Supplementary Material for: Encephalography Connectivity on Sources in Male Nonsmokers after Nicotine Administration during the Resting State

We present an encephalography (EEG) connectivity study where 30 healthy male nonsmokers were randomly allocated either to a nicotine group (14 subjects, 7 mg of transdermal nicotine) or to a placebo group. EEG activity was recorded in an eyes-open (EO) and eyes-closed (EC) condition before and after drug administration. This is a reanalysis of a previous dataset. Through a source reconstruction procedure, we extracted 13 time series representing 13 sources belonging to a resting-state network. Here, we conducted connectivity analysis (renormalized partial directed coherence; rPDC) on sources, focusing on the frequency range of 8.5-18.4 Hz, subdivided into 3 frequency bands (α₁, α₂, and β₁) with the hypothesis that an increase in vigilance would modulate connectivity. Furthermore, a phase-amplitude coupling (mean resultant vector length; VL) analysis, was performed investigating whether an increase of vigilance would modulate phase-amplitude coupling. In the VL analysis we estimated the coupling of the phases of 3 low frequencies (α₁, α₂, and β₁), respectively, with the amplitude of high-frequency oscillations (30-40 Hz, low γ). With rPDC we found that during the EC condition, nicotine decreased feedback connectivity (from the precentral gyrus to precuneus, angular gyrus, cuneus and superior occipital gyrus) at 10.5-12.4 Hz. The VL analysis showed nicotine-induced increases in coupling at 10.5-18.4 Hz in the precuneus, cuneus and superior occipital gyrus during the EC condition. During the EO condition, no significant results were found in connectivity or phase-amplitude coupling measures at any frequency range. In conclusion, the results suggest that nicotine potentially increases the level of vigilance in the EC condition.

本研究报道一项脑电图（electroencephalography, 简称EEG）连接性研究：纳入30名健康男性非吸烟者，将其随机分配至尼古丁组（14名受试者，予以7 mg经皮尼古丁贴剂）与安慰剂组。研究采集了给药前后睁眼（eyes-open, 简称EO）与闭眼（eyes-closed, 简称EC）状态下的脑电图活动。本研究为既往数据集的重新分析工作：通过源重构流程，我们提取出13个代表静息态网络脑内源的时间序列。本研究对上述脑内源开展连接性分析（归一化部分定向相干，renormalized partial directed coherence, 简称rPDC），分析聚焦于8.5~18.4 Hz的频域范围，并将其划分为3个子频段（α₁、α₂与β₁），研究假设为警觉性提升可调节脑连接性。此外，本研究还开展了相位振幅耦合（平均结果向量长度，mean resultant vector length, 简称VL）分析，以探究警觉性提升是否可调节相位振幅耦合特性。在VL分析中，我们分别以3个低频段（α₁、α₂与β₁）的相位，与高频振荡（30~40 Hz，即低γ频段）的振幅进行耦合估计。通过rPDC分析，我们发现：在闭眼（EC）状态下，尼古丁可在10.5~12.4 Hz频段降低反馈连接性（从中央前回投射至楔前叶、角回、楔叶与枕上回）。VL分析结果显示：在闭眼（EC）状态下，尼古丁可使楔前叶、楔叶与枕上回在10.5~18.4 Hz频段的耦合强度显著提升。而在睁眼（EO）状态下，所有频域范围的连接性与相位振幅耦合指标均未发现显著差异。综上，本研究结果表明，尼古丁可在闭眼状态下潜在提升受试者的警觉性水平。