123. The Late Positive Potential Response to Olfactory Stimuli in Combat Veterans with Posttraumatic Stress Disorder

Abstract: Background: A potential treatment moderator for PTSD is severity of emotional dysregulation. The late positive potential (LPP) amplitude from EEG has been used to assess individual differences in emotional reactivity. There is evidence that olfaction plays a key role in emotional processing in PTSD. The current study examines pre- and post-treatment LPP amplitudes in response to olfactory stimuli in combat veterans with PTSD. Methods: 28 veterans with PTSD and 28 non-veteran controls were assessed prior to a three-week exposure-based treatment. Data was available for 22 veterans following treatment. An olfactometer delivered three scents (n_butanol, rotten egg, and diesel fuel) during EEG recording. Results: All scents were perceived as negative in valance. The groups did not differ in LPP amplitude or behavioral ratings prior to treatment. In the veteran group, increased pre-treatment Clinician-Administered PTSD Scale (CAPS) Hyperarousal scores related to an increased early window LPP amplitude in response to the diesel fuel scent (β = .52, p = .004). Veterans with larger pre-treatment LPP amplitudes across scents showed larger pre- to post-treatment reduction in the CAPS Hyperarousal score, after covarying for pre-treatment CAPS Hyperarousal scores, r(20) = −.42, p = .05. Conclusions: There were no group-level relationships or treatment changes with behavioral ratings or LPP amplitudes. However, a larger amplitude LPP response to negatively-valanced scents prior to treatment was related to greater improvement in hyperarousal symptoms from the exposure-based treatment. It is possible that emotional responsivity to negative odors may serve as a treatment response moderator in combat veterans with PTSD, particularly for hyperarousal symptoms.