Although the first year of an infant’s life is a key developmental stage and infants spend the majority of that period sleeping, the role of sleep in the brain development of an infant is still not well known.1

However, studies have shown that sleep benefits infants’ memories and general cognitive and emotional development.

The Effect of Sleep on Infants’ Memories
In multiple studies, researchers have been able to demonstrate that infants’ memories did improve with the increase of sleep duration.2 In one such study, researchers observed that infants who spent more time sleeping had better performance in working memory tasks.2

Although physiological explanations could have an effect on the observed improved performance, the increased deep sleep duration during the night was found to have a significant impact on the completion of the tasks.2 

In another study, researchers observed that infants aged 15 months who napped for 4 hours were better able to retain general grammatical patterns of their native language.2 These findings indicate that infants’ frequent napping may play an important role in developing long-term memory.

Another study demonstrated that sleep played a major role in preserving an infant’s individual experiences and distinguishing them from general knowledge.3 Scientists investigated this relationship using an EEG, which made clear that the brain of children who had slept responded differently in the memory test than those who had stayed awake during the same period. 3

Emotional Regulation
Sleep has also been demonstrated to have effects on emotional regulation, which could be traced back to the neonatal period.2 In one study, it was observed that neonatal smiles, which involve both lip corner and cheeks raising, tend to predominate in active sleep. This observation suggests sleep may have a potential correlation with early components of emotional development.2

Researchers have also found that sleep may be associated with emotional regulation among infants. For example, one study found that sleep deprivation led to an increase in negative emotions and a decrease in positive emotions among infants.2

To investigate this further, a systematic review examined the association between sleep duration and health in children aged 0 to 4 years. During the study, the researchers observed that a shorter sleep duration was associated with poorer ability to emotionally regulate.2

Sleep and General Cognitive Development
Other researchers focused on examining the relationship between sleep and general cognitive development, as well as the specific development of language. For example, one study found that frequent awakening after sleep was linked with poorer outcomes on the Bayley Scales of Infant and Toddler Development second edition (BSID-II) Mental Development Index (MDI).2

In the study conducted, frequent nighttime awakenings reported by the babies’ caregivers were found to be associated with a lower MDI in BSID-II in toddlers aged between 12 and 30 months.2

Additionally, a longitudinal study examined the link between sleep-wake consolidation at 6, 18, and 30 months and language skills at 18, 30, and 60 months. The results demonstrated that poor sleep consolidation during the first 2 years of life may be a risk factor for language learning problems in later childhood.2

Due to this understanding that sleep may have a role on cognitive development in infants, researchers also looked into whether a positive relationship existed between sleep, cognition, and physical growth.1 Although the researchers did find that sleep plays a role in the development of these domains, the mechanism by which that relationship would be established remained unclear during the study.1

In light of these data showing the impact of sleep on infants’ brains and the potential it may have to affect their development more broadly, more studies remain necessary in order to delineate the exact effects of sleep on brain structural and functional network in infants in order to understand the correlation further.2

REFERENCES
  1. Elaine KH Tham, Nora Schneider,and Birit FP Broekman. Infant sleep and its relation with cognition and growth: a narrative review. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5440010/. Accessed January 10, 202
  2. Fan Jiang, Sleep and Early Brain Development. https://www.karger.com/Article/Fulltext/508055. Accessed January 15, 2021.
  3. Max Planck. Babies retain even detailed events during a nap: During sleep, toddlers' brains consolidate details without generalizing them. ScienceDaily. ScienceDaily, https://www.sciencedaily.com/releases/2020/04/200407131435.htm. Accessed January 10, 2021.