Decreased coherence in higher frequency ranges (beta and gamma) between central and frontal EEG in patients with schizophrenia: A preliminary report.

Schizophrenia is associated with a dysfunction of cognitive integration that may be due to abnormalities in inhibitory neural circuitry. A previous study found a failure of gamma band (25-45 Hz) synchronization in patients with schizophrenia compared to controls. Another recent study also stressed the importance of investigating high frequencies in the scalp-recorded sleep electroencephalogram (EEG). In this study, we compared coherence between first episode drug-naïve patients with schizophrenia (n=8) and age- and sex-matched normal controls (n=8) using two 32-s epochs of C4 and F4 EEG. The coherence was obtained using 4096 data points (128 Hz signal) using cross-spectral analysis with Blackman-Tukey window in beta (15.25-24.75 Hz) and gamma (25-44.75 Hz) frequency bands. We used wake, non-rapid eye movement (NREM) and rapid eye movement (REM) sleep periods for the analyses. Our results show a significant decrease in coherence in both beta and gamma frequency bands in patients. Post-hoc 't' tests revealed a significantly lower coherence only during the wake stage in patients with schizophrenia in beta as well as gamma frequency bands. These results further support the importance of the analyses of high-frequency bands in the EEG and support previous findings of abnormal neural synchrony in patients with schizophrenia. These results have been discussed further in relation to wake and sleep stages.