Sharma Pawan, Rampersaud Hema, Shah Prithvi K
Division of Rehabilitation Sciences, Department of Physical Therapy, School of Health Technology and Management, University of Louisville, Louisville, KY, USA.
Kentucky Spinal Cord Injury Research Center, University of Louisville, 220 Abraham Flexner Way, Louisville, KY, 40202, USA.
Exp Brain Res. 2024 Dec 12;243(1):22. doi: 10.1007/s00221-024-06965-x.
Spinal evoked motor responses (SEMR) are utilized in longitudinal pre-clinical and human studies to reflect the in-vivo physiological changes in neural networks secondary to a spinal cord injury (SCI) or neuro-rehabilitative treatments utilizing epidural stimulation (ES). However, it remains unknown whether the repeated ES exposure during SEMR testing itself modulates spinal cord physiology and accompanying SEMR characteristics. To answer this, ES was delivered to the cervical spinal cord using standard stimulation paradigms during multiple SEMR data acquisition sessions (~ 17 h spanning across 100 days) in ten healthy adult rats. Cervical SEMR at rest and forelimb muscle activity during reaching and grasping task were collected before and after 100 days. We noted a persistent increase in SEMR activity relative to baseline, with prominent changes in the mono and poly-synaptic components of SEMR. The findings indicate increased spinal cord excitability. Increased spinal cord excitability translated into increased forelimb muscle activation during the reaching and grasping task. For the majority of SEMR and muscle activity increase, effect size was large or very large. Cervical SEMR are amenable to modulation by routine ES testing protocols, with prominent changes in the mono and poly-synaptic components of SEMR. Since repeated stimulation during multiple testing alone increases cord excitability, we recommend (1) SEMR may be used with caution to infer the physiological status of the spinal circuitry (2) utilizing appropriate control groups and motor behavioral correlates for meaningful functional interpretation in longitudinal neuromodulation studies involving multiple SEMR testing sessions following a SCI.
脊髓诱发运动反应（SEMR）被用于纵向临床前研究和人体研究，以反映脊髓损伤（SCI）或利用硬膜外刺激（ES）的神经康复治疗继发的神经网络体内生理变化。然而，在SEMR测试期间反复暴露于ES本身是否会调节脊髓生理和伴随的SEMR特征仍不清楚。为了回答这个问题，在10只健康成年大鼠的多个SEMR数据采集阶段（跨越100天，约17小时），使用标准刺激范式将ES施加到颈脊髓。在100天前后收集静息时的颈SEMR以及抓握任务期间的前肢肌肉活动。我们注意到相对于基线，SEMR活动持续增加，SEMR的单突触和多突触成分有显著变化。这些发现表明脊髓兴奋性增加。脊髓兴奋性增加转化为抓握任务期间前肢肌肉激活增加。对于大多数SEMR和肌肉活动增加，效应大小为大或非常大。颈SEMR易于通过常规ES测试方案进行调节，SEMR的单突触和多突触成分有显著变化。由于仅在多次测试期间的重复刺激就会增加脊髓兴奋性，我们建议：（1）在推断脊髓回路的生理状态时，使用SEMR时应谨慎；（2）在涉及SCI后多个SEMR测试阶段的纵向神经调节研究中，利用适当的对照组和运动行为相关性进行有意义的功能解释。
