Out of Body Experiences and Multisensory Integration – by Don Alhambra

Don Alhambra is a research fellow in Neuroscience at the University of Birmingham, UK. He can be found mainly at the Heathen Hangout or the Heathen Hub.

“I am laying in bed at night and I fall asleep, but the room starts spinning really fast and there is a noise like a record being played too fast. Next thing I know I am looking down at my husband, my son and myself sleeping on the bed. Then I start floating through the house and checking to see if the doors are locked, and checking on my daughter asleep as well. I must say it is a bizarre feeling to see myself sleeping from up above myself! It doesn’t last very long because I start to realize I am “not awake” and I wake myself up and realize I was actually asleep in the first place. I don’t go out of the house when it happens because I am afraid I will not be able to get back to my body. This sometimes happens as many as 4 or 5 times a night and at least 3 days a week. I would like to get it under control and be able to “trust myself” to get back where I started from. Is this an actual OBE?”

This is a fairly typical report of a so-called ‘out-of-body experience’ (OBE) in which people claim that they have experienced the sensation of being outside of their bodies, usually looking down on themselves from above. Proponents of mysticism claim that these experiences are ‘proof’ that a separate, spiritual realm exists outside of the drab materialistic domain we inhabit day by day. More sceptical heads assert that these tales are simply dreams, illusions or hallucinations. But who is right? In this article I investigate the arguments of those who wish to lay claim to a paranormal explanation for these occurrences, and also see what mainstream science has to say about possible explanations. I don’t have space to cover absolutely all the ground, but I will attempt to rebut the most common pro-supernatural arguments and present data from both neuropsychological studies of phantom limbs and experimental studies that attempt to alter body representation (e.g. the rubber hand illusion) to support my case.

While there are sources that are relatively balanced when it comes to reporting and discussing OBEs it is impossible to search the Internet for ‘out of body experiences’ and not chance upon websites dedicated to a paranormal explanation for these phenomena. The central message of such websites seems to be that OBEs are caused by the ‘spirit’ actually leaving the physical body and travelling around the physical world. (What this ‘spirit’ is, of course, is anyone’s guess. Does the ‘spirit’ control attention, voluntary action, emotional responses, visual processing, movement, sexual excitement, all or none or a combination of the above? But I digress.) There are several arguments for this position, and I reproduce the most common below here.

The feeling of ‘realness’
People who have OBEs often report feeling that these experiences feel more real than when they are dreaming, even as real as they do when they are awake. Therefore, they argue, these experiences must be more than simply their own brains fooling them. Unfortunately this argument is flawed in a couple of ways. Firstly, this ‘hyper-realness’ is not exclusive to OBEs. It has been reported most commonly in dream research (a much maligned and thankless area of study, I must add) where researchers routinely wake up their participants at different stages of sleep to see what they are dreaming about.

Secondly, feelings of ‘realness’ do not automatically scale with the ‘reality’ of an experience. Virtual reality environments, for example motion simulators, exploit known laws of physics to fool the brain into thinking that it is on a rollercoaster ride when in fact it is merely being jerked around inside a box while watching a movie that exactly matches the twists and turns of the box’s movements. This illusion works because we are sensitive to changes in velocity and not to constant velocities, so once the rollercoaster appears to be moving at a constant speed, the box does not have to move at all to maintain the illusion. Actually, this comes straight out of Newton’s First Law, where a body moving at a constant velocity will continue to do so unless acted upon by an external force. Our brains have evolved and developed in a Newtonian world, after all.

Impossible experiences
There are many stories of hospital patients who have out of body experiences and feel themselves ‘floating’ above their body, looking down on it. Such people often claim that they can hear or see things outside their sensory range, and OBEs have even allegedly been experienced during brain death – one woman claimed to have experiences when allegedly clinically brain-dead. The most obvious explanation in this case of course is that she wasn’t actually brain-dead, because if she had been then she would not have recovered from the operation. Registering no vital signs is not the same as the tissue actually being dead, as the best we can do in these situations is to make measurements, and these measurements could easily be wrong. It is also suspicious that for all the vaunted ‘she had a flat EEG’ statements, no actual data is shown. As a scientist myself, if I want to know what you’ve done I’m not going to take your word for it. I want to see it for myself. Another important point is that the recall of the experience is going to be faulty, as memory is a slippery thing and the brain is very good indeed at making up memories to fit the facts, even if this happens accidentally (for a good discussion on this, see The Demon-Haunted World by Carl Sagan, chapter 4).

