EEG of facial emotion judgment task including tactile probes

EEG data recordings of 35 participants who gave informed written consent before taking part in a facial emotion judgement task. The study was approved by City, University of London, Psychology Research Ethics Committee. 
Participants were seated in an electromagnetically shielded, sound attenuated, dimly lit room, viewing a 60 Hz computer monitor at a distance of 80 cm. EEG was recorded from 64 Ag/AgCL active electrodes of which 60 were mounted equidistantly on an elastic cap (M10 montage; EasyCap GmBH, Herrsching, Germany) and standard EEG recording preparation procedures were used to ensure good signal quality (i.e. degreasing of skin and use of electrolyte). Electrodes were referenced to the right earlobe. The horizontal electrooculogram (HEOG) was recorded by placing electrodes 62 and 63 about 1 cm lateral to the external canthi of each eye, and the ECG was recorded by placing electrode 64 about 2 cm under the left collarbone. Continuous EEG was recorded using a BrainAmp amplifier (BrainProducts; amplifier bandpass 0.01–100Hz) and a 500 Hz sampling rate.
A set of 80 face pictures (20 per emotion) depicting angry, sad, happy, and neutral emotions from the Karolinska Directed Emotional Faces set (Lundqvist et al., 1998) were grey scaled and enclosed in a rectangular frame (1.40 X 1.57 inches), excluding most of the hair and non-facial contours. Face stimuli were presented centrally on a black background using the E-prime 2 software (Psychology Software Tools, Pittsburgh, PA), which also controlled delivery of the tactile stimuli. These tactile stimuli were completely task-irrelevant, and their purpose was to probe somatosensory activity. They were delivered by 12 V solenoids (5 mm in diameter) attached with microporous tape to the tip of the left index finger. When a current passed through the solenoid tactile stimulation was delivered by driving a metal rod with a blunt conical tip that contacted participants’ fingertip. To mask sounds made by the tactile stimulators, white noise (65 dB, measured from the participants’ head) was presented through a loudspeaker placed 70 cm in front of the participants.
Each trial of the emotion judgement task started with the presentation of a fixation cross (500ms), followed by a neutral, sad, happy, or angry face (600ms; trigger codes ending in 1, 2, 3, or 4, respectively). On half of the trials, in addition to a face picture, participants received brief (5ms), task-irrelevant tactile stimulation. During the visual–tactile conditions tactile stimuli were delivered 105ms after face onset (Pitcher et al., 2008; Sel et al., 2014; trigger codes S11 – S14 and S111 – S114). The other half of trials were visual-only trials, where the same facial stimuli were presented an equal number of times as in the visual-tactile condition but without tactile stimulation; however, a trigger code (codes S21 – S24 or S121 - S124) was delivered with the same timing as on visual-tactile trials (i.e. 105 ms after image / visual onset). We used 20 practice trials that did not contain any experimental material (5 trials per condition, with 8 trials followed by a question asking about the emotion expression). The overall experiment consisted of 800 randomized trials, presented in four blocks, including 200 neutral, 200 angry, 200 sad and 200 happy faces. In 10% of the trials of each block (trigger codes S111 – S114 or S121 – S124), participants were asked whether the face stimulus was happy, sad or angry. Participants were told to closely observe the faces presented on the screen, ignore all tactile stimuli, and to respond vocally (yes/no) as soon as possible if a question was presented (maximum response time 3000 ms). The inclusion of the question was to ensure that participants directed attention to the task and judged each facial expression. Participants were offered a break in between blocks. 

References
Lindquist, K. A., Wager, T. D., Kober, H., Bliss-Moreau, E., & Barrett, L. F. (2012). The brain basis of emotion: a meta-analytic review. The Behavioral and Brain Sciences, 35(3), 121–143. https://doi.org/10.1017/S0140525X11000446
Pitcher, D., Garrido, L., Walsh, V., & Duchaine, B. C. (2008). Transcranial magnetic stimulation disrupts the perception and embodiment of facial expressions. The Journal of Neuroscience, 28(36), 8929–8933. https://doi.org/10.1523/JNEUROSCI.1450-08.2008
Sel, A., Forster B. & Calvo-Merino, B. (2014) The emotional homunculus: ERP Evidence for Independent Somatosensory Responses during Facial Emotional Processing. Journal of Neuroscience, 34(9), 3263-7.

