Lucid Dreaming
Out-of-body experiences: what the neuroscience has managed to reproduce
A sensation of floating above your own body, seeing yourself from outside. It can be induced by electrical stimulation of a specific brain region, and by a rubber hand and two paintbrushes.
Out-of-body experiences — the sensation of being located outside one's physical body, usually above it, often looking down at it — are reported by roughly 5 to 10 per cent of the general population at some point, with higher rates in specific circumstances.
They occur during sleep paralysis, during near-death and critical illness, in epilepsy, in migraine, under ketamine and some other drugs, during extreme fatigue, and spontaneously in healthy people. The phenomenology is consistent enough across these very different triggers to suggest a common mechanism.
The brain region
The clearest evidence comes from Olaf Blanke's group in Geneva and Lausanne.
In 2002 they reported a patient undergoing electrical stimulation mapping before epilepsy surgery. Stimulation of the right angular gyrus, at the temporoparietal junction, reliably induced out-of-body sensations — the patient reported seeing herself lying in bed from above. Lower stimulation intensities produced sensations of sinking or falling, and of distorted body parts.
The effect was reproducible, dose-dependent and localised. Subsequent lesion and imaging studies have converged on the same region.
The temporoparietal junction is where visual, vestibular, proprioceptive and tactile information is integrated into a coherent sense of where the body is and that it is yours. Disrupting that integration disrupts the sense of embodiment.
Hide a participant's real hand, place a rubber hand in view in a plausible position, and stroke both with paintbrushes in synchrony. Within a minute or two, most people report the rubber hand feeling like their own — and show a physiological stress response when it is threatened.
Blanke and Henrik Ehrsson independently extended this to the whole body, using video goggles showing a participant's own back from behind while their chest and the projected image were stroked in synchrony. Participants reported feeling located in the projected body. Body ownership turns out to be a construction from multisensory input, and it can be reassigned in a laboratory in minutes.
The sleep connection
A substantial proportion of spontaneous out-of-body experiences occur at sleep onset, on waking, or during sleep paralysis.
This makes sense. Sleep paralysis involves REM atonia with waking consciousness — the body's motor output is blocked and proprioceptive processing is altered while the person is aware. The vestibular-motor cluster of sleep paralysis phenomenology includes exactly these sensations: floating, flying, falling, and separation from the body.
The overlap with the lucid dreaming literature is substantial. Techniques for inducing wake-initiated lucid dreams and techniques described in out-of-body-experience manuals are, in practical terms, frequently identical — lie still, remain aware through sleep onset, pass through vibrations and paralysis. The difference is interpretive rather than procedural.
Researchers including Jason Braithwaite have argued that many reported out-of-body experiences in healthy populations are best understood as a variety of sleep-related experience, and that the same individuals report higher rates of other anomalous sleep phenomena.
Near-death experiences
The most contested context, and the one where the stakes are highest.
Reports of leaving the body during cardiac arrest, observing the resuscitation, passing through a tunnel toward light, encountering deceased relatives, and reviewing one's life are consistently described and cross-culturally reported with some variation in content.
Physiological explanations have been proposed for individual elements: cerebral hypoxia and hypercapnia; a surge of neural activity documented in the dying rat brain and, in a small number of human cases, in EEG recordings during withdrawal of life support; endorphin release; ketamine-like NMDA receptor effects; and temporoparietal disruption for the out-of-body component specifically.
The AWARE studies, led by Sam Parnia, attempted to test veridical perception directly by placing visual targets in resuscitation areas that would only be visible from above. Across the published work, no patient reported seeing a target — though the number of patients who both survived and recalled an experience while in a room containing a target was very small, which limits what can be concluded either way.
How to hold this
The out-of-body experience is unambiguously real as an experience. It is vivid, it is consistent across contexts, and people who have had one are frequently profoundly affected.
The neuroscience has demonstrated that the felt location of the self is a construction, that the construction depends on multisensory integration at the temporoparietal junction, and that it can be disrupted by electrical stimulation or by a paintbrush and a rubber hand.
What has not been demonstrated is any perception of the environment that could not have been obtained through the ordinary senses. That is the claim that would distinguish an out-of-body experience from an altered sense of embodiment, and despite repeated attempts, it has not been established.
Which leaves a phenomenon that is genuinely fascinating for what it reveals about how the brain builds a self, and considerably less mysterious than the interpretation usually attached to it.
