The Relationship between Sleep and Memory
As children we often fell asleep on our way to school and soccer practice because we stayed up late. We sneaked comics to our bed and stayed up reading them till the end. That resulted in foggy first moments after waking up, dozing in class and lack of attention.
These were few visible results of sleep deprivation that we could understand even as children. However, there are other complex connections between sleep and brain function, which even adults struggle to understand.
Not getting enough sleep before tests, studying until the morning and living on caffeine till the exams are over are familiar scenarios for almost everyone. It often happens that we go through the same lesson over and over again and yet we fail to recollect the precise information during the examination.
That’s a nightmare that everyone has gone through at least once in their lives and is a result of the huge amounts of stress we put ourselves through. The lack of sleep keeps us from performing at our very best.
Proper rest affects more than your physical appearance. Namely, It improves your memory too. So, when you stay up all night going over your lessons and revising the notes, you deprive your brain of the necessary rest it needs to transfer the information from temporary memory to long-term memory. And long-term memory is what you need during examinations and interviews, as in such situations we often pull the details from our long-term memory.
What Is the Memory? How Are Sleep and Memory Related?
Deep sleep or slow-wave sleep (SWS) can promote the consolidation of all memories you have formed recently, small facts like where you put your keys yesterday after coming home or have you turned the oven off before leaving home. Yes, you do not need to remember them forever, but you need to remember these small details for your convenience and safety.
How memory forms and how sleep aids in the conversion of short-term memory to long-term was once a mystery to the scientists. Now, thanks to the advances in sleep studies and neuroscience, scientists learned the intricate relationships between memory formation and sleep.
Having enough of a quality sleep at night and several daytime naps can consolidate memories, stabilize them and link them through common facts. That is how we can apply the unitary method while calculating gas prices or use simple arithmetic to calculate the final payable at the POS of a store. Whatever we have learned during high school and college starts to make sense later in life, even if we are not consciously making an effort to remember it.
Which Parts of Our Brain Help in the Formation of Memory?
Every memory consists of three parts: acquisition, consolidation, and recall. The acquisition is a part of our wakefulness and precedes the consolidation process. Consolidation involves the transfer of the short-term memory to the hippocampus. It also consists of updating old memories and that is why we call it an ongoing process and how we can learn new facts and recall them later.
All three types of sleep (light, sleep, and REM) are necessary for the formation of memories. Sleep and memory share an intricate relationship that scientists have been trying to explore for a very long time.
Our brain has an extraordinary mechanism for choosing which memories to store and which to retrieve. That fact has always baffled both ordinary people and scientists. A term that is used for this is “cherry picking”. It refers to the way our brain picks which memories to consolidate and which ones to leave behind.
The hippocampus and neocortex use separate mechanisms to store the memories. The hippocampus emphasizes the consolidation of episodic memory, whereas the neocortex paves the way for understanding patterns. Scientists state that the neocortex enables the formation of semantic memory.
While the short-term episodic memory is a function of the neural activity patterns, the long-term memories are the result of more permanent changes in the brain structure. The latter involves the formation of new neuronal connections that remain longer. That is one way to understand the impacts of short-term amnesia on the memories that are less than 12 hours old and the persistence of long-term memories in spite of the short-term amnesia.
How Does the Brain Selectively Store Memories?
A 2004 publication shows that the pruning happens at night. According to Ken A. Paller and Joel L. Voss, the brain shuffles the memories and selects the ones that will go into declarative memory which is the ability to recollect specific facts. The communication between the neocortex and the hippocampus allows the recent information you have learned to “brush up” the memories in the neocortex.
Interestingly, even when the specific memory of an event gets lost, the emotional impact remains. You could say that the instance still contributes to the overall knowledge a long time after the loss of the initial episodic memory. The unique directional communication between the hippocampus and the neocortex allows the brain to “remember” the overall impact of episodic memory, even when the actual memory is gone.
What Happens to Your Memories when You Sleep?
