POSTURAL STABILIZATION AND VISUAL ORIENTATION IN ELDERLY

这个项目的总体目标是确定通常用于头部稳定的机制，包括来自前庭耳石和耳道的信号以及它们与被动机械特性的相互作用，是如何被自愿视觉处理任务的同时需求所改变的。具体地说，这项建议探讨了老年人和年轻人在面对同时进行的视力和姿势稳定任务时如何协调头部和躯干的运动。我们假设，如果视觉控制头部的位置，应该不会有冲突--头部总是会努力稳定视野。但是，如果头部是整个身体协同作用的一部分，以应对提升的力量，可能就必须做出选择。当头部的稳定相对于空间(即视觉方向)和相对于躯干(即身体方向)进行调节时，我们期望姿势稳定动作的神经和生物力学特征不同。在前后平移和侧向平移中的反应，即在功能性运动中表现出显著力量的运动平面，将在坐着、躯干固定或自由移动和站立的情况下进行检查。受试者将看到一个立体视野，其中包含一个稳定的焦点图像，一个与躯干旋转同相的图像，以及一个与躯干异相移动的视觉图像。将使用平滑的位置斜坡、正弦和PRBS刺激，并允许我们得出响应的时域和频域特性。鉴于头部视觉目标和头部到身体的稳定可以毫无问题地同时运行，我们预计会发现，特别是在老年人中，存在一些限制(例如机械)，需要做出一些决定，偏爱一种功能，而不是另一种功能。将分析颈部和躯干肌肉的空间组织和反应幅度，以表征神经反应策略。将头部和颈部位置的反射控制与下降控制和系统力学相结合的模型将用于辅助分析和预测姿势控制机制。澄清姿势稳定的机制之间的关系应有助于临床医生评估跌倒和平衡障碍的原因，并应改进对老年人和中枢神经系统缺陷患者的治疗干预。

The overall goal of this project is to determine how the mechanisms normally used for head stabilization, including signals from vestibular otoliths and canals and their interaction with passive mechanical properties, are modified by the simultaneous demands of a voluntary visual processing task. Specifically, this proposal explores how elderly and young adults coordinate their head and trunk movements when confronted with simultaneous visual acuity and postural stabilization tasks. We hypothesize that if vision controls head position, there should be no conflict - the head will always work to stabilize the visual field. But, if the head is part of a whole body synergy in response to ascending forces, a choice might have to be made. We would expect different neural and biomechanical characteristics of postural stabilizing actions when stabilization of the head is regulated with respect to space (i.e., visual orientation) versus with respect to trunk (i.e., body orientation). Responses during anterior- posterior and lateral translations, the planes of motion where significant power has been demonstrated during functional locomotion, will be examined in subjects seated with the trunk fixed or free to move and when standing. Subjects will be presented with a stereo visual field containing a stable focal image, an image that is in phase with the rotation of the trunk, and a visual image that moves out of phase with the trunk. Smoothed position ramps, sinusoids, and PRBS stimuli will be used and will permit us to derive both time and frequency domain characteristics of the response. Given that head4o-visual target and head-to-body stabilization can operate without problems together, we expect-to find, particularly in the elderly, that there are limits (e.g. mechanical) which call for some decision to favor one function at the cost of the other. Both the spatial organization and response magnitudes of the neck and trunk muscles will be analyzed to characterize the neural response strategies. Models that incorporate reflex control of head and neck position with descending controls and system mechanics will be used to assist in the analysis and prediction of postural control mechanisms. Clarification of relations between the mechanisms responsible for postural stabilization should assist clinicians in evaluating the causes of falling and balance disturbances, and should improve therapeutic interventions applied both to the elderly and to patients with central nervous system deficit.