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.

Explanatory profiles of models of consciousness - towards a systematic classification.

Models of consciousness aim to inspire new experimental protocols and aid interpretation of empirical evidence to reveal the structure of conscious experience. Nevertheless, no current model is univocally accepted on either theoretical or empirical grounds. Moreover, a straightforward comparison is difficult for conceptual reasons. In particular, we argue that different models explicitly or implicitly subscribe to different notions of what constitutes a satisfactory explanation, use different tools in their explanatory endeavours and even aim to explain very different phenomena. We thus present a framework to compare existing models in the field with respect to what we call their 'explanatory profiles'. We focus on the following minimal dimensions: mode of explanation, mechanisms of explanation and target of explanation. We also discuss the empirical consequences of the discussed discrepancies among models. This approach may eventually lead to identifying driving assumptions, theoretical commitments, experimental predictions and a better design of future testing experiments. Finally, our conclusion points to more integrative theoretical research, where axiomatic models may play a critical role in solving current theoretical and experimental contradictions.

Duplication of the bodily self: a perceptual illusion of dual full-body ownership and dual self-location.

Previous research has shown that it is possible to use multisensory stimulation to induce the perceptual illusion of owning supernumerary limbs, such as two right arms. However, it remains unclear whether the coherent feeling of owning a full-body may be duplicated in the same manner and whether such a dual full-body illusion could be used to split the unitary sense of self-location into two. Here, we examined whether healthy human participants can experience simultaneous ownership of two full-bodies, located either close in parallel or in two separate spatial locations. A previously described full-body illusion, based on visuo-tactile stimulation of an artificial body viewed from the first-person perspective (1PP) via head-mounted displays, was adapted to a dual-body setting and quantified in five experiments using questionnaires, a behavioural self-location task and threat-evoked skin conductance responses. The results of experiments 1-3 showed that synchronous visuo-tactile stimulation of two bodies viewed from the 1PP lying in parallel next to each other induced a significant illusion of dual full-body ownership. In experiment 4, we failed to find support for our working hypothesis that splitting the visual scene into two, so that each of the two illusory bodies was placed in distinct spatial environments, would lead to dual self-location. In a final exploratory experiment (no. 5), we found preliminary support for an illusion of dual self-location and dual body ownership by using dynamic changes between the 1PPs of two artificial bodies and/or a common third-person perspective in the ceiling of the testing room. These findings suggest that healthy people, under certain conditions of multisensory perceptual ambiguity, may experience dual body ownership and dual self-location. These findings suggest that the coherent sense of the bodily self located at a single place in space is the result of an active and dynamic perceptual integration process.

Schizophrenia as a disorder of embodied self. / Schizofrenia jako zaburzenie "ja" ucielesnionego.

Theories of schizophrenia propose numerous mechanisms underlying development of this disorder, yet the account including satisfactory etiological explanation is still lacking. Current trend is to indicate core, basic factors which may further give rise to whole diversity of symptoms. Experimental data and patients' reports show that such key factor may be selfexperience disturbed on a basic, pre-reflective level, which can then lead to many higher-order symptoms. In this article we review and analyze these data, as well as the most influential cognitive theories focusing on mechanisms influencing the clinical picture of schizophrenia and giving rise to the anomalous experience of embodied self. These approaches pay attention to different, but complementary aspects of experience, such as body schema and body image, sense of ownership and sense of agency, or hyperreflexivity and diminished self-affection. Predictive coding approach is also introduced - the theory which, by appealing to the disturbance in a process of neural prediction, complements previous accounts and links various cognitive functions by means of single common predictive mechanism. Although very broad in its possible meanings, the self appears to be a concept of high explanatory value, grasping in the single framework many schizophrenic symptoms - these observable on neural, low-level of information processing, as well as on the level of phenomenology of subjective experience. Such approach appears to be valuable and useful for both research and practice.

Tool use changes the spatial extension of the magnetic touch illusion.

Characterizing the brain mechanisms that allow humans to use tools to interact with the environment is a major goal in neuroscience. It has been proposed that handheld tools are incorporated into the multisensory representation of the body and its surrounding (peripersonal) space, underlying our remarkable tool use ability. One single-cell recording study in tool-using monkeys provided qualitative support for this hypothesis, and the results from a vast number of human studies employing different experimental paradigms have been ambiguous. Here, we made use of the recently reported magnetic touch illusion-a perceptual correlate of peripersonal space-to examine the effect of tool use on the representation of visuotactile peripersonal space. The results showed that active tool use leads to an extension of the "illusion volume" around the entire length of a tool, which was significantly greater compared with a manual control task. These findings support the notion that the multisensory representation of peripersonal space is extended to incorporate handheld tools and provide a three-dimensional estimation of this remapping process. (PsycINFO Database Record