“ Out - of - body experiences , ” dreams , and REM sleep

An out-of-body experience (OBE) is characterized by the sensation of leaving the physical body and functioning independently of it. Such sensations also occur during some lucid dreams. Some authors aver that OBEs and lucid dreams are completely different phenomena. The present investigation tested an explanatory model of OBEs as a form of dreaming similar in nature to lucid dreaming. Study 1 consisted of scored content analysis on 107 lucid dream (LD) reports verified by eye movement signals during REM sleep. Ten LD reports (9.3%) from 5 of the 14 subjects qualified as OBEs. LDs initiated from brief REM awakenings were significantly more likely (4.4 times, p<.02) to be judged as OBEs than LDs initiated during uninterrupted REM sleep. Study 2 was a survey of 604 subjects assessing the frequency of reported OBEs and dream phenomena. Frequent OBE reporting was related to frequent reporting of dreams and dream-related events; frequency of OBE reporting was significantly lower than lucid dream reporting, and similar to that found in the laboratory in Study 1. These studies support the close association of OBEs and lucid dreaming. REM sleep and states favorable to OBEs share the feature of high CNS arousal under sleep or sleeplike conditions. Such states are conducive to the generation of somatosensory hallucinations interpretable as the experience of rising “out-of-body.” The discussion highlights the importance of semantic interpretations of such experiences, and presents a three-part model for analyzing “metachoric” experiences such as lucid dreams and OBEs. Further discussion considers the role of cortical activation in the generation of OBEs and lucid dreams. The conclusion argues that all states of consciousness, sleeping or waking, derive from the same basic brain functions, which act to model the world based on perceptual maps. OBEs, dreams, and the reality experienced in the waking state are all mental constructions, and further efforts in consciousness research may benefit from avoiding an arbitrary distinction between sleeping, dreaming and waking states. OUT-OF-BODY EXPERIENCES AND DREAMS 2 An “out of body experience” (OBE), is characterized by the perception that one’s locus of awareness has separated from the physical body(1). According to surveys, 5-35% of people report having had an OBE at least once in their lives (2). OBE-type events have surely been part of the human experience for time immemorial. Nineteenth century occultists are responsible for the first known attempts to place these experiences within a theoretical framework. The original occultist formulation of the OBE held that human consciousness can separate from the body and travel in nonphysical realities, so-called “astral projections” (3, 4; for historical reviews see 5, 6). Later authors modified the theory, asserting that the discorporate consciousness was capable of traveling in the physical world (7, 8). Contemporary scientific thinkers consider OBEs to be complex hallucinatory experiences (2, 9). The consistency of phenomenology (10) across experiences and individuals suggests that a common set of events underlies the OBE. To the occultists and the naïve thinker, the literal interpretation of consciousness leaving the body is the commonality. For the model of the OBE as an hallucination to have explanatory power requires postulating a specific set of internal events common to individuals experiencing OBEs. Potential sources of the predilection to have OBEs are: personality, psychopathology, mental or physical trauma, or a natural extension of ordinary psychological processes. The data presented here support the latter idea. A number of writers have proposed that OBEs are evidence of psychological dysfunction. For example, Freud wrote that OBEs are hallucinations resulting from infantile complexes, and other authors have suggested that OBEs occur as defense reactions to guilt, stress, grief, or as a symptom of psychopathology (11, 12). The DSM-IV (13) includes out-of-body feelings (“...a sensation of being an outside observer of one’s mental processes, one’s body, or parts of one’s body”) within the diagnostic criteria for depersonalization disorder (p. 488). However, there is little indication of any substantial correlation between psychopathology and OBEs. Gabbard and Twemlow (14) compared measures of psychological adjustment in people who reported OBEs with those from various other groups, including psychiatric patients. They concluded that the OBE group represented “a very close approximation of the ‘average healthy American.’” (p. 31) More recent neurocognitive theories offer an alternative to literal and pathological explanations of OBEs. Blackmore (1, 2) and LaBerge (15-17) have suggested that OBEs can result when real-time sensory input from the external environment and body is lost and is replaced by internally generated perceptual constructs. In support of this model is a growing body of data describing perceptual and cognitive “maps” operating at multiple levels of the central nervous system (18-20). Activation of these maps could support conscious, perceptual and cognitive activity in the absence of sensory input (21). This would explain how the mind can create fully realistic perceptions of a “out-of-body” body and an external world in circumstances in which conscious cognition persists despite the loss of externally provided sensory data. As discussed below, this theory additionally explains the typical phenomena at the initiation of an OBE and the sensation of lifting out of the physical body. The juxtaposition of consciousness and diminished sensory input is not a rare event. It occurs several times a night in normal REM sleep. In this state, the sleeping mind creates vivid sensory experiences without data from external environment or the sleeper’s body, and the dreamer thinks about and acts upon these perceptions (22). In fact, the perceptual aspects of OBEs and dreams are similar in the sense of being what Green and McCreery OUT-OF-BODY EXPERIENCES AND DREAMS 3 term “metachoric experiences” (9), “in which the normal perceptual environment is entirely replaced by a hallucinatory one, which may on occasion be a convincing replica of the world of normal perception” (p. 56). As further elaborated below, the mechanisms underpinning OBEs and dreams are likely to be the same as those responsible for normal conscious experience, thus accounting for the extraordinary verisimilitude to waking reality described in reports of OBEs and dreams (23). A primary difference between typical dreams and OBEs is that the world perceived in a dream is not usually a representation of the sleeper’s current physical environment. This may be one reason why many people say that OBEs feel more real than dreams (14). The reason for the continuity of experience in OBEs is likely to be