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

Summary

Heautoscopy, a rare condition affecting only 9 out of over 140 reviewed cases, presents a disturbing experience of body duplication and ambiguous self-location. Patients report sensations of "bilocation," linked to shifts in body ownership rather than cognitive delusions. This phenomenon often confuses with other experiences like autoscopy and out-of-body episodes. The findings highlight heautoscopy's unique nature, suggesting it reflects a somatesthetic-proprioceptive illusion, offering insights into the brain's boundaries regarding bodily perception and the first-person perspective.

Abstract

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. 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. 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. 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. 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.

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