State-dependent changes in intrahemispheric EEG coherence for patients with acute exacerbation of schizophrenia

Abstract

Abnormalities of electroencephalographic (EEG) coherence in schizophrenia are thought to reflect functional disconnections between different brain regions associated with the onset of this disease. To clarify whether these abnormalities change in a symptom-dependent manner in individual patients, we analyzed the coherence of resting EEGs recorded at two time points with a 36.6-day interval during the course of treatment for 14 patients who had been hospitalized for acute exacerbation of schizophrenia. Symptom severity was quantitatively measured by means of the Brief Psychiatric Rating Scale (BPRS). Beta (13–20 Hz) coherence for the left frontal (F7)–temporal (T5) electrode pair was less than that for the corresponding right pair (F8–T6) at the initial test. At the second test, when symptoms had improved, the left frontal–temporal beta coherence had increased, resulting in disappearance of the laterality. This change in beta coherence for the left frontal–temporal pair correlated negatively with the change in the total BPRS score, particularly the positive symptom score. Similar correlations were found for eight patients who had been drug-free at the first examination. These results suggest that a functional disconnection between the frontal and the temporal lobe in the left hemisphere may be associated with the generation of acute psychotic symptoms in schizophrenia.