ELI5. Why are we able to move around, adjust blankets, and understand words when asleep, and then not remember anything when we wake up? Why can tell people to scoot over in bed and they do it, but they are still basically asleep?
In: Biology
When we sleep, particularly during lighter stages, our brain doesn’t shut down entirely. Instead, it operates in a standby mode, performing background processing. This partial alertness to our surroundings enables us to make minor adjustments, like moving in bed or fixing our blankets, without fully awakening. Our brain processes sufficient information for these small actions, yet it isn’t as actively engaged as when we are awake.
In deeper sleep stages, including REM sleep, the brain’s memory recording is notably reduced. During this time, it focuses on consolidating daily memories, sorting emotions, and bodily repair. Consequently, it doesn’t record trivial activities such as adjusting blankets or shifting in bed in response to someone else.
Moreover, in these deep sleep phases, the brain’s higher-order functions, responsible for complex decision-making and detailed memory formation, are less active. As a result, responses to external stimuli, like replying to someone or moving upon request, are typically automatic and rudimentary. It’s akin to the brain operating on autopilot, doing just enough to respond but not enough to fully engage or retain the interaction in memory.
Even when you’re asleep, your brain isn’t *competely* off (or you’d be dead).
Even asleep, your subsconscious brain is still humming away, and still controls your body – making little adjustments to keep you comfortable and warm. If you’re in a light enough sleep, it can even process simple verbal commands and follow them without ever bothering to rouse your conscious mind.
If anything, those responses become more automatic, because your conscious mind isn’t awake to analyse them for value. You just hear “move over” and your body moves over.
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