By stopping actions even after their initiation, humans can flexibly adapt ongoing behavior to changing circumstances. The neural processes underlying the inhibition of movement during action-stopping are still controversial. In the 1990s, a fronto-central event-related potential (ERP) was discovered in the human EEG response to stop-signals in the classic stop-signal task, alongside a proposal that this "stop-signal P3" reflects an inhibitory process. Indeed, both amplitude and onset of the stop-signal P3 relate to overt behavior and movement-related EEG activity in ways predicted by the dominant models of action-stopping. However, neither EEG nor behavior allow direct inferences about the presence or absence of neurophysiological inhibition of the motor cortex, making it impossible to definitively relate the stop-signal P3 to inhibition. Here, we therefore present a multi-method investigation of the relationship between the stop-signal P3 and GABAergic signaling in primary motor cortex, as indexed by paired-pulse transcranial magnetic stimulation. In detail, we measured short-interval intracortical inhibition (SICI, a marker of inhibitory GABA_a activity in M1) in a group of 41 human participants who also performed the stop-signal task while undergoing EEG recordings. In line with the P3-inhibition hypothesis, we found that subjects with stronger inhibitory GABA activity in M1 also showed both faster onsets and larger amplitudes of the stop-signal P3. This provides direct evidence linking the properties of this ERP to a true physiological index of motor system inhibition. We discuss these findings in the context of recent theoretical developments and empirical findings regarding the neural implementation of motor inhibition.

中文翻译：

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配对脉冲 TMS 和头皮脑电图揭示了 M1 抑制性 GABAa 信号传导与动作停止期间额中央皮质活动之间的系统关系

通过即使在行动开始后停止行动，人类也可以灵活地调整正在进行的行为以适应不断变化的环境。在动作停止期间抑制运动的神经过程仍然存在争议。在 1990 年代，在经典停止信号任务中人类脑电图对停止信号的反应中发现了额中枢事件相关电位 (ERP)，同时提出这种“停止信号 P3”反映了抑制过程。事实上，停止信号 P3 的幅度和开始都与明显的行为和与运动相关的脑电图活动相关，这些活动以主要的动作停止模型所预测的方式进行。然而，脑电图和行为都不允许直接推断运动皮层是否存在神经生理抑制，使得不可能明确地将停止信号 P3 与抑制联系起来。在这里，我们因此对初级运动皮层中停止信号 P3 和 GABAergic 信号之间的关系进行了多方法研究，如配对脉冲经颅磁刺激所指示的那样。详细地，我们测量了短间隔皮质内抑制（SICI，抑制性 GABA 的标志物_{M1 中的一项}活动）在一组 41 名人类参与者中进行，他们在进行脑电图记录时也执行了停止信号任务。与 P3 抑制假设一致，我们发现在 M1 中具有更强抑制性 GABA 活性的受试者也表现出更快的起始和更大的停止信号 P3 的振幅。这提供了将这种 ERP 的特性与运动系统抑制的真实生理指标联系起来的直接证据。我们在最近的理论发展和关于运动抑制的神经实施的经验发现的背景下讨论这些发现。