In order to assess whether transient GBRs quantified with total power, evoked power, and PLF time-frequency measures are compromised early in the course of schizophrenia, we compared young schizophrenia patients, clinical high risk patients, and healthy controls on these measures. Based on previous studies reporting reduced gamma band evoked power and PLF in schizophrenia, we predicted that young schizophrenia patients, still early in their illness course, would show diminished evoked power and PLF in the GBR. Based on the hypothesis that abnormal GBRs may be physiological risk markers for the development of psychosis, we predicted that patients at clinical high risk for psychosis would also be abnormal on these measures. However, given the heterogeneous nature of clinical high risk samples, with only a minority of patients destined to convert to schizophrenia, we predicted that, as a group, their abnormalities would be intermediate relative to early illness schizophrenia patients and healthy controls. Finally, we predicted that clinical high risk patients who subsequently converted to psychosis would have greater GBR abnormalities.
