Many new parents have had the same question: "Why won't my baby just sleep through the night?". This question, asked in frustration to nobody in particular, has certainly been said thousands of times. Many parents may be inclined to come to the conclusion that "maybe I just have a bad baby". However, research revolving around the sleep schedules of newborns and infants has provided us with, if nothing else, a start toward a possible explanation. All signs point toward the underdevelopment of the brain regions that regulate the circadian rhythm. Circadian rhythm refers to the internal biological clock that is present in animals, including humans. Adult humans typically have a 24-hour circadian clock, controlled by specific parts of the brain such as the hypothalamus or, more specifically, the suprachiasmatic nuclei. In infants, this regulation is not present, and this results in sleep spread out over the 24-hour day instead of in one consolidated sleep event. This presents researchers with some interesting tasks, such as finding out when the circadian clock emerges, or what effects it has on the infant other than a consolidated sleep cycle.
An article, titled "What is 'Normal' Infant Sleep? Why We Still Do Not Know" by Elaine S. Barry et al. published in SAGE journals, explores the irregularities in infant sleep patterns and reasons for why we still do not understand the underlying mechanisms. Dr. Barry understands that "normal" sleep for an infant is highly subjective, as there is no real definition out there for what is "normal". She also writes that the architecture underlying sleep in infants is very different from that of adults, and this results in the large differences in sleep that are typically described as an "irregular sleep schedule" in infants. There are many different definitions of what "normal" sleep is meant to look like in infants, and these disparities have made it challenging for researchers to collaborate and expand on one another's work. Thus, there is still a need for a better definition of "normal" sleep, as this could lead to greater collaboration between researchers and a possible breakthrough in the field of sleep.
Despite these challenges, there have still been some relatively recent developments in the field of infant sleep. In an article titled "Developmental emergence of sleep rhythms enables long-term memory capabilities in Drosophila" published by Dan Cavanaugh et al., the developmental period at which a Drosophila (fruit fly) larva begins to sleep "regularly" is described. It was found that circadian rhythm began altering the sleep-wake cycle in larvae in the 3rd instar stage of development. What's even more interesting was the observation that long-term memory began to emerge in these larvae as well, at around the same time as circadian emergence. This suggests a possible link between circadian sleep regulation and the formation of long-term memories. This points to the lack of regular sleep as the reason nobody can remember their infancy. This discovery could have possible applications in memory disorders, or hyperactivity disorders, such as ADHD, that prevent an individual from getting adequate deep sleep. Patients with Schizophrenia are also at risk of not achieving consistent deep sleep. Now that the link between circadian sleep and memory has been established, the door is open for more research revolving around interactions between sleep and other brain functions.
References:
Barry, E. S. (2021). What is “normal” infant sleep? Why we still do not know. Psychological reports, 124(2), 651-692.
Poe, A. R., Zhu, L., McClanahan, P. D., Szuperak, M., Anafi, R. C., Thum, A. S., ... & Kayser, M. S. (2022). Developmental emergence of sleep rhythms enables long-term memory capabilities in Drosophila. bioRxiv, 2022-02.
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