本研究收集了35名参与者在进行面部情感判断任务前，经书面知情同意后的脑电图（EEG）数据记录。该研究已获得伦敦城市大学心理学研究伦理委员会的批准。参与者被安排在一个电磁屏蔽、隔音、昏暗的房间里，距离80厘米处观看60赫兹的计算机显示器。从64个Ag/AgCL活性电极中记录EEG，其中60个均匀分布在弹性帽（M10 montage；EasyCap GmBH，Herrsching，德国）上，并采用了标准的EEG记录准备程序以确保信号质量优良（即皮肤脱脂和使用电解质）。电极参照右侧耳垂。水平眼电图（HEOG）通过将电极62和63放置在每只眼睛的外眦约1厘米处进行记录，而心电图（ECG）则通过将电极64放置在左侧锁骨下约2厘米处进行记录。使用BrainAmp放大器（BrainProducts；放大器带通0.01–100Hz）和500Hz的采样率连续记录EEG。

一套80张面部图片（每种情感20张），描绘了愤怒、悲伤、快乐和中性情感，来自Karolinska定向情感面部集（Lundqvist等，1998），这些图片被转换为灰度并封装在矩形框架中（1.40 X 1.57英寸），大部分头发和非面部轮廓被排除在外。面部刺激物通过E-prime 2软件（Psychology Software Tools，Pittsburgh，PA）在黑色背景上中央呈现，该软件还控制了触觉刺激的传递。这些触觉刺激与任务完全无关，其目的是探测触觉活动。它们通过附着在左手中指指尖的12V电磁铁（直径5毫米）传递。当电流通过电磁铁时，通过驱动一个带有钝锥形尖端的金属棒接触参与者的指尖来传递触觉刺激。为了掩盖触觉刺激器的声音，通过放置在参与者前方70厘米处的扬声器播放白噪声（65 dB，从参与者头部测量），以掩盖触觉刺激器的声音。

情感判断任务的每个试验均以呈现注视点（500毫秒）开始，随后呈现中性、悲伤、快乐或愤怒的面部（600毫秒；触发代码分别以1、2、3或4结尾）。在试验的一半中，除了面部图片外，参与者还接收了短暂的（5毫秒）、与任务无关的触觉刺激。在视觉-触觉条件下，触觉刺激在面部呈现105毫秒后传递（Pitcher等，2008；Sel等，2014；触发代码S11 – S14和S111 – S114）。试验的另一半是仅视觉试验，其中呈现与视觉-触觉条件中相同的面部刺激物，次数相等，但不进行触觉刺激；然而，触发代码（代码S21 – S24或S121 - S124）在视觉-触觉试验中相同的时序下传递（即图像/视觉开始后105毫秒）。我们使用了20次练习试验，不包含任何实验材料（每种条件5次试验，其中8次试验后询问关于情感表达的问题）。整个实验由800个随机试验组成，分为四个块，包括200个中性、200个愤怒、200个悲伤和200个快乐的表情。在每个块的10%的试验中（触发代码S111 – S114或S121 - S124），参与者被问及面部刺激是否快乐、悲伤或愤怒。参与者被告知要仔细观察屏幕上呈现的面部，忽略所有触觉刺激，并在出现问题时尽快以声音（是/否）形式做出回应（最大响应时间3000毫秒）。包含问题的目的是确保参与者将注意力集中在任务上，并对每种面部表情进行判断。参与者被允许在每个块之间休息。

参考文献
Lindquist, K. A.，Wager, T. D.，Kober, H.，Bliss-Moreau, E.，& Barrett, L. F.（2012）。情感的大脑基础：一项元分析综述。行为与大脑科学，35（3），121–143。https://doi.org/10.1017/S0140525X11000446
Pitcher, D.，Garrido, L.，Walsh, V.，& Duchaine, B. C.（2008）。经颅磁刺激破坏面部表情的感知和具身化。神经科学杂志，28（36），8929–8933。https://doi.org/10.1523/JNEUROSCI.1450-08.2008
Sel, A.，Forster B. & Calvo-Merino, B.（2014）情感异人：ERP证据表明在面部情感处理期间存在独立的触觉反应。神经科学杂志，34（9），3263-7。