Sleep After Reading: Sleep’s Role in Memory Formation
In 2018 I saw my favorite band twice, driving from Phoenix to Las Vegas for one, and Los Angeles for the other. What strikes me about them is my memory from each show, more specifically the lack thereof for the second. After sleeping less than six hours and waking up early in the morning to make the drive to Las Vegas, I still have a vivid memory of the show. For my trip to Los Angeles, I am unable to recall many details of the show despite significantly more sleep the night before and regular start time to my day. In Matthew Walker’s Why We Sleep; Unlocking the Power of Sleep and Dreams, I realized the vital impact sleep has on memory, and why my memory of each experience varies so drastically.
Short Term Memory
During sleep, the brain creates proteins in the hippocampus where memories are formed during the day. When sleep deprived going into the day fewer memories will be able to be formed, and the ones that are will be weaker leading to them being forgotten more quickly in the days following. While these memories are formed and stored temporarily in the hippocampus, during sleep electrical pulses can be found going between the hippocampus and the neocortex, where our long term memories are stored. Not only does this store memories in a more permanent way, but it also clears out the hippocampus to generate new memories the next day.
Sleep before and after learning or an experience is important, but it can be easy to decrease the hippocampus’s ability to create new memories during an extremely long day, especially when lacking sleep the night prior as well. When deciding to stay up the extra hour to study, you are weakening the memories of what you have already learned, and are less likely to remember the next items well. In many situations, it becomes beneficial to sleep and better retain what has been covered up to that point.
Sleep Quality
From the onset of constant lighting and temperature control, large consumption of caffeine and medications, many aspects of modern life aren’t conducive to a good night’s sleep. Getting enough sleep can be critical to the storage and integration of memories, but sleep quality plays just as important of a role and one of the most common and biggest disrupters of quality sleep and the formation of memories is alcohol. Walker explains a study where students learned a new topic, and those who drank that night before staying sober the rest of the week only retained 50% of the information taught compared to those abstaining all week. The integration of memory is not just a one-night event though, as students who only drank on the third night after learning were able to recall just 60% of the material.
While non-rapid eye movement sleep sees the activity between the hippocampus and neocortex storing memories, it is rapid eye movement sleep that replays these memories in the mind while integrating them with prior knowledge, which is why dreams may seem related to both prior and distant memories. Alcohol suppresses rapid eye movement sleep, so the day’s memories are not integrated with other experiences in the mind, making it weaker memory and harder to recall. What isn’t stored in the neocortex completely, or at all, stands a high chance of being completely forgotten as memories in the hippocampus can only be retained for so long.
Subconscious Memory
While getting quality sleep regularly is critical to remember what we learn, the timing of our sleep with when we learn might be just as important. In his research, Walker found that those who learned a memory-based task shortly before sleep showed better memory and performance of it twelve hours later than those who were taught in the morning and similarly tested after twelve hours, with no sleep in between. This is due to the memory moving to the neocortex, which processes many of our subconscious activities as well as stores memories. When recalling the task during the day it is a purely conscious action to recite, while after sleep it can become partially subconscious, enhancing the ability to recall and perform the task.
When things can be done subconsciously, it takes no effort to recall, uses no willpower, and there is often less room for error. All of these are beneficial to remembering something specific and is the same way humanity has continuously improved as economist Friedrich Hayek concluded: “Civilization advances by extending the number of important operations we perform without thinking.” By being more intentional about getting enough sleep, more of what we learn throughout the day can be integrated into our subconscious memory, freeing us to focus on and learn new items in the future.
Sleep Well Beast
Here I realize my memory of the two shows, fittingly promoting an album called Sleep Well Beast, was not affected by my sleep prior, but to what happened after either show. In Las Vegas, I had a short walk back to my hotel, and about 16 hours after waking up I had fallen asleep. After the show in Los Angeles though, I made the six-hour drive back to Phoenix, arriving at sunrise some 22 hours after beginning my day.
From studying to memorable experiences, getting sleep soon after can help create better-integrated memories in the near and distant future to increase the ability to be recalled or performed subconsciously. The next time you see or learn something you want to better remember, you can assist yourself in the process by getting enough quality sleep shortly after.
Beyond the vital role sleep plays in the creation and storage of memories, it has far more effects on our daily lives as Walker highlights throughout his book, “Sleep is more than a pillar; it is the foundation on which [health and exercise] sit.”
Learn more about Matthew Walker’s work on sleep and its wide range of other implications at his website:
Evan Stufflebeam is a graduate student at West Texas A&M University pursuing a Master of Science in Finance and Economics and an alumnus of Arizona State University where he attained a Bachelor of Science in Finance and Certificate in Business Data Analytics.
