Quantitative electroencephalogram examination of effects of risperidone in schizophrenic patients

The objective of this study was twofold: (1) to describe the effects of risperidone on the quantitative electroencephalogram (EEG) in schizophrenic patients and (2) to explore the relationships between EEG changes and clinical improvement. The subjects were nine male schizophrenic patients participating in a placebo-controlled, double-blind clinical trial (duration, 9 weeks) aimed to assess the effects of risperidone. The EEG effects of risperidone were compared with those of haloperidol. Nine haloperidol patients were selected from a separate treatment study that had a similar design and selection criteria and used identical EEG methods. We found that risperidone treatment induced widespread changes in interhemispheric power asymmetry. Furthermore, overall clinical improvement was related to two EEG measures: (1) absolute power changes in the beta frequency band and (2) power asymmetry in the theta and delta bands. Both relationships were most expressed in the anterior areas. The first relationship could not be linked to any specific cluster of behavioral symptoms. The second relationship was linked to improvements of affective symptoms and hostility-suspiciousness. The relationships observed in the risperidone group could not be detected in the haloperidol-treated patients. We hypothesized that the first relationship is attributable to an interaction between the serotonergic and dopaminergic system; the second relationship was associated with serotonergic mechanisms.