Planning of Ballistic Movement following Stroke: Insights from the Startle Reflex
Planning of Ballistic Movement following Stroke: Insights from the Startle Reflex
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DOI：
10.1371/journal.pone.0043097
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发表时间：
2012-08-30
期刊：
影响因子：
3.7
通讯作者：
Perreault, Eric Jon
中科院分区：
文献类型：
--
作者：
Honeycutt, Claire Fletcher;Perreault, Eric Jon
在划水之后，到达的动作是缓慢的、分段的和可变的。目前尚不清楚这些缺陷是由于运动计划结构不佳还是无法自主执行适当的计划造成的。声惊吓反射提供了一种不自觉地启动运动计划的手段。在有运动计划的情况下，令人吃惊的声音刺激会触发计划运动的非自愿的早期执行，这种现象被称为start - treact反应。在未受损的个体中，启动反应与自愿发起的运动相同，除了它被激发30-40毫秒。由于startReact反应被认为是由脑干通路介导的，我们假设中风受试者的startReact反应是完整的。如果startReact是完整的，它可能会引发更多的与任务相适应的肌肉激活模式，而不是自愿引起的。我们发现中风后startReact反应完好无损。反应开始的速度与未受损的受试者一样快，肌肉协调模式与未受损的意志运动相似。肘关节屈曲运动的结果是惊人的，这表明在卒中和未受损的受试者组中引起的start - treact反应没有显著差异。对于中风受试者来说，计划伸展运动的结果不那么直接，因为开始反应在屈肌中表现出任务不适当的活动。这种不适当的活动随着时间的推移而减少。这种适应表明，不适当的活动本质上是短暂的，与潜在的运动计划无关。我们假设，在伸展过程中，任务不适当的屈肌活动是由于无法抑制经典的惊吓反射，这主要影响屈肌，并迅速适应连续的刺激。这些结果表明中风受试者能够计划弹道肘运动，并且当这些计划的运动不由自主地执行时，它们可以像未受损的个体一样快速和适当。
Following stroke, reaching movements are slow, segmented, and variable. It is unclear if these deficits result from a poorly constructed movement plan or an inability to voluntarily execute an appropriate plan. The acoustic startle reflex provides a means to initiate a motor plan involuntarily. In the presence of a movement plan, startling acoustic stimulus triggers non-voluntary early execution of planned movement, a phenomenon known as the startReact response. In unimpaired individuals, the startReact response is identical to a voluntarily initiated movement, except that it is elicited 30-40 ms. As the startReact response is thought to be mediated by brainstem pathways, we hypothesized that the startReact response is intact in stroke subjects. If startReact is intact, it may be possible to elicit more task-appropriate patterns of muscle activation than can be elicited voluntarily. We found that startReact responses were intact following stroke. Responses were initiated as rapidly as those in unimpaired subjects, and with muscle coordination patterns resembling those seen during unimpaired volitional movements. Results were striking for elbow flexion movements, which demonstrated no significant differences between the startReact responses elicited in our stroke and unimpaired subject groups. The results during planned extension movements were less straightforward for stroke subjects, since the startReact response exhibited task inappropriate activity in the flexors. This inappropriate activity diminished over time. This adaptation suggests that the inappropriate activity was transient in nature and not related to the underlying movement plan. We hypothesize that the task-inappropriate flexor activity during extension results from an inability to suppress the classic startle reflex, which primarily influences flexor muscles and adapts rapidly with successive stimuli. These results indicate that stroke subjects are capable of planning ballistic elbow movements, and that when these planned movements are involuntarily executed they can be as rapid and appropriate as those in unimpaired individuals.