Does sleep de-contextualize fear learning? The effect of a daytime nap on the consolidation and generalization of conditioned fear learning.

This study examined the role of sleep in the consolidation and generalization of fear learning. 31 healthy, young adult participants (16 in the wake group and 15 in the sleep group) underwent a fear acquisition procedure in which a geometrical figure imposed on a background image was repeatedly presented and paired with a mild electric shock, making it a conditioned stimulus (a CS+). Another geometrical figure imposed on another background image was also repeatedly presented but never paired with the shock, making it a safety stimulus (a CS-). After a ~three-hour delay interval containing either a two-hour nap opportunity or an equivalent amount of time spent awake, participants performed a fear memory and generalization test. Here, participants viewed four different stimuli: the CS+ and CS- seen before, as well as two novel stimuli composed of the same two geometrical figures seen before imposed on novel background images. This design allowed us to examine a) whether sleep consolidates the original fear memory and b) whether sleep affects the degree of generalization of fear learning to when the originally fear-eliciting stimulus is presented in a novel context. Results revealed no group differences for either the consolidation or generalization of fear learning in either of our outcome measures (skin conductance responses, subjective ratings of unpleasantness, shock expectancy ratings, or explicit memory performance). Previous work on the effect of sleep on consolidation and generalization of fear learning has revealed mixed findings and there is currently limited evidence for sleep having an effect in either direction.