Before you are even fully awake, your heart is racing.
You wanted to take a brief “power nap,” not to fall into a deep slumber. Before you gather the nerve to look at the clock and see how much time you've wasted, you consider the schedule gymnastics you'll have to perform now because of the sleep mishap. It's not going to be pretty.
But when you look, only a few minutes have passed. All those dreams, the entire world your subconscious built, was erected and demolished in a relative blink of an eye.
This is a temporal quirk in the part of sleep known as hypnagogia, when the brain makes its clumsy transition between wakefulness and sleeping, when all sorts of weird stuff happens. It’s also a state of mind tied to other times when humans are on the precipice between the unconscious and the conscious—even life or death.
So, what goes on during this eerie state? A 2015 investigation by Cambridge researchers explains the hallucinatory feeling of hypnagogia like so:
The complexity and intensity of hypnagogic imagery can range from vague and fleeting impressions to fully formed images or even hallucinated dreams, and the most common forms of hypnagogic images are visual, auditory, and bodily experiences. […] [O]ther types of hypnagogia may include awareness of sleep onset, distorted perception of space, and time, as well as linguistic alterations.
This process is not always benign. The hypnagogic state's also responsible for the “invisible presence” felt during episodes of sleep paralysis, recently brought into the mainstream with the documentary The Nightmare. Its cousin “night terrors,” meanwhile, occurs in a deep REM phase of the sleep cycle.
Hypnagogia is also the state in which lucid dreaming, that moment when the dreamer becomes aware of the state they're in and takes control of the wheel, can occur. In 1985, Stanford professor Stephen LaBerge published the first scholarly treatise, Lucid Dreaming, wherein he spends an entire chapter explaining the strangest quirk of lucid dreaming, the out-of-body experience:
A person having an OBE may for example find his sense of identity apparently associated with a second, non-physical body—a “soul,” “astral body,” “spirit,” or, to suggest a term having a certain charm, “out-of-body body” (OBB)! Equally, while “out-of-body”, one may entirely dispense with the inelegance of bodies of any sort, and experience oneself as a point of light or a freely mobile center of awareness.
These OBEs are also a trait of another piece of neurological weirdness: Near-death experiences (NDE).
Defined in 1975 by Raymond Moody, NDEs are “any conscious perceptual experience which takes place during an event in which a person could very easily die or be killed, but nonetheless survives, and continues physical life.” That seems fairly straightforward but what actually is felt during these NDEs where things get freaky. There are white lights, and tunnels, and communing with the dead. But also among Moody's list of 15 “common elements” that recur in adult NDEs are “hearing unusual noises” and “being 'out of body'.” And there we have our overlap.
Lucid dreams, which occur in the hypnagogic state we all experience, occasionally features the feeling of being outside of one's body. And near-death experiences feature these same feelings of being outside of one's body. So, is there a relationship between the two?
Kevin Nelson, professor of neurology at the University of Kentucky, believes so. In a 2011 interview with the Guardian, Nelson points towards a common element that links all near-death experiences together—the fact they're occurring to a person that's just almost died. That kind of stress can play havoc on one's body, and brain. “If blood flow to the brain is threatened in some way one of the brain's crisis reactions has to do with a consciousness switch,” Nelson told the Guardian. “What we found in subjects who've had near-death experience is that instead of moving smoothly from waking to REM consciousness, their brain switch is more likely to blend these two conscious states together.
If Nelson is correct, and NDEs occur because of a short circuit in the brain, and we can know which area is short-circuiting, well, the effect can be replicated in the lab. And, it has. In 2002, Olaf Blanke at the Laboratory of Cognitive Neuroscience in Switzerland reproduced the feeling of OBEs by using specifically-placed electrodes to disrupt temporal pariental regions in the brains of study participants. Essentially, Blanke flipped a switch and the participant felt as if they were out of their body.
So, case closed? We found the component that can be tweaked and NDEs are somehow connected to our normal sleep cycle? Well, not entirely.
“All the evidence I've seen is that Kevin Nelson is wrong,” said David Hufford, professor at Penn State College of Medicine, who's been studying sleep paralysis since the 1970s. “There is no significant connection between sleep paralysis and near-death experiences. For starters, phenomenologically they don't look anything alike.”
What he means is that while some aspects of the two experiences may take part in the same area of the brain, there are enormous differences in the emotional content of each state. “Sleep paralysis is accompanied by a threatening figure in the room,” said Hufford. “They hear footsteps, it comes over, it presses on them, it makes them short of breath, stuff like that.” This is in pretty direct conflict with the quite pleasant feeling that comes after someone experiences NDE. (In fact, Moody's list of 15 NDE elements also includes “feelings of peace and quiet,” “experiencing a realm of bewildered spirits,” and “elimination of fear of death.”)
Perhaps more damning is that various studies have shown there's no correlation between the people who experience sleep paralysis and the people who have NDEs. If both events were caused by the same body processes, there should be some level of crossover in the people experiencing them. But, according to Hufford, there is none, which pokes holes in Nelson's theory that NDEs being caused by a breakthrough from the sleep cycle.
To Hufford, suggesting a link between NDEs and sleep isn't an inconsequential mistake, but rather a huge misstep with important ramifications. “I have a missionary zeal about this because the psychiatric stigma attached,” said Hufford. “It's very important we start to have a more intelligent attitude towards NDEs.” It’s important, he continued, to not to just call people who claim to experience this “crazy” as a way of ignoring their stories. When it comes to pinpointing what is going on between conscious and unconscious states, humans can’t seem to fully wake up.