Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA.
J Neural Eng. 2012 Apr;9(2):026019. doi: 10.1088/1741-2560/9/2/026019. Epub 2012 Mar 14.
The production of graceful skeletal movements requires coordinated activation of multiple muscles that produce torques around multiple joints. The work described herein is focused on one such movement, stance, that requires coordinated activation of extensor muscles acting around the hip, knee and ankle joints. The forces evoked in these muscles by external stimulation all have a complex dependence on muscle length and shortening velocities, and some of these muscles are biarticular. In order to recreate sit-to-stand maneuvers in the anesthetized feline, we excited the hind limb musculature using intrafascicular multielectrode stimulation (IFMS) of the muscular branch of the sciatic nerve, the femoral nerve and the main branch of the sciatic nerve. Stimulation was achieved with either acutely or chronically implanted Utah Slanted Electrode Arrays (USEAs) via subsets of electrodes (1) that activated motor units in the extensor muscles of the hip, knee and ankle joints, (2) that were able to evoke large extension forces and (3) that manifested minimal coactivation of the targeted motor units. Three hind limb force-generation strategies were investigated, including sequential activation of independent motor units to increase force, and interleaved or simultaneous IFMS of three sets of six or more USEA electrodes that excited the hip, knee and ankle extensors. All force-generation strategies evoked stance, but the interleaved IFMS strategy also reduced muscle fatigue produced by repeated sit-to-stand maneuvers compared with fatigue produced by simultaneous activation of different motor neuron pools. These results demonstrate the use of interleaved IFMS as a means to recreate coordinated, fatigue-resistant multi-joint muscle forces in the unilateral hind limb. This muscle activation paradigm could provide a promising neuroprosthetic approach for the restoration of sit-to-stand transitions in individuals who are paralyzed by spinal cord injury, stroke or disease.
优雅的骨骼运动需要多个肌肉的协调激活，这些肌肉在多个关节处产生扭矩。本文所描述的工作集中在一种这样的运动，即站立，这需要围绕髋关节、膝关节和踝关节的伸肌进行协调激活。这些肌肉在外力刺激下产生的力与肌肉长度和缩短速度有复杂的依赖性，其中一些肌肉是双关节的。为了在麻醉的猫中重现从坐到站的动作，我们通过坐骨神经肌支、股神经和坐骨神经主支的肌内多电极刺激（IFMS）来兴奋后肢肌肉。刺激是通过急性或慢性植入的犹他斜电极阵列（USEA）的子集来实现的，这些子集（1）激活髋关节、膝关节和踝关节伸肌的运动单位，（2）能够引起大的伸展力，（3）表现出对目标运动单位的最小共激活。研究了三种后肢力产生策略，包括独立运动单位的顺序激活以增加力，以及三个六组或更多 USEA 电极的交错或同时 IFMS 刺激髋关节、膝关节和踝关节伸肌。所有力产生策略都能引起站立，但与不同运动神经元池的同时激活相比，交错 IFMS 策略还能减少由反复从坐到站的动作引起的肌肉疲劳。这些结果表明，交错 IFMS 可用于在单侧后肢中重现协调的、抗疲劳的多关节肌肉力量。这种肌肉激活范式可能为因脊髓损伤、中风或疾病而瘫痪的个体恢复从坐到站的过渡提供一种有前途的神经假体方法。
