Splitting the Unity of Bodily Self: Toward a Comprehensive Review of Phenomenology and Psychopathology of Heautoscopy.

BACKGROUND

Heautoscopy refers to a pathological experience of visual reduplication of one's body with an ambiguous sense of self-location and a disturbing sensation of owning the illusory body. It has been recognized to occur in the course of strikingly diverse psychiatric and neurological disorders, such as schizophrenia, space-occupying lesions, frequently of the temporal or parietal lobes, migraine, epilepsy, and depression. The literature on the subject suffers from numerous conceptual inconsistencies, scarcity of clinical data, and a lack of theoretical integratory framework that could explain the uniqueness of these symptoms.

AIMS: In the study, we aimed to review all case reports on heautoscopy we could cull from the literature with an attempt to extract common factors and to foster a theoretical synthesis.

METHODS

All medical and psychological databases were rigorously searched, along with reference lists of the preselected articles. First-person reports were classified according to aspects of bodily self-consciousness primarily affected: body ownership, self-location, sense of agency and consequently, collated with their etiological backgrounds.

RESULTS

Out of over 140 case studies, a total of only 9 patients with heautoscopy were selected as satisfying functional criteria, carefully distinguishing heautoscopy from other typically conflated full-body anomalies: autoscopy, out-of-body experience, or feeling of presence. Numerous cases turned out to be mislabeling autoscopy or out-of-body experience as heautoscopy. In addition, several problems with existing neuroimaging experiments were identified.

CONCLUSION

Phenomenological analysis revealed that from the patients' perspective, heautoscopy resembles a somatesthetic-proprioceptive illusion, rather than a cognitive delusion, and occurs much less frequently than reported. A most peculiar symptom, described by some as a sense of "bilocation," appears to stem from dynamic shifts in self-location and expanded body ownership, rather than an expanded first-person perspective. Although extremely rare in its pure form, heautoscopy gives a unique opportunity to explore the brain limits to the plasticity of bodily boundaries and the origin of the first-person spatial perspective.