Marked clozapine-induced slowing of EEG background over frontal, central, and parietal scalp areas in schizophrenic patients

The authors studied how clozapine treatment of patients with chronic schizo phrenia affects the scalp topographic distribution of different frequency b ands on EEG. Twenty-one patients treated with clozapine, in addition to zer o to two typical neuroleptics (13 patients were treated with clozapine as t he 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 wer e 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 sig nificantly from each other. These results suggest that the topographic EEG features caused by clozapine are quite specific to it and can be differenti ated from those of other neuroleptics.