the direct transition from normal perception of the external environment to a state of dissociation from sensory input, without an intervening period of unconsciousness such as usually occurs in sleep. Other common aspects of the experience include “electrical” sensations, vibrations, loud rushing sounds, and a feeling of heaviness or bodily paralysis that precedes the feeling of “leaving” the body(4, 14, 24, 25). These strange sensations are remarkably reminiscent of descriptions of a phenomenon observed by sleep researchers, referred to as “sleep paralysis.” Sleep paralysis generally occurs during sleep onset, particularly under conditions of sleep deprivation, when one is more likely to enter REM sleep directly from waking. The individual is usually in bed, (except in the notable case of narcolepsy in which the sudden onset of catalepsy during waking activity is a classic symptom of the disease) (28). As the individual falls asleep, the skeletal muscle atonia of REM sleep manifests and is perceived consciously, while the sleeper maintains continuous conscious cognition (26). Again, no state of diminished awareness such as non-REM sleep has intervened between waking and sleep. To an observer, the person appears to be asleep, yet the sleeper’s experience is of being awake but paralyzed and, in some cases, experiencing unusual auditory, tactile, or visual perceptions. Everett (27) collected descriptions of sleep paralysis from a group of 52 medical students (an excellent population for the study of sleep deprivation!), eight (15%) of whom reported having had the experience. The subjects reports included phrases such as, “I feel completely removed from myself,” “feeling of being separated from my body,” “eerie, rushing experiences,” hearing “hissing in the ears,” and “roaring in the head.” Fear was also a common component of the subjects’ paralysis experiences. The parallels between the phenomena suggest that at least some OBEs arise from conditions similar to sleep paralysis, and that the two terms may actually be naming different aspects of the same phenomenon. Corroboration of this hypothesis comes from investigation of the circumstances in which OBEs occur. Because there is no clear subjective transition between waking and sleeping during sleep paralysis, subjective reports are not always helpful in determining if an OBE has occurred during sleep onset. Lack of awareness of entering REM sleep would lead the sleeper to believe that subsequent events occur in the waking state. However, the literature also supplies indirect clues in the form of information on what percentage of OBEs arise in states potentially conducive to sleep and sleep paralysis, for instance, while resting or lying down. In one survey, 85% of people claiming to have had OBEs said they had occurred during resting, sleeping or dreaming (29). Other surveys also showed that the majority of OBEs happen when people are in bed, ill, or resting, with a smaller percentage associated with being drugged or medicated (1, 30, 31). OUT-OF-BODY EXPERIENCES AND DREAMS 4 Not all OBEs occur during sleep or sleep onset. Some people who can deliberately induce OBEs appear to do so in hypnagogic or auto-suggested trance states (32), and OBEs no doubt arise in other states of consciousness as well. Nonetheless, certain essential features may be characteristic of all states in which OBEs occur. Among these are likely to be: loss of proprioceptive input from the body and visual and tactile input from the external environment, as these sensory modalities locate our awareness in space; continuity of conscious cognition during the period of loss of sensory input; and profound muscular relaxation or paralysis leading to a sensation of heaviness in the physical body. Muscular relaxation similar or identical to the atonia of sleep paralysis can occur during hypnosis and following anesthesia (33, 34), and profound relaxation also may be sufficient to reduce proprioceptive input. Intense focus of attention (as in hypnosis) or psychoactive substances (such as dissociative anesthetics) can attenuate exteroceptive sensory input. Several studies have examined whether those who report OBEs are also more likely to report dream-related phenomena, such as lucid dreams (dreaming while knowing one is dreaming), falling and flying dreams, and hypnagogic imagery (24). Eight of ten of these studies showed a significant positive relationship between the reported frequency of lucid dreams and OBEs. Blackmore found a statistically significant association between an individual’s claim of having had OBEs and high reported frequencies of hypnagogic imagery, falling dreams, flying dreams, false awakenings and dream control (willful alteration of the events of a dream) (1, 29). Glicksohn (35) found that individual OBE incidence correlated positively with the incidence of hypnopompic (but not hypnagogic) imagery, flying dreams, falling dreams, the ability to discontinue dreams, and lucid dreams. Thus, there is a background of evidence supporting a relationship between the tendency to experience OBEs and a variety of dream-related phenomena. The studies discussed here support a specific relationship between REM sleep and OBEs. These studies derived from an observation that arose in the context of research on lucid dreaming. In a laboratory study of the onset of 76 lucid dreams from 13 subjects, approximately 10% of the lucid dream reports collected included descriptions of events such as lying in bed, feeling strange bodily sensations (often vibrations), hearing loud humming noises, and rising “out of body” to float above the bed. The study, which utilized LaBerge’s eye-movement signaling methodology to mark the time of lucidity onset (16, 36, 37) revealed that lucid dreams have two modes of initiation. In the more common variety, the “dream-initiated lucid dream” (DILD) the dreamers acquired awareness of being in a dream while being fully involved in it. DILDs were initiated in a state showing all of the physiological signs of REM sleep: suppressed muscle tone, low-amplitude, mixed-frequency EEG, and intermittent burst of rapid eye movements (38). DILD-type lucid dreams accounted for 72% of the signal-verified lucid dreams. In the other 28%, dreamers reported awakening from a dream and returning to the dream state with unbroken awareness—one moment they were aware that they were awake in bed in the sleep laboratory, and the next moment they were aware that they had entered a dream and were no longer perceiving the room around them. Entry into these “wake-initiated lucid dreams” (WILDs) shared many features of sleep paralysis (17). A preliminary examination of the dream content and physiological records suggested that OBE-type dream content was more common in WILDs. Study 1 was a test of this hypothesis by retrospective analysis of the data set just discussed. OUT-OF-BODY EXPERIENCES AND DREAMS 5