Early Automatic Hyperarousal in Response to Neutral Novel Auditory Stimuli Among Trauma-exposed Individuals with and Without PTSD: An ERP Study

ERP studies have associated posttraumatic stress disorder (PTSD) with enhanced P3 amplitudes in response to trauma-related stimuli, along with reduced amplitudes in the context of neutral (trauma-unrelated) stimuli. Additionally, a bias toward trauma-related stimuli is also observed among trauma-exposed participants not meeting criteria for PTSD, suggesting that trauma exposure itself, and not only the severity of posttraumatic stress (PTS), is a critical factor in information processing changes. However, previous examination of the response of trauma-exposed (PTSD and non-PTSD) participants to novel, neutral stimuli has produced conflicting findings. The current study examined ERPs in response to a novelty oddball paradigm comprised of neutral distractor sounds. Participants were 16 individuals with PTSD, 21 trauma-exposed individuals without PTSD, and 12 nontraumatized controls. Detailed trauma histories and PTS symptoms were collected. A significant effect of group on early ERPs was observed, showing an increase in the N1-P2 complex peak amplitude among the PTSD group, relative to controls. Among the entire sample, significant positive correlations were observed between PTS symptom severity, as well as trauma history, and early N1-P2 complex peak amplitudes, in response to novel stimuli. Furthermore, trauma-exposed participants with no PTS symptoms exhibited larger N1 amplitudes compared to participants with no trauma history. No trauma-related alterations in later ERP components were observed. These results suggest that trauma exposure may lead to hyperarousal at early processing levels, even in response to neutral novel stimuli. The findings concur with the neurocircuitry model that associates PTSD with hyperresponsivity of the amygdala.