First-episode schizophrenics show normal duration and topography of quasistationary EEG segments as compared to controls, during rest as well as during active tasks

Abstract

In patients suffering from chronic schizophrenia, both altered temporospatial structure of the EEG and impaired activation during cognitive tasks have repeatedly been demonstrated. The present study evaluates whether similar abnormalities are present in drug-naive first-episode schizophrenics. The EEGs of 32 schizophrenic patients and of 52 healthy controls were recorded during a simple and a complicated motor task, a simple and a complicated auditory stimulus, and during resting periods between the tasks. The temporospatial characteristics were evaluated by adaptive segmentation of EEG, which decomposes an EEG into temporal segments of quasistationary activity. No differences in the temporal and topographic aspects of the EEGs were found between the first-episode schizophrenic patients and the controls, neither during the resting EEGs nor during active tasks. Moreover, the dynamic course of the EEGs, defined as the alternation between task-related changes of temporospatial patterns and the reappearance of resting patterns, was identical in patients and controls. The present findings suggest that while abnormal EEG power spectra seem a consistent finding in treated as well as in never-treated schizophrenics, altered temporospatial patterns and reduced task-related EEG changes are inconsistent signs.