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

Heautoscopy is a rare experience where a person sees a double of their own body while feeling uncertain about where their self is located and sensing that the illusory body belongs to them. It occurs in diverse conditions like schizophrenia, brain tumors, migraine, epilepsy, and depression. A review of over 140 case studies found only 9 that met strict criteria for heautoscopy, distinguishing it from similar phenomena such as autoscopy and out-of-body experiences, which are often mislabeled. From the patient's perspective, heautoscopy feels like a bodily illusion rather than a false belief. The sense of being in two places at once arises from shifting self-location and expanded body ownership, not from having two viewpoints. The phenomenon offers insight into how the brain constructs bodily boundaries and spatial perspective.

Study at a glance

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.