INVESTIGATING THE SOCIAL EFFECTS OF SHARED TRAUMA - PROJECT SUMMARY SOCIAL DYSFUNCTION FOLLOWING TRAUMA IS A PERVASIVE REALITY FOR TRAUMA VICTIMS IN THE UNITED STATES, WITH ONE STUDY FINDING THAT NEARLY HALF (45.2%) OF TRAUMA PATIENTS EXPERIENCE SOCIAL DEFICITS AFTER THE TRAUMATIC EVENT. TRAUMATIC EVENTS ARE OFTEN EXPERIENCED IN SOCIAL CONTEXTS, YET MOST PRECLINICAL STUDIES MODEL TRAUMA-RELATED DISORDERS WITH STRESSORS EXPERIENCED IN ISOLATION. THEREFORE, THERE IS A GAP IN KNOWLEDGE ABOUT HOW THE SOCIAL CONTEXT IN WHICH TRAUMA IS EXPERIENCED AFFECTS FUTURE SOCIAL BEHAVIOR. THE EXPERIMENTS OUTLINED IN THIS PROPOSAL WILL FILL THIS GAP, AND ADDRESS GOAL 1 OF THE NIMH STRATEGIC PLAN FOR RESEARCH TO "DEFINE THE BRAIN MECHANISMS UNDERLYING COMPLEX BEHAVIORS." HUMAN STUDIES HAVE REPORTED THAT AN INTERESTING PHENOMENON FOLLOWING TRAUMA IS SOCIAL AFFILIATION- THE TENDENCY TO COME TOGETHER AFTER TRAUMATIC EVENTS. SOCIAL BUFFERING, WHICH DESCRIBES THE PRESENCE OF A CONSPECIFIC ATTENUATING THE BIOLOGICAL RESPONSE TO A TRAUMATIC EXPERIENCE, IS THOUGHT TO BE A MECHANISM UNDERLYING THE PROTECTIVE EFFECTS OF SOCIAL SUPPORT. YET, OUR UNDERSTANDING OF THE NEURAL MECHANISMS UNDERLYING SOCIAL BUFFERING IS POOR. DESPITE THE WORK FROM THE FIELD OF SOCIAL BUFFERING THAT HAS STUDIED THE IMPACT OF SOCIAL SUPPORT DURING SHARED TRAUMA, NO RESEARCH TO DATE HAS STUDIED ALTERATIONS IN THE NEURAL REGULATION OF SOCIAL AFFILIATION AFTER SHARED TRAUMA. THE NEURONS OF THE ANTERIOR CINGULATE CORTEX (ACC) ARE POISED TO FACILITATE THIS PHENOMENON AS THEY ARE KNOWN TO BE INVOLVED IN EMPATHY, STRESS REGULATION, AND OBSERVATIONAL FEAR LEARNING. USING CUTTING-EDGE TECHNIQUES IN BEHAVIORAL POSE-ESTIMATION (AIM 1), AND MICROENDOSCOPE CALCIUM IMAGING IN ACC (AIM 2), THIS PROPOSAL WILL TEST THE CENTRAL HYPOTHESIS THAT SHARED TRAUMA, AS OPPOSED TO SOLITARY TRAUMA, ALTERS THE NEUROBIOLOGY OF ACC TO FOSTER SOCIAL AFFILIATION. AS SEX IS AMONG THE MOST SIGNIFICANT RISK FACTORS FOR THE DEVELOPMENT OF PTSD, WITH FEMALES HAVING A TWO TO THREE TIMES HIGHER RISK OF DEVELOPING PTSD, BOTH AIMS WILL BE CONDUCTED IN MALE AND FEMALE MICE. A SUCCESSFUL OUTCOME OF THIS PROJECT WOULD PROVIDE A MECHANISTIC UNDERSTANDING OF HOW SHARED TRAUMA AFFECTS SOCIAL BEHAVIOR, REVEALING A CIRCUIT-LEVEL TARGET TO DEVELOP INTERVENTIONS FOR SOCIAL DYSFUNCTION IN TRAUMA-RELATED DISORDERS. THE PROPOSED RESEARCH WILL TAKE PLACE IN THE LABORATORY OF KAY TYE AT THE SALK INSTITUTE IN AFFILIATION WITH THE UNIVERSITY OF CALIFORNIA, SAN DIEGO. THROUGH GRADUATE COURSEWORK, MENTORSHIP, AND HANDS-ON LEARNING, JIANNA WILL GAIN EXPERIENCE IN RODENT BEHAVIOR AND CALCIUM IMAGING TECHNIQUES AND ANALYSIS. THESE SKILLS WILL BE VALUABLE FOR THE COMPLETION OF THE PROPOSED RESEARCH, AND FOR JIANNA'S FUTURE CAREER AS A PHYSICIAN-SCIENTIST.