Lamontagne Anouk, Fung Joyce, McFadyen Bradford J, Faubert Jocelyn
School of Physical and Occupational Therapy, McGill University and Jewish Rehabilitation Hospital Research Center (CRIR), Montreal, Canada.
J Neuroeng Rehabil. 2007 Jun 26;4:22. doi: 10.1186/1743-0003-4-22.
Walking speed, which is often reduced after stroke, can be influenced by the perception of optic flow (OF) speed. The present study aims to: 1) compare the modulation of walking speed in response to OF speed changes between persons with stroke and healthy controls and 2) investigate whether virtual environments (VE) manipulating OF speed can be used to promote volitional changes in walking speed post stroke.
Twelve persons with stroke and 12 healthy individuals walked on a self-paced treadmill while viewing a virtual corridor in a helmet-mounted display. Two experiments were carried out on the same day. In experiment 1, the speed of an expanding OF was varied sinusoidally at 0.017 Hz (sine duration = 60 s), from 0 to 2 times the subject's comfortable walking speed, for a total duration of 5 minutes. In experiment 2, subjects were exposed to expanding OFs at discrete speeds that ranged from 0.25 to 2 times their comfortable speed. Each test trial was paired with a control trial performed at comfortable speed with matching OF. For each of the test trials, subjects were instructed to walk the distance within the same time as during the immediately preceding control trial. VEs were controlled by the CAREN-2 system (Motek). Instantaneous changes in gait speed (experiment 1) and the ratio of speed changes in the test trial over the control trial (experiment 2) were contrasted between the two groups of subjects.
When OF speed was changing continuously (experiment 1), an out-of-phase modulation was observed in the gait speed of healthy subjects, such that slower OFs induced faster walking speeds, and vice versa. Persons with stroke displayed weaker (p < 0.05, T-test) correlation coefficients between gait speed and OF speed, due to less pronounced changes and an altered phasing of gait speed modulation. When OF speed was manipulated discretely (experiment 2), a negative linear relationship was generally observed between the test-control ratio of gait speed and OF speed in healthy and stroke individuals. The slope of this relationship was similar between the stroke and healthy groups (p > 0.05, T-test).
Stroke affects the modulation of gait speed in response to changes in the perception of movement through different OF speeds. Nevertheless, the preservation of even a modest modulation enabled the persons with stroke to increase walking speed when presented with slower OFs. Manipulation of OF speed using virtual reality technology could be implemented in a gait rehabilitation intervention to promote faster walking speeds after stroke.
中风后步行速度通常会降低，其可能会受到视觉流（OF）速度感知的影响。本研究旨在：1）比较中风患者与健康对照者对OF速度变化的步行速度调节情况；2）研究操纵OF速度的虚拟环境（VE）是否可用于促进中风后步行速度的自主变化。
12名中风患者和12名健康个体在自定速度的跑步机上行走，同时通过头戴式显示器观看虚拟走廊。同一天进行了两项实验。在实验1中，扩展OF的速度以0.017赫兹的频率呈正弦变化（正弦持续时间 = 60秒），从0到受试者舒适步行速度的2倍，总时长为5分钟。在实验2中，受试者接触以离散速度扩展的OF，速度范围为其舒适速度的0.25至2倍。每个测试试验都与以舒适速度且匹配OF的对照试验配对。对于每个测试试验，受试者被要求在与紧接在前的对照试验相同的时间内走完这段距离。VE由CAREN - 2系统（Motek）控制。对比两组受试者的步态速度瞬时变化（实验1）以及测试试验与对照试验的速度变化比率（实验2）。
当OF速度持续变化时（实验1），在健康受试者的步态速度中观察到异相调节，即较慢的OF会导致较快的步行速度，反之亦然。中风患者在步态速度与OF速度之间的相关系数较弱（p < 0.05，t检验），这是由于变化不太明显以及步态速度调节的相位改变。当离散操纵OF速度时（实验2），在健康个体和中风个体中，步态速度的测试 - 对照比率与OF速度之间通常观察到负线性关系。中风组和健康组之间这种关系的斜率相似（p > 0.05，t检验）。
中风会影响步态速度对通过不同OF速度的运动感知变化的调节。然而，即使是适度调节的保留也使中风患者在面对较慢的OF时能够提高步行速度。使用虚拟现实技术操纵OF速度可应用于步态康复干预，以促进中风后更快的步行速度。
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