EEG responses to mood induction

Measurements were performed at the EEG-laboratory of the University of Akureyri between end of July and beginning of October 2019. After completion of informed consent, participants answered all questionnaires mentioned in section 2.3 and the EEG-cap was mounted. The first two conditions recorded were at rest for 3 min with eyes open and 3min with eyes closed, with the screen of the stimulus computer turned off and dimmed light. Subsequently participants performed an emotional pictures memory task, which was not used for the present study. The next condition was a Stroop task.
In the final condition participants received a printed three part form containing questions about current mood. All instructions were given verbally through headphones or on the screen of the stimulus computer.
Firstly, participants answered one question on their current mood. Next, a 5 min musical piece, thought to evoke temporary sadness or dysphoria, was played and participants were asked to freely experience any emotions they might feel. We used a musical excerpt from Prokofiev’s “Russia Under the Mongolian Yoke”, remastered at half speed. This has been used and found to be effective in inducing a transient dysphoric mood in previous research on cognitive vulnerability to depression (Jarrett et al., 2012; Lau et al., 2004; Olafsson et al., 2020).
Immediately after the music had finished, participants answered again the question on their current mood.
They were then instructed to wait for 5 minutes for a challenging cognitive task. Finally, participants answered once again the question regarding their current mood. After this, participants were informed that no difficult task would follow and that the study was completed.

EEG recording
EEG data was gathered using BrainVision BrainAmp Recorder and Amplifier (Brain Products GmbH, Gilching, Germany) and digitized at a sampling rate of 256 Hz. Recording was conducted using 32 electrodes (Fp1, Fp2, F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T7, T8, P7, P8, Fz, Cz, Pz, FC1, FC2, CP1, CP2, FC5, FC6, CP5, CP6, FT9, FT10, TP9, TP10) referenced to FCz and grounded at AFz. One additional electrode served as lower vertical electrooculogram. Electrode positioning was in accordance with the standardized international 10-20 system by using an EasyCap. Electrodes were filled with electrolyte containing a mild abrasive (OneStep Abrasive Plus) in order to achieve low impedance of <10kOhm in all channels.
We present here EEG-data from 3min rest with eyes open condition and the first 3min of the free-thinking period after listening to the sad music.

本次测量于2019年7月底至10月初在阿库雷伊里大学的脑电图实验室进行。在签署知情同意书后，参与者回答了第2.3节中提到的所有问卷，并佩戴了脑电图帽。首先记录的两个条件为静息状态下的3分钟（双眼睁开）和3分钟（双眼闭合），此时刺激计算机的屏幕处于关闭和昏暗光线状态。随后，参与者完成了情感图片记忆任务，但该任务在本研究中并未使用。下一个条件为斯特罗普任务。在最终条件中，参与者接收了一份包含关于当前情绪问题的打印三部分表格。所有指令均通过耳机或刺激计算机的屏幕以口头形式给出。首先，参与者回答了关于他们当前情绪的一个问题。接着，播放了一首5分钟的音乐作品，旨在唤起暂时的悲伤或不适感，参与者被要求自由体验任何可能感受到的情绪。我们使用了普罗科菲耶夫的《蒙古统治下的俄罗斯》音乐片段，以半速重制。该片段在先前关于认知脆弱性对抑郁的研究中被证明能够有效诱导短暂的抑郁情绪（Jarrett等人，2012年；Lau等人，2004年；Olafsson等人，2020年）。音乐结束后，参与者再次回答关于他们当前情绪的问题。随后，他们被告知需等待5分钟以完成一项挑战性的认知任务。最后，参与者再次回答关于他们当前情绪的问题。在此之后，参与者被告知后续将没有困难的任务，研究已告完成。脑电图记录：使用BrainVision BrainAmp Recorder和Amplifier（Brain Products GmbH，吉尔钦，德国）采集脑电图数据，并以256 Hz的采样率进行数字化。记录使用32个电极（Fp1、Fp2、F3、F4、C3、C4、P3、P4、O1、O2、F7、F8、T7、T8、P7、P8、Fz、Cz、Pz、FC1、FC2、CP1、CP2、FC5、FC6、CP5、CP6、FT9、FT10、TP9、TP10），以FCz为参考点，在AFz接地。一个额外的电极作为下垂直眼电图。电极位置按照国际标准10-20系统使用EasyCap定位。电极填充了含有轻微研磨剂的电解质（OneStep Abrasive Plus），以实现所有通道的低阻抗（<10kOhm）。在此，我们展示了双眼睁开静息状态下3分钟的数据以及听悲伤音乐后的自由思考期的最初3分钟数据。