et al., 1997). Although several studies supported the concept that both structural (e.g., Barta et al., 1990; Rossi et al., 1992; Bilder et al., 1994; Faux et al., 1993; Falkai et al., 1995; Vita et al., 1995) and functional abnormalities in schizophrenia as measured by P3 amplitude during target detection (‘oddball’) tasks involve primarily the left side of the brain (e.g., McCarley et al., 1993, 2002; Salisbury et al., 1998; Strik et al., 1994; van der Stelt et al., 2004), other studies failed to find abnormal structural (e.g., Flaum et al., 1995; Kulynych et al., 1996; Weinberger et al., 1991) or electrophysiological asymmetries (e.g., Pfefferbaum et al., 1989; Ford et al., 2000; Kayser et al., 2001; for a review, see Ford, 1999). This inconsistency may be related to the clinical heterogeneity of schizophrenic samples and other methodological issues, which, with regard to the functional abnormalities, include ERP paradigm, stimulus characteristics and modality, response requirements and component definition (e.g., Strik et al., 1994; Ford et al., 2000; Salisbury et al., 2001; Kayser et al., 2001, 2006).
