Abstract
Out-of-body experiences (OBEs) provide fascinating insights into our understanding of bodily self-consciousness and the workings of the brain. Studies that examined individuals with brain lesions reported that OBEs are generally characterized by participants experiencing themselves outside their physical body (i.e., disembodied feeling) (Blanke and Arzy, 2005). Based on such a characterization, it has been shown that it is possible to create virtual OBEs in immersive virtual environments (Ehrsson, 2007; Ionta et al., 2011b; Bourdin et al., 2017). However, the extent to which body-orientation influences virtual OBEs is not well-understood. Thus, in the present study, 30 participants (within group design) experienced a full-body ownership illusion (synchronous visuo-tactile stimulation only) induced with a gender-matched full-body virtual avatar seen from the first-person perspective (1PP). At the beginning of the experiment, participants performed a mental ball dropping (MBD) task, seen from the location of their virtual avatar, to provide a baseline measurement. After this, a full-body ownership illusion (embodiment phase) was induced in all participants. This was followed by the virtual OBE illusion phase of the experiment (disembodiment phase) in which the first-person viewpoint was switched to a third-person perspective (3PP), and participants' disembodied viewpoint was gradually raised to 14 m above the virtual avatar, from which altitude they repeated the MBD task. During the experiment, this procedure was conducted twice, and the participants were allocated first to the supine or the standing body position at random. Results of the MBD task showed that the participants experienced increased MBD durations during the supine condition compared to the standing condition. Furthermore, although the findings from the subjective reports confirmed the previous findings of virtual OBEs, no significant difference between the two postures was found for body ownership. Taken together, the findings of the current study make further contributions to our understanding of both the vestibular system and time perception during OBEs.
Highlights
Out-of-body experiences (OBEs) are a type of autoschopic phenomena characterized by a sense of disembodiment (Blanke and Arzy, 2005)
During OBEs, most people experience themselves in an elevated position, and this feeling is usually followed by the sensation of floating or flying localized in an extracorporeal space (Blanke et al, 2004; Bradford, 2005; Pfeiffer et al, 2014b)
OBEs were reported in various situations, including during seizures (Devinsky et al, 1989), after artificial brain stimulation (Blanke et al, 2002, 2004), and after damage to certain brain regions [i.e., the temporoparietal junction (TPJ)] (Blanke and Mohr, 2005; Blondiaux et al, 2021)
Summary
Out-of-body experiences (OBEs) are a type of autoschopic phenomena characterized by a sense of disembodiment (Blanke and Arzy, 2005). It was suggested that the vestibular system and its significant role in body orientation is the main modulator of multisensory processing (Lopez et al, 2009; Lopez and Blanke, 2011; Kaski et al, 2016) This was evidenced by a wide range of experimental studies revealing that body orientation influences different aspects of bodily self-consciousness, such as perspective and self-location change (Lopez et al, 2008b, 2015; Lenggenhager et al, 2009; Thür et al, 2019; Tekgün and Erdeniz, 2021). These differences are likely explained by the reduced vestibular signals available when in the supine position (Lopez and Blanke, 2010; Lenggenhager et al, 2015), similar to findings observed in microgravity environments (Lackner, 1992; Oman, 2003; Clément and Reschke, 2008; Erdeniz and Tükel, 2020; Meirhaeghe et al, 2020) and space flight analog studies, involve bed-rest (Moore et al, 2011; Koppelmans et al, 2013; Mulavara et al, 2018)
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