What do out-of-body experiences tell us about the brain?
BBC Focus Magazine September 2017, pp 70-75
Note – this is the draft version I sent to Focus. It was then edited and illustrations added.
Have you ever felt as though you were lifting up out of your body, floating near the ceiling and looking down on the world and your own body below? If so, by definition, you’ve had an out-of-body experience, or OBE. This definition is the kind scientists studying OBEs use, and is important because it defines the OBE purely as an experience. If you feel you are out-of-body that’s an OBE. This leaves open to research the big question; does anything actually leave the body in an OBE? If it doesn’t we have to find out why OBEs happen and what is going on in the brain. If it does, the implications are profound. If someone could truly leave their body then mind or consciousness must be able to exist beyond the brain and even potentially survive death. If this were so, much of science as we know it would have to be overthrown.
Most people who have OBEs are, at least briefly, convinced that their soul or spirit or astral body has really gone travelling because the experience is so realistic. About twelve to twenty per cent of the population in many different countries have had the experience at least once, with a very few expert OBErs able to induce it at will. Although the experience can happen at any time, when walking, washing up, or even riding a bike, most OBEs occur when people are relaxed and lying down. Some happen on the verge of sleep, especially in combination with sleep paralysis – that unpleasant feeling of waking up unable to move. A few happen on the verge of death as part of the near-death experience. But why?
Until recently the most common explanation was ‘astral projection’, an idea developed in the late nineteenth century as part of Theosophy, a scheme loosely based on Hindu and Buddhist teachings that involved seven ‘bodies of man’, ranging from the gross physical body right up to higher spiritual bodies. In between is supposed to be the ‘astral body’, a subtle vehicle of consciousness that can separate temporarily during life and permanently at death – leading to eternal life after death.
In the twentieth century psychical researchers and parapsychologists tried, but failed, to detect astral bodies using psychic mediums or a variety of physical instruments. They set up ESP experiments to test whether OBErs could see targets placed in distant rooms, but no convincing results were ever obtained and OBEs remained a dubious topic for research on the fringes of the paranormal.
Then with the turn of the century everything changed. In a hospital in Switzerland, neurosurgeon Olaf Blanke was carrying out a tricky operation on a woman whose severe epilepsy could not be treated unless the focus of her frequent seizures was found. To locate it, an array of electrodes was positioned under the dura, the strong membrane surrounding her brain, so that different spots could be electrically stimulated. She could remain awake throughout because there are no pain receptors in the brain itself. To the surgeon’s immense surprise, when he gently stimulated a spot near the right temporo-parietal junction [I could explain here where that is or we can have an illustration to explain], his patient described sensations of falling and sinking, as well as bodily distortions; with stronger stimulation she was floating near the ceiling. Repeating the process her OBEs could be repeatedly elicited and controlled. As the famous paper in the journal Nature declared, ‘The part of the brain that can induce out-of-body experiences has been located.’
You might think this proves that OBEs are a perfectly natural phenomenon, requiring no spirits, souls or astral bodies, but some disagree – arguing that this special spot is the place from where the astral body leaves, or the spot through which God communicates with our consciousness. To provide a better explanation we need to know what this part of the brain is doing. The answer is that it constructs our sense of self. Right there at the TPJ, our ‘body schema’ is maintained. This is a detailed and constantly updated model of our whole body that is essential for us, as for any other animal, to keep track of where we are and what we are doing. Closely related to the body schema is our body image, our rich sense of personality and appearance. At this crucial junction point, information flows in from the senses and from memory to construct a rich sense of who we are, including our sense of inhabiting and owning our own body, and being able to control it.
Now the surgeon’s discovery begins to make sense. If the body schema is disrupted by electrical stimulation it would fail to track properly what the body is doing and so might drift from the body’s actual location. This would explain the peculiar distortions; getting larger or smaller or limbs growing and shrinking. These sensations occur not just with direct intervention in the brain but on the verge of sleep, with some drugs and before spontaneous OBEs. With more serious disruption the body schema might completely split in two and this, researchers have suggested, is the cause of the OBE.
