The University of Sydney, Australia.
The University of Sydney, Australia.
Neuropsychologia. 2019 Feb 18;124:55-65. doi: 10.1016/j.neuropsychologia.2019.01.008. Epub 2019 Jan 14.
The time required to abort an initiated response can be measured as the Stop Signal Reaction Time (SSRT). We determined whether GABAergic activity in the primary motor cortex (M1), measured using paired-pulse Transcranial Magnetic Stimulation (TMS) was related to SSRT. GABAergic activity in M1 was assessed by measuring Short-Interval Intracortical Inhibition (SICI). In two experiments, participants (males and females) completed the Stop Signal Task while we measured SICI from the first dorsal interosseous muscle. In Experiment 1, SICI was measured at fixed time points after Stop signal onset on Stop trials (50ms, 100ms, 150ms, 200ms), and at corresponding time points for Go trials. In Experiment 2 SICI was measured at fixed time points before the end of the SSRT interval (125ms, 75ms, 25ms) on Stop trials, and at corresponding time points for Go trials. In each experiment, 30 participants were classified as fast stoppers or slow stoppers based on a median split of their SSRTs. Fast stoppers had more SICI than slow stoppers, both when executing a response (Go trials) and when inhibiting a response (Stop trials). Indeed, the correlation between mean SICI and SSRT on successful Stop trials was 0.81. Experiment 2 showed that for fast stoppers (relative to baseline) there was reduced SICI on Go trials and recovery of SICI on Stop trials. Slow stoppers however, showed reduced SICI on Stop and Go trials relative to baseline. Our results show that individuals who are faster at stopping not only show more GABAergic activity in M1, but can more effectively control M1 GABAergic activity to inhibit motor cortical excitability when stopping a response and disinhibit excitability when executing a response.
中止已启动反应所需的时间可以用停止信号反应时间（SSRT）来衡量。我们确定初级运动皮层（M1）中的 GABA 能活动是否与 SSRT 相关，该活动通过使用成对脉冲经颅磁刺激（TMS）来测量。M1 中的 GABA 能活性通过测量短程皮质内抑制（SICI）来评估。在两项实验中，参与者（男性和女性）在完成停止信号任务的同时，我们从第一背侧骨间肌测量 SICI。在实验 1 中，SICI 在停止试验的停止信号出现后固定时间点（50ms、100ms、150ms、200ms）进行测量，并在相应的 Go 试验时间点进行测量。在实验 2 中，SICI 在停止试验的 SSRT 间隔结束前固定时间点（125ms、75ms、25ms）进行测量，并在相应的 Go 试验时间点进行测量。在每个实验中，根据 SSRT 的中位数将 30 名参与者分为快速停止者或慢速停止者。无论是在执行反应（Go 试验）还是抑制反应（停止试验）时，快速停止者的 SICI 都比慢速停止者多。实际上，成功停止试验中平均 SICI 与 SSRT 之间的相关性为 0.81。实验 2 表明，与基线相比，快速停止者在 Go 试验中 SICI 减少，而在停止试验中 SICI 恢复。然而，与基线相比，慢速停止者在停止和 Go 试验中 SICI 减少。我们的结果表明，停止反应更快的个体不仅在 M1 中表现出更多的 GABA 能活动，而且在停止反应时能够更有效地控制 M1 GABA 能活动以抑制运动皮质兴奋性，并在执行反应时解除抑制兴奋性。
