Due to life-saving medical advances, the diagnosis and treatment of disorders of consciousness (DOC) has become a more commonly occurring clinical issue. One recently developed intervention option has been non-invasive transcranial direct current stimulation. This dichotomy of patient responders may be better understood by investigating the mechanism behind the transcranial direct current stimulation (tDCS) intervention. The combination of transcranial magnetic stimulation and electroencephalography (TMS-EEG) has been an important diagnostic tool in DOC patients. We therefore examined the neural response using TMS-EEG both before and after tDCS in seven DOC patients (four diagnosed as in a minimally conscious state and three with unresponsive wakefulness syndrome). tDCS was applied over the dorsolateral prefrontal cortex, while TMS pulses were applied to the premotor cortex. None of the seven patients showed relevant behavioral change after tDCS. We did, however, find that the overall evoked slow activity was reduced following tDCS intervention. We also found a positive correlation between the strength of the slow activity and the amount of high-frequency suppression. However, there was no significant pre-post tDCS difference in high frequencies. In the resting-state EEG, we observed that both the incidence of slow waves and the positive slope of the wave were affected by tDCS. Taken together, these results suggest that the tDCS intervention can reduce the slow-wave activity component of bistability, but this may not directly affect high-frequency activity. We hypothesize that while reduced slow activity may be necessary for the recovery of neural function, especially consciousness, this alone is insufficient.

中文翻译：

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在意识障碍中 tDCS 后诱发的慢活动减少

由于挽救生命的医学进步，意识障碍 (DOC) 的诊断和治疗已成为更常见的临床问题。最近开发的一种干预选择是非侵入性经颅直流电刺激。通过研究经颅直流电刺激 (tDCS) 干预背后的机制，可以更好地理解患者反应者的这种二分法。经颅磁刺激和脑电图 (TMS-EEG) 的组合已成为 DOC 患者的重要诊断工具。因此，我们在七名 DOC 患者（四名诊断为最低意识状态，三名诊断为无反应觉醒综合征）的 tDCS 前后使用 TMS-EEG 检查了神经反应。tDCS 应用于背外侧前额叶皮层，而 TMS 脉冲应用于前运动皮层。7 名患者在 tDCS 后均未表现出相关的行为改变。然而，我们确实发现在 tDCS 干预后整体诱发的缓慢活动减少了。我们还发现缓慢活动的强度与高频抑制量之间呈正相关。然而，高频没有显着的前后 tDCS 差异。在静息态脑电图中，我们观察到慢波的发生率和波的正斜率都受 tDCS 的影响。综上所述，这些结果表明 tDCS 干预可以减少双稳态的慢波活动成分，但这可能不会直接影响高频活动。我们假设，虽然减少慢活动可能是神经功能恢复所必需的，