The feeling of brain fog that comes after a poor night’s sleep is familiar to most of us. But did you know that lack of sleep can affect your long- and short-term memory and that a good night’s sleep is key to retaining information and making new memories?
The different phases of sleep
Every night, we cycle between two phases of sleep every 90 minutes: rapid eye movement (REM) sleep, and non-rapid eye movement (NREM) sleep. During the first part of the night, we experience more NREM sleep in each 90-minute cycle. As the night progresses, the cycle changes to include more REM sleep and less NREM sleep.
The brain is highly active while we are asleep, organizing thoughts and memories and doing general cellular housekeeping in each brain cell. Non-REM sleep includes different phases of deep, slow-wave sleep. During deep sleep the heart rate slows, and brain waves become synchronized, as if all the brain cells are working in unison. The brain waves shift memories from short term storage in the hippocampus area of the brain, into longer term storage in the cortex.
During REM sleep, the brain focuses on integrating these new experiences with older ones already in storage. This is when new memories are consolidated in the mind. Dreams are part of this process and reflect the brain’s efforts to organise all this information.
How does lack of sleep affect memory?
Missing out on sleep in the first part of the night means experiencing less of the slow-wave deep sleep that is part of NREM sleep. This can affect your ability to process new information and skills that have been learned that day. Waking up too soon disrupts REM sleep, and the ability to integrate new information into memory structures.
For example, if you go to bed at 11pm and normally wake at 7am you will have enjoyed a full 8hrs sleep. However, if you wake at 5am you have lost 25% of your normal total sleep, a greater proportion of which is REM sleep that influences your ability to embed new memories and strengthen neural connections.
Sleep tips to boost memory
Try these simple sleep tips to support your memory:
- Give yourself the opportunity for 7-9hrs sleep each night
- Go to bed as early as you comfortably can, to enjoy more NREM sleep. The adage “an hour before midnight is worth two after” is true when it comes to supporting your memory!
- Ensure your sleeping space is as dark as possible and well aired. Use blackout blinds if you have streetlights outside your window and open the window during the day to air the room.
- If you find yourself waking in the early hours to use the bathroom, use low level lighting rather than switching on a main light. Bright light signals the brain to stop producing melatonin, the sleep hormone.
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
Walker, M. 2017. Why We Sleep London: Penguin Random House.