The propagating pattern of sleep slow waves (high-amplitude oscillations < 4.5 Hz) serves as a blueprint of cortical excitability and brain connectivity. Phase-locked auditory stimulation is a promising tool for the modulation of ongoing brain activity during sleep; however, its underlying mechanisms remain unknown. Here, eighteen healthy young adults were measured with high-density electroencephalography in three experimental conditions; one with no stimulation, one with up- and one with down-phase stimulation; ten participants were included in the analysis. We show that up-phase auditory stimulation on a right prefrontal area locally enhances cortical involvement and promotes traveling by increasing the propagating distance and duration of targeted small-amplitude waves. On the contrary, down-phase stimulation proves more efficient at perturbing large-amplitude waves and interferes with ongoing traveling by disengaging cortical regions and interrupting high synchronicity in the target area as indicated by increased traveling speed. These results point out different underlying mechanisms mediating the effects of up- and down-phase stimulation and highlight the strength of traveling wave analysis as a sensitive and informative method for the study of connectivity and cortical excitability alterations.

中文翻译：

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通过锁相听觉刺激的神经调节影响睡眠期间兴奋性和连通性的关键标志物

睡眠慢波（高振幅振荡 < 4.5 Hz）的传播模式可作为皮质兴奋性和大脑连接性的蓝图。锁相听觉刺激是调节睡眠期间正在进行的大脑活动的有前途的工具。然而，其潜在机制仍然未知。在这里，用高密度脑电图在三个实验条件下测量了 18 名健康的年轻人；一种无刺激，一种上相刺激，一种下相刺激；十名参与者被纳入分析。我们表明，右前额叶区域的上相位听觉刺激可局部增强皮层参与，并通过增加目标小振幅波的传播距离和持续时间来促进行进。相反，下相刺激证明在扰动大振幅波方面更有效，并通过分离皮质区域和中断目标区域的高同步性来干扰正在进行的行进，如行进速度增加所示。这些结果指出了调节上相和下相刺激效果的不同潜在机制，并强调了行波分析的强度作为研究连通性和皮质兴奋性改变的一种敏感且信息丰富的方法。