Hammell, Abbey2019-08-202019-08-202019-05https://hdl.handle.net/11299/206177University of Minnesota M.A. thesis. May 2019. Major: Psychology. Advisor: Shmuel Lissek. 1 computer file (PDF); v, 54 pages.One key conditioning abnormality in posttraumatic stress disorder (PTSD) is heightened generalization of fear from a conditioned danger-cue to similarly appearing, safe stimuli. Such over-generalization is often assumed to be a stable feature of PTSD, yet several lab-based conditioning findings suggest that over-generalization in PTSD can be reduced with sufficient learning trials. The present study represents the first effort to track the trial by trial timecourse of heightened generalization in PTSD with the prediction of heightened PTSD-related over-generalization in earlier trials that reduces toward the end of the learning record. Combat veterans with PTSD (n = 15), subthreshold PTSD (SubPTSD: n = 18) and trauma controls (TC: n = 19) completed a conditioned fear-generalization task. Trial by trial group differences in generalized perceived risk of electric shock were assessed to three classes of (safe) generalization stimuli parametrically varying in similarity to a conditioned danger-cue paired with electric shock. Data were analyzed using nonparametric regression. Results demonstrated those with PTSD and SubPTSD, relative to TC, displayed elevated generalization to all generalization stimuli combined, in early but not late learning trials. Over-generalization in PTSD and SubPTSD also persisted across trials to a greater extent for classes of generalization stimuli bearing higher resemblance to the conditioned danger-cue. Current findings support the use of prolonged courses of exposure therapy in PTSD that maximize violations of threat-related expectancies for safe stimulus-events resembling the traumatic encounter, especially as safe stimulus-events increase in similarity to trauma-related threat cues.enThesis or Dissertation