Trait-related neural basis of attentional bias to emotions: a tDCS study

Abstract

Negative emotional stimuli can strongly bias attention, particularly in individuals with high levels of dispositional negative affect (NA). The current study investigated whether the prefrontal cortex (PFC), a brain region involved in the top-down regulation of emotional processing, plays a different role in controlling attention to emotions, depending on the individual NA. Sham and anodal transcranial direct current stimulation (tDCS) was delivered over the right or left PFC while assessing attentional bias (AB) to emotions (happy, angry, sad faces) in individuals with higher and lower trait NA. When tDCS was inactive (sham), individuals with higher trait NA showed AB toward angry and away from sad faces, while individuals with lower trait NA presented with no AB. Right anodal-tDCS abolished the AB toward angry faces and induced an AB toward sad faces in individuals with higher trait NA, while no effect was found in individuals with lower trait NA. Left anodal-tDCS abolished any AB in individuals with higher trait NA and induced an AB away from happy faces in individuals with lower trait NA. These findings confirm a critical role of trait NA in AB to emotions and demonstrate a different involvement of PFC in emotional processing based on dispositional affect.

Keywords: Attentional bias; Emotion; Negative affect; Prefrontal cortex; tDCS.

Fig. 1

Dot-probe task. In each trial, a fixation cross appeared on the screen for 500 ms; then, emotional (happy, angry, sad) and neutral faces were displayed on either side of the cross. After 1,000 ms, a dot-probe appeared in place of one of the two faces until the participant responded

Fig. 2

Study flow diagram. A) All participants completed three sessions separated by a break of 72 h. The three sessions were similar except for the type of tDCS (sham, right anodal, left anodal) delivered with counterbalanced order across participants. B) In each session, before the stimulation (pre-tDCS), participants filled in the PANAS-state form. Then, participants underwent the dot-probe task while receiving tDCS stimulation (lasting 20 minutes). After the stimulation (post-tDCS), participants completed the PANAS-state form again and the tDCS questionnaire

Fig. 3

Electrode montage (left panel) and electric field strength (right panel) on a model head for stimulation of the right (A) and the left prefrontal cortex (B). Estimated electric field strength obtained on a standardized brain by HD-Explore software (HD-Explore 2018, Soterix Medical, NY) shows that the montage used is suitable to stimulate the right and left prefrontal cortex, with some small spread to surrounding brain areas. The red color indicates higher electrical field intensity

Fig. 4

Attentional bias scores for happy (red), angry (blue), and sad faces (green) for higher trait NA (left panel) and lower trait NA individuals (right panel). Dashed lines and solid lines indicate significant differences between groups and across conditions, respectively. Asterisks indicate p < 0.05. The hashtags show significant comparisons against zero (p < 0.05). Bars represent standard errors