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Whilst it is not clear, yet, precisely what occurs during an OBE several ideas have been put forward to account for the pattern of reported behaviours. It would not be accurate to call them ‘theories’ in the strict sense that a theory allows for the development of clear predictions which in turn can be tested. Nevertheless, the ideas proposed can be grouped under the three broad headings of psychological, neurological and projection accounts.
Psychological accounts have attempted to explain the OBE in terms of reduced sensory input, a form of lucid dreaming, reliance upon an altered model of reality and the combination of dissociation and absorption.
Reduced proprioceptive input
Proprioception refers to the perception and movement of body parts, based on sensory information from those body parts. Proprioception is what allows you to know where your arms and legs are without having to look. As such, the idea here is that there is some change in proprioceptive feedback from the body which leads to a subtle change in body concept. This change in the perceived body concept was suggested to represent a threat to the individual’s sense of identity and as a result of this unconscious processes were assumed to be activated in an attempt to re-establish the individual’s sense of a coherent identity (Palmer, 1978). This approach appeals to Freudian descriptors relating to psychodynamics, possibly including fantasies and/or hallucinatory experiences, which may lead to a sense of self existing outside of the body which is what produces the OBE. Once the normal body concept has been reestablished the OBE comes to an end. There is only limited support for this idea based on the changes in body concept that occur during an OBE (e.g., Neppe & Palmer, 2005).
During a lucid dream the dreamer becomes consciously aware of the fact that they are dreaming and this conscious awareness provides them with a level of control over the content and nature of the dream itself. In addition, as with most dreams, sleep paralysis ensures that the physical body does not move and this can help to create the feeling of dissociation from the physical body. Indeed, LaBerge (1985) has suggested that OBEs may be similar to the lucid dreams that occur during the hypnogogic phase of sleep onset. The hypnogogic phase refers to the transitional state that takes a person from full conscious wakefulness to sleep. During this state individuals may experience sleep paralysis, lucid dreaming and subjective paranormal experiences (Holt et al., 2012). The idea that OBEs are lucid dreams gains some support from two areas. First, is the idea that OBEs often rely on lucid dreaming, or dream control, to elicit an OBE (Rogo, 1983), and second are the reported associations between those who experience an OBE and those who have lucid dreams (Irwin, 1985; Palmer, 1979). For instance, Palmer (1979) reported a positive correlation between the reported incidence of OBEs and lucid dreams. Poynton (1975) also found a clear increase in the number of reported OBEs as participants moved from simply being relaxed (16%), through dozing (20%) to sleeping (27%). Such changes were argued to be the result of a clear relationship between sleep, dreaming and the OBE state.
However, Rogo (1984) has argued that lucid dreams are simply a sub-type of normal dreaming and that they exhibit distinct psychophysiological profiles from those seen when an individual is undergoing an OBE. Others have also reported that whilst changes in the EEG can occur during the OBE they are not characteristic of normal sleep and dreaming stages (Blackmore, 2005; Twemlow et al., 1982). The possible relationship between lucid dreams and OBEs has also been questioned by Alvarado et al. (1999) who found no evidence of a link between OBEs and reports of lucid dreams. In addition, others have argued that in an OBE there is no clouding of consciousness as is commonly reported in dreams (Twemlow et al., 1982). Furthermore, OBEs are often reported as being more real than a dream in the sense that the individual feels more awake and aware and their experiences seem more vivid and real than those occurring whilst dreaming (see e.g., Alvarado, 2000; Blackmore, 1982). One suggestion put forward by Hurd (2016) is that the OBE may co-occur with certain sleep related phenomena such as lucid dreaming, sleep paralysis and hypnogogic hallucinations. Hence, there may be a common factor that underpins all these behaviours but at present the findings are not consistent with the idea that OBEs simply represent a form of lucid dreaming.
Altered model of reality
This idea is based on the assumption that the cognitive system works by creating multiple models of the world and at any time only one of these models is taken to serve or indicate the external reality of the world (Blackmore, 1984, 2005). In particular, one model is thought to relate to the body image of the individual and relies on the input of somatosensory, visual and other sensory input along with memory. If sensory input is either interrupted or inhibited, as may be the case in meditation or deep relaxation for example, then other pre-constructed models may come to the fore and take over. According to Blackmore (1984) this may rely on the cognitive system building a model that provides a best guess regarding what external reality is. Such a model will be influenced by memory and imagination and many memories are often built from a ‘bird’s eye view’ perspective and it may be this change in perspective that results in the feeling of being distinct from the physical body as well as providing the elevated viewpoint often reported in OBEs. Hence, the suggestion is that if the model based on sensory input is inhibited or breaks down in some way then a model based on memory and imagination takes over. It is the reliance on a model based upon a constructed imaginary world that leads the individual to incorrectly feel as though they are somehow distant and/or distinct from their physical body. Thus, according to this view, for an OBE to occur there needs to be an inhibition and/or failure of sensory input resulting in a switch to a model based on memory and imagination.
