Utilizing tDCS to augment the formation of safety signals for fear inhibition in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) can be understood as a disorder in the processing of traumatic fear memories due to hyperactivity in amygdala-based threat reactivity, exacerbated by a failure to down-regulate this threat responding attributed to hypoactivity in ventromedial prefrontal cortex (VMPFC) and hippocampal aberrations. Here we test whether transcranial direct current stimulation (tDCS) targeting the VMPFC can augment the inhibition of fear responses in the context of extinction learning and recall as well as exposure to trauma cues in individuals with PTSD. In all experiments, tDCS involved 2 mA intensity with the anode placed around EEG locations Fp1/AF3 and the cathode over EEG location P08, and we assessed skin conductance reactivity (SCR) as a biologically relevant measure of emotional arousal. First, we demonstrate that the modulation of extinction learning and memory by tDCS may depend on the timing of stimulation, such that when applied during synaptic consolidation immediately following extinction learning of conditioned fear tDCS may prevent the return of fear during extinction recall. Yet we also observed a possible generalization of the fear response because of tDCS. Next, we demonstrate that the repeated application of tDCS during exposure to virtual reality trauma cues may bolster anxious habituation in individuals with warzone PTSD. Yet again we appear to observe a seemingly initial increase in emotional arousal before a more rapid reduction of emotional arousal and subsequent reduction of PTSD symptom severity. Taken together this research highlights the importance of the application of tDCS in context, including the timing of stimulation in relation to safety learning and memory processing and the importance of repeated sessions for clinical benefit.

Clinical Research: 9. Transcranial Direct Current Stimulation (tDCS)

Keywords: Fear, tDCS, Extinction, PTSD