It was Shakespeare’s Hamlet who said “to sleep, perchance to dream”. Since that time, over a century’s worth of scientific investigations has led us to realize that, “to sleep” may also improve our ability to remember. Our biological need to sleep everyday has proven to have a significant positive role on our abilities to acquire new knowledge as well as prevent us from forgetting retained information through a process of memory consolidation.
Sleeping – A Two Stage Process
To understand how our memories are affected by the number of hours we sleep every night, we first need to grasp that sleeping is not as simple as it sounds. While we slumber we enter into the first stage of sleep identified as “slow wave sleep” (SWS), which can be considered as restful or deep sleep. The second phase of sleeping is known as Rapid Eye-Movement (REM) sleep. This is characterized by movements of the eyes as well as potentially vivid dreams because of the almost wakeful like electrical stimulations in our brains. REM sleep is a unique sleeping function that is only experienced by birds and mammals (including humans). These two stages of sleep have been recorded since the 1930s but are only now starting to be understood.
Slow Wave Sleep
For a long time, sleep was thought to have a “passive” role in memory consolidation, whereas by sleeping, we eliminate new stimuli by remaining unconscious for several hours. However as researchers dig deeper into understanding the stages of sleep we can recognize that sleeping is an active and integral part of learning and remembering new information. Investigations have shown that receiving a full nights rest after studying or learning new information has resulted in a higher chance of recollection.
Research is also showing that having a 60 to 90 minute nap can also improve memory performance mainly due to the effects of slow wave sleeping cycles. According to publications in the Neuroscientist Journal, slow wave sleep plays an important part in memories stored in the Hippocampus section of the brain. This part of the brain spearheads the conversion of short term into long term memories. The Harvard Medical School also hypothesizes that slow wave sleep is key to remembering declarative or factual memories, which may include your knowledge of capital cities or the ingredients to your favorite recipe.
Rapid Eye Movement Sleeping
Rapid eye movement sleep on the other hand, is being shown to be integral in procedural memory, or “how” we perform certain tasks, from riding a bike to cooking your favorite recipe. It is also thought that REM sleep may assist in consolidating newly formed long-term memories acquired from slow wave sleep, by actively stimulating the newly formed neurons. Studies have shown the various impacts that both SWS and REM sleep have on human and animal learning proficiencies. These studies are often conducted by depriving the subjects of a certain stage of sleep by administering certain hormones including the stress hormone cortisol.
Through these studies scientists have established a sound understanding that well rested sleep has a strong correlation and causation with improved recollection. Yet despite this advancement in understanding the impacts, surprisingly little is known as to how exactly sleep affects memory on a microscopic level. A study released in 2014 in the Journal of Science however, conducted on lab mice, has shown that REM sleep not only strengthens our neurons but also creates new dendritic spines on our neurons which aid us in retaining and recalling our memories. This essentially means that by sleeping, we are actively trying to create and maintain the newly acquired information.
What does this mean for us?
By comprehending the different stages of sleep, from slow wave sleep to rapid eye movement sleep, we begin to understand the hidden benefits of sleep. By achieving a full night’s rest or even by taking a short nap during the day we can boost our own daily performances. Strive to skip all night projects or study sessions in favor of well deserve bed rest, and if you think you will have trouble remembering that, try taking a nap now to let this information consolidate in your long term memory.
- Nicolas Dumay, 2016, Sleep not just protects memories against forgetting, it also makes them more accessible, Cortex Journal, pg. 289 – 296 , http://www.sciencedirect.com/science/article/pii/S0010945215002099
- Guang Yang et Al, 2014, Sleep promotes branch-specific formation of dendritic spines after learning, Science Journal, pg. 1173-1178, http://science.sciencemag.org/content/344/6188/1173
- Harvard Medical School, 2007, Sleep, Learning & Memory, http://healthysleep.med.harvard.edu/healthy/matters/benefits-of-sleep/learning-memory
- Susan J. Sara, 2017, Sleep to Remember, Journal of Neuroscience, pg. 457-463, http://www.jneurosci.org/content/37/3/457
- Jan Born, Bjorn Rasch, Steffen Gais, 2006, Sleep to Remember, The Neuroscientist, pg. 410 - 424http://journals.sagepub.com/doi/abs/10.1177/1073858406292647
- WebMD, Sleep Deprivation and Memory Loss, http://www.webmd.com/sleep-disorders/sleep-deprivation-effects-on-memory#1
- Bjorn Rasch, Jan Born, 2013, About Sleep’s Role in Memory, American Psychological Society, pg. 681-766, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768102/
- William Shakespeare, 1609, Hamlet, Act 3, Scene 1