Efficacy of tDCS to Enhance Virtual Reality Exposure Therapy Response in Acrophobia

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.

The VRET was adapted on the basis of Öst's single exposure treatment paradigm and conducted by experienced psychotherapists following a standard exposure treatment manual.. An exposure therapy was divided into three parts: psychological education, exposure intervention and summary. Each scene started with a 10-min psychological education followed up with the tDCS stimulation. In exposure trail, participants ought to take an elevator to 100th, observe the environment and look down on the platform. The psychotherapist guided participants to be exposed to the VR environment and helped them experience the process of anxiety decline in the exposure trail.