This view is to some extent similar to that put forward by Palmer (1978) in that both propose OBEs occur in part due to alterations in the body concept. Moreover, it may be able to account for the various inaccuracies of the world perceived during an OBE as it is constructed from memory and likely to contains errors. Nevertheless, the evidence to support such a view is both limited and tenuous. For instance, Blackmore (1987) has found that OBE reports are more likely from people who are better able to perceive the world from an external observer or bird’s-eye-view. Cook and Irwin (1983) also reported that those reporting OBEs were better able to imagine a scene from another perspective. Such findings confirm the intuitive notion that individuals who experience an OBE should be better at external perspective taking and imagery manipulation. However, others have found that those reporting OBEs are poorer at shifting perspective (e.g., Braithwaite & Dent, 2011b; Easton, Blanke, & Mohr, 2009) which led to the suggestion that the processes underlying such perspective taking are not the same as those involved in experiencing an OBE. Furthermore, it is not clear how a change in visual perspective would or should be linked to a change in the feeling that one’s self has shifted. Indeed, Neppe (2011) argues that such a view denies the subjective experience of the OBE.
Dissociation and absorption
Irwin (2000) put forward a dissociation model to account for the OBE. The idea here is that sensory dissociation and cognitive absorption leads to a perception that the ‘self’ is no longer located within the physical body and the individual becomes highly absorbed in this idea. There may be a variety of factors that underlie such a dissociation but it should not be assumed to be indicative of any pathological symptoms. Nevertheless, according to Irwin (1985, 2000) the OBE is due to a dissociation between somatic inputs, in which cross modal synaesthetic type experiences take place, resulting in a feeling that the sense of self as located within the physical body is undermined and in turn leads to a disembodied consciousness represented as the self, floating free from the physical body. The individual then becomes highly absorbed in such a dissociated self which explains the high levels of absorption reported by those who have experienced an OBE (e.g., Irwin, 1985, 2000). Indeed, Irwin (2000) argues that high levels of absorption are responsible for the experienced realism of the OBE. In a similar way Murray and Fox (2005) argue that experients of an OBE have a weak sense of physical embodiment which is characterised by a general dissociation between their self and their physical body. However, as noted above, the association between reports of OBEs and absorption is not consistent. There are those who have experienced an OBE but do not exhibit greater levels of absorption (e.g., Gow et al., 2004). In addition, it is important to keep in mind that this view primarily addresses the notion of dissociation which is only one aspect of the OBE range of experiences. Hence, it may be able to account for some of the data but not all of it.
Neurological attempts to explain the OBE have perhaps unsurprisingly taken a pathological approach, viewing the behaviour as the result of abnormal brain activity, particularly around the temporoparietal junction (TPJ).
The idea here is that the healthy normal brain maintains a continuous representation of the sense of self and that a disruption of the sensory information, possibly from damaged and/or disrupted neural pathways, in or around the temporoparietal junction (TPJ), means that this sense of self becomes distorted. Hence, the assumption is that during an OBE there is a failure to integrate sensory information and because of this the normal sense of ‘self’ that is resident in the physical body is disrupted and becomes located outside the physical body. This gives the ‘illusion’ of being separate, though it is only an illusion brought about by disrupted sensory information leading to an altered sense of self. Thus, a central assumption of this view is that an OBE is caused by a disintegration of visual, vestibular, proprioceptive and tactile information at the TPJ in the brain which may inhibit the creation of a coherent representation of the sense of self (e.g., Blanke & Arzy, 2005; Blanke, Landis, Spinelli, & Seeck, 2004; Blanke & Mohr, 2005; Bunning & Blanke, 2005). Such cortical disruption leads the individual to mistakenly feel as though their visual perspective has shifted outside the physical body. There are various lines of evidence that have been put forward to support this view. For instance, Easton et al. (2009) showed that when people who had reported having an OBE were asked to imagine that a figure was their own or a mirror image (i.e., reflected) they were poorer at switching between the imagined positions. This poor performance was taken to suggest some potential ‘deficit’ in the integration of information at the TPJ, hence highlighting a possible link between an OBE and impaired TPJ function. Further support for the TPJ view comes from a study in which healthy volunteers had to imagine themselves experiencing an elevated visual perspective similar to that reported during an OBE. During this task EEG recordings showed the TPJ was significantly more active and that performance on the task was disrupted when transcranial magnetic stimulation was used to disrupt the TPJ (Blanke & Arzy, 2005). Others have also found support for this view when using sensitive equipment to stimulate the brain. For instance, when a weak current was passed through the right angular gyrus of an epileptic patient they reported feeling their body was moving and being able to view their lower body from above (Blanke, Ortigue, Landis, 8c Seeck, 2002). Such findings are also consistent with reports that those who experience an OBE have a relatively high level of activation of their right hemisphere (e.g., McCreery 8c Claridge, 1996; Munro 8c Persinger, 1992), and relatively high levels of temporal lobe abnormalities (Braithwaite et al., 2013). Some have even suggested that OBEs reliant on TPJ disfunction may be caused by epilepsy or migraine (Bunning 8c Blanke, 2005).
