Reading Time: 11 minutes

 

Sleep is probably the most unrecognized, yet, one of the most efficient studying methods. Sleep is essential for memory because memory traces are created and strengthened during sleeping hours. If you are a professional or a student who constantly needs to learn new facts, and you want to save time on re-studying, this article is for you!

You will learn:

  • Why and how getting 8 hours of sleep can significantly improve your memory and help you learn faster
  • What is the scientifically studied study-sleep-study method and start using it in your life
  • How sleeping prior to studying can enhance learning by 40 %

Learning and remembering (every day)

We are constantly learning. It might be reading an academic paper, improving professional skills, or practicing a life skill such as how to invest money or raise a baby. Movement, such as practicing a dance, is also information that needs to be stored encoded in the brain.

I have a question for you: have you ever read a fascinating article and then tried telling your friend its content only to realize that you already forgot?

You are not alone.

Forgetting information is very common in today’s society where the amount of information increases gradually. Luckily, there is plenty of things you can do to protect your memory and prevent forgetting. Interestingly, one of the most efficient ways to do this is the one that many of us struggle with the most: sleeping.

In this article, I will tell why sleeping is important and how to use it, in order to improve memory.

Why you forget?

When you can’t recall information, two processes may have gone wrong:

1) Consolidation: The memory did not consolidate to your brain. That is, you did not learn it in the first place. Instead what happened is that somewhere between the reading and trying to make a mental note of it, the information got lost and you just forgot. Thus, the neural pathways which would have been needed to recall the information were not formed. Sleep is very important for forming the neural pathway, and thus neglecting sleep will decrease your ability to create the necessary brain pathway of the memory trace.

2) Recall: The other option is that you can’t recall it. That is, you have learned it (the neural pathway is formed), but you can’t bring it back to your mind (you can’t activate the pathway). This is called the tip-of-the-tongue effect.

This article focuses on the first process, consolidation, where the neural pathway is formed to the brain and the memory moves into so-called long-term memory storage. The most common mistake to prevent moving the memory to long-term storage is neglecting sleep.

 

Why pulling an allnighter is a bad idea?

It is very common to try to cram a huge amount of information to the brain in one day or night. This actually leads to a psychological illusion; you feel like you have learned a lot, however, crammed information is fragile and easy to forget. Simply put, the memory for crammed knowledge is not sustainable. Also, cramming is more tiring than studying in small bits and sleeping in between. Thus, it is both counterproductive and time-consuming. Simply put, it is not an efficient way to learn.

Substantial evidence shows that you can use sleep in order to improve your learning even by 40 % and to reinforce your memory. Sleep also prevents forgetting and can protect from Alzheimer’s disease. Especially the scientifically studied study-sleep-study method will help you to learn faster and save time.

The two-step process of storing memory to your brain

There are two processes in learning information and storing it into long-term memory: 1. acquisition and 2.consolidation.

In acquisition, you literally acquire the information. In other words, you hear it or read it for the first time, and you process it in your working memory. This is a form of “online processing” of information , which means that it happens here-and-now. Working memory processes happen at the front parts of the brain (prefrontal cortex or PFC), just behind and above your forehead. Maybe you have noticed that when you are learning something intensively, you rub your temples and your forehead, just above the eyes. This is exactly pointing to the part of the brain where working memory processes take place.

Information consolidates during rest and sleep. During consolidation, new information gets integrated with the information that you already know. This happens in so-called “offline hours”, i.e. when you are concentrating on other activities. Most of it happens during sleeping. This process is linked to the function of two brain areas: hippocampus and neocortex.(S)

 

 

Hippocampus sits deep in the brain below your ears. Binding new information to old knowledge during sleep takes place in the hippocampus. Hippocampus sends the information to your cortex, the outermost layer of the brain. Hippocampus is also activated when you “pick up” the information later from the neocortex back to working memory. Thus, it’s like a bridge between your “online”-memory processes and “offline”-memory storage. (S)(S)

What science reveals about sleep and memory

It has been shown that storing information to long-term memory happens mostly during sleep. This applies to both motor skills (motor memory) and factual knowledge. Scientific studies show that sleep helps to recall information and improves the potential to learn compared to so-called “allnighters” or cramming information.

The typical way to test this is by comparing two groups of people who both learn information (word-pairs, word lists, motor skills etc). One group is a “Sleep group” and uses the study-sleep-study technique. They learn information in the evening (for example, 9 pm) and are tested in the morning (for example 9 am). No-sleep group learns information in the morning (9 am) and is tested in the evening (9 pm). That also leaves 12 hours between learning and the test. Nothing else between these groups changes; the testing interval is exactly the same and no artificial sleep-deprivation is caused.An extensive review of the studies has been offered by sleep researcher Matthew Walker in his book Why we sleep. Here are some research highlights:

 

1. Sleep improves motor accuracy and speed

In this study, two groups were learning fine motor skills, specifically finger tapping. The sleep group had a 20 % better motor speed and accuracy than the no-sleep group (S). Other studies have confirmed these findings (S).

