The authors studied how clozapine treatment of patients with chronic schizophrenia affects the scalp topographic distribution of different frequency bands on EEG. Twenty-one patients treated with clozapine, in addition to zero to two typical neuroleptics (13 patients were treated with clozapine as the only neuroleptic), were compared with two control groups: one of healthy subjects and another of patients with schizophrenia receiving one to three typical neuroleptics and no clozapine. Significant differences in the EEG topography were seen between the groups: The theta and delta powers and were increased in the clozapine group compared with the two other groups (P < 0.001). Changes were observed over all electrodes, and were most prominent at the frontal, central, and parietal electrode locations. The nonclozapine-treated group of patients and the healthy control group did not differ significantly from each other. These results suggest that the topographic EEG features caused by clozapine are quite specific to it and can be differentiated from those of other neuroleptics.

We have earlier reported an increased theta-power value in clozapine (CLO)-treated patients with schizophrenia, nonresponsive to conventional antipsychotics. We also found that the decrease in the production of reactive oxygen species (ROS), induced by CLO, by peripheral blood monocytes (MO) of these patients correlates with clinical improvement. MO share the capability of ROS production with their more mature descendants, microglia of the brain. We hypothesized that the CLO-related changes in peripheral blood MO might be related to a parallel process in microglia and thus be reflected in brain activity. In those 8 patients for whom both QEEG and MO data were available, we explored possible relationships between these parameters. A clear-cut correlation between ROS production (R² = 0.929, p < 0.05) for nonstimulated MO, and (R² = 0.907, p < 0.001) for stimulated MO and theta-power values in the central frontal electrode (F_z) was found. It is intriguing to speculate that the EEG slowing is a result of the modulatory action of the activated microglial cells in the central nervous system via production of ROS or cytokines or both. However, this proposition has to be confirmed by future research.

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These findings indicate that the change in the theta frequency in QEEG and particularly in the midline electrodes over the fronto-central scalp area might be a more sensitive indicator for the evaluation of CLO treatment adequacy than the serum CLO level.

BackgroundResearch of QEEG activity power spectra has shown intriguing results in patients with schizophrenia. Different symptom clusters have been correlated to QEEG frequency bands. The findings have been to some extent inconsistent. Replication of the findings of previous research is thus an important task. In the current study we investigated the correlations between the absolute powers of delta, theta, alpha, and beta frequency bands over the fronto-central scalp area (FC) with the PANSS subscales and the Liddle's factors in 16 patients with schizophrenia.The authors hypothesised a priori the correlations reported by Harris et al (1999) of PANSS negative subscale with delta power, Liddle's psychomotor poverty with delta and beta powers, disorganisation with delta power and reality distortion with alpha power on the midline FC.MethodsThe sample consisted of 16 patients with chronic schizophrenia considered as having insufficient clinical response to conventional antipsychotic treatment and evidencing a relapse. The correlations between quantitative electroencephalography (QEEG) absolute powers of delta (1.5–3.0 Hz), theta (3.0–7.5 Hz), alpha (7.5–12.5 Hz), and beta (12.5–20.0 Hz) frequency bands over the fronto-central scalp area (FC) with PANSS subscales and Liddle's factors (reality distortion, disorganisation, psychomotor poverty) were investigated.ResultsSignificant positive correlations were found between the beta and psychomotor poverty (p < 0.05). Trends towards positive correlations (p < 0.1) were observed between delta and PANSS negative subscale and psychomotor poverty. Alpha did not correlate with reality distortion and delta did not correlate with disorganisation.Post hoc analysis revealed correlations of the same magnitude between beta and psychopathology generally over FC.ConclusionThe a priori hypothesis was partly supported by the correlation of the beta and psychomotor poverty. Liddle's factors showed correlations of the same magnitude with PANSS subscales. Supplementary analysis showed beta frequency correlating non-specifically over FC with a wide range of psychiatric symptomatology in patients with schizophrenia having a relapse.