Lifting the veil on the dynamics of neuronal activities evoked by transcranial magnetic stimulation.
Lifting the veil on the dynamics of neuronal activities evoked by transcranial magnetic stimulation.
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DOI：
10.7554/elife.30552
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发表时间：
2017-11-22
期刊：
影响因子：
7.7
通讯作者：
Benali A
中科院分区：
文献类型：
--
作者：
Li B;Virtanen JP;Oeltermann A;Schwarz C;Giese MA;Ziemann U;Benali A
经颅磁刺激（TMS）是一种广泛使用的非侵入性工具，用于研究和调节人脑功能。然而，由于TMS诱导的电磁场很大，TMS诱发的单个神经元的活动在很大程度上仍然不可访问。在这里，我们提出了一个一般的方法，提供直接在体内电生理访问TMS诱发的神经元活动0.8-1毫秒后TMS发作。我们将人类单脉冲TMS翻译给啮齿动物，并揭示了运动皮层第V层神经元的时间粒度诱发活动，这些神经元在前6 ms内显示出高频尖峰，这取决于TMS诱导的电流方向，以及在6-300 ms时期内在兴奋和抑制之间交替的多相尖峰节律，所有这些都可以与在脊髓和肌肉水平记录的各种人类TMS反应联系起来。这一进展促进了对TMS-大脑相互作用的新水平的深入了解，这对于开发这种非侵入性工具以有目的地探索和有效治疗人类大脑至关重要。通过将一圈电线举过头顶就能进入一个人的大脑活动，听起来有点像科幻小说。然而，这种被称为经颅磁刺激或TMS的技术被用于研究和治疗许多大脑疾病。经颅磁刺激会发出脉冲磁场，在底层脑组织中诱导微小电流，激活大脑的该区域。但这些电流究竟如何影响激活的大脑区域内的单个神经元和网络仍不清楚。其主要原因是我们不能使用传统的基于电极的技术来研究TMS期间的神经元活动，因为其强烈的电磁干扰掩盖了来自电极的信号。几个团体已经找到了解决这个问题的方法。然而，他们的方法在技术上要求很高，并且只适用于一种动物模型-这些限制可能会给许多实验室带来障碍。因此，Li等人开始开发一种简单且广泛使用的方法来研究TMS下的神经元活动。由此产生的方法使得在应用TMS后大约1/1，000秒测量单个神经元的活动成为可能。为了证明该技术有效，Li等人通过将TMS应用于控制前肢的大脑区域，同时测量神经元的活动，诱导大鼠前肢的小运动。这首次揭示了负责前肢运动的神经元如何对TMS做出反应。在TMS脉冲结束后，观察到的TMS触发的神经元活动持续很长时间。活动也根据TMS诱导的电流在大脑中的方向而变化。这种新方法开辟了方便研究的可能性-在啮齿动物或其他动物-如何TMS程序中使用的患者影响神经元活动。Li等人希望这将使开发、研究和改进这些程序变得更容易，并导致TMS疗法的进步。
Transcranial magnetic stimulation (TMS) is a widely used non-invasive tool to study and modulate human brain functions. However, TMS-evoked activity of individual neurons has remained largely inaccessible due to the large TMS-induced electromagnetic fields. Here, we present a general method providing direct in vivo electrophysiological access to TMS-evoked neuronal activity 0.8–1 ms after TMS onset. We translated human single-pulse TMS to rodents and unveiled time-grained evoked activities of motor cortex layer V neurons that show high-frequency spiking within the first 6 ms depending on TMS-induced current orientation and a multiphasic spike-rhythm alternating between excitation and inhibition in the 6–300 ms epoch, all of which can be linked to various human TMS responses recorded at the level of spinal cord and muscles. The advance here facilitates a new level of insight into the TMS-brain interaction that is vital for developing this non-invasive tool to purposefully explore and effectively treat the human brain. Being able to tap into someone’s brain activity by holding loops of wires above their head sounds a little like the stuff of science fiction. And yet this technique, known as transcranial magnetic stimulation or TMS, is used in research and to treat many brain disorders. TMS emits a pulsed magnetic field that induces tiny electrical currents in the underlying brain tissue, activating that region of the brain. But exactly how these currents affect the individual neurons and networks within activated brain regions remains unclear. The main reason for this is that we cannot use conventional electrode-based techniques to study neuronal activity during TMS because its strong electromagnetic interferences mask the signals from the electrodes. Several groups have found ways to overcome this problem. However, their methods are technically demanding and specific to one single animal model –limitations that could present an obstacle for many laboratories. Li et al. therefore set out to develop a simple and widely accessible method to study neuronal activities under TMS. The resulting method makes it possible to measure the activity of individual neurons roughly 1/1,000th of a second after applying TMS. To show that the technique works, Li et al. induced small movements in the forelimbs of rats by applying TMS to the brain region that controls the forelimbs, while measuring the activity of neurons at the same time. This revealed, for the first time, how the neurons responsible for the forelimb movements responded to TMS. The observed TMS-triggered neuronal activity continued long after the TMS pulse had ended. The activity also varied depending on the direction of TMS-induced currents in the brain. This new method opens up the possibility to conveniently study – in rodents or other animals – how TMS procedures that are used in patients affect neuronal activity. Li et al. hope this will make it easier to develop, study and refine these procedures, and lead to advances in TMS therapies.