Department of Health Sciences and Research, College of Health Professions, Medical University of South Carolina , Charleston, South Carolina.
United Technologies Aerospace Systems, Windsor Locks, Connecticut.
J Neurophysiol. 2019 Mar 1;121(3):853-866. doi: 10.1152/jn.00557.2018. Epub 2019 Jan 9.
Foot drop is very common among people with chronic incomplete spinal cord injury (SCI) and likely stems from SCI that disturbs the corticospinal activation of the ankle dorsiflexor tibialis anterior (TA). Thus, if one can recover or increase the corticospinal excitability reduced by SCI, motor function recovery may be facilitated. Here, we hypothesized that in people suffering from weak dorsiflexion due to chronic incomplete SCI, increasing the TA motor-evoked potential (MEP) through operant up-conditioning can improve dorsiflexion during locomotion, while in people without any injuries, it would have little impact on already normal locomotion. Before and after 24 MEP conditioning or control sessions, locomotor electromyography (EMG) and kinematics were measured. This study reports the results of these locomotor assessments. In participants without SCI, locomotor EMG activity, soleus Hoffmann reflex modulation, and joint kinematics did not change, indicating that MEP up-conditioning or repeated single-pulse transcranial magnetic stimulation (i.e., control protocol) does not influence normal locomotion. In participants with SCI, MEP up-conditioning increased TA activity during the swing-to-swing stance transition phases and ankle joint motion during locomotion in the conditioned leg and increased walking speed consistently. In addition, the swing-phase TA activity and ankle joint motion also improved in the contralateral leg. The results are consistent with our hypothesis. Together with the previous operant conditioning studies in humans and rats, the present study suggests that operant conditioning can be a useful therapeutic tool for enhancing motor function recovery in people with SCI and other central nervous system disorders. NEW & NOTEWORTHY This study examined the functional impact of operant conditioning of motor-evoked potential (MEP) to transcranial magnetic stimulation that aimed to increase corticospinal excitability for the ankle dorsiflexor tibialis anterior (TA). In people with chronic incomplete spinal cord injury (SCI), MEP up-conditioning increased TA activity and improved dorsiflexion during locomotion, while in people without injuries, it had little impact on already normal locomotion. MEP conditioning may potentially be used to enhance motor function recovery after SCI.
足下垂在慢性不完全性脊髓损伤（SCI）人群中非常常见，可能源于 SCI 干扰了踝背屈肌胫骨前肌（TA）的皮质脊髓激活。因此，如果可以恢复或增加因 SCI 而降低的皮质脊髓兴奋性，可能有助于运动功能恢复。在这里，我们假设在因慢性不完全性 SCI 而导致背屈无力的人群中，通过操作性条件反射增强 TA 运动诱发电位（MEP）可以改善运动时的背屈，而在没有任何损伤的人群中，它对已经正常的运动几乎没有影响。在 24 次 MEP 条件反射或对照治疗前后，测量了运动肌电图（EMG）和运动学。本研究报告了这些运动评估的结果。在无 SCI 的参与者中，运动 EMG 活动、比目鱼肌霍夫曼反射调节和关节运动学没有变化，表明 MEP 条件反射增强或重复单次经颅磁刺激（即对照方案）不会影响正常运动。在 SCI 参与者中，MEP 条件反射增强了摆动-摆动站立过渡阶段的 TA 活动和运动时受条件腿的踝关节运动，并一致增加了行走速度。此外，对侧腿的摆动相 TA 活动和踝关节运动也得到了改善。结果与我们的假设一致。与之前在人类和大鼠中进行的操作性条件反射研究一起，本研究表明，操作性条件反射可以成为增强 SCI 和其他中枢神经系统疾病患者运动功能恢复的有用治疗工具。
本研究检查了旨在增加踝背屈肌胫骨前肌（TA）皮质脊髓兴奋性的运动诱发电位（MEP）经颅磁刺激操作性条件反射对功能的影响。在慢性不完全性脊髓损伤（SCI）患者中，MEP 增强条件反射增加了 TA 活动，并改善了运动时的背屈，而在没有损伤的患者中，对已经正常的运动几乎没有影响。MEP 条件反射可能有潜力用于增强 SCI 后的运动功能恢复。