This gives a rather bleak account of OBEs, attributing them to ‘failed integration at the TPJ’ or a ‘break-down of body processing’. So are OBEs a sign of something wrong, or even of mental illness? Although there are some links with pathology (see Box) the evidence says no. Researchers in the USA gave an extensive questionnaire called the ‘Profile of adaptation to life’ to several hundred OBErs and found them to be as healthy as, or even more healthy than, the average American; a study in the UK compared a small group of patients with schizophrenia to a control group and although the schizophrenics reported more bizarre experiences of various kinds, the two groups included the same number of OBErs.
A more positive way to understand OBEs fuels a recent debate between those who think they represent a failure and others who say they reveal a skill. The earliest psychological theories suggested that imagery might be the relevant skill but many experiments showed no obvious differences in richness or vividness of imagery. Some small differences were found in the ability to switch viewpoints, for example between imagining a scene from eye level or from a bird’s eye view, and OBErs were found more often to dream in bird’s eye view. These were clues leading to recent research showing the relevance of what is called ‘perspective taking’. This is the ability to see things from someone else’s point of view and is related to empathy. Interestingly this ability also depends on areas of the brain close to the TPJ. So it may turn out that OBEs, far from being a failure are linked with the important social skill of being able to understand someone else’s perspective.
It is early days for serious OBE research but now it has begun we may find that an experience that was once dismissed as fantasy and ignored by mainstream science is now contributing to our understanding of consciousness and the nature of self.
Boxout: Could you have an OBE?
Almost anyone can have an OBE but certain characteristics make it more likely. One is ‘psychological absorption’. Scoring high on this measure means you are easily engrossed in films, books or music, ignoring everything else around you. You may be susceptible to hypnosis, have a rich fantasy life and remember having imaginary playmates as a child. Another is ‘positive schizotypy’. This sounds as though it’s related to schizophrenia and in a way it is. The idea is that everyone lies on a continuum from low to high schizotypy. High schizotypes have unusual dissociative experiences, disorganised thoughts, flat emotions and unstable moods, but are more imaginative and creative too. They include many writers, artists and poets, as well as OBErs. A third indication is ‘temporal lobe lability’, meaning the brain’s temporal lobes are more unpredictable or unstable. Labile types not only report more OBEs but more lucid dreams, sleep paralysis, visions, and hallucinations.
These connections have been known for some time but a new discovery is revealing more about the underlying brain function. OBErs react differently to the ‘pattern glare task’. Look for a minute at the pattern of black and white stripes [note – I may need to change the wording slightly depending on the image included]. If you see just black and white stripes, that’s fine. But if you are susceptible to pattern-glare the stripes will jiggle and shift, with strange shapes and illusory colours drifting across the stripes. In this case you are more likely to have OBEs.
This test is thought to reveal cortical hyper-excitability, meaning that those who see the illusions have more easily excitable brains. Hyper-excited visual systems produce tunnel experiences, excited auditory systems produce the whirring and grinding noises associated with sleep paralysis, and when our vestibular systems go wild we feel floating and flying. In other words, this tendency to excitation leads to classic OBEs.
Boxout: Out-of-body in Virtual Reality
Can you imagine becoming convinced that a pink, rubber hand is your own? Unlikely as it seems, this is the famous ‘rubber hand illusion’. The person’s own hand, lying next to a rubber hand, is concealed from view and if both are stroked simultaneously in exactly the same way people start to feel the touch as though it is on the rubber hand.
Now a similar ‘whole body illusion’ has been created using virtual reality. Neuropsychologist Bigna Lenggenhager and her colleagues in Zurich place cameras two meters behind participants. They wear head-mounted displays, so they are looking at their own backs, and when the experimenter gently strokes their back they can watch as well as feel it. Gradually the sensation shifts towards the virtual body and they may feel they have moved closer too.
In Sweden, neuroscientist Henrik Ehrsson uses a different method. Cameras are again two metres behind but this time Ehrsson strokes participants’ chests in synchrony with a stick moving up and down in front of the cameras. With this method people feel they have moved backwards towards the cameras. These may be just tricks but their effects can be profound. When the illusion is strong, body temperature drops, pain is felt less intensely and threatening the real body with a knife produces weaker reactions.
The illusions have even been induced inside an fMRI scanner, revealing just one region where changes in activity reflect changes in self-location. That is the TPJ – the same area discovered by Blanke’s stimulation.
These illusions are not the same as full OBEs but they do reveal how our usual sense of being inside our own body is a feeling that can be manipulated. And this may explain how we can sometimes be convinced that we are outside our body.