The memory benefits of two naps per day during infancy: A pilot investigation

• Published in: Infant behavior & development 2021-11, Vol.65, p.101647-101647, Article 101647
• Main Authors: Mason, Gina M., Kurdziel, Laura B.F., Spencer, Rebecca M.C.
• Format: Article
• Language: English
• Subjects: declarative memory; infancy; Naps; polysomnography; slow-wave activity
• ISSN: 0163-6383; 1879-0453; 1934-8800
• DOI: 10.1016/j.infbeh.2021.101647

•A two-nap sleep schedule supports new memory in 9-month-olds•Skipping the morning nap leads to memory decline over the afternoon nap•Presence/absence of the morning nap may affect afternoon nap slow wave activity-memory relations In infancy, sleep occurs in multiple nap and overnight bouts that change developmentally in quantity and distribution. Though studies suggest that infant memory benefits from a single nap, no work has assessed the relative benefits of different naps (morning vs. afternoon), nor how multiple naps support memory across the day. We investigated the memory benefit of a morning nap, relative to morning wake, and the effect of these intervals on afternoon nap function in 9-month-olds (n = 15). Infants participated in two within-subjects conditions (separated by 1-2 weeks). In the Nap-Nap condition, infants took their morning and afternoon naps; in the Wake-Nap condition, infants were kept awake during morning naptime, but napped unrestricted in the afternoon. Before each nap/wake interval, infants completed an imitation memory task, with memory assessed again shortly after the nap/wake interval. In the Nap-Nap condition, infants showed memory retention across morning and afternoon naps. In contrast, infants tended to forget items learned across morning wake in the Wake-Nap condition. Moreover, morning wake was associated with a significant decline in post-nap retention of items learned in the afternoon. Furthermore, relations between nap slow-wave activity (SWA) and memory varied across naps, with SWA either not predicting (morning naps) or positively predicting (afternoon naps) memory change in the Nap-Nap condition, but negatively predicting afternoon memory change in the Wake-Nap condition. We conclude that two naps per day (rather than one) aids memory at 9 months, and that skipping the morning nap may moderate relations between afternoon nap physiology and memory.