Successful models of movement should encompass the flexibility of the human motor system to execute movements under different contexts. One such context-dependent modulation is proactive inhibition, a type of behavioural inhibition concerned with responding with restraint. Whilst movement has classically been modelled as a rise-to-threshold process, there exists a lack of empirical evidence for this in limb movements. Alternatively, the dynamical systems view conceptualises activity during motor preparation as setting the initial state of a dynamical system, that evolves into the movement upon receipt of a trigger. We tested these models by measuring how proactive inhibition influenced movement preparation and execution in humans. We changed the orientation (PA: postero-anterior and AP: antero-posterior flowing currents) and pulse width (120 us and 30 us) of motor cortex transcranial magnetic stimulation to probe different corticospinal interneuron circuits. PA and AP interneuron circuits represent the dimensions of a state space upon which motor cortex activity unfolds during motor preparation and execution. AP30 inputs were inhibited at the go cue, regardless of proactive inhibition, whereas PA120 inputs scaled inversely with the probability of successful inhibition. When viewed through a rise-to-threshold model, proactive inhibition was implemented by delaying the trigger to move, suggesting that motor preparation and execution are independent. A dynamical systems perspective showed that proactive inhibition was marked by a shift in the distribution of interneuron networks (trajectories) during movement execution, despite normalisation for reaction time. Viewing data through the rise-to-threshold and dynamical systems models reveal complimentary mechanisms by which proactive inhibition is implemented.

中文翻译：

---

主动抑制的上升阈值和动力学系统视图

成功的运动模型应包含人体运动系统在不同环境下执行运动的灵活性。这样一种与情境有关的调节是主动抑制，这是一种与抑制反应有关的行为抑制。虽然经典地将运动建模为上升到阈值的过程，但是在肢体运动中对此缺乏经验证据。替代地，动力学系统将运动准备期间的活动概念化为设置动力学系统的初始状态，该初始状态在接收到触发时演变为运动。我们通过测量主动抑制如何影响人类的运动准备和执行来测试这些模型。我们更改了方向（PA：后后方和AP：运动皮质经颅磁刺激的前后流动电流和脉宽（120 us和30 us），以探测不同的皮质脊髓神经元回路。PA和AP内部神经元电路代表状态空间的尺寸，在运动准备和执行过程中运动皮层活动在该状态空间上展开。无论主动抑制如何，AP30输入都会随时受到抑制，而PA120输入则与成功抑制的可能性成反比。通过上升到阈值模型查看时，通过延迟触发动作来实施主动抑制，这表明运动准备和执行是独立的。动力学系统的观点表明，在执行运动过程中，主动抑制的特征在于中间神经元网络（轨迹）的分布发生了变化，尽管反应时间正常化。通过上升到阈值和动力学系统模型查看数据揭示了互补机制，通过这种机制可以实现主动抑制。