Short Communication Abnormal P300 in a case of delusional misidentification with coinciding Capgras and Fre ´goli symptoms Charalabos Papageorgiou a, *, Lefteris Lykouras a , Errikos Ventouras b , Nikolaos Uzunoglu c , George N. Christodoulou a a Psychophysiology Laboratory, Department of Psychiatry, Eginition Hospital, Medical School, University of Athens, 74 Vas. Sophias Avenue, Athens, GR-11528, Greece b Department of Medical Instrumentation Technology, Technological Educational Institution of Athens, Agiou Spyridonos Street, Egaleo, 12210 Athens, Greece c Department of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechneiou Street, Zografou, Athens, 15773, Greece Abstract The Delusional Misidentification Syndrome (DMS) is thought to be related to dissociation between recognition and identification processes. Working memory (WM) is considered responsible for the integration and online manipulation of information, so that it is available for further processing. Since the P300 component of event-related potentials (ERPs) is considered as an index of the on-line updating of WM, the present study is focused on auditory P300 elicited during a WM test in DMS, compared with that in healthy controls. ERPs, elicited during a WM test, in a case suffering from coinciding Capgras and Fre ´goli symptoms, were recorded. Peak amplitude and latency of the averaged P300 waveforms, as well as memory performance of this case, were compared to the patterns obtained from healthy controls. In relation to normal controls, the patient exhibited significantly attenuated amplitude of P300 at the F4, P3 and Pz abductions. The patient also showed significantly prolonged latencies of P300 at all abductions used. These findings suggest that DMS may be accompanied by WM dysfunction affecting brain regions outside the prefrontal cortex, as well as within, and by diffuse failure to allocate attention resources to a stimulus, as they are reflected by P300 amplitudes and latencies respectively. Additionally, it may be suggested that techniques designed to explore cognitive operations, such as recording of ERPs, and more specifically P300, during WM tasks, could provide further insights into the relationship between neural functioning and the cognitive deficits in DMS. D 2002 Elsevier Science Inc. All rights reserved. Keywords: Delusional Misidentification Syndrome; Event-related potentials; P300; Working memory 1. Introduction The essential feature of Cagras symptomatology is hypoidentification, the patient failing to recognize familiar people, although resemblance may be realized (Signer, 1987; Christodoulou, 1991). In the Fre ´goli symptomatology there is a state of hyperidentification, during which indi- viduals foreign to the patient are identified as familiar (Christodoulou, 1978; Feinberg et al., 1999). Both Capgras and Fre ´goli symptoms are contained to Delusional Mis- identification Syndrome (DMS), which is characterized as dissociation between recognition and identification pro- cesses (Luaute and Bidault, 1994; Mentis et al., 1995; Phillips and David, 1995). Neodissociation theories view dissociation as a mech- anism involving a weakening of the highest-order executive control functions that leave to infrastructures more freedom to operate independently (Hilgard, 1994; Rossini et al., 1996; Walter et al., 1996). Moreover, as indicated by recent neuropsychological findings executive control is integral to working memory (WM) functions (Duncan and Owen, 2000). WM refers to the ability to keep information actively in mind and manipulate it in ways required by a given task (Baddeley and Logie, 1999). WM comprises those functional components of cognition that allow humans to comprehend and mentally represent their imme- diate environment, to retain information about their past experience, to support the acquisition of new knowledge, to solve a problem as well as to formulate, relate and act on 0278-5846/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved. PII:S0278-5846(01)00293-7 Abbreviations: DMS, Delusional Misidentification Syndrome; EEG, Electroencephalogram; EOG, Electrooculogram; ERPs, Event-related potentials; WM, Working memory * Corresponding author. Tel.: +301-728-9117. E-mail address: panchris@otenet.gr (C. Papageorgiou). Progress in Neuro-Psychopharmacology & Biological Psychiatry 26 (2002) 805 – 810