Crawford Research Institute, Shepherd Center, Atlanta, Georgia, United States of America.
Program in Applied Physiology, Georgia Institute of Technology, School of Biological Sciences, Atlanta, Georgia, United States of America.
PLoS One. 2024 May 14;19(5):e0300053. doi: 10.1371/journal.pone.0300053. eCollection 2024.
Considering the growing interest in clinical applications of neuromodulation, assessing effects of various modulatory approaches is increasingly important. Monosynaptic spinal reflexes undergo depression following repeated activation, offering a means to quantify neuromodulatory influences. Following spinal cord injury (SCI), changes in reflex modulation are associated with spasticity and impaired motor control. To assess disrupted reflex modulation, low-frequency depression (LFD) of Hoffman (H)-reflex excitability is examined, wherein the amplitudes of conditioned reflexes are compared to an unconditioned control reflex. Alternatively, some studies utilize paired-pulse depression (PPD) in place of the extended LFD train. While both protocols induce similar amounts of H-reflex depression in neurologically intact individuals, this may not be the case for persons with neuropathology. We compared the H-reflex depression elicited by PPD and by trains of 3-10 pulses to an 11-pulse LFD protocol in persons with incomplete SCI. The amount of depression produced by PPD was less than an 11-pulse train (mean difference = 0.137). When compared to the 11-pulse train, the 5-pulse train had a Pearson's correlation coefficient (R) of 0.905 and a coefficient of determination (R2) of 0.818. Therefore, a 5-pulse train for assessing LFD elicits modulation similar to the 11-pulse train and thus we recommend its use in lieu of longer trains.
鉴于人们对神经调节的临床应用越来越感兴趣，评估各种调节方法的效果变得越来越重要。单突触脊髓反射在反复激活后会发生抑制，这为量化神经调节的影响提供了一种方法。脊髓损伤（SCI）后，反射调节的变化与痉挛和运动控制受损有关。为了评估反射调节的中断，检查霍夫曼（H）反射兴奋性的低频抑制（LFD），其中条件反射的幅度与未条件反射的对照反射进行比较。或者，一些研究使用成对脉冲抑制（PPD）代替扩展的 LFD 训练。虽然这两种方案在神经功能正常的个体中都会引起类似程度的 H 反射抑制，但对于患有神经病理学的个体可能并非如此。我们比较了 PPD 和 3-10 脉冲的 LFD 训练在不完全性 SCI 患者中引起的 H 反射抑制。PPD 产生的抑制量小于 11 脉冲的训练（平均差异=0.137）。与 11 脉冲的训练相比，5 脉冲的训练具有 0.905 的 Pearson 相关系数（R）和 0.818 的确定系数（R2）。因此，用于评估 LFD 的 5 脉冲训练会引起与 11 脉冲训练相似的调制，因此我们建议使用它代替更长的训练。
