Prioritize Sleep for Optimum Learning
You may have heard the infamous phrase “Grades, fun, or sleep, pick two.” If you didn’t pick sleep, now would be a good time to reconsider. Although scientists debate how sleep affects learning and memory, it has been known for a long time that sleep is necessary for proper brain function. New studies using fruit flies show that sleep weakens or severs the synapses in the brain, making way for new information. These proteins found in the connections between neurons grow in the fruit fly brains while they are conscious. Recent studies by Giorgio Gilestro, Giulio Tononi and Chiara Cirelli of the University of Wisconsin–Madison show that the levels of synapses in the fruit fly brains decrease while the flies are sleeping. Their finding could support the theory of synaptic homeostasis, which states that sleep decreases the strength of the stronger synapses while severing the weaker ones. The result of this activity would be the magnification of the signal of important memories (Sae, 2009).
The sleep which flies experience is very similar to human sleep. When flies are deprived of sleep for example, they will try to make up for the loss by sleeping for a longer period of time the next session. Paul Shaw, Ph.D., assistant professor of neurobiology at Science Daily University School of Medicine in St. Louis, conducted a study in 2006 on fruit flies and revealed that learning increased the need for sleep in the flies. (Science Daily, 2009). In Cirelli’s research however, the team genetically modified the flies in order to track the number of synapses in the fly brain. When flies slept, the number of new synapses formed during social enrichment decreased. When researchers deprived them of their sleep, the decline did not occur. (Science Daily, 2009).
Cirelli states, “We assume that if this is happening, it is a major function, if not the most important function, of sleep.” Their study however, contradicts previous studies which suggest that sleep has the complete opposite effect on the synapses – strengthening them rather than weakening them. Cirelli’s and Tononi’s research measured the synaptic strength using proteins as markers, rather than measuring the synaptic electrical activity due to the flies’ small brain sizes. (Sae, 2009). Some scientists argue that the use of proteins vs. the electrical activity does not prove that the synapses are being weakened.
Shaw is among those scientists who are skeptic about the synaptic homeostasis theory. He conducted similar studies on fruit flies, measuring synaptic destruction during sleep. He increased the flies’ need for sleep through social interactions and counted the synapses before and after the flies were allowed to sleep. His results were the same as Tononi’s and Cirelli’s, the number of synapses decreased after sleep. However, Shaw believes that the decrease in the number of synapses is more complex than is thought to be. He believes that sleep may weaken synapses in some circuits while strengthening connections in others. "Right now a lot of people are worried about their jobs and the economy, and some are no doubt losing sleep over these concerns," Shaw says. "But these data suggest the best thing you can do to make sure you stay sharp and increase your chances of keeping your job is to make getting enough sleep a top priority." (Science Daily, 2009).
Shaw wishes to continue his research on fruit fly sleep. The next goal? He plans to further investigate the relationship between memory and sleep, including how increased synapses induce the need for sleep. (Science Daily, 2009). So until the secrets of sleep are clearly known, it’s better to be safe than sorry. Pick sleep.
An example of the marked synapses in the fly brain.
The longer fruit flies stay awake, the more proteins active at synapses build up (right). Sleep lowers levels of these proteins (left), indicating that one of sleep's functions may be to reduce or eliminate synapses to make room for learning the next day. (Sae, 2009).