Bugnariu Nicoleta, Fung Joyce
School of Rehabilitation Sciences, University of Ottawa, 451 Smyth Road, Room 3057, Ottawa, Ontario, K1H 8M5, Canada.
J Neuroeng Rehabil. 2007 Jun 20;4:19. doi: 10.1186/1743-0003-4-19.
The maintenance of upright equilibrium is essentially a sensorimotor integration task. The central nervous system (CNS) has to generate appropriate and complex motor responses based on the selective and rapid integration of sensory information from multiple sources. Since each sensory system has its own coordinate framework, specific time delay and reliability, sensory conflicts may arise and represent situations in which the CNS has to recalibrate the weight attributed to each particular sensory input. The resolution of sensory conflicts may represent a particular challenge for older adults given the age-related decline in the integrity of many postural regulating systems, including musculoskeletal and sensory systems, as well as neural processing and conduction of information. The effects of aging and adaptation (by repeated exposures) on the capability of the CNS to select pertinent sensory information and resolve sensory conflicts were thus investigated with virtual reality (VR) in the present study.
Healthy young and older adults maintained quiet stance while immersed in a virtual environment (VE) for 1 hour during which transient visual and/or surface perturbations were randomly presented. Visual perturbations were induced by sudden pitch or roll plane tilts of the VE viewed through a helmet-mounted display, and combined with or without surface perturbations presented in a direction that was either identical or opposite to the visual perturbations.
Results showed a profound influence of aging on postural adjustments measured by electromyographic (EMG) responses and displacements of the center of pressure (COP) and body's center of mass (COM) in the recovery of upright stance, especially in the presence of sensory conflicts. Older adults relied more on vision as compared to young adults. Aging affects the interaction of the somatosensory and visual systems on the control of equilibrium during standing and the ability of CNS to resolve sensory conflicts. However, even with a one-hour immersion in VE and exposure to sensory conflicts, it is possible for the CNS to recalibrate and adapt to the changes, while improving balance capability in older adults.
Preventive and rehabilitation programs targeting postural control in older adults should take into account the possible impairment of sensory organization or sensorimotor integration and include VE training under conditions of sensory conflicts.
维持直立平衡本质上是一项感觉运动整合任务。中枢神经系统（CNS）必须基于对来自多个来源的感觉信息进行选择性和快速整合，来产生适当且复杂的运动反应。由于每个感觉系统都有其自身的坐标框架、特定的时间延迟和可靠性，感觉冲突可能会出现，这代表着中枢神经系统必须重新校准赋予每个特定感觉输入的权重的情况。鉴于许多姿势调节系统（包括肌肉骨骼和感觉系统以及神经信息处理和传导）的完整性会随着年龄增长而下降，感觉冲突的解决对于老年人而言可能是一项特殊挑战。因此，本研究利用虚拟现实（VR）研究了衰老和适应（通过反复暴露）对中枢神经系统选择相关感觉信息并解决感觉冲突能力的影响。
健康的年轻人和老年人在沉浸于虚拟环境（VE）中1小时的过程中保持安静站立姿势，在此期间会随机出现短暂的视觉和/或表面扰动。视觉扰动由通过头戴式显示器观看的虚拟环境在俯仰或横滚平面上的突然倾斜引起，并与以与视觉扰动相同或相反方向呈现的表面扰动相结合或不结合。
结果表明，衰老对通过肌电图（EMG）反应、压力中心（COP）和身体质心（COM）在恢复直立姿势时的位移所测量的姿势调整有深远影响，尤其是在存在感觉冲突的情况下。与年轻人相比，老年人更多地依赖视觉。衰老会影响体感和视觉系统在站立时对平衡控制的相互作用以及中枢神经系统解决感觉冲突的能力。然而，即使在虚拟环境中沉浸1小时并暴露于感觉冲突，中枢神经系统仍有可能重新校准并适应这些变化，同时提高老年人的平衡能力。
针对老年人姿势控制的预防和康复计划应考虑到感觉组织或感觉运动整合可能受到的损害，并包括在感觉冲突条件下的虚拟环境训练。
