Sleep has long been linked with an ability to successfully remember and learn things. Although scientists claim that there are many questions unanswered and many processes not fully understood, there has been a significant amount of research and interesting, unambiguous discoveries as to what sleep does for our memory.
Sleep deprivation always shows negative, detrimental effects not only on our concentration but also on memory consolidation. We shouldn’t only be concerned about the length of our sleep, but also on the quality of our sleep.
Sleep stages and memory – what we know
Recording brainwaves using an EEG (electroencephalogram) allowed the scientists to track our sleep. How is that possible? Our brain produces certain types of brainwaves in each sleep stage. There are four stages – two of them are light sleep, one is deep sleep (slow-wave sleep) and one is the famous REM (rapid eye movement) sleep.
Brainwaves tell us which stage a person is in, and they show us how long each of those stages lasts. Some research has shown that people who studied a new language had more REM sleep after their language lessons. This means that REM sleep is linked with declarative memory (explicit memory) – that is – facts, events, and data (for example, birthdays, horsepower of your car, when your flight is scheduled, etc), especially if we are somehow emotionally involved and the information we’ve learned is complex.
However, research has shown that deep sleep is also very important for declarative memory because our brain processes and consolidates new information at this time.
Both REM and deep sleep play a role in procedural memory – which is not focused on facts, but rather on processes and procedures. Procedural memory answers the question of how to do things. For example, how to drive a car, how to do a physical exercise, how to make an origami. These two sleep stages seem to be engaged in the visual aspects of our memory, whereas physical, motor aspects are dealt with during light sleep.
Learning and memory
People usually think of memory as the ability to recall certain events, information or processes. However, before we are able to recall things, we first have to learn them.
When a piece of information is presented to us, this input is called acquisition. After the acquisition, the information is stored in our short-term memory, meaning we have access to it for some time, but there is a high chance of forgetting if it doesn’t reach our long term memory.
The process of transferring data from our short-term into long-term memory is called consolidation. After a memory is consolidated, the process of learning has finished. Sleep helps us consolidate memories and it ‘replays’ new and old events, so that the neural connections are strengthened – that is, the memory of them is stronger, and we can easily recall them.
Sleep also affects our learning processs in the following way – if we are exhausted, we are unable to focus and the new information just goes by, sometimes barely noticed, and sometimes unnoticed. In that case, there is almost no acquisition, almost no memory of it ever happening.
What are the benefits of a good night’s sleep on our memory?
This is how you benefit from a healthy sleep:
- Better attention. You can notice things around you and respond to them quickly.
- Easy learning. When we are sleepy, it’s difficult to input new information.
- Successfully solving problems. Whether you have an important meeting or a physics exam, you’ll perform better and more creatively if well-rested.
- Excellent recall. With a brain cleared out from adenosine (product of the activity of neurons and a substance which makes us sleepy) you are more likely to pull the information from the back of your mind.
Many students try to cut back on sleep and increase caffeine intake in order to have more time for studying. This practice is far from being healthy and could be a lot less effective because sleep helps with memory processing and this is true of all types of memory.
The reason why an ‘all-nighter’ works for some people is that our brains are able to prioritize information – we are likely to remember things when we know that someone is going to examine us. Therefore, if several lessons from a textbook are our number one priority, we may be successful in remembering that information even if we are deprived of sleep but are also less likely to remember anything else. Poor attention can lead to unpleasant situations, like forgetting our arrangements or walking past our friend, but it can also be extremely dangerous if driving while being sleepy.
Good time management and daily naps are a lot healthier choice and more sustainable. Having enough sleep at a young age has proven to be a good investment for the old age, as the risks of developing dementia and Alzheimer’s disease are significantly lower.
Sleep habits and memory
It is good to take a nap or go to sleep after learning. The reason is simple. When we learn new things, this ‘raw’ information can get ‘buried’ under lots of other new information we encounter during the day. As we live in a busy, technology-driven, information-dependent world, this is very easy to happen in wakefulness.
