Long-term replicability of EEG spectra and auditory evoked potentials in schizophrenic and normal subjects.

The spectral characteristics and average, auditory evoked potentials (AEPs) were determined from EEGs repeatedly recorded over a span of several years. Data from a vertex lead is presented for 4 chronic schizophrenic patients and 5 normal subjects. Measurements were made under identical conditions. For each subject characteristic spectra and AEPs were exhibited despite the passage of time. Patients had recordings performed both on and off antipsychotic medication. While receiving antipsychotic medication the patients' EEG spectra showed an increase in alpha activity. Less consistently there was a decrease in delta or an increase in beta activity; theta activity was unchanged. These latter effects are different from those generally reported for an acute antipsychotic dose and may be more representative of antipsychotic effects (which occur after days or weeks of treatment). Psychopathology tended to be inversely related to alpha power, the magnitude of the AEP N100, and medication.