Design of the emotion processing task. Emotion i (i = 1,…,4) represents a certain emotional picture set comprising 10 pictures of happiness (H), sadness (S), fear (F), or disgust (D). Each picture was randomly displayed for 3 seconds, giving each emotional picture set a total presentation length of 30 seconds. The time intervals for each set of instructions and each rest were 15 and 30 seconds, respectively. The total task length was 5 minutes and 15 seconds.