Taking a nap after learning prevents new stimuli from interfering and creates a perfect environment for memory consolidation. Our brain activity is focused on strengthening new neural pathways and we are likely to remember what we had learned. Of course, we shouldn’t neglect the power of repetition – being exposed to the same learning materials over and over has an immense effect on memorizing and learning. However, the importance of sleep shouldn’t be underestimated either.
A group of German researchers has conducted a study with a group of people who were given two sets of cards to memorize. The first set was to be tested, whereas the second set acted as interfering stimuli. Half of the group took a nap after learning the first set of cards, whereas the other half just had a 40-minute break while awake. After the break, everybody was given the second set of cards to remember.
Upon testing, the first group was able to recall 85% of the cards whereas the no-sleep group managed with a 60% of accuracy. This proved that what we learned is easy to deteriorate if more information is introduced. However, sleep lets our memory settle down and be easy to recall.
Practically, we can use these findings to make a sleep-and-learning schedule. For example, we can plan our day so that after studying for a couple of hours, we take a nap, revise after waking up, and then continue with our daily tasks. Another good time for studying or revision can be before bed – but only if we are studying from an actual book, not a computer. The blue light emitted from screens can confuse our circadian rhythm and result in an inability to fall asleep and/or have poor sleep quality.
Parents might want to consider incorporating such a schedule into their children’s sleep habits.
Sleep disturbances, sleep deprivation, and memory
Memory consolidation, along with brain, body and immune system restoration, is considered one of the primary reasons why we sleep. Poor memory is a frequent symptom of sleep disorders such as OSA (obstructive sleep apnea), restless leg syndrome, and other problems that cause sleep loss.
Cognitive impairment is one of the main signs of non-restorative sleep. Other symptoms include mood disorders, headaches, excessive daytime sleepiness, and poor motor skills. Not only are we not able to learn and recall information, but we also tend to make bad and risky decisions when we haven’t had enough sleep. Numerous studies have found a link between chronic exhaustion and poor life decisions. Teenagers and young people who are sleep-deprived tend to underperform at school and work and often engage in promiscuous and unhealthy behavior, whereas older adults are prone to faster cognitive decline.
Good sleep preserves good memory
In order to keep our neurons in good working order, we have to give them some ‘maintenance’ time. Just like a mechanic can’t fix your car unless you’ve shut it down and got out, your brain can’t clean up and consolidate if you are awake. Pay attention to your sleep habits and make sure they are healthy.
Even if you are extremely busy throughout the week, try as much as possible to have a sufficient sleep time every night. Everyone’s sleep needs are different – hours of sleep you need could be higher than what you are getting. To find what’s enough sleep for you, try experimenting with sleeping a slightly different amount of time each night. Once you wake up fully refreshed, happy and satisfied, you are likely to have hit the right number of hours. It is also a good idea to make a sleep schedule and stick to it.
Remember that caring about your sleep is a long-term investment you’ll be thanking yourself for.
- Sleep, Learning, and Memory. Healthy Sleep. Harvard. http://healthysleep.med.harvard.edu/healthy/matters/benefits-of-sleep/learning-memory Accessed January 10, 2019.
- Breus M. Sleep and Memory. PsychCentral. October 8, 2018. https://psychcentral.com/lib/sleep-and-memory/ Accessed January 10, 2019.
- Can Poor Sleep Lead To Dementia? American Academy of Neurology. https://www.aan.com/PressRoom/Home/PressRelease/1326 Accessed January 10, 2019.
- Klemm W. R. How Sleep Helps Memory. Psychology Today. March 11, 2011. https://www.psychologytoday.com/us/blog/memory-medic/201103/how-sleep-helps-memory Accessed January 10, 2019.
- Diekelmann S, Büchel Born J, and Rasch B. Labile or stable: opposing consequences for memory when reactivated during wakefulness and sleep. Nature Neuroscience. January 23, 2011. https://www.ncbi.nlm.nih.gov/pubmed/21258327 Accessed January 10, 2019.
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