Cortical regional differences of delta waves during all-night sleep in schizophrenia

Delta sleep is mediated by thalamocortical circuits and is postulated to be abnormal in schizophrenia. Delta wave deficits during sleep have been observed in patients with schizophrenia. Negative symptoms have been reported to reflect frontal lobe dysfunction and to be associated with decreased delta wave sleep. This investigation was undertaken to identify cortical functional abnormalities in patients with schizophrenia shown on the electroencephalogram.

We compared seventeen male, medically treated or neuroleptic-naive outpatients with schizophrenia and 18 healthy male volunteers by all-night polysomnography and investigated cortical regional differences of delta waves. All-night sleep data was evaluated by period amplitude analyses. Delta waves during sleep were investigated in bilateral frontal, central, parietal, and occipital regions by computer analysis. The associations between delta waves in all regions and measures of clinical variables were also estimated.

Patients with schizophrenia showed lower total delta wave counts during all-night sleep than did control subjects in all regions. Control subjects showed significantly higher delta wave counts in the right frontal and central region than in the left, which was not observed in patients with schizophrenia. Significant inverse correlations were observed between negative symptom scores and delta wave counts in all regions. Control subjects showed significant inverse correlations between delta wave counts and age, which were not identified in patients with schizophrenia.

Delta wave deficits in all regions may reflect thalamocortical dysfunction in schizophrenia. Reduced right frontal and central delta wave dominance is suggested to be involved in the pathophysiology of schizophrenia.