阴极和头侧 10 cm 处的阳极（~T9），内侧腘绳肌、胫骨前肌和比目鱼肌的最大响应幅度在统计上相等（p < .05），但不是股直肌，而所有肌肉的运动阈值没有显着差异。在测试的电极配置中，起始潜伏期和成对脉冲抑制也没有显着差异，从而证实了双极短潜伏期响应的反射性质。我们得出结论，双极配置（阴极 T11/12，阳极~T9）产生反射响应，其特征表面上类似于标准单极配置引起的反射响应。这为神经调节干预提供了一种替代方法。