What about the stories of looking down on the room, being able to see things that would be impossible to see from a recumbent position? Unfortunately these stories are almost all anecdotal… and, as we all should know, “the plural of anecdote is not data” (a phrase with a sadly obscure origin, incidentally). The basic idea is clear: anecdotal stories cannot be relied upon for rigorous information about the world, because people are not only prone to bias and misinterpretation but also because there’s no way to tell which of two anecdotes carries greater weight. As an example of this, here’s a brief anecdote about the time my girlfriend was first diagnosed with narcolepsy and had several OBEs. They were happening fairly regularly; she would ‘feel’ herself as being above her body and was able to perceive the room in a sort of bird’s eye view fashion. As scientific then as she is now (she works in developmental psychology), she agreed with her sister that while she lay in bed, her sister would write a number between 1 and 100 on a piece of paper and place it face up on top of the bookcase high above the bed. The next time she had an OBE, she would then attempt to read the number. Needless to say, the number she thought she had read was wrong.

Seeing things from a different position from the one your eyes are in is a problem in itself. In order to perceive objects in the world, the reflected light from these objects must interact with the photocells on the retina. These cells then send impulses via the optic nerve to the visual cortex and beyond, where they are processed into a coherent percept. There are obvious biological problems with ‘seeing’ from a particular vantage point whilst being physically detached from any kind of light-sensing equipment. (This, incidentally, is the same problem that is often ignored in Star Trek episodes where the protagonists find themselves ‘outside’ of the ‘dimension’ their fellow crew members inhabit. They cannot be seen, but they are perfectly capable of seeing other things. Considering that photons are absorbed by the retina during their interaction with it, the clueless fellow crew members would expect at the very least to see a dark area in the air around eye level. And let’s not even get started on the problems with being able to walk through walls while not falling through floors… but I digress, again.)

Scientific approaches : the integration of sensory information
From the perspective of the materialist atheist such as myself, there is no spirit or soul inhabiting the brain or body, no homunculus sitting inside the pineal gland watching events unfold and making decisions, no dualist interpretation at all of the phenomenology of consciousness. There is merely a bunch of neurons, connected to one another in interesting ways. These neurons are responsible for all of our experiences: sensing the world around us, producing voluntary action, experiencing love, grief, joy, pain. Modern neuroscience has not yet answered all the extant questions as to how this feat is accomplished (and some modern philosophers hold that it never will and never can be accomplished; that is another debate), but we are getting closer every day. There are certain things we know about how the brain processes information, how it represents the world around us and how it represents the body in the world. This last is very important in our investigation into how the brain might produce OBEs.

Before answering the question of ‘how does our consciousness appear to float out of our bodies?’, it’s worth considering the processes that keep our consciousness seemingly in our bodies in the first place. In considering how this might be possible, first we need to think about how the brain gets information about the world. We have not five but (at least) seven senses: vision, audition, tactile sensation, olfaction, gustation, proprioception and the vestibular sense (those first five are seeing, hearing, touch, smell and taste by the way). The last two are the ones most people are unfamiliar with. Proprioception is the body’s position sense – using signals from the muscle spindles within the fleshy part of the muscle, the motor system can tell where a body part is without looking at it and without it touching anything. It’s not as accurate as vision, but it is an important sense to have when you’re looking in one place and doing something else with your hands, for example. The vestibular system consists of the semicircular canals inside the ears, which mostly deal with balance by acting as mini spirit levels. When you spin around quickly, the fluid in the ear canals continues to move after you’ve stopped, and this mismatch in visual and vestibular sensation causes the familiar feeling of dizziness.

