Independence of Movement Preparation and Movement Initiation
Independence of Movement Preparation and Movement Initiation
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DOI：
10.1523/jneurosci.3245-15.2016
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发表时间：
2016-03-09
影响因子：
5.3
通讯作者：
Krakauer, John W.
中科院分区：
文献类型：
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作者：
Haith, Adrian M.;Pakpoor, Jina;Krakauer, John W.
根据神经传输延迟，启动响应视觉刺激的运动所需的时间比预期的要长得多，但原因尚不清楚。在视觉引导的到达任务中，我们强迫人类参与者以低于正常的反应时间移动，以测试正常的反应时间是否是准确移动所必需的。我们发现，事实上，参与者能够准确地移动，比他们的反应时间建议早 80 毫秒。因此，反应时间包括看似不必要的延迟，约占其持续时间的三分之一。对参与者在传统反应时间条件下的行为的仔细检查表明，他们在反应时间异常短的试验中偶尔会产生自发错误。这些错误的模式可以通过一个简单的模型来很好地解释，其中运动开始的时间与运动准备的时间无关。这种独立性解释了为什么反应时间通常如此缓慢：相对于准备延迟运动开始的时间，可以降低在适当准备之前开始运动的风险。我们的结果表明，运动的准备和启动在机制上是独立的，并且可能具有独特的神经基础。结果还表明，即使在强烈刺激驱动的任务中，刺激的呈现也不会直接触发运动。相反，刺激似乎触发了是否采取行动的内部决定，反映了自愿而非反应性的控制模式。
Initiating a movement in response to a visual stimulus takes significantly longer than might be expected on the basis of neural transmission delays, but it is unclear why. In a visually guided reaching task, we forced human participants to move at lower-than-normal reaction times to test whether normal reaction times are strictly necessary for accurate movement. We found that participants were, in fact, capable of moving accurately similar to 80 ms earlier than their reaction times would suggest. Reaction times thus include a seemingly unnecessary delay that accounts for approximately one-third of their duration. Close examination of participants' behavior in conventional reaction-time conditions revealed that they generated occasional, spontaneous errors in trials in which their reaction time was unusually short. The pattern of these errors could be well accounted for by a simple model in which the timing of movement initiation is independent of the timing of movement preparation. This independence provides an explanation for why reaction times are usually so sluggish: delaying the meantime of movement initiation relative to preparation reduces the risk that a movement will be initiated before it has been appropriately prepared. Our results suggest that preparation and initiation of movement are mechanistically independent and may have a distinct neural basis. The results also demonstrate that, even in strongly stimulus-driven tasks, presentation of a stimulus does not directly trigger a movement. Rather, the stimulus appears to trigger an internal decision whether to make a movement, reflecting a volitional rather than reactive mode of control.