Conditioned Fear Extinction and Generalization in Posttraumatic Stress Disorder
Annual rept. 1 Aug 2010-31 Jul 2011
EMORY UNIV ATLANTA GA
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Post-traumatic stress disorder PTSD can affect an individual following exposure to a traumatic event. The exposure to trauma can evoke intense physical and emotional responses. Psychophysiological symptoms of PTSD can include an enhanced startle response an effect that may result from an inability to inhibit fear. Conditioned fear can be measured using paradigms such as fear conditioning and fear extinction. Fear-potentiated startle is the process by which an individual s acoustic startle response is enhanced upon presentation of a conditioned stimulus e.g., a colored shape that was paired with an unpleasant unconditioned stimulus e.g., an aversive airblast to the throat. We have analyzed fear-processing in PTSD patients from recent conflicts in the Middle East and healthy volunteers. One colored shape served as the reinforced conditioned stimulus CS, danger and another colored shape served as the nonreinforced condition stimulus CS-, safety. A 140 p.s.i airblast to the throat was used as the unconditioned stimulus. Subjects were fear-conditioned and, after a 10 minute interval, the subjects were trained to extinguish the fear. PTSD patients from the OIF theaters displayed greater fear-potentiated startle to the safety cue as well as delayed extinction of fear-potentiated startle in comparison to the healthy volunteers. In addition, we have observed a dissociation between physiological levels of fear and cognitive awareness of danger and safety in PTSD patients.
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