Student Justus, Engel David, Timmermann Lars, Bremmer Frank, Waldthaler Josefine
Department of Neurophysics, University of Marburg, Marburg, Germany.
Department of Neurology, University Hospital of Marburg, Marburg, Germany.
Front Hum Neurosci. 2022 Mar 2;16:762380. doi: 10.3389/fnhum.2022.762380. eCollection 2022.
Postural instability marks a prevalent symptom of Parkinson's disease (PD). It often manifests in increased body sway, which is commonly assessed by tracking the Center of Pressure (CoP). Yet, in terms of postural control, the body's Center of Mass (CoM), and not CoP is what is regulated in a gravitational field. The aim of this study was to explore the effect of early- to mid-stage PD on these measures of postural control in response to unpredictable visual perturbations. We investigated three cohorts: (i) 18 patients with early to mid-stage PD [Hoehn & Yahr stage (1-3); 1.94 ± 0.70]; (ii) a group of 15 age-matched controls (ECT); and (iii) a group of 12 young healthy adults (YCT). Participants stood on a force plate to track their CoP, while the movement of their entire body was recorded with a video-based motion tracking system to monitor their CoM. A moving room paradigm was applied through a head-mounted virtual reality headset. The stimulus consisted of a virtual tunnel that stretched in the anterior-posterior direction which either remained static or moved back and forth in an unpredictable fashion.We found differences in mean sway amplitude (MSA) and mean velocities of CoP and CoM between the groups under both conditions, with higher MSA of CoP and CoM for PD and higher mean velocities of both variables for PD and ECT when compared with YCT. Visual perturbation increased mean CoP velocity in all groups but did not have effects on mean CoM velocity or MSA. While being significantly lower for the young adults, the net effect of visual perturbation on mean CoP velocity was similar between patients with PD and age-matched controls. There was no effect of the visual perturbation on mean CoM velocity for any of the groups.Our simultaneous assessment of CoP and CoM revealed that postural control is reflected differently in CoM and CoP. As the motion of CoM remained mostly unaffected, all groups successfully counteracted the perturbation and maintained their balance. Higher CoP velocity for PD and ECT revealed increased corrective motion needed to achieve this, which however was similar in both groups. Thus, our results suggest increased effort, expressed in CoP velocity, to be an effect of age rather than disease in earlier stages of PD.
姿势不稳是帕金森病（PD）的常见症状。它通常表现为身体摇摆增加，这通常通过跟踪压力中心（CoP）来评估。然而，在姿势控制方面，在重力场中受到调节的是身体的质心（CoM），而非CoP。本研究的目的是探讨帕金森病早期至中期对这些姿势控制指标在应对不可预测视觉扰动时的影响。我们调查了三组人群：（i）18例早期至中期帕金森病患者[Hoehn & Yahr分期（1 - 3期）；1.94 ± 0.70]；（ii）一组15名年龄匹配的对照者（ECT）；以及（iii）一组12名年轻健康成年人（YCT）。参与者站在测力板上以跟踪其CoP，同时使用基于视频的运动跟踪系统记录其整个身体的运动，以监测其CoM。通过头戴式虚拟现实耳机应用移动房间范式。刺激由一个在前后方向延伸的虚拟隧道组成，该隧道要么保持静止，要么以不可预测的方式来回移动。我们发现在两种情况下，各组之间的平均摇摆幅度（MSA）以及CoP和CoM的平均速度存在差异，与YCT相比，帕金森病患者的CoP和CoM的MSA更高，且帕金森病患者和ECT的这两个变量的平均速度更高。视觉扰动增加了所有组的平均CoP速度，但对平均CoM速度或MSA没有影响。虽然年轻成年人的平均CoP速度明显更低，但帕金森病患者和年龄匹配的对照者之间视觉扰动对平均CoP速度的净效应相似。视觉扰动对任何一组的平均CoM速度均无影响。我们对CoP和CoM的同步评估表明，姿势控制在CoM和CoP中的反映有所不同。由于CoM的运动大多未受影响，所有组都成功抵消了扰动并保持了平衡。帕金森病患者和ECT的CoP速度更高，表明实现这一点需要增加纠正运动，然而两组的情况相似。因此，我们的结果表明，在帕金森病早期阶段，以CoP速度表示的努力增加是年龄而非疾病的影响。
