Abstract
One strategy to address new potential dangers is to generate defensive responses to stimuli that remind learned threats, a phenomenon called fear generalization. During a threatening experience, the brain encodes implicit and explicit memory traces. Nevertheless, there is a lack of studies comparing implicit and explicit response patterns to novel stimuli. Here, by adopting a discriminative threat conditioning paradigm and a two-alternative forced-choice recognition task, we found that the implicit reactions were selectively elicited by the learned threat and not by a novel similar but perceptually discriminable stimulus. Conversely, subjects explicitly misidentified the same novel stimulus as the learned threat. This generalization response was not due to stress-related interference with learning, but related to the embedded threatening value. Therefore, we suggest a dissociation between implicit and explicit threat recognition profiles and propose that the generalization of explicit responses stems from a flexible cognitive mechanism dedicated to the prediction of danger.
Highlights
Encountering a novel stimulus demands an organism to predict its emotional implications to properly react
Underwent an implicit two-alternative forced-choice (2AFC) test, in which subjects were presented with a pseudorandom sequence of tone pairs, each composed of a conditioned stimulus (CS+ or CS−) and a novel stimulus similar to the CS+ (NS+, 466 Hz) or to the CS− (NS−, 1046 Hz)
In line with previous studies[5,13,14], event-related skin conductance responses (SCRs) were recorded for the assessment of autonomic responsiveness. Another group (n = 18) underwent an explicit 2AFC task in which participants heard the same sequence of com/scientificreports stimulus (CS−)NS pairs used during the implicit test, and they had to identify which stimulus of each pair was the one previously paired with the unconditioned stimulus (US) or the one previously learned as not associated with the US
Summary
Encountering a novel stimulus demands an organism to predict its emotional implications to properly react. Survival requires an adaptive balance between generalization and discrimination[1,5] When this delicate mechanism undergoes dysregulation, the resulting behavior can be maladaptive, and overgeneralization has been proposed as a pathogenetic marker of the anxiety disorders spectrum[6,7,8,9,10]. The human brain encodes implicit and explicit memory traces that are mediated by different neural circuits[11,12]. In this framework, fear generalization dynamics have been characterized by recording implicit autonomic indicators (for example, skin conductance responses, SCRs).
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