[Delusional Misidentification Syndromes in Organic Brain Disorders]

Delusional misidentification syndromes (DMSs) are a fascinating group of disorders involving a fixed, false belief about the identity of persons, places, and objects in one's environment. DMSs include Capgras syndrome, Frégoli syndrome, intermetamorphosis, the syndrome of subjective doubles, and reduplicative paramnesia. Although DMSs have been described in patients with focal neurological lesions, they are more commonly associated with neurodegenerative diseases, specifically dementia with Lewy bodies. Lesion network mapping was used to identify brain regions functionally connected to the lesion locations in patients with lesion-induced DMSs. The left retrosplenial cortex and the right ventral frontal cortex/anterior insula were functionally connected to almost all lesion locations. In a model of Capgras symptom as a mirror of prosopagnosia, there are two routes of visual recognition; one covert and one overt. Capgras symptom represents an interruption to the covert route with an intact overt route. This model, however, does not explain other DMSs. Therefore, propose a new model where the delusional belief content in DMSs results from dysfunctional linking between externally perceived objects and appropriately retrieved internal autobiographical memories associated with an object.