 

2. Sleep improves memory for facts

Sleep is important for consolidating memory to the long-term memory and prevent loss of this information or prevent learning new information. In this following study, not sleeping, impaired recall for already “learned” information when people made learn new facts. This setting resembles a situation many of us face often: we are constantly learning, and sometimes the information overload just keeps coming day after day. Yet, if we don’t sleep well in between learning periods, we might lose the information we put so much time and effort to learn. Thus, this is especially useful knowledge if you are a student or trying to memorize a lot of facts in a short amount of time. You need to sleep in between learning, in order not to lose it.

In this study (S), groups studied word pairs, where the words were related to each other (easy to learn) or non-related to each other (harder to learn)

Sleep-group’s recall was 95 %
No-sleep group’s recall was 80 %

 

3. Sleep prevents interference of other information (S)

Ellenbogen, J. et al. (2006). 

This study is the second part of the previously mentioned word-pair study. The setting was the same, only this time both groups had to study a second list of words (interference list) just before the test. Thus, the sleep-group studied the second list after a night sleep (in the morning) and no-sleep group studied it on the same day (in the evening). Now the recall for the original words dropped, but the difference between sleep and the no-sleep group was huge (see the graph above)

Sleep group’s memory for the original words declined 15 %-points
Non-sleep group’s memory for the original words declined 40 %-points

 

4. Sleeping before learning improves the potential to learn (S)

Walker, M. P., & Stickgold, R. (2006). 

“Should I pull an all-nighter and just cram this information in my head in the next couple of days?” The question many of us have asked from ourselves at least once, whether in college or prior to a training week. The answer is simple, short and comforting: no. You will learn more efficiently if you sleep because sleeping also prepares your brain for subsequent learning.

In one study college students were assigned into two groups: sleep-group and sleep-deprivation group (for 36 hours). After that, students had to learn a list of facts inside a brain scanner.

The sleep-deprivation group learned 40 % less information compared to the group who slept before learning.
The sleep group had healthy and beautiful hippocampal activity while they were learning meanwhile the sleep-deprivation group showed almost no hippocampal activity at all.

In other words, staying awake all night will lessen your ability to learn information on the following day.

 

5. Sleep increases memory for positive information (S)

In addition, in one setting students were learning either positive or negative valenced words.

The sleep-deprived group showed better recall for the negative information than the positive one (so-called negativity bias, which is observed for example in depressed individuals)
The sleep group recalled twice as much positive information than the sleep-deprived group.

Thus, a good night’s sleep will not only make you a better learner but it also improves your memory for the information that shows you the bright side of life!

Why sleep improves memory?

Brain scans show that during sleep hippocampus is active and makes your brain “train” the information even when you are not awake an actively processing it. Actually, brain activity in certain sleep stages resembles the same activity that was shown when you were learning the information. This means, your brain is practicing meanwhile you are happily resting and sleeping! (S) (S)

There is some evidence for specific sleep stages for a specific type of memories. Yet, we should keep in mind that this is really a line drawn in water and there is still a lot more to learn about the sleep stages and memory.

Current evidence links especially REM sleep to motor skills training. REM is also linked to a brain process called neuroplasticity, which means that REM is important in causing brain structure changes. This happens because during the REM-sleep stage, the genes that help neuroplastic changes to happen, increase in activity. Studies have also found that selectively inhibiting only REM sleep and stage 2 sleep, cause impairments in motor learning (S) However, as deep sleep is also important for muscle recovery and the post-exercise muscle growth, and also helps building and strengthening the neuromuscular connections, both sleep stages are important for motor skills training. (S) (S)

Deep Sleep. Deep sleep has shown to be especially important for learning facts. It has been shown that during the early hours of sleep (deep sleep) there are more sleep spindles in response to more learning. (S) (S).

How poor sleep can cause Alzheimer’s disease

Human studies show that sleep deprivation, especially deep sleep deprivation, increases toxins in the brain and this can cause Alzheimer’s disease.

One of the reasons for Alzheimer’s disease is the accumulation of a harmful substance called beta-amyloid in the hippocampus. Deep sleep deprivation can increase the risk of Alzheimer’s. This was demonstrated in one study were people were deprived of deep sleep and the next morning they had 20 % more beta-amyloid circulating in their cerebrospinal fluid (S)

This happens because during deep sleep brain detoxifies with the help of the glymphatic system (i.e. the lymphatic system operated by the glial cells in the brain). The intriguing and astonishing process that detoxes the brain is the shrinkage of brain cells, called glial cells, during the night. Glial cells occupy the space between other brain cells, neurons, which are relaying messages (such as memories and motor actions!). When glial cells shrink during sleep, they create even 60 % more space to the brain, which allows more detoxifying fluids between brain cells to flow (S). This fluid has shown to flush the toxins (such as beta-amyloid) away from the brain during the night and help prevent the accumulation of the substances that can cause memory diseases (S).

