Mirror contractions refer to unintended contractions of the contralateral homologous muscles during voluntary unilateral contractions or movements. Exaggerated mirror contractions have been found in several neurological diseases and indicate dysfunction or lesion of the cortico-spinal pathway. The present study investigates mirror contractions and the associated interhemispheric and corticomuscular interactions in adults with spinal cord injury (SCI) – who present a lesion of the cortico-spinal tract – compared to able-bodied participants (AB). Eight right-handed adults with chronic cervical SCI and ten age-matched right-handed able-bodied volunteers performed sets of right elbow extensions at 20% of maximal voluntary contraction. Electromyographic activity (EMG) of the right and left elbow extensors, interhemispheric coherence over cerebral sensorimotor regions evaluated by electroencephalography (EEG) and corticomuscular coherence between signals over the cerebral sensorimotor regions and each extensor were quantified. Overall, results revealed that participants with SCI exhibited (1) increased EMG activity of both active and unintended active limbs, suggesting more mirror contractions, (2) reduced corticomuscular coherence between signals over the left sensorimotor region and the right active limb and increased corticomuscular coherence between the right sensorimotor region and the left unintended active limb, (3) decreased interhemispheric coherence between signals over the two sensorimotor regions. The increased corticomuscular communication and decreased interhemispheric communication may reflect a reduced inhibition leading to increased communication with the unintended active limb, possibly resulting to exacerbated mirror contractions in SCI. Finally, mirror contractions could represent changes of neural and neuromuscular communication after SCI.

中文翻译：

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颈脊髓损伤后镜像肌意外收缩强度的增加与半球间和皮质肌肉一致性的变化有关


镜像收缩是指在自主单侧收缩或运动过程中，对侧同源肌肉的无意识收缩。在几种神经系统疾病中发现了过度的镜像收缩，这表明皮质脊髓通路的功能障碍或病变。本研究调查了患有脊髓损伤（SCI）的成年人（其存在皮质脊髓束损伤）与健全参与者（AB）相比的镜像收缩以及相关的半球间和皮质肌肉相互作用。 8 名患有慢性颈椎 SCI 的右手成年人和 10 名年龄匹配的右手健全志愿者以最大自主收缩的 20% 进行了一组右肘伸展。对左右肘伸肌的肌电活动（EMG）、通过脑电图（EEG）评估的大脑感觉运动区域的半球间一致性以及大脑感觉运动区域和每个伸肌的信号之间的皮质肌肉一致性进行了量化。总体而言，结果显示，SCI 参与者表现出 (1) 主动肢体和非有意主动肢体的肌电图活动增加，表明镜像收缩更多，(2) 左侧感觉运动区域和右侧活动肢体信号之间的皮质肌肉一致性降低，皮质肌肉一致性增加在右侧感觉运动区域和左侧非预期活动肢体之间，（3）降低了两个感觉运动区域信号之间的半球间一致性。皮质肌肉通讯的增加和半球间通讯的减少可能反映了抑制的减少，导致与非预期活动肢体的通讯增加，可能导致 SCI 中镜像收缩的加剧。 最后，镜像收缩可以代表 SCI 后神经和神经肌肉通讯的变化。