Transcranial direct current stimulation may modulate extinction memory in posttraumatic stress disorder.

Mascha Van‘T Wout,Noah S Philip,Madhavi K Reddy,Sharon M Longo,Marguerite T Bowker,Benjamin D Greenberg

doi:10.1002/brb3.681

Abstract

BackgroundAbnormalities in fear extinction and recall are core components of posttraumatic stress disorder (PTSD). Data from animal and human studies point to a role of the ventromedial prefrontal cortex (vmPFC) in extinction learning and subsequent retention of extinction memories. Given the increasing interest in developing noninvasive brain stimulation protocols for psychopathology treatment, we piloted whether transcranial direct current stimulation (tDCS) during extinction learning, vs. during consolidation of extinction learning, might improve extinction recall in veterans with warzone‐related PTSD.MethodsTwenty‐eight veterans with PTSD completed a 2‐day Pavlovian fear conditioning, extinction, and recall paradigm. Participants received one 10‐min session of 2 mA anodal tDCS over AF3, intended to target the vmPFC. Fourteen received tDCS that started simultaneously with extinction learning onset, and the remaining 14 participants received tDCS during extinction consolidation. Normalized skin conductance reactivity (SCR) was the primary outcome measure. Linear mixed effects models were used to test for effects of tDCS on late extinction and early extinction recall 24 hr later.ResultsDuring early recall, veterans who received tDCS during extinction consolidation showed slightly lower SCR in response to previously extinguished stimuli as compared to veterans who received tDCS simultaneous with extinction learning (p = .08), generating a medium effect size (Cohen's d = .38). There was no significant effect of tDCS on SCR during late extinction.ConclusionsThese preliminary findings suggest that testing the effects of tDCS during consolidation of fear extinction may have promise as a way of enhancing extinction recall.

Highlights

Posttraumatic stress disorder (PTSD) is a disabling and often long-term condition among returning veterans (Hoge et al, 2004; Terhakopian, Sinaii, Engel, Schnurr, & Hoge, 2008)
The selection of transcranial direct current stimulation (tDCS) parameters and location was based on our prior work, and our intention to target the ventromedial prefrontal cortex (vmPFC) given its importance for extinction learning and recall
Veterans who received tDCS during extinction showed similar adequate extinction learning as veterans who received sham stimulation at that time, evidenced by the nonsignificant differences between tDCS groups and the two previously conditioned stimuli vs. the never conditioned stimulus during late extinction

Summary

| INTRODUCTION

Posttraumatic stress disorder (PTSD) is a disabling and often long-term condition among returning veterans (Hoge et al, 2004; Terhakopian, Sinaii, Engel, Schnurr, & Hoge, 2008). Given that tDCS modulates ongoing intrinsic neuronal activity, the evaluation of tDCS combined with PTSD-relevant emotional learning and memory processes, such as fear extinction and recall, in veterans suffering from PTSD would inform its usefulness as a possible adjunct to improve existing cognitive and/or behavioral treatments for PTSD. The selection of tDCS parameters and location was based on our prior work (van ‘t Wout et al, 2016), and our intention to target the vmPFC given its importance for extinction learning and recall We conducted this pilot study to test the following hypotheses: (1) whether active tDCS during extinction learning compared to sham stimulation would augment late extinction learning, and (2) whether the effects of tDCS during extinction learning vs during extinction consolidation, that is, immediately after extinction learning, on early extinction recall tested 24 hr later would differ. Testing the effects of tDCS during consolidation of fear extinction provides a first step to examining various possibly important time points in which noninvasive brain stimulation could be used to enhance components of extinction learning and memory (Marin & Milad, 2015)

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Findings

CONFLICTS OF INTEREST