or roommates may call annoying. An estimated two in three people talk in their sleep at

some point in their lives. But why do we do this

and who do we think we’re speaking to?

Many people think of sleep as the brain shutting

off. Curtains. Lights out. But our brains are actually quite active during slumber.

Throughout the night, we cycle through two types of sleep: Rapid Eye Movement, or REM,

and non-REM, which has three stages. As we move through each stage, our brain waves progressively

fall into lower frequencies and higher amplitudes until we reach deep, slow-wave sleep at stage

3. Sleep talk can happen at any point during

what scientists call “transitory arousal”, which is when a sleeper becomes half awake

while transitioning from one stage to the next. Interestingly, the quality of our speech

here decreases as we move closer toward stage 3.

After stage 3 we enter REM sleep. This is when our eyes rapidly move behind closed lids

and our brain activity becomes closer to how it is when we're awake.

There are two different structures in the brain that control when we’re awake and

when we’re asleep, sort of like a light switch. One is the Reticular Activating System,

or RAS, a complex network of neurons located in the brain stem. It releases chemical messengers

called neurotransmitters that promote wakefulness and help regulate our sleep-wake cycles. The

other system, the Ventrolateral Preoptic Nucleus, or VLPO, is located in the hypothalamus. It

releases neurotransmitters that bring on sleep by suppressing neural activity to the RAS.

During REM, the VLPO structure releases powerful neurotransmitters that work together to inhibit

motor neurons and prevent you from acting out your dreams of flying. Which ends up being

pretty useful, because most of our dreams occur during REM sleep, and they’re typically

more vivid. Any sleep talking that may accompany those dreams is related to the failure of

neurotransmitters in the VLPO to fully stop you from moving around.

This is what researchers call a “motor breakthrough.” Our mouth and vocal cords, usually inactive

during REM sleep, are briefly switched on causing us to sleep talk. And there’s

no telling what you might say. Everything from polite conversation to full-on monologues

have been reported! Sleep talking is also linked to the nervous

system being overstimulated by anxiety and stress. Alcohol, caffeine, and too much screen time

before bed can also have an effect.

Although a lot of us have talked in our sleep at some point in our lives,

overall it’s still relatively

rare. Even frequent sleep talkers may only talk every four nights or so and it might

just consist of only a few words. Up until now, people assumed that talking

to someone sleeping was about as productive as speaking to a log. But an international

team of researchers is trying to shift this notion by taking an interactive approach to

studying sleep. They’re using lucid dreaming, a state in which the sleeper is aware they’re

dreaming, to probe the slumbering mind. So far, they’ve found that lucid dreamers can

be trained to do simple math, answer yes-or-no questions, and even tell the difference between

sensory stimuli...all while in REM sleep! Perhaps one day, researchers will be able

to hear about our dreams directly from our nocturnal chit-chat. We could ask people questions

while they’re dreaming, coach them through nightmares, and be inspired by the wild surrealism

of the dream world. Now that’s what I call pillow talk!

Sleep experts say that a routine before bed can help you get a night of uninterrupted

sleep. And if you watch Maren’s video on how cerebrospinal fluid cleans the brain as

you sleep, you will understand why that’s so important! What’s the weirdest thing

you’ve ever said, or heard someone say while sleeping? Let us know in the comments below.

Make sure to subscribe and thanks for watching.