During the slow-wave sleep, human brain experiences a decoupling process from the sensory neurons. The neurons do not provide new information to the mind during deep sleep, but the brain and several areas in it remain active.
Hippocampus, a small part of the limbic system, remains active during this point. In an EEG you should be able to see sharp wave ripples emanating from this region. Large-amplitude slow oscillations are ubiquitous to the outer layers of the cerebrum aka the cortex. During sound sleep, the brain goes through alternate periods of activity and passivity.
During this phase, the episodic memories you have acquired during your wakefulness, travel from the hippocampus to the cortex. This transfer of memory from the hippocampus to the cortex results in the formation of long-term memory.
Slow oscillations during the slow wave sleep are susceptible to the brain wave activity of the hippocampus. These patterns determine the changes in the synaptic wave patterns in the cortex. The synaptic changes can affect the pattern of the slow waves that can reinforce specific patterns of slow oscillations resulting from the sequential firing of neurons in the cortex. It leads to the replay of one or more particular memories.
That brings us to the next question – why do we spend one-third of our lives sleeping? By now it must be clear that sleeping is anything but a complete state of brain inactivity. Our brains never go into a complete state of stasis even during the deepest slumbers. Throughout the day we gather new information, and at night our brains process it to create new memories or to update the old ones.
According to the synaptic homeostasis hypothesis, our brains collect the information by strengthening the connections between our brain cells and finally, our mind saturates itself with the info. That requires incredible amounts of energy. That is why we need sleep. When we sleep, the energy expenditure of our brain goes down. Rest gives us the chance to consolidate our memories and begin the next morning fresh.
Why Does the Brain Need Sound Sleep for Proper Memory Consolidation?
A fascinating study from Nature Communications shows that when the brain is in a sleep-deprived state, it can be easily excited. Eleven men and nine women between the age of 19 and 25 were the test subjects. Nissen and his students subjected the entire group to the same tests, under same measurable parameters either after a whole night of rest or after an entire night without sleep.
The coordinators watched closely during the nights of wakefulness. They did not get caffeine or other stimulants on those nights. They stayed up by playing games, taking walks and cooking food. The next morning, Nissen subjected them to the first round of testing. The staff used magnetic pulses to fire neurons in the brains of the participants. That caused a muscle in the left hand to twitch.
Results showed that on the days following nights of wakefulness, weaker pulses were enough to make the muscles twitch. On the other hand, strong vibrations were necessary to make the muscles move after a night of sound sleep. That shows that rest deprived brains can be easily excited.
In another study, the group wanted to mimic the neuron firing sequence during memory consolidation. Nissen and his group found it difficult to reproduce the mechanism when the subjects did have enough sleep. That shows how a lack of proper rest can impair the formation of new memories.
Both tests show that rest is necessary for the brain to form new memories by calming its activity. You can think of a sleep-deprived brain as non-working machinery with loose cogs. It will make a lot of noise, but its production level will remain minimal. Any sleep-deprivation test will show that tired volunteers will perform much worse than the well-rested.
How Does Sleep Affect the Formation of Overnight Memory?
This far, we have learned that the lack of proper rest can cause memory loss and it can affect the formation of long-term declarative memory. Insomnia is a common problem among the elderly. People suffering from undiagnosed REM-sleep behavior disorder and other forms of parasomnia often experience worsening symptoms of temporary forgetfulness with age.
Poor quality of sleep in the elderly leads to the loss of memory. The older adults have less deep sleep than younger population which also means that they have worse memory functions as well. They experience worsening symptoms of dementia unless they receive medical care for their sleep-related problems.
Age-related memory loss can occur due to the worsening quality of sleep. As people grow old, the quality of their night’s rest decreases. Young adults experience better rest than the elderly on any given day.
Early studies state that REM sleep is necessary for the creation of declarative memory. However, more recent research shows that the memory formation remains constant in people who do not experience REM sleep.
One study by Matthew Walker, a UC Berkeley sleep researcher shows that the non-REM stages of slumber facilitate the production of slow waves from the frontal lobe. This part of the brain deteriorates as we grow old. A majority of the senior population suffers from the lack of restorative sleep due to the depreciation of the structure of the middle frontal lobe which prevents the permanent storage of memories at night.
