Double dissociation of N1 and P3 abnormalities in deficit and nondeficit schizophrenia

It has been proposed that the presence of enduring, idiopathic negative symptoms define a group of patients with a disease (deficit schizophrenia, DS) that is separate from other forms of schizophrenia (nondeficit schizophrenia, NDS). Although several findings support this hypothesis, the possibility that DS represents the severe end of a single schizophrenia continuum cannot be excluded yet. We tested the hypothesis that DS and NDS differ relative to event-related potentials (ERPs). Amplitude, scalp topography and cortical sources of the ERP components were assessed in clinically stable DS and NDS outpatients and in matched healthy subjects (HCS). Twenty subjects per group were recruited. Among the subjects who completed the target detection task, there were no group difference in accuracy. For N1, only patients with DS, as compared with HCS, showed an amplitude reduction over the scalp central leads and a reduced current source density in cingulate and parahippocampal gyrus. For P3, only patients with NDS, as compared with HCS, showed a lateralized amplitude reduction over the left posterior regions and reduced current source density in left temporal and bilateral frontal, cingulate and parietal areas. The DS and NDS groups differed significantly from each other with regard to N1 amplitude and topography, as well as P3 amplitude and cortical sources. The N1 was affected in DS but not in NDS patients, whereas P3 was affected in NDS only. This double dissociation is consistent with the hypothesis that DS represents a separate disease entity within schizophrenia.