Neuromodulation of heart rate and heart rate variability in a randomized controlled trial of tDCS-augmented in vivo exposure for specific fears

This study evaluated the prediction that tDCS-augmented in vivo exposure (IVE) for specific fears would result in durable changes in heart rate (BPM) and heart-rate variability (HRV) during and just after exposure to feared targets. In a double-blind, placebo-controlled trial, participants with contamination- and animal phobia (N = 49) were randomized to active tDCS (1.7 mA, 20 min; n = 27), or sham tDCS (1.7 mA, 30 s; n = 22), followed by a single session of 30 min of IVE. Active tDCS targeted excitation of the left mPFC and inhibition of the right dlPFC. BPM and HRV were acquired during behavioral approach tasks involving brief (30 s) exposure to feared targets at pre-treatment, post-treatment, and a 1-month follow-up, as well as during six 5-min. trials of exposure. Active tDCS produced significantly greater reductions in BPM, and marginally greater increases in HRV from pre-treatment to 1-month in an extinction context, compared to sham tDCS. Similarly, active tDCS produced significantly greater reductions in BPM, and increases in HRV during IVE, relative to the sham tDCS group. Findings for the generalization context were non-significant. Consistent with the main outcome findings, tDCS may offer an effective means of enhancing outcomes in exposure therapy, perhaps through top-down modulation of autonomic arousal.