The current study adds to this more differentiated picture of P3 generator patterns by clearly identifying the contributions of lateral frontocentral sinks to the late parietal old/new source effects (cf. Kayser et al., 2007). These sinks were broader and asymmetrically enhanced in schizophrenic patients during the auditory task, predominantly affecting the left lateral temporal recording site (T7), reminiscent of left hemisphere overactivation in schizophrenia during verbal processing (cf. Gur 1978; Ragland et al., 2005). Although the implications of this unexpected finding remain unclear, it is obvious that the neuronal generator patterns underlying the (left) parietal old/new effect (i.e., the relative orientation of the lateral frontocentral sinks compared to the parietal sources) differed between patients and controls, a group difference with profound implications for ERP studies relying on referenced surface potentials. Given that the generator patterns of the old/new effects resembled the pattern for auditory P3 but differed from that for visual P3, one may contemplate whether this pattern reflects phonological processing common to both modalities (e.g., Price, 2000), and therefore indicates disturbed temporal integration in schizophrenia within a recognition memory network involving frontal and parietal regions (e.g., Kim et al., 2003; Iidaka et al. 2006).
