You’re lying there, staring at the ceiling, and then—click. You’re gone. One second you're thinking about that weird thing you said to a coworker in 2019, and the next, you’re essentially a paralyzed ghost in your own bedroom. Most people think of sleep as a "blackout" period, like turning off a computer, but that’s a total lie. Your brain is actually screaming with activity. When you ask where do we go when we fall asleep, you aren't really asking about a physical location, but a massive neurological migration.
The truth is, you don't go anywhere. You stay right there, but your consciousness gets hijacked by a series of chemical gates that slam shut. It's honestly a bit terrifying if you think about it too hard.
The Thalamus: The Physical Gatekeeper
Think of your brain like a busy hotel. During the day, the lobby is wide open. People (sensory inputs like sight, sound, and touch) are rushing in and out constantly. But the moment you start nodding off, a specific part of your brain called the thalamus starts acting like a very aggressive bouncer.
The thalamus is the relay station. It decides what information reaches your cerebral cortex, the part of you that actually "knows" things. When you fall asleep, the thalamus stops passing along the outside world. This is why you can sleep through a car driving by or a bird chirping, but your brain might still let a loud bang through if it thinks there's a threat. You haven't left your room; your brain has just pulled the curtains and locked the door.
Dr. Matthew Walker, a neuroscience professor at UC Berkeley and author of Why We Sleep, describes this as a "sensory blockade." It’s the first step in the journey of where do we go when we fall asleep. If this gate doesn't close properly, you get stuck in that weird "half-awake" limbo where every tiny noise makes your heart race.
The Glymphatic Wash
While you’re "away," your brain is actually doing the dishes. This is a relatively recent discovery in the world of sleep science. For decades, we didn't really know how the brain got rid of waste because it doesn't have a traditional lymphatic system like the rest of the body.
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In 2012, researchers at the University of Rochester identified the glymphatic system. When you hit deep sleep, your brain cells actually shrink by about 60%. This creates more space between the cells, allowing cerebrospinal fluid to rush in and flush out metabolic "trash," specifically a protein called beta-amyloid. That’s the stuff linked to Alzheimer’s. So, when you’re wondering where you went, you’re basically in a biological car wash.
Entering the Dreamscape (REM)
This is where things get trippy. About 90 minutes into the night, you enter Rapid Eye Movement (REM) sleep. This is the "where" most people are interested in.
In REM, your brain activity looks almost identical to when you’re awake and drinking a double espresso. Your heart rate goes up. Your breathing gets ragged. But you’re paralyzed. Your brain stem sends a signal to your muscles to go limp so you don't actually try to fight that giant squirrel you're dreaming about. This is called REM atonia.
Why Dreams Feel Like Reality
Ever notice how dreams have zero logic but you just roll with it? Like, you're at your high school, but your teacher is a literal house cat, and you're just like, "Yeah, that makes sense."
That happens because your prefrontal cortex—the logical, decision-making part of your brain—is basically powered down. Meanwhile, the amygdala (the emotion center) and the hippocampus (the memory center) are firing like crazy. You are essentially experiencing a state of "controlled psychosis." You are "going" into a world of raw emotion and uncurated memory, without the "logic filter" that usually keeps you sane.
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The Misconception of "Dead Time"
We spend about a third of our lives asleep. If you live to be 75, you've spent 25 years in this "other place." It’s easy to feel like that’s wasted time, or that sleep is just a passive state of recovery.
It’s not.
Sleep is an active cognitive process. During the "where" of sleep, your brain is performing memory consolidation. It’s moving information from short-term storage (the hippocampus) to long-term storage (the cortex). It’s like moving files from a cluttered desktop to a secure hard drive. If you don't go "there," the files get deleted. This is why pulling an all-nighter before an exam is usually a terrible idea; you’re literally preventing the "saving" process from happening.
Stages of the Journey
- N1 (Light Sleep): That "falling" sensation (hypnic jerk) happens here. You're still partially in the room.
- N2 (The Bulk): Your heart rate drops. Your body temperature falls. You spend about half your night here.
- N3 (Deep Sleep): This is the restorative stuff. This is where the tissue repair and the glymphatic cleaning happen. If you wake up here, you feel like a zombie.
- REM: The dream world. The emotional processing.
What Happens When the "Where" Goes Wrong?
Sometimes, the transition between being "here" and being "there" gets messy.
Take sleep paralysis, for example. This happens when your brain wakes up, but the REM atonia (the muscle paralysis) hasn't switched off yet. You’re conscious, but you’re still "gone" in terms of physical control. It’s a glitch in the system. People often report seeing a "shadow person" or a "demon" sitting on their chest. It’s just your panicked brain trying to make sense of why you can't move while you're still half-dreaming.
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Then there's somnambulism (sleepwalking). This is the opposite. Your body is "here" and moving, but your consciousness is still in a deep N3 sleep state. You aren't dreaming during sleepwalking; you're basically operating on autopilot without any "self" behind the wheel.
The Science of Dreaming of the Future
There’s a lot of talk about "prophetic dreams" or "astral projection" when people discuss where do we go when we fall asleep. Science doesn't really back up the idea of your soul leaving your body.
However, there is evidence that dreaming is a form of threat simulation. Evolutionary psychologists suggest we "go" to these stressful dream scenarios to practice how we’d react in real life. It’s a VR training simulation for survival. If you dream about your teeth falling out or being naked in public, your brain might just be processing social anxiety and preparing you for "social survival."
Real Insight: Sleep is Subjective
Interestingly, your experience of "where you go" depends heavily on your age. Infants spend about 50% of their sleep in REM. They are basically living in a dream world because their brains are growing at a terrifyingly fast rate. As you get older, your deep sleep (N3) starts to drop off. This is why older adults often feel like they don't sleep as well; they aren't "going" as deep into the restorative layers as they used to.
Actionable Steps for a Better "Trip"
Since you’re going to spend a third of your life in this state, you might as well make sure the transition is smooth. You can't force yourself to "go" to sleep, but you can invite it.
- Fix the light: Your brain produces melatonin (the "it's time to go" signal) when it's dark. Blue light from your phone mimics the sun and tells your thalamus to stay wide open. Turn it off an hour before bed.
- Cool the room: Your core body temperature needs to drop by about 2 to 3 degrees Fahrenheit to initiate sleep. If your room is a sauna, your brain will stay in the lobby all night. Aim for around 65°F (18°C).
- Don't "try" to sleep: Sleep is an act of let-go, not an act of will. If you’re lying there frustrated, you’re triggering a stress response (cortisol) that keeps the "gate" locked. If you aren't asleep in 20 minutes, get out of bed, go to another room, and do something boring in dim light until you feel sleepy.
- Consistency is king: Going to bed and waking up at the same time—even on weekends—anchors your circadian rhythm. It makes the "where do we go" question much easier for your brain to answer because it knows exactly when the bus is leaving.
The mystery of sleep isn't about some far-off dimension. It’s about the incredible, violent, and messy biological renovation that happens inside your skull every single night. You don't go anywhere, but in a way, you become someone else for a few hours. And that’s probably for the best.
To improve your own nightly transition, start by auditing your evening light exposure and sticking to a rigid wake-up time. Your brain's internal "gatekeeper" thrives on predictability, and the better you manage your environment, the more restorative your time "away" will be.