Neuroimaging studies have consistently reported reduced activation of the medial prefrontal cortex (mPFC) in patients with posttraumatic stress disorder (PTSD) while they recall and imagine stressful personal events. During script-driven imagery (SDI) sessions, patients with PTSD exhibit increased psychophysiologic (eg, heart rate, skin conductance, and facial electromyographic) responses to trauma-related memories. However, the origin of the responses remained unclear. Are they familial, acquired, or resulting from trauma exposure?
Researchers from Harvard University, University of California Los Angeles, and University of New England conducted a study of 26 male identical twin pairs to help find the answer. The participants were divided into 4 groups: combat-exposed with PTSD (ExP+), their combat-unexposed twins without PTSD, combat-exposed participants without PTSD, and their combat-unexposed twins without PTSD. They engaged in SDI during functional magnetic resonance (fMRI) imaging and concurrent skin conductance measurement.
The results of the fMRI tests showed diminished activation in the medial prefrontal cortex of the patients with PTSD compared with the other groups. The SC response scores did not correlate significantly with PTSD symptom severity.
Contrary to the researchers’ predictions, mPFC activation was not inversely correlated with PTSD symptom severity. However, they say their finding of reduced mPFC activation in the ExP+ group provides evidence that the abnormality is an acquired characteristic. If those findings are replicated, such objectively measured biologic characteristics could potentially aid in diagnosing PTSD or assessing treatment response.
Dahlgren MK, Laifer LM, VanElzakker MB, et al. Psychol Med. 2018;48(7):1128-1138.