Low-intensity transcranial ultrasound stimulation (TUS) is a promising non-invasive brain stimulation technique that can modulate the excitability of cortical and deep brain structures with a high degree of focality. Previous human studies showed that TUS decreases motor cortex (M1) excitability measured by transcranial magnetic stimulation (TMS), but whether the effects appear beyond sonication and whether TUS affects the excitability of other interconnected cortical areas is not known. The time course of M1 TUS on ipsilateral and contralateral M1 excitability was investigated in 22 healthy human subjects via TMS-induced motor-evoked potentials. With sonication duration of 500 ms, we found suppression of M1 excitability from 10 ms before to 20 ms after the end of sonication, and the effects were stronger with blocked design compared to interleaved design. There was no significant effect on contralateral M1 excitability. Using ex-vivo measurements, we showed that the ultrasound transducer did not affect the magnitude or time course of the TMS-induced electromagnetic field. We conclude that the online-suppressive effects of TUS on ipsilateral M1 cortical excitability slightly outlast the sonication but did not produce long-lasting effects. The absence of contralateral effects may suggest that there are little tonic interhemispheric interactions in the resting state, or the intensity of TUS was too low to induce transcallosal inhibition.

低强度经颅超声刺激 (TUS) 是一种很有前途的非侵入性脑刺激技术，可以高度聚焦调节皮质和深部脑结构的兴奋性。以前的人体研究表明，TUS 降低了经颅磁刺激 (TMS) 测量的运动皮层 (M1) 兴奋性，但这种影响是否出现在超声处理之外以及 TUS 是否影响其他相互连接的皮层区域的兴奋性尚不清楚。通过 TMS 诱导的运动诱发电位在 22 名健康人类受试者中研究了 M1 TUS 对同侧和对侧 M1 兴奋性的时间过程。超声处理持续时间为 500 ms，我们发现 M1 兴奋性从超声处理结束前 10 ms 到结束后 20 ms 受到抑制，与交错设计相比，分块设计的效果更强。对侧 M1 兴奋性没有显着影响。使用离体测量，我们表明超声换能器不影响 TMS 感应电磁场的幅度或时间进程。我们得出结论，TUS 对同侧 M1 皮质兴奋性的在线抑制作用略长于超声处理，但没有产生持久的影响。没有对侧效应可能表明在静息状态下几乎没有强直的纵裂相互作用，或者 TUS 的强度太低而无法诱导经胼胝体抑制。我们发现超声换能器不影响 TMS 感应电磁场的幅度或时间进程。我们得出结论，TUS 对同侧 M1 皮质兴奋性的在线抑制作用略长于超声处理，但没有产生持久的影响。没有对侧效应可能表明在静息状态下几乎没有强直的纵裂相互作用，或者 TUS 的强度太低而无法诱导经胼胝体抑制。我们发现超声换能器不影响 TMS 感应电磁场的幅度或时间进程。我们得出结论，TUS 对同侧 M1 皮质兴奋性的在线抑制作用略长于超声处理，但没有产生持久的影响。没有对侧效应可能表明在静息状态下几乎没有强直的纵裂相互作用，或者 TUS 的强度太低而无法诱导经胼胝体抑制。