So, the brain gets information from all these different modalities, and it is coming in pretty much continuously. In order to deal with the vast array of data flowing into the brain, some kind of integration process is necessary to make sense of everything. For example, let’s say you’re watching a video image of a person talking. You see the lips move on the image, and you hear sounds generated through the speakers of the computer. But it seems as though the sounds are coming directly from the mouth of the person in the video. The brain has integrated the visual and auditory information to create a percept of the sound coming from the mouth of the person on the screen. This is only to be expected, really – throughout our lives we have been trained to expect speech to come from people’s mouths, and the very slight discrepancy in the position is overridden by the brain’s insistence that the vision and sound come from the same source. Incidentally, this is also how puppeteers and ventriloquists make their inanimate props appear to ‘talk’.

What, you may be wondering, does this have to do with OBEs? Well, vision and audition aren’t the only modalities to combine in the brain. In order for the motor system to tell the arm to reach for an object, for example, it needs to know where the arm is first. More specifically, it needs to know where the arm is in relation to the object. The object will usually be located by vision and the position of the arm by the signals from the proprioceptive receptors in the joints. These two disparate sources of information must therefore be integrated somewhere in the brain before the appropriate motor command can be sent to initiate the arm on a trajectory toward the object. Of course, we don’t notice this integration process; to us, it just ‘feels like’ we have a body that we are able to control at will. The vast amounts of computing power required to do this are staggering, and smooth motor control based on visual input is still a huge problem in robotics.

Phantom limbs and rubber hands
Now we have an idea about how information is integrated in the brain, the obvious question with regard to out-of-body experiences is: can this process be disrupted somehow? There is ample evidence that it can. There are many different approaches to these kinds of problems in the study of the brain, from work with neurological patients to experiments on healthy participants. I am going to focus here on two major yet related strands in research into body representation, namely the rubber hand illusion, and phantom limbs.

Phantom limbs are experienced by almost all amputees in one way or another. Losing a limb is generally an extremely traumatic experience, and in the early days of amputation, amputees tended to keep quiet about the ‘sensations’ they felt from their missing limb for fear of being thought mad. But phantoms are an extremely persistent and common phenomenon. Usually the amputee insists that he or she can still ‘feel’ the limb, and that it can be moved into different positions voluntarily. In fact, mental control of phantoms is very important in early adaptation to prosthetics, as patients are often told by doctors to try to ‘put’ their phantom into the prosthetic so that they can control it as they would a normal limb. A recurring problem with phantoms is that they can often appear to ‘seize up’ and cause real pain to the amputee, who can feel sensations like nails digging into the palm of the hand. V.S. Ramachandran (author of the excellent book, Phantoms in the Brain) has had some success in treating phantom limb pain in single-limb amputees through the use of mirror boxes, where the remaining arm is reflected onto the other side of the body, therefore giving the visual system something to work with, and often causing the patient’s pain to subside.

And it’s not just amputees who have phantoms – there are reports that the phenomenon occurs in those born without limbs, who have never had any experience of moving their own limbs throughout their lifetime. (Whether these congenital phantoms are a hard-wired property of the brain’s motor control system or are somehow impressed onto the system through observation and imitation of others is still an open question.) What makes phantoms so interesting in this context is what their existence implies about the integration processes in the brain. Clearly, those who experience phantom limbs have no visual, proprioceptive or tactile input to the brain from their phantom. Yet, somewhere, a representation of the limb is still encoded in the brain to such an extent that the phantom appears to generate sensations and respond to commands! Thus, there appears to be a fundamental disconnect in this case between the actual body in the world and the brain’s representation of it. Can this disconnect occasionally lead to the phenomena we know as out-of-body experiences? Research into both phantom limbs and phantom bodies (led by Peter Brugger, a neuropsychologist specifically interested in these questions) suggests that it can, at least in neuropsychological patients.

