Can P300 distinguish among schizophrenia, schizoaffective and bipolar I disorders? An ERP study of response inhibition.

Research utilizing visual event-related brain potentials (ERPs) has demonstrated that reduced P300 amplitude and prolonged latency may qualify as a biological marker (biomarker) for schizophrenia (SZ). We examined P300 characteristics in response inhibition among three putatively distinct psychopathology groups including schizophrenia (SZ), bipolar I disorder (BD) and schizoaffective disorder (SA) in comparison with healthy controls (CT) to determine their electrophysiological distinctiveness. In two separate studies, deficits in response inhibition indexed by the P300 component were investigated using a lateralized Go/NoGo task. We hypothesized that deficits in response inhibition would be present and distinctive among the groups. In both studies, SZ showed response inhibition deficits as measured by P300 when stimuli were presented to the right visual field. In Study 2, delayed cognitive stimulus evaluation was observed in BD as indexed by prolonged P300 latency for NoGo trials. Six selected NoGo P300 variables out of thirty six NoGo P300 variables (18 amplitude, 18 latency) correctly classified SZ (79%), SA (64%) in Study 1 and seven variables selected in Study 2 classified CT (80%), and SZ (61%), BD (67%) and CT (68%) with the accuracy higher than chance level (33%). The findings suggest that distinct P300 features in response inhibition may be biomarkers with the capacity to distinguish BD and SZ, although SA was not clearly distinguishable from SZ and CT.