These cases of neural stimulation suggest that it is clearly possible to disrupt the sense of self by stimulating the TPJ which many have argued clearly implicates this region of the brain in mediating OBE-like experiences. However, whilst many report a sense of dislocation, or separateness, they do not report a disruption of the sense of self. Indeed, the sense of self remains intact and coherent; it is simply the location in space-time that is at odds with expected reality. Furthermore, Murray and Fox (2005) point out that it is not clear at all why interference in activity at the TPJ would occur in relaxed and meditative states, nor why, or how a dissociated visual representation of the body is constructed. Neppe (2011) has also raised some concerns regarding the consistency of such cortical stimulation studies noting that stimulation of different regions of the brain have produced similar experiences. For instance, when A. Smith and Messier (2014) examined the cortical activity of a healthy participant who was able to imagine themself outside of their physical body they found increased levels of activation in the left supplementary motor area. More recently Daltrozzo et al. (2016) found that stimulation of the right TPJ had no impact on abnormal body perceptions. Hence, they argue that the right TPJ may not play a specific role in this process. Others agree and suggest that a more cautious approach needs to be adopted when attempting to interpret OBE-like experiences which are induced and assumed to provide insights into real OBE experiences (Neppe, 2011; Neppe 8c Palmer, 2005; Sellers, 2018). Overall, they suggest that such procedures may be useful in attempting to understand and/or shed light on specific features of the OBE, such as the notion of a distinct perceptual experience, or the feelings of floating and dislocation. In addition, Sellers (2018) has argued that there may be many differences between the induced experience of some altered state via cortical stimulation and a full-blown OBE. Hence, whilst there may be similarities there are also likely to be many differences and the former should not be confused as fully representing the latter.
The idea that each person has a spiritual body that may mirror their physical one is not new and has been reported across many cultures such as Greek and Egyptian as well as having a rich history in folklore (Alvarado, 2000). The projection model is intuitively appealing as it suggests quite simply that an aspect of conscious awareness, capable of sustaining perceptual and volitional control, leaves the physical body and travels to distant locations. Hence, the core sense of self leaves the body. Such an idea fits with the assumption that an objective aspect of mind is capable of separating from the physical body and can exist independently (e.g., Alvarado, 1989; Crookall, 1970; Crookall & Shepard, 1972). Such an idea is intuitively plausible, particularly to those who undergo an OBE, as there is a distinct feeling of leaving the physical body. Conceptually, it is also parsimonious in the sense that all reported findings are easily and fully accounted for by some form of self-consciousness leaving the physical body (Crookall, 1973). However, robust empirical support for this view is currently lacking. On the one hand the idea that something leaves the physical body during an OBE has some support from anecdotal accounts (Alvarado, 1989, 2000). Unfortunately, whilst such accounts remain interesting and potentially informative, they also carry with them a range of inherent limitations. More objective attempts to detect the ‘double’ of a person undergoing an OBE have met with limited success (see, Alvarado, 1989; Blackmore, 2005). For instance, whilst some have reported unusual recordings from technical equipment (e.g., Osis & McCormick, 1980) overall the results do not clearly support the notion that anything ‘detectable’ leaves the physical body. In addition, Irwin and Watt (2007) rightly point out how such an approach attempts to hedge its bets in terms of attempting to account for both accurate and inaccurate information. For instance, if during an OBE an individual reports back something accurate that could not have been obtained via ordinary means this is taken as evidence that the individual’s consciousness left the physical body and travelled to the target location. However, if during an OBE the individual reports back information that is not consistent with the reality of the physical world then this is accounted for in terms of the individual’s consciousness leaving the physical body and travelling to a related astral world which may be similar but not identical to the physical world (see e.g., Monroe, 1971; Steiger, 1982). Hence, whilst such an approach is superficially appealing there is no clear evidence to support it. Furthermore, it is not helpful in that it does not make any clear predictions in terms of the individuals who are more or less likely to have an OBE, or the situations and circumstances in which such events occur.
Need for a multi-etiological approach
Neppe (2011) argues that many of the prior accounts of the OBE offer a unitary approach to understanding the process and experience, that is, the assumption that there is a single broad cause and explanation. The problem with such proposals is that they attempt to account for the OBE as a unitary experience with one single cause when in fact there may be many different types of OBE and hence a multiperspective may provide a better account. Others agree, pointing out that there is no one single culture less type of OBE (Hurd, 2016; Sellers, 2018). Each OBE may be uniquely bound to the individual, their background, culture, experience and expectations. Given this, it is very likely that there is more than one reason why such experiences occur.