Is there any way of changing how the body is represented in the brain in those with all their limbs and without brain abnormalities? There have been many strands of research that have explored this question, but I will discuss here one of the first and most successful: the rubber hand illusion. The basic idea is that the experimental participant sits down at a table, on top of which lies a rubber hand. They put their own hand behind a screen so that it is hidden from their view. Then, the experimenter begins to stroke the rubber hand and the participant’s own hand in a synchronous fashion. The illusion is more effective and can be maintained for longer if the stroking is unpredictable rather than rhythmic. After a couple of minutes of this, the participant tends to get the feeling that his or her own hand is actually the rubber hand! Clearly the brain is being fooled into thinking that if something is touching an effector (i.e. the participant’s own hand) at the same time as it sees something touch the rubber hand, then the effector must be the rubber hand.

The rubber-hand-like phenomenon has been addressed in a variety of different settings. One of my favourites is called the Pinocchio illusion, and follows from the observation that if the biceps tendon in the participant’s arm is vibrated at a certain frequency, the arm feels like it is extending even though it isn’t. Essentially, proprioception is disrupted. Now if the participant touches their finger to their nose and then the tendon is vibrated, the arm feels like it’s extending… and so does the nose. The brain is still receiving tactile information from the fingers and the nose, so it has the information about their relative positions. But if it thinks the finger is moving away from the stationary head, then the nose ‘must’ also be extending. Once again we can see how easily the brain is fooled into thinking that the body is a different shape or in a different place from usual.

Tying it all together
So, now we’ve seen that the brain’s representation of the body is by no means the sure and solid thing it appears to be. Before I finish, I want to talk about a couple of recent papers that follow on from the work I have already discussed. These papers were published in Science last year, and the first is a small study by Henrik Ehrsson. Building on the previous work with the rubber hand illusion, Ehrsson got his participants to wear video goggles linked to a camera placed behind them. Ehrsson began to stroke the chest of the participant at the same time as he stroked the chest of the ‘illusory body’ just below the camera, i.e. just below the participant’s viewpoint. The participants reported that their sense of ‘self’ had shifted – that they ‘felt’ they were outside their own bodies, viewing them from behind. In the same issue, Olaf Blanke’s group in Switzerland published an article on similar experiments with similar results: participants’ perceptions of where their bodies were located in space were found to shift towards the location of an illusory body.

I have not touched on other aspects of investigation into OBEs. For example, Blanke and his colleagues have actually induced out-of-body experiences and the feeling of their ‘self’ being in a different place in patients using direct current brain stimulation. These reports lend even more evidence to the idea that an OBE is nothing more than a glitch in the brain’s sensory integration system. The fact that people usually experience OBEs when lying in bed and drifting off to sleep, or under times of great stress like during operations, means nothing more than that it is at these times, when shutting down for the night or undergoing trauma, that the fragile integration of our sensory perceptions is most at the risk of being disrupted. There is, as ever, no evidence at all for anything supernatural going on – it is much simpler and makes far more sense to attribute out-of-body experiences to not yet completely understood sensory integration in the brain.

Further reading

For those interested further in disembodiment and the scientific case for naturalistic explanations of OBEs, I recommend the following books, websites and journal articles (if you have access).

Cline, A. (2006). Out-of-Body Experiences Induced Mechanically. atheism.about.com [accessed 26 Jan 2008]

Ehrsson, H.H. (2007). The Experimental Induction of Out-Of-Body Experiences. Science 317: 1048.

Giummara, M.J., Gibson, S.J., Georgiou-Karistianis, N. & Bradshaw, J.L. (2008). Mechanisms underlying embodiment, disembodiment and loss of embodiment. Neuroscience and Biobehavioural Reviews 32: 143-160.

Lenggenhager, B., Tadi, T., Metzinger, T. & Blanke, O. (2007). Video Ergo Sum: Manipulating Bodily Self-Consciousness. Science 317: 1096-1099.

Ramachandran, V.S. & Blakeslee, S. (1998). Phantoms in the Brain: probing the mysteries of the human mind. New York: HarperCollins.

Sagan, C. (1997). The Demon-Haunted World: Science as a Candle in the Dark. New York: Ballantine Books.


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