Sleep forms flexible context representations in toddlers

Abstract

Sleep consolidates episodic memory through a hippocampus-dependent process in adults. Whether and how sleep supports memory consolidation during early life, when hippocampal function is immature, remains unclear. Here, we examined effects of sleep on the consolidation of spatial context, a core component of episodic memory, in toddlers aged 2 -3 years. Toddlers were familiarized with two spatial contexts, followed by a [~]90-min nap or an equivalent wake period. Afterwards, with a hide-and-seek game we tested their ability to relocate toys within these contexts. Only after post-familiarization sleep, the toddlers showed significant context memory and formed stronger associations between toys and specific contexts compared to wakefulness. Contextual memory was positively correlated with spindle density and slow oscillation-spindle phase-amplitude coupling during non-rapid eye movement (NonREM) sleep. Despite hippocampal immaturity, the sleeping toddlers brain seems to engage consolidation processes similar to those in adults to form spatial context memory for the flexible use in novel situations.