Feasibility of Combining Transcranial Direct Current Stimulation and Active Fully Embodied Virtual Reality for Visual Height Intolerance: A Double-Blind Randomized Controlled Study

Abstract

Background: Transcranial Direct Current Stimulation (tDCS) and Virtual Reality Exposure Therapy (VRET) are individually increasingly used in psychiatric research.

Objective/hypothesis: Our study aimed to investigate the feasibility of combining tDCS and wireless 360° full immersive active and embodied VRET to reduce height-induced anxiety.

Methods: We carried out a pilot randomized, double-blind, controlled study associating VRET (two 20 min sessions with a 48 h interval, during which, participants had to cross a plank at rising heights in a building in construction) with online tDCS (targeting the ventromedial prefrontal cortex) in 28 participants. The primary outcomes were the sense of presence level and the tolerability. The secondary outcomes were the anxiety level (Subjective Unit of Discomfort) and the salivary cortisol concentration.

Results: We confirmed the feasibility of the association between tDCS and fully embodied VRET associated with a good sense of presence without noticeable adverse effects. In both groups, a significant reduction in the fear of height was observed after two sessions, with only a small effect size of add-on tDCS (0.1) according to the SUD. The variations of cortisol concentration differed in the tDCS and sham groups.

Conclusion: Our study confirmed the feasibility of the association between wireless online tDCS and active, fully embodied VRET. The optimal tDCS paradigm remains to be determined in this context to increase effect size and then adequately power future clinical studies assessing synergies between both techniques.

Keywords: anxiety; therapy; transcranial direct current stimulation; treatment; virtual reality; visual height intolerance.

Figure 1

The study including two diagnostic sessions (V1 and V4) and two exposure sessions with tDCS or sham stimulation (V2 and V3).

Figure 2

Flow-Chart. Abbreviations: SUD: Subjective Unit of Discomfort; tDCS: transcranial Direct Current Stimulation; VRET: Virtual Reality Exposure Therapy; VR: Virtual Reality.

Figure 3

The participant on the plank is equipped with a tDCS cap, a VR helmet and two trackers attached to his feet. The computers in the room provided a 1st and 3rd person view of the participant’s virtual environment in real time.

Figure 4

Screenshot of the elevator in the virtual environment (image on the left), including a stool at the bottom of the elevator, the SUD scale on the wall on the left of the image and a button to go to the upper floors on the wall on the right of the image. The detail of the gauge, representing the SUD score from 0 to 10, is on the right of the image.

Figure 5

Screenshot of two elevators allow to climb the building (A). Cross between two platforms on a plank allows to reach the next elevator in a building with 99 floors (B).

Figure 6

Electrode placement and current modelization. Adapted from the figure published in Junghöfer et al., 2017 [42] with permission of the author.

Figure 7

SUD score evolutions according to floor elevations during VRET. Abbreviations: SUD: Subjective Unit of Discomfort; VRET: Virtual Reality Exposure Therapy.

Figure 8

Boxplots of clinical scale scores between V1 and V4. In blue, the tDCS + VRET group (n = 11) and in red, the sham + VRET group (n = 14). Abbreviations: AQ: Acrophobia Questionnaire; ATHQ: Attitude Towards Heights Questionnaire; STAI: State-Trait Anxiety; vHISS: visual Height Intolerance Severity Scale; vHIQ: visual Height Intolerance Questionnaire; VRET: Virtual Reality Exposure Therapy.