Protective Balance and Startle Responses to Sudden Drop Perturbations in Aging

 描述（由申请人提供）：福尔斯及其后果是老年人医疗保健中的主要问题。我们的中心假设是，与年龄相关的过度和不习惯的惊吓/姿势FTR异常增加跌倒风险和相关损伤，通过干扰有效的姿势运动，通过过度的肌肉反应和关节僵硬，并通过增加有害的跌倒冲击力，或两者兼而有之。然而，随着年龄的增长，这种异常可能会通过剩余的惊吓可塑性能力进行修改。在突然失衡期间，意外的姿势紊乱类似于可能导致跌倒的惊人事件。第一次试验姿势反应（FTR）中的过度惊吓样反应通常会随着习惯化而减少。因为所有的福尔斯都包括身体在重力作用下的向下运动，这可能会引发惊吓，所以了解突然跌落扰动期间的FTR是否会增强保护性平衡恢复或存在问题，这将是重要的。此外，FTR是否随着年龄的增长而变化也是至关重要的，因为平衡和惊吓都显示出与年龄相关的异常。此外，通过确定调节性影响，如行为习惯化，通过通常修改惊吓反应的运动预测（中央集）或通过下降扰动（前刺激抑制）之前的感觉前刺激，确定治疗正常化异常惊吓对FTR的影响的方法将是重要的。将通过肌电图（EMG）记录、动作捕捉和测力平台记录评估全身姿势性肌肉激活模式、运动运动学和着陆冲击力。具体目的是：1）确定影响惊吓/姿势FTR和外部激活后反应习惯化的神经肌肉和运动机制的年龄相关变化通过测量指示随着年龄增长的感觉运动传导和脑干处理以及躯体感觉和前庭信息的整合受损的定时和幅度参数来测量站立支撑表面的（反应性）跌落扰动;和2）确定a）通过比较全身惊吓/姿势对反应性跌落扰动和自激活的FTR的调节作用，（预测性）扰动对FTR和反应习惯化的影响，以及B）声预刺激对FTR幅度和随后由反应性液滴扰动诱发的姿势反应的调节作用。预期的结果是，异常的神经生理机制，造成过度惊吓的贡献，以姿势FTR与老年人将与受损的平衡稳定性。此外，确定对惊吓的急性调节作用将是开发新的未来康复干预措施的第一步，以最大限度地减少破坏性FTR反应并预防福尔斯和相关损伤。

 DESCRIPTION (provided by applicant): Falls and their consequences are among the major problems in the medical care of older individuals. Our central hypothesis is that age-associated abnormalities of excessive and poorly habituated startle/postural FTRs increase fall risk and related injuries by interfering with effective postural movements through excessive muscle responses and joint stiffening, and by increasing injurious fall impact forces, or both. However, such abnormalities with older age may be modified through residual startle plasticity capacity. During sudden imbalance, unexpected postural disturbances resemble startling events that may precipitate a fall. The excessive startle-like reaction incorporated into the first trial postural response (FTR) normally diminishes with habituation. Because all falls include downward motion of the body with gravity that may trigger a startle, understanding whether the FTR during sudden drop perturbations either enhances protective balance recovery or is problematic for it would be important to determine. Furthermore, whether the FTR is changed with aging would also be essential to know because both balance and startle show age-related abnormalities. Moreover, identifying ways to therapeutically normalize abnormal startle contributions to FTRs with aging by determining the modulatory influences such as behavioral habituation, subject awareness through motor prediction (central set) that normally modifies startle responses, or through a sensory prestimulus before the drop perturbation (prestimulus inhibition) would be important to identify. Whole body postural muscle activation patterns, movement kinematics, and landing impact forces will be assessed by electromyographic (EMG) recordings, motion capture, and force platform recordings. The specific aims are 1) to determine the age-associated changes in neuromuscular and kinematic mechanisms affecting startle/postural FTRs and response habituation after externally-activated (reactive) drop perturbations of the standing support surface by measuring the timing and magnitude parameters indicative of impaired sensorimotor conduction and brainstem processing and integration of somatosensory and vestibular information with older age; and 2) To determine a) the modulatory effects of motor prediction in relation to older age on FTRs by comparing the whole-body startle/postural responses to reactive drop perturbations and self-activated (predictive) perturbations on FTRs and response habituation, and b) the modulatory effects of an acoustic prestimulus on the FTR magnitude and subsequent postural responses evoked by reactive drop perturbations. Expected outcomes are that abnormal neurophysiological mechanisms causing excessive startle contributions to postural FTRs with older age will be linked with impaired balance stability. Moreover, determining the acute modulatory influences on startle will be first steps in the development of novel future rehabilitation interventions to minimize disruptive FTR reactions and prevent falls and related injuries.