Altered evoked γ-band responses as a neurophysiological marker of schizophrenia?

Evoked gamma-band responses (GBRs) were shown to be involved in different aspects of human cognition and behavior. They have been linked to the integration and processing of incoming information leading to an adequate behavioral outcome. Consequently, altered evoked GBRs have been associated with impaired cognitive and behavioral states present in a variety of psychiatric disorders. However, to the best of our knowledge, there are no reports directly comparing evoked GBRs of different clinical groups in the same experimental setting. Thus, the purpose of the present study was to shed light on the question, whether evoked GBRs, as a kind of a neurophysiological biomarker of pathological states, might serve for characterization and distinguishing of groups suffering from diverse psychiatric disorders. We measured EEG during a passive auditory oddball-paradigm. Participants were patients diagnosed with schizophrenia, mood disorder, and personality disorders as well as a fourth group consisting of healthy participants. Our results indicate that evoked GBRs significantly differed from healthy participants only in schizophrenic patients whereas no difference could be observed for the other clinical groups. Our findings support the notion that early evoked GBRs could be indeed a trait variable of schizophrenia and are not a general marker of pathological brain states.