Summary: Researchers at the University of Massachusetts Amherst report that daytime naps combined with subsequent overnight sleep can work together to strengthen emotional memory consolidation in young children.
Source: University of Massachusetts Amherst
Researchers at the University of Massachusetts Amherst have provided the first evidence that naps and overnight sleep interact to support memory consolidation in early childhood. Their results, led by Rebecca Spencer, were published in Scientific Reports.
In the study, Spencer and colleagues—including former doctoral student Laura Kurdziel and former undergraduate Jessica Kent—found that, for the preschool-aged children tested, neither the nap nor the overnight sleep alone produced a measurable change in memory. Instead, benefits of napping emerged only when the full 24-hour period that included both a nap and the subsequent night’s sleep was considered. The authors conclude this pattern indicates an interplay between daytime and overnight sleep stages in consolidating memories during early childhood.
The team also reports that naps contribute to emotional processing in preschool children. Parents and early childhood educators often observe mood changes—children becoming irritable or unusually cheerful—when naps are skipped. The researchers’ findings align with these observations by showing that naps do affect emotion-related processing, even if the measurable improvements in memory content are delayed. The delay could reflect a short-term destabilization of enriched memories, meaning behavioral benefits may appear before measurable memory improvements are evident.
Earlier adult studies have shown that sleep enhances emotional memory and emotional regulation, and some evidence suggested naps might offer similar benefits for toddlers. A prevailing theory—the REM sleep hypothesis—posits that REM sleep is especially important for emotional processing. Because typical naps include little or no REM sleep, the hypothesis raises questions about whether naps alone can support emotional memory. In this study, researchers note that slow-wave sleep is a substantial component of many toddlers’ naps, with about 42 percent of naps containing slow-wave sleep, suggesting a different route for memory benefits.
To test how naps influence memory that carries emotional valence, the researchers worked with 49 children aged approximately 34–64 months (about three to five years old). Each child was shown neutral photographs of men’s and women’s faces paired with short statements that described the person as “nice” or “mean,” such as “Lena is always nice. Today she helped us pour milk into our cups at lunch time.” Recognition was tested at three time points: immediately after learning, after a delay that either included a nap or an equivalent interval awake, and again the following day after overnight sleep. Children who remained awake during the delay engaged with quiet play items to match conditions.
The immediate recognition tests showed no strong effect of emotional valence on memory, and the change in recognition accuracy after a single nap did not differ significantly from the change following an equivalent awake period. Critically, however, children who had napped before the overnight period showed larger improvements in memory accuracy the next morning after a night’s sleep than children who had remained awake during the daytime delay.
Electroencephalography (EEG) recordings taken during naps revealed a complex relationship between slow-wave activity and memory. Higher slow-wave activity during naps was linked to greater short-term memory decay across the nap itself. Paradoxically, that same nap slow-wave activity predicted stronger overnight gains in memory performance. Taken together, these findings suggest sleep-dependent processes unfold across multiple sleep bouts: slow-wave events during a nap may initially destabilize or reorganize memory traces, which then become strengthened during subsequent overnight sleep.
Overall, the authors note that the pattern observed here mirrors results from studies of procedural memory consolidation in preschool-aged children, where both a nap and subsequent overnight sleep were necessary to observe benefits. They emphasize that naps—on average about 70 minutes in this age group—appear to support socio-emotional learning goals in early childhood programs.
“This study demonstrates that napping supports memory processing and emotional information in young children,” the researchers write. “Because socio-emotional learning is central to preschool education, preserving time for naps in early childhood schedules is important.”
Funding: Supported by grants from the National Institutes of Health and an Honors Research Grant from UMass Amherst’s Commonwealth Honors College to Jessica Kent.
Source: University of Massachusetts Amherst
Publisher: Organized by NeuroscienceNews.com
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Original Research: “Sleep-dependent enhancement of emotional memory in early childhood” by Laura B. F. Kurdziel, Jessica Kent & Rebecca M. C. Spencer. Scientific Reports. Published August 22, 2018. doi: 10.1038/s41598-018-30980-y
MLA: University of Massachusetts Amherst. “Naps Plus Sleep Enhances Emotional Memory in Early Childhood.” NeuroscienceNews, 22 August 2018.
APA: University of Massachusetts Amherst (2018, August 22). Naps Plus Sleep Enhances Emotional Memory in Early Childhood. NeuroscienceNews.
Chicago: University of Massachusetts Amherst. “Naps Plus Sleep Enhances Emotional Memory in Early Childhood.” (accessed August 22, 2018).
Abstract
Sleep-dependent enhancement of emotional memory in early childhood
Naps in early childhood support declarative memory consolidation. Emotional memories, however, have a distinct neural encoding profile and may rely on different sleep physiology for consolidation. While declarative memory consolidation has been linked to slow-wave sleep, prevailing theories often emphasize REM sleep for emotional memory consolidation. We tested children aged 34–64 months by pairing faces with “mean” or “nice” descriptions and assessed recognition immediately, after a nap or wake interval, and again after overnight sleep. There were no main effects of emotional valence on recognition immediately or across a single nap interval. However, children who napped showed greater improvement in recognition after overnight sleep than those who remained awake. Greater slow-wave activity during naps was associated with short-term memory decay across the nap but with larger overnight memory gains. These results indicate that multiple sleep bouts can interact to enhance memory in early childhood.