Department of Clinical Neurophysiology, Georg-August University of Göttingen, 37075 Göttingen, Germany.
Curr Biol. 2012 Jul 24;22(14):1314-8. doi: 10.1016/j.cub.2012.05.021. Epub 2012 Jun 7.
Functional cortical circuits for central executive functions have been shown to emerge by theta (~6 Hz) phase-coupling of distant cortical areas. It has been repeatedly shown that frontoparietal theta coupling at ~0° relative phase is associated with recognition, encoding, short-term retention, and planning; however, a causal link has not been demonstrated so far. Here we used transcranial alternating current stimulation simultaneously applied at 6 Hz over left prefrontal and parietal cortices with a relative 0° ("synchronized" condition) or 180° ("desynchronized" condition) phase difference or a placebo stimulation condition, whereas healthy subjects performed a delayed letter discrimination task. We show that exogenously induced frontoparietal theta synchronization significantly improves visual memory-matching reaction times as compared to placebo stimulation. In contrast, exogenously induced frontoparietal theta desynchronization deteriorates performance. The present findings provide for the first time evidence of causality of theta phase-coupling of distant cortical areas for cognitive performance in healthy humans. Moreover, the results demonstrate the suitability of transcranial alternating current stimulation to artificially induce coupling or decoupling of behaviorally relevant brain rhythms between segregated cortical regions.
功能皮质回路的中央执行功能已经被证明是通过遥远的皮质区域的θ波（6Hz）相位耦合而出现的。已经反复证明，额顶叶θ波耦合在0°的相对相位与识别、编码、短期保留和规划有关；然而，到目前为止还没有证明因果关系。在这里，我们使用经颅交流电刺激，同时在左前额叶和顶叶皮层上施加 6Hz 的交流电，相对相位差为 0°（“同步”条件）或 180°（“去同步”条件），或施加安慰剂刺激条件，而健康受试者则执行延迟字母辨别任务。我们发现，与安慰剂刺激相比，外源性诱导的额顶叶θ同步显著改善了视觉记忆匹配的反应时间。相比之下，外源性诱导的额顶叶θ去同步会降低表现。本研究结果首次为健康人类认知表现中远距离皮质区域的θ波相位耦合的因果关系提供了证据。此外，这些结果表明经颅交流电刺激适合人工诱导分离的皮质区域之间与行为相关的脑节律的耦合或去耦。