Another study conducted by a group of researchers from Germany showed that better sleep can be achieved through stimulation of the brain, especially its middle frontal lobe. A deeper resting state through electric stimulation improved the formation of memory during the night.
Both studies have opened up new areas for research on age-related dementia and pointed to the possible treatments for memory loss in the elderly. They put forth key findings that illustrate the mechanisms of overnight memory formation and their direct relationship with sleep quality.
What Can You Do to Improve Your Memory at an Old Age?
We need to invest in our health while we are still young by adopting healthy sleeping habits and consulting a sleep expert if you have any problems with your sleep. This will improve and preserve your memory as you age.
Several studies show that white noise and pink noise help us fall asleep. White noise consists of different frequencies of sound. It has a fixed amplitude throughout the entire audible frequency. Therefore, you can find it in nature, in factories and even in traffic.
The sea, rain, crickets, washing machine, air conditioning units, and even an aircraft interior are sources of white noise. Even a continually rotating fan without any creaking is a source of it. Other than that, you can always download free applications on your smartphone for enjoying relaxing white noise before falling asleep.
Older adults, as well as newborns, can enjoy the benefits of white noise during their phase of rest. It calms the cognitive system and stimulates better sleep.
On the other hand, pink noise is exclusively beneficial for the elderly. It is a collection of soothing, soft sounds. Each octave belonging to this sound category possess equal energy.
A study by Dr. Phyllis Zee and his colleagues involved 13 older adults between the age of 60 and 84. They subjected the senior participants to acoustic simulation during one night and fake simulation during the other. These simulations were seven days apart. The acoustic simulation was pink noise, and the team synced this simulation to their brain wave as the volunteers slept.
Each session involved two memory recall tests, one after and one before the resting periods. The memory recall was much better after the participants had enough of a quality night’s sleep. Pink noise stimulated rest resulted in three times the average improvement. The improvement of the memory recall was a result of the enhanced quality of the slow wave sleep (SWS).
Acoustic simulation is a smart way to improve sleep quality at an old age and it doesn’t have any side effects. While sleeping medication can always pose some physical or mental health risks in the elderly, pink noise does not have any negative impacts. Many researchers are thinking of adopting pink noise as a long-term solution to insomnia and parasomnia.
How Can You Improve Your Memory Function With Regular Sleep?
This brings us to the favorite part of this article, where we tell you to get more sleep. Sadly, less than one-third of the American adults get enough rest each night. Most of them need at least one more hour of rest than they get right now.
The lack of rest can take a significant toll on the memory functions. Several studies showed that children who had had the chance to get enough sleep on the night before the exams performed much better than those who didn’t get enough rest. The hours of preparation did little to help when the brain was in a state of easy excitability.
Another interesting study shows that getting enough sleep helps people memorize new skills. For example, while you are learning how to play the piano getting the right amount of rest will help you turn everything you learn into more permanent skills. If you take a short nap of 30 to 40 minutes right before your next piano lesson, you should be able to learn the next lesson much better.
Most people who tend to memorize things fast are great sleepers. Sleep is the key to a brilliant memory. If you compound the time of your nighttime rest, you might have to study or practice way less than you do right now.
What Happens When You Choose to Call It a Day?
Right before bedtime you should shut down your laptop, turn off the sound on your phone, use some relaxing essential oil and switch off the lights. It will help you set the mood and prepare yourself for the sleep you deserve. Your brain might remain in a state of high activity, but you need to prepare yourself for a quality restorative sleep.
Clean the Trash
The cerebrospinal fluid circulates through the brain more effectively during your sleep. Think of it like a vacuum cleaner mechanism. Not cleaning the waste including the molecular debris and toxic protein deposits can worsen symptoms of dementia. When you are fast asleep, the CSF acts as a vacuum cleaner which removes these toxins so you can wake up refreshed.
