Elyamany Osama, Iffland Jona, Bak Josef, Classen Cornelius, Nolte Guido, Schneider Till R, Leicht Gregor, Mulert Christoph
Centre of Psychiatry, Justus-Liebig University, Klinikstrasse 36, Giessen, Hessen, 35392, Germany; Centre for Mind, Brain and Behaviour (CMBB), Hans-Meerwein-Strasse 6, Marburg, 35043, Hessen, Germany.
Centre of Psychiatry, Justus-Liebig University, Klinikstrasse 36, Giessen, Hessen, 35392, Germany.
Brain Stimul. 2025 May-Jun;18(3):780-793. doi: 10.1016/j.brs.2025.04.011. Epub 2025 Apr 11.
Dual-site transcranial alternating current stimulation (tACS) provides a promising tool for modulating interregional brain connectivity by entraining neural oscillations. However, prior studies have reported inconsistent effects on connectivity and behavioral outcomes. They often focused on individualized stimulation-frequency as a key entrainment factor, while typically not focusing on the role of endogenous phase lags. To address this gap, we explored the predictive value of endogenous phase lags in dual-site tACS to modulate interhemispheric connectivity during dichotic listening.
Thirty healthy participants (16 females) completed a dichotic listening task while undergoing simultaneous electroencephalography and tACS, including four bitemporal verum conditions with varying phase lags (0°, 45°, 90°, and 180°), and a sham condition across five sessions. Each session involved 20 min of 40-Hz tACS at a 0.5 mA peak-to-baseline amplitude applied to the temporal regions, with phase lags differing across sessions. Endogenous phase lags between the auditory cortices were calculated to explain changes in the laterality index (LI) across stimulation conditions by defining optimal and disruptive stimulation conditions for each participant.
Consistent with our hypothesis, our personalized analysis based on the calculated endogenous phase lags showed a significantly lower LI during the closest (optimal) stimulation condition compared to both the sham and farthest (disruptive) conditions. Conversely, the farthest stimulation condition did not statistically increase the LI compared to sham.
These findings highlight the importance of incorporating endogenous phase dynamics into dual-site tACS protocols, paving the way for more consistent and individualized neuromodulatory interventions.
双部位经颅交流电刺激（tACS）为通过诱导神经振荡来调节脑区之间的连接提供了一种有前景的工具。然而，先前的研究报告了其对连接性和行为结果的影响并不一致。这些研究通常将个体刺激频率作为关键的诱导因素，而通常没有关注内源性相位滞后的作用。为了填补这一空白，我们探讨了双部位tACS中内源性相位滞后对在双耳分听过程中调节半球间连接性的预测价值。
30名健康参与者（16名女性）在进行脑电图（EEG）和tACS同步监测时完成了一项双耳分听任务，包括四个具有不同相位滞后（0°、45°、90°和180°）的双侧颞部真实刺激条件，以及一个假刺激条件，共进行五个疗程。每个疗程包括在颞部区域施加20分钟、峰值到基线幅度为0.5毫安、频率为40赫兹的tACS，各疗程的相位滞后不同。通过为每个参与者定义最佳和干扰性刺激条件，计算听觉皮层之间的内源性相位滞后，以解释不同刺激条件下偏侧性指数（LI）的变化。
与我们的假设一致，基于计算出的内源性相位滞后进行的个性化分析显示，与假刺激和最远（干扰性）刺激条件相比，在最接近（最佳）刺激条件下LI显著降低。相反，与假刺激相比，最远刺激条件下的LI在统计学上并未增加。
这些发现突出了将内源性相位动态纳入双部位tACS方案的重要性，为更一致和个性化的神经调节干预铺平了道路。
