Consciousness during sleep: what science describes, and what is pure speculation

The body rests, but the mind keeps working. It's from the gap between those two facts that the video "What happens when you sleep?", from the channel Mistérios do Universo, takes off. It claims that, during sleep, the brain creates landscapes, encounters, and events, sometimes as emotionally charged as waking life. From that observation, the channel moves into speculation: sleep would be a portal to other dimensions.

This piece separates what the video presents as scientific fact from what is spiritual or philosophical interpretation. The second part isn't accepted by neuroscience, and the first, for its part, has gaps the video doesn't fill with sources.

What science describes

REM sleep, the phase where the most vivid dreams concentrate, is also called paradoxical sleep precisely because the brain shows fast, desynchronized waves, similar to those of wakefulness. In this phase, regions tied to attention and emotional processing, such as the amygdala, the cingulate cortex, and the thalamus, become active. The video cites this intense activation in areas of emotion and imagery.

On why dreams are forgotten, the channel repeats a common neuroscientific explanation: low activity in the hippocampus, a region tied to memory, would make it harder to fix what was dreamed. It also says the brain processes time differently during sleep, and that subjective time in lucid dreams, those in which the dreamer realizes they're dreaming, follows no fixed pattern. Lucid dreaming is now studied by universities and is described as a trainable cognitive skill.

Open questions remain, which the video lists: why some people report dreaming of future events, how out-of-body experiences arise, and how a dream can feel like it lasted years in just minutes.

Where interpretation begins

From there, the video suggests consciousness isn't confined to the brain and can, during sleep, move through other spheres. Reports of astral projection, the sensation of leaving the body, lucid dreams, déjà vu, and premonitory dreams are read as evidence of this. Tibetan Buddhism and Vedic Hinduism are cited as traditions for which the waking world would be just one more layer of reality.

On time, it proposes that consciousness, while sleeping, operates outside linearity, in a field where past, present, and future coexist. It says some quantum physics theories suggest this, without naming them. Forgetting dreams appears as a protective mechanism: remembering everything could blur the line between waking life and imagination.

Out of the body, DMT, and Monroe

In discussing astral projection, the video mentions Robert Monroe, the American businessman and sound engineer who popularized the topic with his 1971 book Journeys Out of the Body, and claims there have been later confirmations of unfamiliar environments seen during projections. It also says the brain releases small amounts of DMT, a psychedelic substance associated with visionary states and near-death experiences, during sleep.

Neither claim is settled science. DMT is, in fact, synthesized by the human body, but there's no conclusive answer about its function, nor about which organ produces it, and the idea that the pineal gland produces it at moments like sleep is a hypothesis. The video doesn't cite sources for the supposed confirmations.

Are we awake?

The final question gives the video its weight: on waking up, are we truly awake, or just emerging into another layer of the dream? It's an old doubt, one the channel links to Descartes and to the fourth-century-BCE Chinese thinker Zhuangzi, known for the butterfly parable: upon waking, he didn't know whether he was a man who had dreamed of being a butterfly, or a butterfly dreaming of being a man.

The video concludes that sleep would be a journey of the soul, a daily chance to explore hidden dimensions. Science describes in ever-greater detail what the brain does while the body sleeps; where the mind goes, or whether it goes anywhere at all, remains a question for philosophy and belief.