Gradients of Fear Potentiated Startle During Generalization, Extinction, and Extinction Recall, and Their Relations with Worry

It is well established that fear conditioning plays a role in the development and maintenance of anxiety disorders. Moreover, abnormalities in fear generalization, extinction learning, and extinction recall have also been associated with anxiety. However, no study to date has examined extinction learning or extinction recall using a generalization task. Hence, in the present study, participants were shocked following a CS+ and were also presented with stimuli that ranged in perceptual similarity to the CS+ (i.e., 20, 40, or 60% smaller or larger than the CS+) during a fear generalization phase. Participants were also presented with the same stimuli during an extinction learning phase and an extinction recall phase one week later; no shocks were presented during extinction learning or recall. Lastly, participants completed self-report measures of anxiety and worry. Results indicated that fear potentiated startle (FPS) to the CS+ and CS+/-20% shapes was present in generalization and extinction learning, suggesting that fear generalization persisted into extinction. FPS to the CS+ was also evident one week later during extinction recall. Hence, fear may be more resistant to extinction in generalization paradigms, where there is ambiguity regarding the CS+. In addition, higher levels of worry were associated with greater FPS to the CS+ during generalization and extinction learning phases. Moreover, individuals high in worry had fear response gradients that were steeper during both generalization and extinction learning. This suggests that high levels of worry (characteristic of generalized anxiety disorder) are associated with greater discriminative fear conditioning to threatening compared to safe stimuli but less fear generalization to perceptually similar stimuli.