Abstract
Intrusive memories – a hallmark symptom of posttraumatic stress disorder (PTSD) – are often triggered by stimuli possessing similarity with cues that predicted or accompanied the traumatic event. According to learning theories, intrusive memories can be seen as a conditioned response to trauma reminders. However, direct laboratory evidence for the link between fear conditionability and intrusive memories is missing. Furthermore, fear conditioning studies have predominantly relied on standardized aversive stimuli (e.g. electric stimulation) that bear little resemblance to typical traumatic events. To investigate the general relationship between fear conditionability and aversive memories, we tested 66 mentally healthy females in a novel conditioned-intrusion paradigm designed to model real-life traumatic experiences. The paradigm included a differential fear conditioning procedure with neutral sounds as conditioned stimuli and short violent film clips as unconditioned stimuli. Subsequent aversive memories were assessed through a memory triggering task (within 30 minutes, in the laboratory) and ambulatory assessment (involuntary aversive memories in the 2 days following the experiment). Skin conductance responses and subjective ratings demonstrated successful differential conditioning indicating that naturalistic aversive film stimuli can be used in a fear conditioning experiment. Furthermore, aversive memories were elicited in response to the conditioned stimuli during the memory triggering task and also occurred in the 2 days following the experiment. Importantly, participants who displayed higher conditionability showed more aversive memories during the memory triggering task and during ambulatory assessment. This suggests that fear conditioning constitutes an important source of persistent aversive memories. Implications for PTSD and its treatment are discussed.
Highlights
Intrusive recollection of aversive memories is a core symptom of posttraumatic stress disorder (PTSD) [1,2,3]
ANOVA main effects of Time are only reported in the text if interacting with conditioned stimuli (CS)-type.) Separate, measure-wise follow-up ANOVAs for ratings during acquisition displayed a CS-type effect on each single rating scale, due to higher ratings on negative valence, fear, and UCS expectancy for the CS+ compared to the CS2
Using a naturalistic fear conditioning paradigm in a healthy sample, the present study revealed that fear conditionability contributes to subsequent aversive memories in the laboratory and in daily life
Summary
Intrusive recollection of aversive memories is a core symptom of posttraumatic stress disorder (PTSD) [1,2,3]. Typical UCSs – supposedly representing traumatic events in this laboratory analog – include electrical stimulation, aversive noises (e.g., loud white noise or human cries), aversive pictures, or other kinds of basic aversive stimulation such as unpleasant smells or air blasts [10,20] Such stimuli only partially depict the typical features (e.g. the dynamic time course) of situations usually involved in fear acquisition. They are unlikely to generate the kind of complex memories that could later give rise to intrusive recollection and are inappropriate to investigate the relationship between fear conditioning and aversive memories such a relationship is strongly supported by clinical observations (see above). Evidence for such relationships would suggest that individual conditionability contributes to persistent aversive memories, a piece of evidence that has been missing in the literature so far
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