Background: Trans-spinal electrical stimulation (tsES) to the intact spinal cord poststroke may modulate the cortico-muscular control in stroke survivors with diverse lesions in the brain. This work aimed to investigate the immediate effects of tsES on the cortico-muscular descending patterns during voluntary upper extremity (UE) muscle contractions by analyzing cortico-muscular coherence (CMCoh) and electromyography (EMG) in people with chronic stroke.Methods: Twelve chronic stroke participants were recruited to perform wrist-hand extension and flexion tasks at submaximal levels of voluntary contraction for the corresponding agonist flexors and extensors. During the tasks, the tsES was delivered to the cervical spinal cord with rectangular biphasic pulses. Electroencephalography (EEG) data were collected from the sensorimotor cortex, and the EMG data were recorded from both distal and proximal UE muscles. The CMCoh, laterality index (LI) of the peak CMCoh, and EMG activation level parameters under both non-tsES and tsES conditions were compared to evaluate the immediate effects of tsES on the cortico-muscular descending pathway.Results: The CMCoh and LI of peak CMCoh in the agonist distal muscles showed significant increases (p < 0.05) during the wrist-hand extension and flexion tasks with the application of tsES. The EMG activation levels of the antagonist distal muscle during wrist-hand extension were significantly decreased (p < 0.05) with tsES. Additionally, the proximal UE muscles exhibited significant decreases (p < 0.05) in peak CMCoh and EMG activation levels by applying tsES. There was a significant increase (p < 0.05) in LI of peak CMCoh of proximal UE muscles during tsES.Conclusion: The cervical spinal cord neuromodulation via tsES enhanced the residual descending excitatory control, activated the local inhibitory circuits within the spinal cord, and reduced the cortical and proximal muscular compensatory effects. These results suggested the potential of tsES as a supplementary input for improving UE motor functions in stroke rehabilitation.

中文翻译：

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经脊柱电刺激无创颈髓神经调节对慢性脑卒中上肢皮质肌下降模式的影响

背景：对中风后完整脊髓进行经脊柱电刺激（tsES）可能会调节脑部有多种病变的中风幸存者的皮质肌肉控制。这项工作旨在通过分析慢性中风患者的皮质肌肉相干性 (CMCoh) 和肌电图 (EMG)，研究 tsES 对自愿上肢 (UE) 肌肉收缩期间皮质肌肉下降模式的直接影响。方法：12 种慢性中风患者招募中风参与者在相应主动屈肌和伸肌的次最大自愿收缩水平下执行腕手伸展和弯曲任务。在任务期间，tsES 通过矩形双相脉冲传递到颈脊髓。从感觉运动皮层收集脑电图 (EEG) 数据，并从远端和近端 UE 肌肉记录 EMG 数据。比较非 tsES 和 tsES 条件下的 CMCoh、峰值 CMCoh 的偏侧性指数 (LI) 和 EMG 激活水平参数，以评估 tsES 对皮质肌肉下行通路的直接影响。 结果：激动剂远端肌肉的峰值 CMCoh 显示显着增加（p< 0.05）在应用 tsES 进行腕手伸展和弯曲任务期间。腕手伸展过程中拮抗远端肌肉的肌电图激活水平显着降低（p< 0.05) 与 tsES。此外，近端 UE 肌肉表现出显着下降（p< 0.05）通过应用 tsES 峰值 CMCoh 和 EMG 激活水平。有显着增加（p< 0.05）在 tsES 期间近端 UE 肌肉峰值 CMCoh 的 LI 中。结论：通过 tsES 的颈髓神经调节增强了残余的下行兴奋控制，激活了脊髓内的局部抑制回路，并减少了皮质和近端肌肉的代偿效应。这些结果表明 tsES 作为补充输入在中风康复中改善 UE 运动功能的潜力。