School of Psychology, Shanghai University of Sport, Shanghai, China; Krembil Research Institute, University Health Network, Toronto, ON, Canada; Division of Neurology, Department of Medicine, University of Toronto, Toronto, ON, Canada.
Krembil Research Institute, University Health Network, Toronto, ON, Canada; Division of Neurosurgery, Department of Surgery, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada.
Neuroimage. 2021 Nov;243:118557. doi: 10.1016/j.neuroimage.2021.118557. Epub 2021 Sep 4.
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，它可以高度聚焦地调节皮质和深部脑结构的兴奋性。以前的人类研究表明，TUS 降低了经颅磁刺激（TMS）测量的运动皮层（M1）兴奋性，但 TUS 的影响是否超出了超声作用范围，以及 TUS 是否影响其他相互连接的皮质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 TUS 对同侧和对侧 M1 兴奋性的时程。在 500ms 的超声作用时间下，我们发现从超声作用结束前 10ms 到结束后 20ms，M1 兴奋性受到抑制，与交错设计相比，阻塞设计的效果更强。对 M1 对侧兴奋性没有显著影响。使用离体测量，我们表明超声换能器不会影响 TMS 诱导的电磁场的幅度或时程。我们得出的结论是，TUS 对同侧 M1 皮质兴奋性的在线抑制作用略长于超声作用时间，但不会产生持久的影响。对侧无影响可能表明静息状态下半球间的紧张性相互作用很小，或者 TUS 的强度太低，不足以引起胼胝体抑制。
