Farina Dario, Castronovo Anna Margherita, Vujaklija Ivan, Sturma Agnes, Salminger Stefan, Hofer Christian, Aszmann Oskar
Department of Bioengineering, Imperial College London, SW7 2AZ London, United Kingdom,
Department of Bioengineering, Imperial College London, SW7 2AZ London, United Kingdom.
J Neurosci. 2017 Nov 15;37(46):11285-11292. doi: 10.1523/JNEUROSCI.1179-17.2017. Epub 2017 Oct 20.
We compared the behavior of motor neurons innervating their physiological muscle targets with motor neurons from the same spinal segment whose axons were surgically redirected to remnant muscles (targeted muscle reinnervation). The objective was to assess whether motor neurons with nonphysiological innervation receive similar synaptic input and could be voluntary controlled as motor neurons with natural innervation. For this purpose, we acquired high-density EMG signals from the biceps brachii in 5 male transhumeral amputees who underwent targeted reinnervation of this muscle by the ulnar nerve and from the first dorsal interosseous muscle of 5 healthy individuals to investigate the natural innervation of the ulnar nerve. The same recordings were also performed from the biceps brachii muscle of additional 5 able-bodied individuals. The EMG signals were decomposed into discharges of motor unit action potentials. Motor neurons were progressively recruited for the full range of submaximal muscle activation in all conditions. Moreover, their discharge rate significantly increased from recruitment to target activation level in a similar way across the subject groups. Motor neurons across all subject groups received common synaptic input as identified by coherence analysis of their spike trains. However, the relative strength of common input in both the delta (0.5-5 Hz) and alpha (5-13 Hz) bands was significantly smaller for the surgically reinnervated motor neuron pool with respect to the corresponding physiologically innervated one. The results support the novel approach of motor neuron interfacing for prosthesis control and provide new insights into the role of afferent input on motor neuron activity. Targeted muscle reinnervation surgically redirects nerves that lost their target in the amputation into redundant muscles in the region of the stump. The study of the behavior of motor neurons following this surgery is needed for designing biologically inspired prosthetic control strategies. Moreover, targeted muscle reinnervation offers a human experimental framework for studying the control and behavior of motor neurons when changing their target innervated muscle fibers and sensory feedback. Here, we show that the control of motor neurons and their synaptic input, following reinnervation, was remarkably similar to that of the physiological innervation, although with reduced common drive at some frequencies. The results advance our knowledge on the role of sensory input in the generation of the neural drive to muscles and provide the basis for designing physiologically inspired methods for prosthesis control.
我们将支配其生理肌肉靶标的运动神经元的行为，与来自同一脊髓节段、轴突经手术重新定向至残余肌肉（靶向肌肉再支配）的运动神经元的行为进行了比较。目的是评估具有非生理性支配的运动神经元是否能像具有自然支配的运动神经元一样，接受相似的突触输入并能被随意控制。为此，我们从5名接受尺神经对肱二头肌进行靶向再支配的男性经肱骨截肢者的肱二头肌，以及5名健康个体的第一背侧骨间肌采集了高密度肌电图信号，以研究尺神经的自然支配情况。另外还对5名健全个体的肱二头肌进行了同样的记录。肌电图信号被分解为运动单位动作电位的放电。在所有情况下，运动神经元在次最大肌肉激活的整个范围内逐步被募集。此外，在各受试者组中，它们的放电率从募集到目标激活水平均以相似的方式显著增加。通过对其放电序列的相干分析确定，所有受试者组中的运动神经元都接受共同的突触输入。然而，与相应的生理性支配运动神经元池相比，手术重新支配运动神经元池在δ（0.5 - 5Hz）和α（5 - 13Hz）频段共同输入相对强度显著较小。这些结果支持了用于假肢控制的运动神经元接口新方法，并为传入输入对运动神经元活动的作用提供了新见解。靶向肌肉再支配通过手术将截肢中失去其靶标的神经重新定向至残端区域的多余肌肉。为了设计受生物启发的假肢控制策略，需要研究该手术后运动神经元的行为。此外，靶向肌肉再支配为研究运动神经元在改变其靶标支配的肌纤维和感觉反馈时控制和行为提供了一个人体实验框架。在此，我们表明，再支配后运动神经元及其突触输入的控制与生理性支配的情况显著相似，尽管在某些频率下共同驱动有所减少。这些结果推进了我们对感觉输入在产生肌肉神经驱动中作用的认识，并为设计受生理启发的假肢控制方法提供了基础。
