receive active tDCS before VRET

receive sham tDCS before VRET

High-definition tDCS (HD-tDCS, 4×1 montage, with 1 anode and 4 cathodes, (Soterix Medical, New York, NY, USA) was applied with battery-driven electrical stimulator (2001&4×1-C3A). The center electrode was anode and placed over FPz (according to the EEG 10-20 system in order to target the medial prefrontal cortex). The reference electrodes were cathodes and placed over AF7, AF8, F3, F4(see fig. 3). Participants were randomized to receive 20 minutes of active(1.5mA) or sham (0 mA) tDCS in a single-blind design. In order to ensure that participants can gradually adapted to the current change, there was a 15-second current rising process before the stimulation and, a 15-second current falling process after the stimulation. For sham tDCS, the device was automatically turned off after current reached 1.5 mA, thus providing 30s of ramping current stimulation, which made it difficult for participants to distinguish which kinds of stimulation they received.

It consists of two scales that assess fear (Anxiety, ranging from 0 to 120, involving 20 height situations scored on a seven-point Likert scale; Cronbach' α = 0.80) and avoidance behaviors (Avoidance, ranging from 0 to 40, involving 20 height situations scored on a three-point Likert scale; Cronbach' α = 0.70) of height. Each scale contains 20 scenarios about height situation, such as "Standing next to an open window on the third floor". AQ is widely used to measure fear of heights and has good reliability.

Change from Baseline AQ at post-intervention was assessed in the study.

This scale is a 16-item self-report questionnaire that are rated on a 5-point Likert scale(1 to 5). It was designed to measure height-relevant interpretations. Total scores range from 16 to 80, with higher scores indicating more height-relevant interpretations.

Change from Baseline HIQ at post-intervention was assessed in the study.