Health Sciences Doctoral Programs, The Graduate Center, City University of New York, 2800 Victory Boulevard, 5N-207, Staten Island, NY 10314, USA.
J Neurophysiol. 2010 Mar;103(3):1304-14. doi: 10.1152/jn.00880.2009. Epub 2009 Dec 30.
Plantar cutaneous afferent transmission is critical for recovery of locomotion in spinalized animals, whereas a phase-dependent reflex modulation is apparent during fictive or real locomotion. In nine people with a chronic spinal cord injury (SCI) the effects of foot sole stimulation on the soleus H-reflex and tibialis anterior (TA) flexion reflex modulation patterns during assisted stepping were established on different days. The soleus H-reflex was elicited by posterior tibial nerve stimulation followed by a supramaximal stimulus 100 ms after the test H-reflex to control for movement of recording electrodes. The flexion reflex was evoked by sural nerve stimulation with a 30-ms pulse train, recorded from the ipsilateral TA muscle, and elicited at 1.2- to twofold the reflex threshold. During assisted stepping, spinal reflexes were conditioned by percutaneous stimulation of the ipsilateral metatarsals at threefold perceptual threshold with a 20-ms pulse train delivered at 9- to 11-ms conditioning-test intervals. Stimuli were randomly dispersed across the step cycle, which was divided into 16 equal bins. The conditioned soleus H-reflex was significantly facilitated at midstance and depressed during midswing when compared with the unconditioned soleus H-reflex recorded during stepping. Foot sole stimulation induced a significant facilitation of the long-latency TA flexion reflex before, during, and after stance-to-swing transition when compared with the unconditioned long-latency TA flexion reflex during stepping. This study provides evidence that plantar cutaneous afferents remarkably influence the soleus H-reflex and TA flexion reflex modulation patterns during stepping and support that actions of plantar cutaneous afferents onto spinal interneuronal circuits engaged in locomotion are manifested in a phase-dependent manner in chronic SCI subjects.
足底皮肤传入的传递对于脊髓损伤动物运动功能的恢复至关重要，而在模拟或真实运动过程中，反射调制呈现出与相位相关的特征。本研究在 9 名慢性脊髓损伤患者中，分别在不同日期，在辅助行走过程中，建立了足底刺激对比目鱼肌 H 反射和胫骨前肌（TA）屈肌反射调制模式的影响。通过胫后神经刺激引发比目鱼肌 H 反射，然后在测试 H 反射后 100 毫秒给予最大刺激，以控制记录电极的运动。通过刺激腓肠神经产生 30 毫秒的脉冲串，从同侧 TA 肌肉记录，刺激强度为反射阈值的 1.2-2 倍，引发屈肌反射。在辅助行走过程中，通过对侧足底的经皮刺激，在三倍感觉阈值下以 20 毫秒的脉冲串，在 9-11 毫秒的条件-测试间隔下，对脊髓反射进行调节。刺激随机分布在整个步周期中，将步周期分为 16 个相等的区间。与行走时记录的未条件化比目鱼肌 H 反射相比，在支撑中期和摆动中期，足底刺激明显促进了条件化比目鱼肌 H 反射。与行走时记录的未条件化长潜伏期 TA 屈肌反射相比，足底刺激在支撑-摆动转换前、转换期间和转换后，显著促进了长潜伏期 TA 屈肌反射。本研究提供的证据表明，足底皮肤传入对行走时比目鱼肌 H 反射和 TA 屈肌反射调制模式有显著影响，并支持足底传入纤维对参与运动的脊髓中间神经元回路的作用，在慢性脊髓损伤患者中表现出与相位相关的方式。
