School of Psychology, Faculty of Health, University of Plymouth, Plymouth, UK.
Brain Research and Imaging Centre, Faculty of Health, University of Plymouth, Plymouth, UK.
Nat Commun. 2023 Sep 1;14(1):5318. doi: 10.1038/s41467-023-40998-0.
Low-intensity transcranial ultrasound stimulation (TUS) is an emerging non-invasive technique for focally modulating human brain function. The mechanisms and neurochemical substrates underlying TUS neuromodulation in humans and how these relate to excitation and inhibition are still poorly understood. In 24 healthy controls, we separately stimulated two deep cortical regions and investigated the effects of theta-burst TUS, a protocol shown to increase corticospinal excitability, on the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and functional connectivity. We show that theta-burst TUS in humans selectively reduces GABA levels in the posterior cingulate, but not the dorsal anterior cingulate cortex. Functional connectivity increased following TUS in both regions. Our findings suggest that TUS changes overall excitability by reducing GABAergic inhibition and that changes in TUS-mediated neuroplasticity last at least 50 mins after stimulation. The difference in TUS effects on the posterior and anterior cingulate could suggest state- or location-dependency of the TUS effect-both mechanisms increasingly recognized to influence the brain's response to neuromodulation.
低强度经颅超声刺激（TUS）是一种新兴的非侵入性技术，可用于局部调节人类大脑功能。TUS 神经调节在人类中的机制和神经化学基础，以及这些机制与兴奋和抑制的关系，仍知之甚少。在 24 名健康对照者中，我们分别刺激两个深部皮质区域，并研究了已被证明可增加皮质脊髓兴奋性的 theta 爆发 TUS 对抑制性神经递质γ-氨基丁酸（GABA）和功能连接的影响。我们发现，theta 爆发 TUS 可选择性地降低后扣带皮层中的 GABA 水平，但不会降低背侧前扣带皮层。刺激后两个区域的功能连接都增加了。我们的研究结果表明，TUS 通过减少 GABA 能抑制来改变整体兴奋性，并且 TUS 介导的神经可塑性变化至少在刺激后 50 分钟内持续存在。TUS 对后扣带和前扣带的影响不同，这可能表明 TUS 效应具有状态或位置依赖性，这两种机制越来越被认为会影响大脑对神经调节的反应。
