They are linked to multisensory and cognitive processing in the brain
"I was in bed and about to fall asleep when I had the distinct impression that I was at the ceiling level looking down at my body in the bed. I was very startled and frightened; immediately (afterwards) I felt that I was consciously back in the (body on the) bed again."1 Out of body experiences, as described by a person here, are characterised by a location of the self (or one's centre of awareness) outside one's body, an impression of seeing the world from an extracorporeal elevated perspective, and an impression of seeing one's own body from this perspective.1-3 They are striking phenomena because they challenge the experienced spatial unity of self and body—or the experience of a real me that resides in one's body and is the subject of experience and action.4 5 Recent neurological evidence shows that these experiences are related to an interference with the temporo-parietal junction of the brain.
A better understanding of out of body experiences might further our scientific concepts about self and body and their experienced spatial unity. These have been influenced by diverse fields such as theology, philosophy, and psychology as well as neurology and psychiatry.1-7 Out of body experiences occur in about 10% of the population, most of the world's cultures, and several medical conditions.1-3 To date only few scientific investigations have been carried out on out of body experiences, probably because they generally occur spontaneously, are of short duration, and happen only once or twice in a lifetime.1 2 Investigations of neurological patients with out of body experiences are also rare, but they have several advantages. Out of body experiences in these patients might occur repetitively, sometimes in short succession, allowing for more detailed questioning of the experiences and associated sensations shortly after they occur. Moreover, researchers can analyse the associated neurological, causative, and anatomical findings.
Some clinicians have observed out of body experiences in association with various neurological conditions, but mainly in epileptic seizures and migraine.6 7 These early reports have also allowed us to link out of body experiences with deficient visual, vestibular, and multisensory processing.7 More recently, the importance of vestibular and multisensory mechanisms in out of body experiences was underlined by their occurrence in several patients with such experiences.3 In addition, vestibular illusions (of elevation, rotation, flying, lightness) and multisensory illusions (of visual limb shortening and movement) could be evoked by electrical stimulation of the same cortical area where higher stimulation currents induced out of body experiences.8 These data indicate that vestibular illusions, multisensory illusions of body parts (such as visual shortening and movement of limbs and phantom limbs9), and multisensory illusions of the entire body (such as out of body experiences) might share similar functional and anatomical mechanisms.3
Devinsky et al described several patients with out of body experiences caused by circumscribed brain damage and found that lesions predominantly affected the temporal lobe.6 More recently, our team analysed the lesions of several patients with out of body experiences and found that the temporo-parietal junction was affected in all patients.3 These patients had epilepsy and migraine. On the basis of these findings, our team proposed a cognitive model for out of body experiences, proposing that they are related to a failure of integration of proprioceptive, tactile, and visual information of one's body (personal space).3 This may lead to the experience of seeing one's body in a position (that is, on the bed) that does not coincide with the felt position of one's body (that is, under the ceiling). In this model disembodiment and elevated visuospatial perspective during out of body experiences are assumed to be related to additional vestibular dysfunction.3 In summary, the neurological evidence shows that out of body experiences are related to a disintegration within personal space (multisensory dysfunction) and a disintegration between personal space (vestibular) and extrapersonal space (visual) due to interference with the temporo-parietal junction.
In science the most challenging phenomena are often the ones we take for granted in our everyday lives. Excellent examples are the perception of the self and the experienced spatial unity between self and body. As argued by others, both folk psychological notions are challenged by out of body experiences.4 5 The reviewed evidence from neurological patients experiencing this striking dissociation between self and body shows that out of body experiences are culturally invariant phenomena that can be investigated scientifically.
The study of the self by neuroscience is in its infancy with no established models, very few data, and often not even the vocabulary to describe notions of the self.10 The investigation of out of body experiences and related mechanisms at the temporo-parietal junction might thus allow us to improve our neuroscientific models of self and corporeal awareness. Although many other cortical areas are involved in self processing, recent neuroimaging studies indicate a key role for the temporo-parietal junction. This is not only true for out of body experiences but also for many aspects of body and self processing, such as the integration of multisensory bodily information, the visual perception of the body, the perception of biological motion, and the distinction between self and other.3 11 12
The experimental investigations of these multisensory and cognitive mechanisms in out of body experiences and related illusions, in combination with neuroimaging and behavioural techniques, will further our understanding of the central mechanisms of self and corporeal awareness—much as previous research was successful with respect to understanding the central mechanisms of phantom limbs.9
Olaf Blanke, professor
Laboratory of Cognitive Neuroscience, Ecole Polytechnique
Fédérale de Lausanne, CH-1015 Lausanne, Switzerland (firstname.lastname@example.org