system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do people only sneeze when awake?
gpt
During REM sleep (the phase where dreams take place), your muscles are paralysed so that you don’t thrash around and hurt yourself. This paralysis extends to reflex muscle contractions, so you can’t sneeze while you are dreaming. In non-REM sleep your muscles are free to move again but the trigeminal motor neurones responsible for triggering a sneeze are still suppressed. It is just about possible to sneeze during this non-REM sleep, but the exertion will normally wake you up.