How memories and dreams come together to help us solve problems at night.
Ever wondered why sleeping on a problem can make the answer seem clear?
Now, sleep scientists think they have a plausible theory.
While we sleep our brains shuttle backwards and forwards between different types of sleep.
Two of these together may provide the key to how we can solve problems overnight.
So-called ‘non-REM’ sleep helps us organise information.
REM stands for Rapid Eye Movement and this is the part of sleep in which we dream.
‘Non-REM’, then, is the part when we are not dreaming — sometimes when we are in deep sleep.
Then, REM sleep allows us to make unexpected connections between different memories.
This could be the source of our nighttime Eureka moments.
Professor Penny Lewis, the study’s first author, explained:
“Suppose I give you a creativity puzzle where you have all the information you need to solve it, but you can’t, because you’re stuck.
You could think of that as you’ve got all the memories that you need already, but you need to restructure them — make links between memories that you weren’t linking, integrate things that you weren’t integrating.”
During non-REM sleep, the hippocampus — a part of the brain critical to memory — decides what memories to replay.
Then, during REM sleep, when we dream, the brain is free to replay stored memories in any combination.
Hence the jumble of juxtapositions we get while dreaming.
Next morning the answer pops into our heads, seemingly unbidden, but actually the result of serious memory crunching.
Professor Lewis said:
“So, what we propose is that, if you’re stuck on some kind of problem, that problem is salient, and we know that salient things are replayed.
The slightly hypothetical part is that, when something else is randomly activated in the cortex that has an element that’s similar, you’ll form a link.”
The study was published in the journal Trends in Cognitive Sciences (Lewis et al., 2018).
