Evidence for two concurrent inhibitory mechanisms during response preparation.
Evidence for two concurrent inhibitory mechanisms during response preparation.
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DOI：
10.1523/jneurosci.5722-09.2010
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发表时间：
2010-03-10
期刊：
影响因子：
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通讯作者：
Ivry RB
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文献类型：
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作者：
Duque J;Lew D;Mazzocchio R;Olivier E;Ivry RB
抑制机制与目标导向行为密切相关。为了进一步了解这种机制如何在反应准备过程中塑造运动表征，在选择反应时间任务中，记录了由经颅磁刺激(TMS)和H反射诱发的左手肌肉运动诱发电位(MEP)。在发出指示所需反应的命令信号之前，总是有一个预备信号。在线索后延迟期，当提示左手进行即将到来的反应时，左侧MEP被抑制，这暗示了一种专门针对选定反应表征的抑制形式。在这些实验中，H反射也被抑制，这表明这种抑制的影响延伸到脊髓回路。此外，当提示右手时，左侧MEP被抑制，但只有在提示开始之前，左手运动是可能的反应选项时，左侧MEP才受到抑制。值得注意的是，在这些试验中，左手H反射没有被调节，这与皮层抑制轨迹一致，该抑制轨迹降低了与任务相关的、但非选择性反应的激活。这些结果表明，在反应准备过程中，两种抑制机制同时运行：一种是在脊髓水平减少选定反应的激活，通过防止过早释放来帮助控制选定动作的启动时间；第二种上游机制有助于确定在竞争性选择过程中做出什么反应。
Inhibitory mechanisms are critically involved in goal-directed behaviors. To gain further insight into how such mechanisms shape motor representations during response preparation, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) and H-reflexes were recorded from left hand muscles during choice reaction time tasks. The imperative signal, which indicated the required response, was always preceded by a preparatory cue. During the post-cue delay period, left MEPs were suppressed when the left hand had been cued for the forthcoming response, suggestive of a form of inhibition specifically directed at selected response representations. H-reflexes were also suppressed on these trials, indicating that the effects of this inhibition extend to spinal circuits. In addition, left MEPs were suppressed when the right hand was cued, but only when left hand movements were a possible response option before the onset of the cue. Notably, left hand H-reflexes were not modulated on these trials, consistent with a cortical locus of inhibition that lowers the activation of task-relevant, but non-selected responses. These results suggest the concurrent operation of two inhibitory mechanisms during response preparation: one decreases the activation of selected responses at the spinal level, helping to control when selected movements should be initiated by preventing their premature release; a second, upstream mechanism helps to determine what response to make during a competitive selection process.