Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
Neuroscientist. 2010 Jun;16(3):285-307. doi: 10.1177/1073858409336227. Epub 2009 Dec 29.
Transcranial stimulation with weak direct current (DC) has been valuable in exploring the effect of cortical modulation on various neural networks. Less attention has been given, however, to cranial stimulation with low-intensity alternating current (AC). Reviewing and discussing these methods simultaneously with special attention to what is known about their mechanisms of action may provide new insights for the field of noninvasive brain stimulation. Direct current appears to modulate spontaneous neuronal activity in a polarity-dependent fashion with site-specific effects that are perpetuated throughout the brain via networks of interneuronal circuits, inducing significant effects on high-order cortical processes implicated in decision making, language, memory, sensory perception, and pain. AC stimulation has also been associated with a significant behavioral and clinical impact, but the mechanism of AC stimulation has been underinvestigated in comparison with DC stimulation. Even so, preliminary studies show that although AC stimulation has only modest effects on cortical excitability, it has been shown to induce synchronous changes in brain activity as measured by EEG activity. Thus, cranial AC stimulation may render its effects not by polarizing brain tissue, but rather via rhythmic stimulation that synchronizes and enhances the efficacy of endogenous neurophysiologic activity. Alternatively, secondary nonspecific central and peripheral effects may explain the clinical outcomes of DC or AC stimulation. Here the authors review what is known about DC and AC stimulation, and they discuss features that remain to be investigated.
经颅弱直流电刺激在探索皮质调制对各种神经网络的影响方面具有重要价值。然而，人们对低强度交流电（AC）的颅刺激关注较少。同时回顾和讨论这些方法，并特别关注它们作用机制的已知内容，可能为非侵入性脑刺激领域提供新的见解。直流似乎以极性依赖的方式调节自发神经元活动，具有特定部位的影响，通过神经元回路的网络在整个大脑中持续存在，对决策、语言、记忆、感官感知和疼痛等高级皮质过程产生重大影响。AC 刺激也与显著的行为和临床影响有关，但与 DC 刺激相比，AC 刺激的机制尚未得到充分研究。即便如此，初步研究表明，尽管 AC 刺激对皮质兴奋性的影响只有适度，但已证明它可以通过 EEG 活动测量的脑活动同步变化来诱导。因此，颅 AC 刺激可能不是通过极化脑组织来发挥其作用，而是通过同步刺激来同步和增强内源性神经生理活动的功效。或者，二次非特异性中枢和外周效应可能解释 DC 或 AC 刺激的临床结果。在这里，作者回顾了已知的 DC 和 AC 刺激，并讨论了仍有待研究的特征。
