Impact of transcranial direct current stimulation on attentional bias for threat: a proof-of-concept study among individuals with social anxiety disorder

Abstract

Cognitive models posit that social anxiety disorder (SAD) is associated with and maintained by attentional bias (AB) for social threat. However, over the last years, it has been suggested that AB in SAD may result from a decreased activation of the left prefrontal cortex, and particularly of its dorsolateral part (dlPFC). Accordingly, a transient increase of neural activity within the left dlPFC via non-invasive brain stimulation decreases AB in non-anxious control participants. Yet, none of these studies focused on SAD. This is especially unfortunate as SAD constitutes the main target for which a genuine reduction of AB may be most appropriate. In this experiment, we sought to investigate the causal influence of left dlPFC neuromodulation on AB among 19 female individuals with a DSM-5 diagnosis of SAD. We adopted a double-blind within-subject protocol in which we delivered a single-session of anodal versus sham transcranial Direct Current Stimulation (tDCS) over the left dlPFC during the completion of a probe discrimination task assessing AB. Consistent with our hypothesis, participants demonstrated a significant decrease in AB during the anodal tDCS over the left DLPFC relative to the sham stimulation. These findings value tDCS as an innovative procedure to gain new insight into the underlying mechanisms of SAD.

Keywords: attention bias modification; attentional bias; neuromodulation; prefrontal cortex; social anxiety disorder; transcranial direct current stimulation.

Fig. 1.

Flowchart depicting passage of participants through the study.

Fig. 2.

Illustration of the probe discrimination task. Note: Each trial began with a central fixation cross which appeared on the screen for 500 ms. Immediately following the disappearance of the cross, a pair of faces appeared on the screen for 500 ms. One face appeared on the top of center screen, whereas the other face appeared on the bottom of center screen. Each pair of faces displayed neutral-disgust facial expressions. Immediately following their disappearance, a probe appeared in the location previously occupied by one of the two faces. The inter-trial interval was 1500 ms. Participants were asked to indicate whether the probe was a dot (i.e. ‘.’) or a colon (i.e. ‘:’) by pressing a corresponding button using the right hand as quickly and accurately as possible. They were also instructed to look at the fixation cross at the start of each trial. The probe remained on screen until a response was given.

Fig. 3.

Change in Attentional Bias for Threat as a Function of tDCS condition. Note: Scores for the attention bias scores (ms) as a function of tDCS condition. Error bars represents standard errors of the mean. **P < 0.01.