Patla Aftab E, Davies T Claire, Niechwiej Ewa
Gait & Posture Lab, Department of Kinesiology, University of Waterloo, Waterloo, Ontario, N2L3G1, Canada.
Exp Brain Res. 2004 Mar;155(2):173-85. doi: 10.1007/s00221-003-1714-z. Epub 2004 Feb 10.
The goal of the study was to examine the accuracy and precision of control of adaptive locomotion using haptic information in normally sighted humans before and after practice. Obstacle avoidance paradigm was used to study adaptive locomotion; individuals were required to approach and step over different sizes of obstacles placed in the travel path under three sensory conditions: full vision (FV); restricted lower visual field (RLVF) using blinders on custom glass frames; and no vision (NV) using haptic information only. In the NV condition, individuals were a given an appropriate-sized cane to guide their locomotion. Footfall patterns were recorded using the GAITRite system, and lead and trail limb trajectories were monitored using the OPTOTRAK system, which tracked infrared diodes placed on the toes and the cane. Approach step lengths were reduced for the haptic condition: this slowed the forward progression and allowed greater time for haptic exploration, which ranged from 2.5 to 4 s and consisted of horizontal cane movements (to detect the width and relative location of the obstacle) and vertical cane movements (to detect the height of the obstacle). Based on feed-forward and on-line sensory (under both vision and haptic conditions) information about location of the obstacle relative to the individual, variability of foot placement reduced as the individual came closer to the obstacle, as has been shown in the literature. The only difference was that the reduction in variability of foot placement under haptic condition occurred in the last step compared with earlier under vision. Considering that the obstacle is detected only when the cane comes in contact, as opposed to vision condition when it is visible earlier, this difference is understandable. Variability and magnitude of lead and trail limb elevation for the haptic condition was higher than the RLVF and FV conditions. In contrast, only the magnitude of lead and trail limb elevation was higher in the RLVF condition when compared with the FV condition. This suggests that it is the inability of the haptic sense to provide accurate information about obstacle characteristics compared with the visual system, and not simple caution that lead to higher limb elevation. In the haptic and RLVF condition when vision was unavailable for on-line monitoring of lead limb elevation, kinesthetic information from lead limb elevation was used to fine-tune trail limb elevation. Both the control of approach phase and limb elevation findings held up even after sufficient practice to learn haptic guidance of adaptive locomotion in the second experiment. These results provide a clear picture of the efficacy of the haptic sensory system to guide locomotion in a cluttered environment.
该研究的目的是检验在正常视力的人类中，练习前后利用触觉信息控制适应性运动的准确性和精确性。采用避障范式来研究适应性运动；要求个体在三种感觉条件下接近并跨过放置在行进路径中的不同尺寸的障碍物：全视觉（FV）；使用定制玻璃框架上的眼罩限制下部视野（RLVF）；仅使用触觉信息的无视觉（NV）。在NV条件下，给个体一根尺寸合适的手杖来引导他们的运动。使用GAITRite系统记录脚步模式，并使用OPTOTRAK系统监测前后肢轨迹，该系统跟踪放置在脚趾和手杖上的红外二极管。触觉条件下接近步长减小：这减缓了向前推进并留出更多时间进行触觉探索，触觉探索持续2.5至4秒，包括水平手杖运动（检测障碍物的宽度和相对位置）和垂直手杖运动（检测障碍物的高度）。根据关于障碍物相对于个体位置的前馈和在线感觉（在视觉和触觉条件下）信息，随着个体靠近障碍物，脚部放置的变异性降低，正如文献中所显示的那样。唯一的区别是，与视觉条件下相比，触觉条件下脚部放置变异性的降低发生在最后一步。考虑到只有在手杖接触时才能检测到障碍物，而在视觉条件下障碍物更早可见，这种差异是可以理解的。触觉条件下前后肢抬高的变异性和幅度高于RLVF和FV条件。相比之下，与FV条件相比，RLVF条件下仅前后肢抬高的幅度更高。这表明与视觉系统相比，触觉无法提供关于障碍物特征的准确信息，而不是简单的谨慎导致更高的肢体抬高。在触觉和RLVF条件下，当无法通过视觉在线监测前肢抬高时，来自前肢抬高的动觉信息被用于微调后肢抬高。即使在第二个实验中经过充分练习以学习适应性运动的触觉引导后，接近阶段的控制和肢体抬高的结果仍然成立。这些结果清楚地表明了触觉感觉系统在杂乱环境中引导运动的功效。
