“What role might sleep play in supporting memory function?”
Ever wondered why we sleep? Scientists still aren’t 100% clear on the answer. But it must be really important – why else would we have evolved to spend hours each day in a vulnerable, unconscious state? There are a few theories on the role of sleep, and a key one is that it supports memory function. This essay reviews the main hypotheses about how sleep does this.
I found this essay quite difficult. One major challenge was that I spent so long reading about this fascinating topic that I ended up with 55 A4 pages of notes. So when I tried to turn all my thoughts into 1500 words, I couldn’t possibly convey all the ideas I wanted to! I submitted the essay feeling quite dissatisfied (not to mention a little annoyed at myself).
Another challenge was that I found that reading loads of information about sleep actually made me feel really sleepy! And the studies I found seriously encouraged me to give in to the temptation to have a nap every few hours to ‘consolidate my learning’…
Despite these two major challenges, I managed to scrape a first class mark by the skin of my teeth. I celebrated with an early night.
(If you fancy jumping straight into the real thing instead, just keep scrolling…)
- Sleep is really complex. Far from just being either ‘asleep’ or ‘awake’, humans have different stages of sleep: rapid-eye-movement (REM) and 3 stages of non-rapid-eye-movement (NREM) sleep. The sleep stages are really quite different – both in terms of the electrophysiological patterns and neurochemicals found across the brain, and in terms of when each stage occurs during the night. The essay argues that if we really want to understand the role sleep plays, we need to study the role of these different characteristics.
- Sleep plays a role in consolidation of memories. When memories are first created, they’re quite fragile, and easy to forget. Memories become stronger through a process called consolidation. There’s evidence to suggest that sleep actively plays a role in this.
- Scientists have been trying to figure out how the different sleep stages play a role in memory consolidation. This has led to 3 key hypotheses:
- The dual-process hypothesis says that NREM and REM consolidate different types of memories. There’s some studies suggesting this could be the case, but lots of contradictory findings too.
- The sequential hypothesis says that NREM and REM play a complementary role, and need to occur in sequence for memories to be consolidated. There’s some evidence supporting this idea, but few studies have tested it directly.
- The active system consolidation hypothesis says that, during sleep, new memories are re-activated and transferred from short-term memory stores to longer-term memory stores. This hypothesis is compelling because it takes into account the characteristics of specific sleep stages, but further work is needed to test it.
- It’s not yet clear exactly how sleep supports memory function! Different studies report different findings. This, in part, might be because the methods used to study sleep aren’t perfectly accurate, and ignore the full complexity of sleep stages.
- There’s lots more to understand about the mystery that is sleep…
If the essay looks too science-y, but the summary has whet your appetite, you might be interested in these:
- ‘Why we sleep’ – a book by Professor Matthew Walker (a sleep scientist). Written for the general public, this describes the challenges of our modern attitude to sleep, and the benefits of getting a good night’s kip. Prof Walker argues that sleep is more important for our health than diet and exercise. Crikey. I wonder whether he also struggled to stay awake when he was writing it…
- A clip from one of my favourite TV shows, BBC’s QI, where they briefly discuss some of the theories of sleep and what the latest view is. Sleep’s role in memory function is an example of what Sandi describes as the brain needing to do some activities ‘offline’ – “think of it as a house party… you can either entertain the guests or clean up the house, but you can’t really do both at the same time”. (Warning – they do get quite off-topic…)
If you’re up for the full essay, read on…Read More »