Schizotypal disorder and schizophrenia: A profile analysis of neuropsychological functioning in Japanese patients MIÉ MATSUI, 1,3 HIROMI YUUKI, 1 KANADE KATO, 1 AI TAKEUCHI, 2 SHIMAKO NISHIYAMA, 1,3 WARREN B. BILKER, 4 and MASAYOSHI KURACHI 1,3 1 Department of Neuropsychology and Neuropsychiatry, Graduate School of Medicine, University of Toyama, Toyama, Japan 2 Section of Liaison Psychiatry and Palliative Medicine, School of Medicine, Tokyo Medical and Dental University, Tokyo, Japan 3 Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Tokyo, Japan 4 Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania (Received September 19, 2006; Final Revision February 19, 2007; Accepted February 21, 2007) Abstract This study compares neuropsychological functioning in a Japanese schizophrenia spectrum disorder group and a group of healthy Japanese volunteers. Participants were 37 patients diagnosed with schizophrenia, 28 schizotypal patients, and 99 psychiatrically-normal volunteers. A wide range of cognitive measures were examined. All participants completed a Japanese version of a neuropsychological battery assessing executive function, working memory, processing speed, language, verbal memory, and spatial organization. Comparisons of neuropsychological function demonstrated similarities and differences between patients diagnosed with schizotypal disorder and those diagnosed with schizophrenia. Impairments in verbal memory, language, and processing speed were common to both patient groups and may represent a vulnerability to schizophrenia. Impairments in aspects of working memory, spatial organization and executive function were preferentially observed in schizophrenia and may be features of the overt manifestation of psychosis. Possible differences in the contributions of prefrontal and temporolimbic structures provide direction for further studies. ( JINS, 2007, 13, 672–682.) Keywords: Verbal memory, Schizotypy, Verbal fluency, Frontal function, Temporolimbic function, Psychosis INTRODUCTION Susceptibility to schizophrenia occurs across a spectrum, with schizotypal (personality) disorder as the prototypic spectrum sharing common genetic and biologic substrates with schizophrenia (Siever et al., 2002). Schizotypal (per- sonality) disorder is characterized by odd behavior and atten- uated forms of the features seen in schizophrenia without manifestation of overt and sustained psychosis (World Health Organization, 1993; American Psychiatric Association, 1994). Clarifying the neurobiological similarities and dif- ferences between established schizophrenia and schizo- typal (personality) disorder would potentially discriminate the pathophysiological mechanisms underlying the core fea- tures of the schizophrenia spectrum from those associated with overt psychosis. Psychophysiological studies have found deficits in the startle response, smooth pursuit eye movements, antisac- cades, backward masking, and N400 and P300 evoked poten- tials within schizotypal subjects and patients diagnosed with schizophrenia (for review see Siever & Davis, 2004). Recently, it has been reported that there is evidence of spe- cific genetic linkages with both schizophrenia and schizo- typal subjects; catechol-O-methyltransferase (COMT) is a genotype that shows such linkages (for review see, Raine, 2006). The brain abnormalities shared between patients diag- nosed with schizotypal disorder and schizophrenia might represent a common denominator in schizophrenia spec- trum disorders, whereas the differences might account for the sparing of schizotypal patients from the development of overt psychotic symptoms. Several recent brain structural imaging studies have identified specific structural abnor- malities in schizotypal patients similar to those seen inschizo- phrenia, although generally to a lesser degree and with sparing of certain brain regions (Dickey et al., 2002; Siever & Davis, 2004; Siever et al., 2002). Previous studies Correspondence and reprint requests to: Dr. Mié Matsui, Depart- ment of Neuropsychology, Graduate School of Medicine, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan. E-mail: mmatsui@ las.u-toyama.ac.jp Journal of the International Neuropsychological Society (2007), 13, 672–682. Copyright © 2007 INS. Published by Cambridge University Press. Printed in the USA. DOI: 10.10170S135561770707083X 672