Precisely targeted brain stimulation for social anxiety: Proactive cognitive control and attentional biases as...

In individuals with high social anxiety (HSAs), threat-related attentional bias is robust. However, traditional attentional bias modification shows small and unstable effects, suggesting that this bias may be more of a symptom than a cause. Additionally, existing transcranial direct current stimulation (tDCS) trials have primarily focused on symptoms or single behavioral outcomes without clarifying the cognitive processes being modulated.

To examine whether high-definition tDCS (HD-tDCS) targeting the left dorsolateral prefrontal cortex (DLPFC) enhances proactive cognitive control, thereby improving attentional bias toward threat cues and alleviating social anxiety symptoms.

In this randomized, sham-controlled, single-blind trial, 59 HSAs received either active or sham HD-tDCS (2 mA, 20 min/day, for 5 consecutive days). Questionnaires, behavioral tasks (AX-continuous performance task, dot-probe) with concurrent EEG recording, and resting-state EEG were collected before and after the intervention. Follow-up questionnaires were completed 1 month post-intervention.

The active group showed a significant reduction in social anxiety symptoms, which was maintained at the one-month follow-up. Active stimulation significantly enhanced proactive control (increased d' Context and cue-locked P3b amplitude), while decreasing the theta/beta ratio at the F3 electrode. Furthermore, active stimulation significantly facilitated disengagement from threat (smaller disengagement index and increased target-locked P3 amplitude), along with enhanced threat avoidance. Mediation analysis further showed that improvements in proactive control partially explained the facilitation of disengagement from threat.

Our findings provide initial multimodal support for a mechanistic pathway linking HD-tDCS over the left DLPFC to symptom reduction through enhanced proactive control and improved disengagement from threat.