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Abstract: Little is known about the role of discrete stimulus features in the regulation of fear. This study examined the effects of feature learning on the acquisition and extinction of fear conditioning. Human participants were fear conditioned to a yellow triangle (CS+) using an electrical shock. We manipulated feature learning through differential conditioning. The nonconditioned control stimulus (CS−) was a red triangle in one group (Color-Relevant), but a yellow circle in the other group (Shape-Relevant). Next, two generalization stimuli were tested that shared the shape- or color-feature with the CS+ (a blue triangle and a yellow square). Online shock-expectancy ratings and skin conductance responding showed that the CS− determined the pattern of fear generalization: the same-color stimulus elicited more fear in Group Color-Relevant, versus the same-shape stimulus in group Shape-Relevant. Furthermore, extinguishing these two generalization stimuli had no detectable effect on fear of the CS+. These results show that fear generalization is influenced by feature learning through differential conditioning, and that exposures to different features of a stimulus are not sufficient to extinguish fear of that stimulus as a whole. [Copyright &y& Elsevier]

Abstract: Disruption of the reconsolidation of conditioned fear memories has been suggested as a non-pharmacological means of preventing the return of learned fear in human populations. A reconsolidation update paradigm was developed in which a reconsolidation window is opened by a single isolated retrieval trial of a previously reinforced CS+ which is then followed by Extinction Training within that window. However, follow-up studies in humans using multi-methods fear conditioning indices (e.g., fear-potentiated startle, skin conductance, US-expectancy) have failed to replicate the retrieval+extinction effects. In the present study, we further investigated the retrieval+extinction reconsolidation update paradigm by directly comparing the acquisition, extinction, and return of fear-potentiated startle in the absence or presence of US-expectancy measures (using a trial-by-trial response keypad) with and without retrieval of a previously acquired CS-US association. Participants were fear conditioned to two visual cue CS+’s, one of which was presented as a single, isolated retrieval trial before Extinction Training and one that was extinguished as usual. The results show that the inclusion of US-expectancy measures strengthens the CS–US association to provide enhanced fear conditioning and maintenance of fear memories over the experimental sessions. In addition, in the groups that used on-line US-expectancy measures, the retrieval+extinction procedure reduced reinstatement of fear-potentiated startle to both previously reinforced CS+’s, as compared to the extinction as usual group. [Copyright &y& Elsevier]

Abstract: In two conditioning experiments with humans, we found that participants’ prior experience exerted considerable influence on later learning of configural discrimination problems. Prior experience was manipulated by pre-training participants before the main acquisition stage. They either received a discrimination problem that encouraged an elemental solution (A+, B−, AB+, CD− in Experiment 1 and A+, AB+, C−, CB− in Experiment 2) or one that required a configural solution (AB+, BC−, CD+, DA− in Experiment 1 and A−, AB+, C+, CB− in Experiment 2). Then, all participants were shown a discrimination that required a configural solution (E+, F+, EF− in Experiment 1 and DE+, EF−, FG+, GD− in Experiment 2). In both experiments, participants who had received elemental pre-training were impaired on the later configural problem compared to participants who had received configural pre-training. The results suggest that organisms can flexibly process stimuli elementally or configurally. [Copyright &y& Elsevier]