Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg im Breisgau, Germany.
BrainLinks-BrainTools Center of Excellence, University of Freiburg, Freiburg, Germany.
J Neural Eng. 2022 Feb 14;19(1). doi: 10.1088/1741-2552/ac5091.
Somatosensory perception is disrupted in patients with a lower limb amputation. This increases the difficulty to maintain balance and leads to the development of neuromuscular adjustments. We investigated how these adjustments are reflected in the co-activation of lower body muscles and are modulated by visual feedback.We measured electromyography (EMG) signals of muscles from the trunk (erector spinae and obliquus external), and the lower intact/dominant leg (tibialis anterior and medial gastrocnemius) in 11 unilateral transfemoral amputees and 11 age-matched able-bodied controls during 30 s of upright standing with and without visual feedback. Muscle synergies involved in balance control were investigated using wavelet coherence analysis. We focused on seven frequencies grouped in three frequency bands, a low-frequency band (7.56 and 19.86 Hz) representing more sub-cortical and spinal inputs to the muscles, a mid-frequency band (38.26 and 62.63 Hz) representing more cortical inputs, and a high-frequency band (92.90, 129 and 170.90 Hz) associated with synchronizing motor unit action potentials. Further, the dynamics of changes in intermuscular coupling over time were quantified using the Entropic Half-Life.Amputees exhibited lower coherency values when vision was removed at 7.56 Hz for the muscle pair of the lower leg. At this frequency, the coherency values of the amputee group also differed from controls for the eyes closed condition. Controls and amputees exhibited opposite coherent behaviors with visual feedback at 7.56 Hz. For the eyes open condition at 129 Hz, the coherency values of amputees and controls differed for the muscle pair of the trunk, and at 170.90 Hz for the muscle pair of the lower leg. Amputees exhibited different dynamics of muscle co-activation at the low frequency band when vision was available.Altogether, these findings point to the development of neuromuscular adaptations reflected in the strength and dynamics of muscular co-activation.
体感感知在下肢截肢患者中受到干扰。这增加了维持平衡的难度，并导致神经肌肉调整的发展。我们研究了这些调整如何反映在下半身肌肉的共同激活中，并受视觉反馈调节。我们在 11 名单侧股骨截肢者和 11 名年龄匹配的健康对照组中测量了 30 秒直立站立时的躯干（竖脊肌和外斜肌）和下完好/优势腿（胫骨前肌和内侧腓肠肌）的肌电图（EMG）信号，同时有无视觉反馈。使用小波相干分析研究了参与平衡控制的肌肉协同作用。我们关注了七个分组为三个频带的频率，低频带（7.56 和 19.86 Hz）代表对肌肉的更多皮质下和脊髓输入，中频带（38.26 和 62.63 Hz）代表更多皮质输入，高频带（92.90、129 和 170.90 Hz）与同步运动单位动作电位有关。此外，使用熵半衰期来量化随时间变化的肌肉间耦合的动态变化。当去除视觉时，截肢者在 7.56 Hz 时显示出较低的相干值。在这个频率下，当闭眼时，截肢者组的相干值也与对照组不同。对照组和截肢者在 7.56 Hz 时表现出与视觉反馈相反的相干行为。对于 129 Hz 的睁眼状态，截肢者和对照组的相干值在躯干肌肉对之间不同，在 170.90 Hz 时在小腿肌肉对之间不同。截肢者在有视觉时在低频带显示出不同的肌肉共同激活动力学。总的来说，这些发现表明神经肌肉适应的发展反映在肌肉共同激活的强度和动态上。