Picking Important Memories
Have you ever noticed how stress impacts your memory? When you are under a constant stress you may often struggle to remember certain things, like where you put your home keys and whether you locked the front door, etc. The lack of sleep takes a toll on trivial memories and more emotional ones like your first date, your first kiss or your child’s graduation.
It Helps Regulate Your Circadian Rhythm
When you sleep, your brain regulates everything. It transfers the episodic memory from the neural cortex to the hippocampus. Sound sleep helps process the melatonin as high levels of melatonin that remain in your body after you wake up can cause excessive daytime sleepiness (EDS) that can impede your cognition and productivity.
Ensures a Complete Stage 4 Sleep
Sleeping correctly at night ensures a complete stage 4 sleep. This stage of rest stops the nerve impulses that relay across the spinal cord. This causes temporary paralysis which protects you from acting out while dreaming and from possible injuries.
Keeps Your Body Healthy
Your body requires sleep to refresh the purification and filtration mechanism. Rest not only helps with memory function and cognition, but it also helps improve the outputs of different organ systems. Proper rest boosts the immune system.
How Can Napping Make You Smarter?
Adults often do not have enough time for 8-hour slumbers. We barely catch 5 to 6 hours during the week, and we try hard to make up for the lost rest on the weekends. But, sleeping longer during the weekends can’t make up for the sleep deprived days.
So what should you do? According to the latest research, people should spend at least 20 to 30 minutes per day napping. Since almost 85% of the mammals are polyphasic sleepers, it is not difficult to switch to a biphasic (siesta) routine, when you have the time. Very few offices have the facility to promote nap hours. Some corporate offices in Japan and the USA are introducing nap rooms for their employees to increase their productivity.
Research shows that napping can stimulate the REM sleep and non-REM deep sleep you are missing at night. That’s why nappers are smarter and more productive that compulsive workers who deprive themselves of necessary rest. Sir Winston Churchill, JF Kenndy, Napoleon, Ronald Reagan, Albert Einstein, George W. Bush, and Thomas Edison valued afternoon naps and were known for their napping rituals.
There are three different napping systems:
- Planned napping – You pick a fixed time for heading to bed in the middle of the afternoon (preferably around 2 pm). You set the alarm for 2:30 or 3:00. It is a great way to gain extra energy, especially when you are sure that you will go to bed later than usual.
- Emergency naps – These are genuinely urgent, and you need them when you think you are about to drop. You might feel super tired due to a late-night party or due to the flu season. These naps can help you recharge your batteries before an important event and prepare you for the upcoming challenge.
- Routine napping – Think about children who always doze off at a particular time during the afternoon. For adults, napping can be a part of the daily routine as well. If you make it a habit of dozing off for an hour or so after lunch every day, you can become a habitual napper. It helps regulate the circadian rhythm and is necessary for those suffering from insomnia or delayed sleep onset syndrome.
A short nap is beneficial. Always stick to a maximum 30-minute nap. Prolonging the resting period during the afternoon or evening can impede your sleep onset at night.
To improve the quality of your sleep and naps you will need a good mattress and if you don’t have one, you can check out our top 10 best mattress reviews and pick a perfect mattress for you.
Why Should You Care More about Your Sleep Quality?
The lack of deep sleep can impact your social life, health and finances. Research shows that the effect of sleep deprivation is similar to that of alcohol. Driving while being sleep-deprived is equally dangerous as driving under the influence of alcohol or some psychoactive substance.
People often go through their entire days feeling fuzzy when they do not get enough sleep for a few nights. But, people fail to understand that the fatality from sleepiness-related car accidents is close to that of DUIs.
Apart from promoting your consciousness, sleep improves your memory. If you tend to forget details about your coursework, office work or your family, it might be the result of sleep deprivation. Several studies have linked the lack of sleep to the early onset of Alzheimer’s and Parkinson’s.
Getting enough restorative rest during the night can delay the onset of almost all neurodegenerative diseases. Senior citizens, who get proper rest at nighttime often have a better memory than those who don’t.