Monica Toselli

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.

Chapter 48 Gates to awakening in early development

Publisher Summary The reason why the gates to awakening are open with a different frequency, or at different times in the 24 hour cycle, as a function of age, is a question that have not received any comprehensive answer so far. To understand the conditions that lead to the event awakening, the sleep state has been investigated. Similar to young adults, infants tend to awake more often from rapid eye movement (REM) sleep than from quiet sleep (QS). This is evident all along the first year of life, although the difference in the likelihood of awakening from the two states is reduced after the sixth month. The awakening could be the result of the interaction between the state of sleep facilitating it and the position in the 24 hour cycle. An interesting remark concerns the comparison between awakenings and sleep onset, as far as the state of sleep, preceding, and following are concerned. During development, it is REM sleep that has a gating role toward sleep onset and awakening; with time, the major change regarding the prevalent state for sleep onset (from REM in early infancy to NREM in the adult) cannot be paralleled by a similar change in the modality of awakening. In other words, the sleep state at the frontier with wakefulness changes with age, whether it is at sleep onset or at the end.