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.

本数据集的采集工作于2019年7月末至10月初在阿克雷里大学（University of Akureyri）脑电图（Electroencephalogram, EEG）实验室完成。受试者在签署知情同意书后，首先完成了2.3章节中提及的全部问卷，随后佩戴脑电图帽。
实验首先记录了两种静息状态：睁眼静息3分钟与闭眼静息3分钟，期间刺激呈现电脑屏幕关闭，环境光线调暗。随后受试者完成了一项情绪图片记忆任务，该任务数据未用于本研究。下一实验任务为斯特鲁普任务。

在最后一项实验环节中，受试者填写了一份包含三部分的打印问卷，用于评估当前情绪状态。所有实验指导均通过耳机口头讲解，或在刺激呈现电脑的屏幕上展示。

首先，受试者需回答一道关于当前情绪的问题。随后播放一段时长5分钟的乐曲，该乐曲被认为可诱发短暂的悲伤或烦躁心境，受试者被要求自由体验自身可能产生的任何情绪。本研究使用的乐曲节选自普罗科菲耶夫的《蒙古统治下的俄罗斯》（Prokofiev’s “Russia Under the Mongolian Yoke”），经处理后以原速一半的速率进行重制。该乐曲曾被多项针对抑郁症认知易感性的研究采用，并被证实可有效诱发短暂的烦躁心境（Jarrett等，2012；Lau等，2004；Olafsson等，2020）。

乐曲播放结束后，受试者需立即再次回答当前情绪相关问题。
随后受试者被要求等待5分钟，以完成一项具有挑战性的认知任务。最终，受试者再次回答当前情绪相关问题。至此，受试者被告知并无后续的困难任务，本实验已全部完成。

### EEG记录
本研究采用BrainVision BrainAmp Recorder与放大器（Brain Products GmbH，德国吉尔兴市）采集脑电图数据，采样率设为256Hz并完成数字化。实验使用32个电极，电极位置包括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作为参考电极，AFz作为接地电极。额外增设1个电极用于记录下垂直眼电图（electrooculogram, EOG）。电极安置按照国际标准10-20导联系统进行，使用EasyCap电极帽完成安装。所有电极均填充含温和研磨剂的电解质（OneStep Abrasive Plus），以确保所有通道的阻抗低于10千欧。

本数据集仅包含睁眼静息3分钟的脑电图数据，以及聆听悲伤乐曲后自由思考阶段的前3分钟脑电图数据。