Posttraumatic Stress Symptom Dimensions and Brain Responses to Startling Auditory Stimuli in Combat Veterans

Posttraumatic stress disorder (PTSD) is marked by alterations in emotional functioning, physiological reactivity, and attention. Neural reactivity to acoustic startle stimuli can be used to understand brain functions related to these alterations. Investigations of startle reactivity in PTSD have yielded inconsistent findings, which may reflect the heterogeneity of the disorder. Furthermore, little is known of how the common cooccurrence of mild traumatic brain injury (mTBI; i.e., concussion) may influence neural reactivity. We examined the event-related potentials (ERPs) of combat veterans (n = 102) to acoustic startle probes delivered during viewing of pleasant, neutral, unpleasant, and combat-related pictures. Interview-based assessments yielded dimensional characterizations of PTSD and mTBI. The P3 ERP response to startle probes was reduced during all affective relative to neutral pictures but failed to be associated with a PTSD diagnosis. However, two separable domains of PTSD symptomatology were associated with startle ERPs regardless of the picture conditions. Maladaptive avoidance was associated with smaller N1, P2, and P3 amplitudes, while intrusive reexperiencing was associated with larger P2 amplitudes. There were no main effects of mTBI. Findings suggest that level of symptomatology rather than a formal diagnosis of PTSD better explains alterations in neural reactivity after traumatic events, while mild brain injuries have little impact. Avoidance symptoms of PTSD may dampen neural functions that facilitate reorientation to threat while intrusive reexperiencing of traumatic events appears to heighten sensory reactivity. Considering specific aspects of symptomatology provides insight into the neural basis of trauma-related psychopathology and may help guide individualization of clinical interventions.