In summary, the role of sleep in preventing Alzheimer’s and improving memory might be partially due to the detoxification of the brain during the night.

Summary

If you want to learn, you should sleep, because sleep consolidates memories and prevents new information interfering new information. Thus it helps to prevent forgetting and saves you time from re-learning information.

Evidence shows that sleep is beneficial both before learning and after the learning. Before learning sleep can improve the ability to take in information even by 60 %. After learning, the night-time hippocampal activity in the brain consolidates the memories from the day.

Brain scans show that during the sleep your brain is training the information you learned during the day. That is, its producing similar neural activation than during day-time learning – all while your conscious mind is happily knocked out. Studies show that the brain can is very efficient in rehearsing information during offline hours, in comparison to staying awake and trying to cram the information to the brain.

You need to sleep approximately 8 hours to get enough REM and deep sleep which and increase your memory performance. But really, it should not be about needing as much as deserving to sleep. Sleeping s fun, it’s healthy and it’s an absolutely efficient way to consolidate memories.

In addition, sleep deprivation can increase negativity bias, whereas after sleeping you are more likely to remember positive information ☺️

Top tips

  • If you can, always get 8 hours of sleep at night
  • Study prior to bed in order to improve memory
  • Sleep in between study periods in order to prevent memories to confuse and get forgotten (study-sleep-study)
  • Remember that the brain needs time to consolidate new information: sometimes you need to wait days or even weeks for really imprint new memories in your brain (rehearsal speeds up this process)
  • Sleep well especially during professional training or exam weeks, when new information is presented to you in a fast phase
  • Don’t pull an all nigher -> you can reduce your potential to learn even by 40 %!
  • Sleep is important for both motor and factual learning
  • Remember that after you have learned, you deserve sleep; make sleep your reward rather than a necessity
  • If you want to improve your sleep, read my 30 powerful tips for getting 8 hours of sleep every night

Tell me in the comments:

  1. Do you use the study-sleep-study technique?
  2. How many hours a night you sleep?
  3. Have you noticed differences in your learning when you have been sleep-deprived compared to times when you have slept well?

If you enjoyed the article, share and pass along the knowledge:

If you gained insights while reading this post, share the good! Go ahead and link this post to your friend or a colleague if you think learning about sleep and memory can improve their lives, entertain them, or help them learn faster.

With gratitude,
Inka

References:

Bird, C. M., & Burgess, N. (2008). The hippocampus and memory: insights from spatial processing. Nature Reviews. Neuroscience, 9(3), 182–194. https://doi.org/10.1038/nrn2335

BREM, A.-K., RAN, K., & PASCUAL-LEONE, A. (2013). Learning and memory. Handbook of Clinical Neurology, 116, 693–737. https://doi.org/10.1016/B978-0-444-53497-2.00055-3

Interfering with theories of sleep and memory: sleep, declarative memory, and associative interference. – PubMed – NCBI. (n.d.). Retrieved May 13, 2019, from https://www.ncbi.nlm.nih.gov/pubmed/16824917

Ju, Y.-E. S., Ooms, S. J., Sutphen, C., Macauley, S. L., Zangrilli, M. A., Jerome, G., … Holtzman, D. M. (2017). Slow wave sleep disruption increases cerebrospinal fluid amyloid-β levels. Brain, 140(8), 2104–2111. https://doi.org/10.1093/brain/awx148

Kuriyama, K., Stickgold, R., & Walker, M. P. (2004). Sleep-dependent learning and motor-skill complexity. Learning & Memory, 11(6), 705–713. https://doi.org/10.1101/lm.76304

Memory for Semantically Related and Unrelated Declarative Information: The Benefit of Sleep, the Cost of Wake. (n.d.). Retrieved May 13, 2019, from https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0033079

Rasch, B., & Born, J. (2013). About Sleep’s Role in Memory. Physiological Reviews, 93(2), 681–766. https://doi.org/10.1152/physrev.00032.2012

Smith, null, & MacNeill, null. (1994). Impaired motor memory for a pursuit rotor task following Stage 2 sleep loss in college students. Journal of Sleep Research, 3(4), 206–213.

Walker, M. P., Brakefield, T., Morgan, A., Hobson, J. A., & Stickgold, R. (2002). Practice with sleep makes perfect: sleep-dependent motor skill learning. Neuron, 35(1), 205–211.

Walker, M. P., & Stickgold, R. (2006). Sleep, memory, and plasticity. Annual Review of Psychology, 57, 139–166. https://doi.org/10.1146/annurev.psych.56.091103.070307

Wible, C. G. (2013). Hippocampal Physiology, Structure and Function and the Neuroscience of Schizophrenia: A Unified Account of Declarative Memory Deficits, Working Memory Deficits and Schizophrenic Symptoms. Behavioral Sciences, 3(2), 298–315. https://doi.org/10.3390/bs3020298

Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., … Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science (New York, N.Y.), 342(6156), 373–377. https://doi.org/10.1126/science.1241224