Toddler brains, not age, determine nap transitions, research suggests

Why are some 4- and 5-year-olds still napping like clockwork every afternoon, while other preschoolers start to give up their usual naps by age 3?

It’s a question many parents are no doubt asking, and one that a sleep scientist at the University of Massachusetts Amherst has been considering for years. Now, in an article published on Monday, October 24, in a special edition about the dream of Proceedings of the National Academy of Sciences, lead author Rebecca Spencer outlines a new theory about why and when toddlers transition from naps. It’s not so much about age as it is about the brain.

“This general theory is based on data that we’ve published in the last two years — it’s about putting the pieces together,” says Spencer, a professor of psychological and brain sciences, who collaborated with co-author Tracy Riggins of the University of Maryland child psychologist specializing in memory development. “Collectively, we provide support for a relationship between nap transitions and underlying memory and brain development. We say this is a critical time of brain development, and sleep has something to do with it.”

The novel theory, which underpins the practice of providing the opportunity to nap for all preschool and preschool children, connects the bioregulatory mechanisms that underlie nap transitions, focusing on the hippocampus, the memory area of ​​the brain. Spencer points out that it can seem counterintuitive for toddlers to give up regular naps. “When young children nap, they consolidate emotional and declarative memories, so one wonders, when this is such an important time for learning, why would they stop napping if napping helps learning? not keep napping?”

Previous research by Spencer and Riggins showed that “there is a difference in hippocampal development between napping and napping children,” says Spencer.

The hippocampus is the short-term location of memories before they go into long-term storage in the cortex. “Naps are used to process memories,” explains Spencer. When young children’s immature hippocampus reaches its limit of memories that can be stored without “interference” or forgetting, children experience increased “sleep pressure.” The researchers look at EEG slow-wave activity, a neurobiological marker in brain waves recorded during sleep, to measure the buildup of sleep homeostatic pressure.

Napping allows memories to move to the cortex, freeing up space for more information to be stored in the hippocampus. Spencer compares the developing hippocampus to a bucket of different sizes.

“When the hippocampus is inefficient, it’s like having a small bucket,” she says. “Your bucket will fill faster and overflow, and some memories will spill over and be forgotten. That’s what we think happens with kids who are still napping. Their hippocampus is less mature and they need to empty that bucket more often.” . .”

When the hippocampus is more developed, children may stop napping because their hippocampus has matured to the point that their “bucket” won’t overflow. They can retain memories until the end of the day, when nighttime sleep can process information from the hippocampus to the cortex, the researchers posit.

Spencer says mounting evidence highlights the importance of giving all young children the opportunity to nap. “Some of them still need it; some of them may not need it, but if they take it, we know it will benefit their learning, and we know that learning is what underlies early education.”

What is needed next to advance the theory is longitudinal research that follows children over time to assess sleep physiology, structural and functional development, and memory changes across sleep transitions. the NAP.

Additional scientific evidence “would help parents and providers appreciate that nap transitions cannot be determined by age, and the opportunity to nap should be protected for those who need it.”

In the long term, Spencer says, researchers can develop a cognitive measure of memory, perhaps by giving children a simple task to determine whether they’ve crossed the threshold of needing regular naps.

For now, though, the evidence supports the important role napping plays in young children’s growth. Forced nap transitions “could lead to suboptimal learning and memory,” says Spencer.

In addition, the new framework the researchers developed “can be used to evaluate multiple untested predictions from the field of sleep science and ultimately generate science-based guidelines and policies regarding napping in child care settings and Early education”.

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