A sleep study on fruit ﬂies, published by US scientists in March 2020, revealed how the brains of adolescents actively halt the development of the area that is important for sleep. This allows them to snooze longer, which is important for brain development and learning. The scientists believe that human brains use similar mechanisms to facilitate the learning capacity of the young.
Sleeping like a baby
Scientists investigated the reasons why young people sleep longer than adults, in the brains of the fruit fly Drosophila melanogaster. The researchers found that one gene, called PMD3, is responsible for sleep patterns of the young. Adolescent fruit flies usually sleep twice as long as adults. When scientists switched off the PMD3 gene, youngsters slept for the same time as grownups.
Researchers found that this gene suppresses the maturation of the brain area that is responsible for sleep- and wakefulness, the central complex. As long as PMD3 is active in the brain, development of the central complex is hindered, allowing the flies to sleep longer. Whereas the rest of the brain continuously evolves. When the flies reach adulthood, PMD3 is no longer active in the brain. Because of that, neuronal connections are made in the central complex, promoting more wakefulness. The brain grows up completely and the fly sleeps less.
“Understanding is the root of improvement.”
How is this study useful for humans?
Working with fruit flies may seem like an odd choice, but actually many genes that control processes in the development from embryo to adult, are the same in Drosophila as well as in humans. The authors of the fruit fly study suggest that sleep disorders could be caused by faulty brain development. Understanding is the root of improvement. Thus, knowing the origin of sleeping disorders can lead to their prevention. This way, a study on flies could be useful for human health.
Why sleep is so important for the young
Many health risks are associated with sleep loss, such as an increased blood pressure, weight gain and depression. But sleep is especially important for the developing brain of children and teenagers. Too little of it can lead to lifelong learning disorders and even pathological behavioral changes.
A developing brain needs to alter existing neuronal connections (synapses) in order to learn new motoric-, language-, or other skills. It furthermore strengthens the synapses of important memories, while the less important ones are weakened. This way, the brain can store knowledge in the long-term memory. All of this happens during sleep and since young people learn more new skills, they need to sleep more.
The younger a child, the more sleep it needs. Until the age of twelve, children require up to twelve hours of sleep, teenagers need eight to ten hours. Interestingly, from the ages of twelve to fifteen children tend to turn into late risers. They cannot help but stay up longer and wake up later. This can be reversed up onto the age of twenty, but especially men tend to remain late risers throughout their life.
When teenagers are forced to get up early for school, they tend to be sleep deprived and this gets in the way of their development and education. Furthermore, the lack of sleep during brain development in adolescents can result in behavioral changes and even cause disorders such as Schizophrenia.
A study showed that up to seventy five percent of teenagers from the USA sleep less than eight hours per night, on a regular basis. This is very alarming, given the effect this can have on their development. Unfortunately, the research conducted on fruit flies does not teach us how to prioritize sleep. But we can come to understand many more diseases, working with these insects, that would otherwise be much harder to investigate (see box). This peculiar test subject has greatly advanced biomedical research and our understanding of human health.
Why scientists work with fruit flies
It is quite common that scientists conduct studies on animals when they try to understand human development or disease. The fruit fly Drosophila melanogaster is a popular model organism for aging, behavior, and development. Flies can be compared to humans since many processes are controlled by the same genes. They are popular since results are obtained quick and easy.
Drosophila was initially used to study the inheritance of genes. Then, scientists started to investigate the influence of genetics on behavior, as well as the processes that occur during the development from embryo to adult. It was due to this work that they realized the similarities to mammals (including humans). Though the insect’s brains are different, the general functionality is similar to ours.
Furthermore, their nervous system and cardiovascular system can be compared to that of mammals. Therefore, researchers could for instance find the genes responsible for sudden cardiac arrest due to their work with Drosophila melanogaster. Scientists also study the metabolism, as well as diseases of liver or kidney, muscular atrophy, Alzheimer’s disease and much more, using flies.
Benzer, S. (1971). From the gene to behavior. Jama, 218(7), 1015-1022.
Dilley, L. C., Szuperak, M., Gong, N. N., Williams, C. E., Saldana, R. L., Garbe, D. S., … & Kayser, M. S. (2020). Identification of a molecular basis for the juvenile sleep state. eLife, 9, e52676.
González-Rueda, A., Pedrosa, V., Feord, R. C., Clopath, C., & Paulsen, O. (2018). Activity-dependent downscaling of subthreshold synaptic inputs during slow-wave-sleep-like activity in vivo. Neuron, 97(6), 1244-1252.
Keyes, K. M., Maslowsky, J., Hamilton, A., & Schulenberg, J. (2015). The great sleep recession: changes in sleep duration among US adolescents, 1991–2012. Pediatrics, 135(3), 460-468.
Marín, O. (2016). Developmental timing and critical windows for the treatment of psychiatric disorders. Nature medicine, 22(11), 1229.
Morgan T.H., Bridges C.B. Sex-Linked Inheritance in Drosophila. Carnegie Institution of Washington; Washington, DC, USA: 1916
Randler, C. (2011). Age and gender differences in morningness–eveningness during adolescence. The Journal of genetic psychology, 172(3), 302-308.
Tolwinski, N. S. (2017). Introduction: Drosophila—A Model System for Developmental Biology.
Ugur, B., Chen, K., & Bellen, H. J. (2016). Drosophila tools and assays for the study of human diseases. Disease models & mechanisms, 9(3), 235-244.
https://www.hopkinsallchildrens.org/ACH-News/General-News/The-importance-of-sleep-for-kids Article published on Mar 12, 2018 Author Rachel Dawkins, viewed 01.05.2020 6.50 p.m.
Wilhelm, I., Rose, M., Imhof, K. I., Rasch, B., Büchel, C., & Born, J. (2013). The sleeping child outplays the adult’s capacity to convert implicit into explicit knowledge. Nature neuroscience, 16(4), 391-393.
https://www.forbes.com/sites/alicegwalton/2016/12/09/7-ways-sleep-affects-the-brain-and-what-happens-if-it-doesnt-get-enough/#38eed701753c Published on Dec 9, 2016, 10:20 a.m. Author Alice G. Walton, viewed of 01.05.2020 7:25 p.m.