Emotional bias of trait anxiety on pre-attentive processing of facial expressions: ERP investigation

Facial expressions are important for understanding the emotional feelings of other human beings. However, individual factors, such as sex, age, and personality traits, can influence the perception of facial expressions. For example, individuals with an elevated level of trait anxiety- which is a measure of the frequency and intensity of occurrence of anxiety- related symptoms- show attentional bias toward emotional stimuli; that is, they pay greater attention to emotional information such as facial expressions. Previous studies focused mainly on the attentional processing stage, but whether trait anxiety affects the pre-attentive processing stage of facial expression perception remains unclear. Pre-attentive processing is an automatic evaluation of whether attention is needed to react to a stimulus, thereby filtering out irrelevant information to conserve cognitive resources and improve information processing efficiency. Hence, the present study is aimed at investigating the pre-attentive processing of facial expressions and the bias toward emotional stimuli of trait-anxious individuals during the pre-attentive processing stage. According to Spielberger State-Trait Anxiety Inventory (STAI) scores, 20 participants who scored in the top 27% were assigned to the high-trait-anxiety group (13 women; mean age 19.02 +/- 0.63 years) and 20 participants who scored in the bottom 27% were assigned to the low-trait-anxiety group (11 women; mean age 19.63 +/- 0.88 years). The stimuli used in the experiment were happy, sad, and neutral face images selected from the Chinese Facial Affective Picture System ( CAFPS) that included 10 pictures (five females and five males) of each of the aforementioned emotions. The deviant-standard-reverse oddball paradigm included four types of facial expression sequences: neutral standard stimuli/happy deviant stimuli; happy standard stimuli/neutral deviant stimuli; neutral standard stimuli/sad deviant stimuli; and sad standard stimuli/neutral deviant stimuli. "Standard stimuli" means that this type of stimulus appeared approximately 80% of the time in the sequence, and the deviant stimuli appeared approximately 20% of the time. Participants were instructed to detect unpredictable changes in the size of a fixation cross at the center of the visual field and to press a corresponding button as quickly and accurately as possible and to ignore facial expressions. The results revealed that the amplitudes of N170 elicited by deviant faces were significantly larger than those of standard faces. Importantly, in the early expression mismatch negativity (EMMN) results, the mean amplitude elicited by sad facial expressions was significantly larger than that elicited by happy facial expressions in the low-trait-anxiety group, but there was no significant difference between happy and sad facial expressions in the high-trait-anxiety group. Moreover, the early EMMN amplitude of happy faces was significantly larger in the high-trait-anxiety group than in the low-trait-anxiety group. These results suggest that the high-trait-anxiety group had a similar amplification of EMMN amplitude for both happy and sad expressions. The results further show that there is a difference between high and low trait anxiety in the pre-attentive processing of facial expressions. This, in turn, suggests that personality traits are important factors influencing the pre-attentive processing of facial expressions, and that high-trait-anxiety individuals may have difficulty in effectively distinguishing between happy and sad emotional faces during the pre-attentive processing stage and have similar processing patterns for both.