The Effect of a Daytime Nap on Priming and Recognition Tasks in Preschool Children

Study Objectives: The beneficial effect of sleep on memory consolidation is widely accepted in the adult population and has recently been shown in children. However, the few available data almost exclusively refer to school-aged children. Here we explore the effect of a daytime nap on memory consolidation in a sample of preschool children. Design: Subjects performed both a figures recognition task and a priming task, in order to differentiate effects on explicit and implicit memory. Setting: Nursery school. Participants: Twenty-three children (mean age: 52.6 +/- 8 mo; 13 males) participated in the study. Intervention: After a study phase in which children had to name 40 pictures of objects and animals, each subject either took an actigraphically monitored nap or stayed awake. At retest, children were administered both an implicit and an explicit memory task. Measurements and Results: The implicit memory task consisted of naming 40 pictures presented at eight ascending levels of spatial filtering. The explicit memory task consisted of judging 40 pictures as old or new. The number of correct answers at the explicit recognition task was significantly higher in the nap compared to the wake condition, whereas priming effects did not differ between conditions. Conclusions: A positive role of sleep in explicit memory consolidation, similar to the one observed in the adult, was detected in our sample of preschool children. In contrast, our data suggest that implicit perceptual learning, involved in priming tasks, does not benefit from sleep.