Hemm Simone, Baumann Denise, Duarte da Costa Vasco, Tarnutzer Alexander Andrea
School of Life Sciences, Institute for Medical Engineering and Medical Informatics, University of Applied Sciences and Arts Northwestern Switzerland, Muttenz, Switzerland.
Neurology, Cantonal Hospital of Baden, Baden, Switzerland.
Front Neurol. 2023 Mar 29;14:1128760. doi: 10.3389/fneur.2023.1128760. eCollection 2023.
The Fukuda-stepping-test (FST), i.e., repetitive walking on the spot while blindfolded, has been proposed as a means to assess the integrity of the vestibular pathways. While its sensitivity to detect abnormalities in patients is limited, it may be useful in studying the physiology of the subjective-straight-ahead (SSA). Considering reported systematic shifts in SSA in humans, we hypothesize that such asymmetries arise from individual differences in the orientation/configuration of the macular organs and in central processing of vestibular input. We hypothesize that such asymmetries are stable over time in individual subjects. Alternatively, such asymmetries may arise from random noise in the sensory/motor systems involved, demonstrating low reproducibility over time.
Twenty-four subjects walked on the spot over 60 s while blindfolded ( = 6 trials per subject). Using an inertial measurement unit (IMU) placed at the chest, angular deviations were recorded and compared to manually-measured final positions. Both static (direction, magnitude) and dynamic (time-to-onset of deviation, pattern of deviations) parameters were retrieved from the yaw slopes.
Significant deviations were found in 15/24 participants for the manual measurements (leftwards = 8; rightwards = 7), whereas when using the IMU-sensor 13/24 participants showed significant shifts (leftwards = 9; rightwards = 4). There was a high correlation (0.98) between manually measured rotation angles (average absolute deviations = 58.0 deg ± 48.6 deg; intra-individual variability = 39 deg ± 24 deg) and sensor-based yaw slopes (1.00 deg/s ± 0.88 deg/s; 0.67 deg/s ± 0.41 deg/s). Relevant yaw deviation was detected 22.1 s ± 12.3 s (range = 5.6 s-59.2 s) after the onset of marching (no relevant yaw-deviation in 15/139 measurements), showing a mostly linear behavior over time.
We observed significant inter-individual variability in task performance in the FST, reproducing findings from previous studies. With test-re-test reliability being moderate only, but at the same time observing a preference in the side of shifts in most trials and subjects, we conclude that likely both individually varying estimates of straight-ahead and random noise contribute to the pattern of angular deviations observed. Using an IMU-sensory based approach, additional dynamic parameters could be retrieved, emphasizing the value of such a quantitative approach over manual measurements. Such an approach may provide useful additional information to distinguish patients from healthy controls.
福田踏步试验（FST），即蒙眼原地重复行走，已被提议作为评估前庭通路完整性的一种方法。虽然其检测患者异常的敏感性有限，但它可能有助于研究主观直线前进（SSA）的生理学。考虑到人类中报道的SSA系统性偏移，我们假设这种不对称性源于黄斑器官的方向/配置以及前庭输入的中枢处理的个体差异。我们假设这种不对称性在个体受试者中随时间是稳定的。或者，这种不对称性可能源于所涉及的感觉/运动系统中的随机噪声，随着时间推移显示出低再现性。
24名受试者蒙眼原地行走60秒（每位受试者 = 6次试验）。使用放置在胸部的惯性测量单元（IMU）记录角度偏差，并与手动测量的最终位置进行比较。从偏航斜率中获取静态（方向、大小）和动态（偏差开始时间、偏差模式）参数。
手动测量时，15/24名参与者存在显著偏差（向左 = 8名；向右 = 7名），而使用IMU传感器时，13/24名参与者出现显著偏移（向左 = 9名；向右 = 4名）。手动测量的旋转角度（平均绝对偏差 = 58.0°±48.6°；个体内变异性 = 39°±24°）与基于传感器的偏航斜率（1.00°/秒±0.88°/秒；0.67°/秒±0.41°/秒）之间存在高度相关性（0.98）。行军开始后22.1秒±12.3秒（范围 = 5.6秒 - 59.2秒）检测到相关偏航偏差（139次测量中有15次无相关偏航偏差），随时间显示出大多为线性行为。
我们在FST任务表现中观察到显著的个体间变异性，重现了先前研究的结果。由于重测信度仅为中等，但同时在大多数试验和受试者中观察到偏移方向的偏好，我们得出结论，可能个体对直线前进的不同估计和随机噪声都导致了观察到的角度偏差模式。使用基于IMU传感的方法，可以获取额外的动态参数，强调了这种定量方法相对于手动测量的价值。这种方法可能为区分患者与健康对照提供有用的额外信息。
