Effects of weak transcranial alternating current stimulation on brain activity-a review of known mechanisms from animal studies.
Effects of weak transcranial alternating current stimulation on brain activity-a review of known mechanisms from animal studies.
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DOI：
10.3389/fnhum.2013.00687
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发表时间：
2013-10-23
影响因子：
2.9
通讯作者：
Parra LC
中科院分区：
文献类型：
--
作者：
Reato D;Rahman A;Bikson M;Parra LC
节律性神经元活动在人脑中普遍存在。这些节律源自各种不同的网络机制，从而产生广泛的振荡频率频谱。在过去的几年中，越来越多的临床研究探索了微弱电流经颅交流电刺激（tACS）作为影响大脑功能的工具。这些干预措施的前提是 tACS 将与持续的大脑振荡相互作用。然而，弱电流影响不同频段神经元振荡的确切机制尚不清楚，这反过来又限制了人体实验的合理优化。在这里，我们回顾了现有的体外和体内动物研究，试图提供机制解释。这些发现可以概括为一些通用原则，例如兴奋性的周期性调节、尖峰时间的变化、放电率的调节以及兴奋和抑制平衡的变化。这些效应是由大量神经元微弱但同时极化引起的。这是否会导致大脑振荡的夹带或调制，或者交流电流是否根本没有影响，完全取决于引起不同大脑节律的特定动态，正如这里讨论的慢波振荡（∼1 Hz）和伽马振荡（∼30 Hz）。最后，我们提出了进一步实验的建议，以研究交流电刺激对其他生理相关脑节律的作用。
Rhythmic neuronal activity is ubiquitous in the human brain. These rhythms originate from a variety of different network mechanisms, which give rise to a wide-ranging spectrum of oscillation frequencies. In the last few years an increasing number of clinical research studies have explored transcranial alternating current stimulation (tACS) with weak current as a tool for affecting brain function. The premise of these interventions is that tACS will interact with ongoing brain oscillations. However, the exact mechanisms by which weak currents could affect neuronal oscillations at different frequency bands are not well known and this, in turn, limits the rational optimization of human experiments. Here we review the available in vitro and in vivo animal studies that attempt to provide mechanistic explanations. The findings can be summarized into a few generic principles, such as periodic modulation of excitability, shifts in spike timing, modulation of firing rate, and shifts in the balance of excitation and inhibition. These effects result from weak but simultaneous polarization of a large number of neurons. Whether this can lead to an entrainment or a modulation of brain oscillations, or whether AC currents have no effect at all, depends entirely on the specific dynamic that gives rise to the different brain rhythms, as discussed here for slow wave oscillations (∼1 Hz) and gamma oscillations (∼30 Hz). We conclude with suggestions for further experiments to investigate the role of AC stimulation for other physiologically relevant brain rhythms.