IEEE Trans Neural Syst Rehabil Eng. 2023;31:2698-2704. doi: 10.1109/TNSRE.2023.3283861. Epub 2023 Jun 16.
Stretch reflexes are crucial for performing accurate movements and providing rapid corrections for unpredictable perturbations. Stretch reflexes are modulated by supraspinal structures via corticofugal pathways. Neural activity in these structures is difficult to observe directly, but the characterization of reflex excitability during volitional movement can be used to study how these structures modulate reflexes and how neurological injuries impact this control, such as in spasticity after stroke. We have developed a novel protocol to quantify stretch reflex excitability during ballistic reaching. This novel method was implemented using a custom haptic device (NACT-3D) capable of applying high-velocity (270 °/s) joint perturbations in the plane of the arm while participants performed 3D reaching tasks in a large workspace. We assessed the protocol on four participants with chronic hemiparetic stroke and two control participants. Participants reached ballistically from a near to a far target, with elbow extension perturbations applied in random catch trials. Perturbations were applied before movement, during the early phase of movement, or near peak movement velocity. Preliminary results show that stretch reflexes were elicited in the stroke group in the biceps muscle during reaching, as measured by electromyographic (EMG) activity both before (pre-motion phase) and during (early motion phase) movement. Reflexive EMG was also seen in the anterior deltoid and pectoralis major in the pre-motion phase. In the control group, no reflexive EMG was seen, as expected. This newly developed methodology allows the study of stretch reflex modulation in new ways by combining multijoint movements with haptic environments and high-velocity perturbations.
伸展反射对于进行准确的运动和对不可预测的扰动提供快速修正至关重要。伸展反射通过皮质传出途径由皮质下结构调节。这些结构中的神经活动很难直接观察到，但在随意运动期间反射兴奋性的特征可以用于研究这些结构如何调节反射以及神经损伤如何影响这种控制，例如中风后的痉挛。我们开发了一种新的方案来量化在弹道式伸展反射时的兴奋性。这种新方法是使用一种定制的触觉设备（NACT-3D）实现的，该设备能够在手臂平面上施加高速（270°/s）的关节扰动，同时参与者在大工作空间中进行 3D 伸展任务。我们在四个患有慢性偏瘫的中风参与者和两个对照组参与者上评估了该方案。参与者从近目标到远目标进行弹道式伸展，在随机捕获试验中施加肘部伸展的扰动。在运动之前、运动早期或接近运动速度峰值时施加扰动。初步结果表明，在伸展运动中，中风组的肱二头肌中会产生伸展反射，通过肌电图（EMG）活动来测量，无论是在运动之前（运动前阶段）还是在运动期间（早期运动阶段）。在运动前阶段，前三角肌和胸大肌也会出现反射性 EMG。在对照组中，如预期的那样，没有看到反射性 EMG。这种新开发的方法通过将多关节运动与触觉环境和高速扰动相结合，以新的方式允许研究伸展反射的调制。
