tDCS and Inhibitory Control in PTSD

Overview

Large samples (\~2,000/yr) of adult undergraduate students at a large southern university will be pre-screened via the University of Kentucky SONA System (IRB#43626) to identify and recruit adult female participants who report a history of IPV and probable PTSD to participate in a one-day lab study. After completing an IRB-approved informed consent, participants will complete a brief psychiatric diagnostic interview and a battery of questionnaires. They will then complete three blocks of the Stop Signal Task (SST). Participants will be randomized (double-blind, stratified by PTSD diagnosis and psychotropic medication use) to receive 15-min of active or sham multifocal tDCS targeting the rIFG. tDCS will be delivered offline for 11.5-mins after block 1 of the SST and online for 3.5-mins during block 2 of the SST. Sham stimulation will be identical to active tDCS, but electrical current will only be ramped in/out at the beginning and end of the 15-mins. The third block of the SST will be completed after tDCS. Lastly, participants will complete a pictorial trauma-related symptom provocation task. Participants will be compensated with course credit.

Inhibitory control deficits may be a hallmark neuropsychological feature of posttraumatic stress disorder (PTSD). Right inferior frontal gyrus (rIFG) activation is associated with stop signal reaction time (SSRT) - a common measure of inhibitory control - in healthy controls and PTSD patients. PTSD patients exhibit hypoactivation of the rIFG during inhibitory control tasks compared to healthy controls. Moreover, individuals with PTSD may exhibit difficulty modulating rIFG activity in response to increased inhibitory control demands. The rIFG is also implicated in emotional expression and inhibition. For example, rIFG lesions are associated with difficulty modulating emotional responses and several imaging studies have found that rIFG activity is positively associated with conscious inhibition of negative affect. Among individuals with PTSD, rIFG activity is negatively associated with the severity of PTSD symptoms and the severity of re-experiencing and dissociative symptoms during symptom provocation tasks. A recent meta-analysis indicates that a single-session of bipolar, anodal (excitatory) neuromodulation of the rIFG with transcranial direct current stimulation (tDCS) can significantly improve SSRT performance (g=0.32). Additionally, multiple studies suggest that anodal tDCS of the rIFG reduce fearful responding to threatening stimuli among psychiatrically healthy participants. One study has examined the effects of tDCS targeting the rIFG on inhibitory control and psychiatric symptoms among a clinical sample that included PTSD patients. Although tDCS did not significantly impact inhibitory control in this study, the use of a mixed psychiatric sample and imprecise tDCS procedures make interpretations difficult. Research has yet to test the effects of tDCS targeting the rIFG on inhibitory control or emotional reactivity in individuals with PTSD. The proposed study would be the first to explore the effects of multifocal tDCS on inhibitory control and emotional reactivity to trauma cues in a sample of individuals with probable PTSD. This study would contribute to a growing body of evidence showing that tDCS can improve cognitive functioning and influence the expression and inhibition of emotions. Findings may support future research exploring rIFG neuromodulation as an adjunctive treatment for PTSD or a preventative intervention following trauma exposure.