The Relationship between sleep & memories has been studied for over 100 years, in short Sleep is vital to memory consolidation.
The relationship between Sleep & Memory is an intricate one. A lot of research is going into the correlation between the two, but for now, this is what we know.
There are different types of memories. Fact-based, the name of Henry VIII’s wives. Some are periodical, based on events in your life. And some are procedural, such as how to drive a car or play the piano.
3 processes must happen for memories to stick:
- Acquisition – learning or experiencing something new
- Consolidation – the memory becomes stable in the brain
- Recall – having the ability to access the memory in the future
Acquisition and recall happen when you are awake. but it is believed sleep is essential for the consolidation of a memory, no matter what the type of memory.
It isn’t known exactly how sleep enhances memory, but it seems to involve the brain’s hippocampus and neocortex. The Neocortex is the part of the brain where long-term memories are stored. The Hippocampus is the part of the brain that is key to making new memories, it is thought that during sleep, the hippocampus replays the events of the day for the neocortex, and the thalamus (which controls the Neocortex) transmits cues from your senses to the cerebral cortex, which interprets and processes information from your memories. The thalamus is essentially inactive during NREM stages, but when REM sleep begins, it will relay images, sounds, and other sensations to the cerebral cortex that are then integrated into your dreams. Difficulty in remembering things is because the brain simply doesn’t get enough time to process this information. Sleeping before study or training helps to prepare your brain for the creation of memories while sleeping after study or training is like hitting the save button of the brain. You’re less likely to forget it.
The stages of sleep continue to be studied too. Some studies have shown that some memories become stable during REM sleep and other memories are most often consolidated during the 4th stage or Non-REM sleep.
The Non -REM stages of the Stages of Sleep are seen as the ones that prep the brain for learning, as it takes 90 minutes for a full cycle of sleep, you need to have good & efficient sleep, a lack of sleep can affect your memory by up to 40%.
Memories are fragile and we create them every second of the day, most will be forgotten, but the brain appears to process the events of the day & decide which ones are important enough to remember & which ones are discarded. It also decides which memories are strengthened.
Research has shown that memories of certain techniques, like playing the piano or learning new skills, can improve while you sleep. Which is incredibly helpful for athletes.
If the Non-REM Stages of sleep prep the brain for learning, then the last stage of sleep, the REM stage brings it all together by linking together the memories & information you’ve learnt. REM sleep also processes the emotional memories made, allowing for better mental and emotional health. So a full night’s sleep is key to problem-solving, it also might be why some ideas can come to you in your sleep!
Because sleep is so important to memory consolidation, some sleep disorders are associated with memory problems. Insomnia is known to reduce memory functioning & sleep disorders that lead to extreme daytime tiredness can cause memory lapses.
As we get older, our sleep patterns change & the memory-strengthening stages of sleep start to diminish up to 70% once we hit 60. Researchers are now studying options for improving deep stages of sleep in older age groups.