Psychophysiological differences in schizophrenics with and without delusional misidentification syndromes: A P300 study Charalabos Papageorgiou a,d, T , Lefteris Lykouras a , Basil Alevizos a , Errikos Ventouras b , Polyxeni Mourtzouchou a , Nicolaos Uzunoglu c , George N. Christodoulou a , Andreas Rabavilas a,d a Psychophysiology Laboratory, Department of Psychiatry, Eginition Hospital, Medical School, University of Athens, 74 Vas. Sophias Avenue, Athens 11528, Greece b Department of Medical Instrumentation Technology, Technological Educational Institution of Athens, Egaleo, Athens, Greece c Department of Electrical and Computer Engineering, National Technical University of Athens, Zografou, Athens, Greece d University Mental Health Research Institute, Athens, Greece Accepted 28 January 2005 Available online 17 March 2005 Abstract There is a debate on whether delusional misidentification syndromes (DMSs) and schizophrenia are distinct disorders. Information- processing deficits have been found in both. Since the P300 component of event-related potentials (ERPs) reflects attention and working memory (WM) mechanisms, the P300 elicited during a WM test was studied in schizophrenic patients with DMS in comparison to schizophrenic patients without DMS and controls. Nine schizophrenic patients with DMS, 11 without DMS and 11 healthy controls were tested with a computerized version of the digit span test of the Wechsler batteries. Auditory ERPs were measured during the anticipatory period of the test. P300 amplitude in prefrontal areas was found to be significantly reduced in schizophrenics without DMS and markedly less in DMS patients compared to controls. P300 latency in the central midline brain region was significantly prolonged in DMS patients compared to the other groups. Memory performance was significantly reduced in both patient groups as compared to healthy controls. The results may indicate abnormalities in both allocation of attentional resources and automatic orienting in schizophrenic patients with DSM. In contrast, even though schizophrenic patients without DMS exhibit partial similarities with patients suffering from DMS, they show excessive reduction of P300 amplitude located at the left frontal area. Future studies might clarify these issues. D 2005 Elsevier Inc. All rights reserved. Keywords: Cognition; Delusional misidentification syndromes; Event-related potentials; P300; Schizophrenia; Working memory 1. Introduction The interest in delusional misidentification syndromes (DMSs) has increased recently. Until the past decade, these syndromes were regarded as very rare, but an increasing number of cases are now being reported (Joseph, 1994; Kirov et al., 1994; Huang et al., 1999). Four main types of DMSs have been described: the Capgras syndrome, the Fre ´goli syndrome, intermetamorphosis, and the syndrome of subjective doubles (Christodoulou, 1977, 1991). However, other types have also been described, and individual cases may show features of more than one type (Christodoulou, 1978; Silva et al., 1997). DMSs are characterized by a misidentification delusion of the self or others (Christodou- lou, 1991). In a more broad approach, Cutting (1991) proposed that DMSs derive from da failure to appreciate the actual identity or uniqueness of something—overriding the issue of whether it is a person, place, event or objectT. 0278-5846/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.pnpbp.2005.01.016 Abbreviations: DSM-IV, Diagnostic and Statistical Manual of Mental Disorders Fourth Edition; EEG, electroencephalogram; EOG, electro- oculogram; ERPs, event-related potentials; ICD-10, International Statistical Classification of Diseases and Related Health Problems; MRI, magnetic resonance imaging; WM, working memory. T Corresponding author. Tel.: +30 2107289408; fax: +30 2107242032. E-mail address: panchris@otenet.gr (C. Papageorgiou). Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 593 – 601 www.elsevier.com/locate/pnpbp