PROJECT SUMMARY The goal of this supplement award is to provide supplemental supports to cover the time and effort the applicant is needed to complete the aims of the parent award (K01MH110647) which was significantly impacted by COVID-19 mitigation efforts. The specific aims that have been pursued during the parent award period are: Aim 1) to examine effects of pharmacologically blocking the orexin system after written narrative exposure (WNE) on sleep, posttraumatic stress disorder (PTSD) symptoms, and intersession habituation; and Aim 2) to use an animal model to elucidate neural mechanisms underlying the effects of inhibiting the orexin system on sleep and memory consolidation following fear extinction. To accomplish Aim 1, the applicant has been conducting a clinical trial in which adult participants with PTSD complete WNE in the evening and morning with intervening sleep, and either suvorexant (a dual orexin receptor antagonist, an FDA-approved drug for treating insomnia) or placebo are administered prior to going to bed following the evening WNE. To accomplish Aim 2, the applicant has been conducting mouse experiments in which orexin neurons in the hypothalamus are inhibited using optogenetic methods following a fear extinction training. For the career development activity, the applicant has been receiving in-lab training to learn advanced animal study methodologies, including optogenetics and telemetric sleep recording. Both clinical and animal studies and career development activities have been significantly delayed due to COVID-19 mitigation efforts. During the proposed supplement award period, the applicant will continue and complete the research and training activities within the scope of the parent grant aims.