Reduced word-repetition effect in the event-related potentials of thought-disordered patients with schizophrenia Kazunori Matsumoto a, T , Hisato Yamazaki a , Masaki Nakamura a , Hirotaka Sakai a , Nobuyoshi Miura a , Tomonori Kato a , Shinya Miwa a , Takashi Ueno b , Hidemitsu Saito a , Hiroo Matsuoka a a Department of Psychiatry, Tohoku University School of Medicine, Sendai, 980-8574, Japan b Faculty of Education, Tohoku University, Sendai, 980-8574, Japan Received 4 February 2004; accepted 11 March 2004 Abstract Repetition effect in event-related potentials (ERPs) was studied in 10 non-thought-disordered (non-TD) patients with schizophrenia, 8 thought-disordered (TD) patients with schizophrenia, and 10 normal control subjects while they performed a semantic categorization task with incidental word repetitions. All patients were in a stable or partially remitted stage. Although both healthy control and non-TD groups produced more positive ERPs to the repeated words than to the new words (ERP repetition effect) for 250–500 ms, the TD group did not show the ERP repetition effect. These findings suggest that the abnormal attenuation of the ERP repetition effect during semantic processing may be more prominent in schizophrenic patients with thought disorder than in those without the symptom. D 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Schizophrenia; Thought disorder; Priming; Semantic processing; Memory; N400; Vulnerability 1. Introduction It has been suggested that schizophrenic sympto- matology is composed of three or more symptom complexes, and formal thought disorder is one of the key features of schizophrenia (Buchanan and Carpen- ter, 1994). Because the clinical manifestations of schizophrenia are heterogeneous, examining a patient group with a more homogeneous form of symptoma- tology, such as formal thought disorder, could help to elucidate the underlying neural and cognitive process- ing abnormalities at the core of the disorder. Recent studies have demonstrated that thought-disordered (TD) schizophrenic patients show abnormal patterns of behavioral response (Kuperberg et al., 1998) and brain activation (Kircher et al., 2001) during semantic processing compared with non-TD patients and healthy controls. 0165-1781/$ - see front matter D 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.psychres.2004.03.013 T Corresponding author. Tel.: +81 22 717 7262; fax: +81 22 717 7266. E-mail address: kaz-mat@umin.ac.jp (K. Matsumoto). Psychiatry Research 134 (2005) 225 – 231 www.elsevier.com/locate/psychres