Abstract:

Sleep-dependent memory consolidation refers to the process during sleep in which the brain reprocesses and reinforces newly acquired information or skills, thereby enhancing the stability and longevity of memories. Sleep plays a pivotal role in consolidating recently acquired knowledge into enduring long-term memories. The influence of sleep-dependent memory consolidation varies depending on the type of memory, with different stages and characteristics of sleep exerting distinct effects on various memory processes.

Given the significant differences in sleep structure and physiological mechanisms between infants and adults, it is imperative not to extrapolate findings from adult studies directly to infants and toddlers. Additionally, owing to the remarkable neuroplasticity of the infant brain and its unique sleep patterns, investigating the impact of sleep on memory consolidation in infants can significantly deepen our comprehension of the neural mechanisms underlying sleep-dependent memory consolidation.

Building upon adult research, we present a synthesis of recent studies focusing on infants and toddlers, highlighting the critical role of sleep in memory consolidation during early development. Infants and toddlers who nap or sleep after learning consistently exhibit superior memory retention and enhanced problem-solving abilities compared to those who remain awake. During sleep, brain regions associated with memory, such as the hippocampus and medial temporal lobe, demonstrate significant activation. Distinct electroencephalogram (EEG) features, such as sleep spindles and slow waves, correlate with memory consolidation in infants and toddlers.

This paper addresses two primary forms of memory: declarative memory and procedural memory, shedding light on the impact of sleep-dependent memory consolidation in infants. In the realm of declarative memory, sleep enhances the quantity and accuracy of various episodic memory components, encompassing cartoon faces, toy manipulation, spatial locations, and chronological sequences. Moreover, distinct sleep features, such as sleep spindles and slow waves, make unique contributions to different episodic memories. Sleep also fosters selective memory consolidation, knowledge transfer, and the activation of memory-related brain regions, including the hippocampus, in infants and young children. These findings furnish valuable insights into the neural mechanisms governing sleep's role in early episodic memory development.

Regarding procedural memory, though limited studies exist on the relationship between infant sleep and procedural memory consolidation, some evidence suggests a positive influence of sleep on infant procedural memory. Future research should explore the interplay between sleep and motor skill development in infants, with particular emphasis on the role of rapid eye movement (REM) sleep, as adult studies underscore its significance in procedural memory consolidation.

Despite the progress in this field, several unresolved questions persist. Future research should aim to address whether sleep exerts a memory-consolidating effect on newborns, elucidate the distinctions between sleep-dependent memory consolidation in infants and adults, systematically investigate the impact of sleep on infants' social and language learning, and discern how different sleep types, durations, and timings in infants and young children contribute to memory consolidation.

Key words: infants and toddlers, sleep, memory consolidation, sleep slow waves, sleep spindles