Illusory Reduplication of One's Own Body: Phenomenology and Classification of Autoscopic Phenomena.

Autoscopic phenomena involve the illusory reduplication of one's own body. The literature on the topic is widely scattered and suffers from considerable terminological and conceptual inconsistencies. This article proposes a classification scheme based on phenomenological criteria. Along with examples of illustrative cases, we outline the main features of autoscopic hallucinations, heautoscopy proper, the feeling of a presence, the out-of-body experience, and negative and inner forms of autoscopic phenomena. We also discuss the need for a differentiation of autoscopic phenomena from reduplicative paramnesias and the misidentification syndromes. Finally, the concept of a neuromatrix (Melzack, 1990) is proposed as a starting point for the understanding of the neuronal mechanisms underlying autoscopic phenomena.