What Do You Hear While Sleeping?
A 2016 study took a close look at how the brain processes sounds while you’re sleeping. They found that during light sleep, such as during short naps or when you’re first falling asleep, you are still processing the things you’re hearing. You can even hear and process words that you hear while you’re in light sleep.
EEG readings of sleeping participants showed that during light sleep, the participants’ brains were still responding to words, and were continuing the verbal recognition tasks they started when awake. They were able to hear and process new words even while sleeping!
As you transition into deep sleep, however, you stop processing external sounds. And that’s not all. When you’re in deep sleep, your night’s rest may even erase from memory whatever sounds you heard when you were in light sleep. Once the participants transitioned into deep sleep, their brains stopped processing words. The brain started ignoring the external sounds and began resting deeply.
When participants transitioned to REM sleep, they still didn’t seem to hear the external sounds, even though they had increased brain wave activity. During REM sleep focus stays inwards, and participants focus on their internal dreams rather than on outside sounds.
