An even balance of REM, deep and light sleep is most likely within the healthy range, provided you are getting enough sleep in total and feel rested throughout the day. Memory consolidation happens in all stages of sleep to a degree, so you’re covered.
Your individual sleep architecture
Everyone has a unique blend of the time spent in each stage of sleep; it’s really a personal thing. The most important factor is how rested you feel after waking and throughout the day. If you find yourself catching up on sleep on the weekends, this is a sign your current sleeping schedule isn’t sustainable or truly adequate to meet your body’s needs.
Sleep spindles and memory
Memory consolidation does happen during light sleep and is associated with sleep spindles, bursts of activity in the brain that first appear during Stage 2 sleep. Spindles in sleep may be a measure of intellectual ability, which is one of the best excuses we’ve ever heard to take an afternoon nap [LO1]
Different memories, different sleep stages
However, memory consolidation also occurs in REM sleep and deep sleep. There are two broad types of memory, declarative and procedural. Different sleep stages appear to be associated with the processing of different kinds of memory:
- Declarative memory, which is about facts and personal experiences, may be processed more strongly in the first half of the night when we spend most of our sleep in deep and light sleep stages.
- Procedural memory, on the other hand, is about processes and skills – how to do things. Procedural memory appears to become more of a focus in the second half of the night, when we spend more time in REM mixed with light sleep
- In addition, hormones may play a big role in memory processing. Throughout the night, levels of the hormone cortisol increase, which appears to help with overall memory processing during sleep.
- Finally, dreaming of a particular task may make a difference in future performance. This 2010 study found that subjects who dreamed of a maze had better recall compared to those who napped but did not recall a dream.
So while many non-sleep factors influence the memory formation process, each sleep stage does play an important role as brain transfers information from short-term to long-term memory.