Spontaneous Slow and Fast MEG Activity in Male Schizophrenics Treated with Clozapine

Abstract

Rationale. The atypical neuroleptic clozapine induces specific electroencephalogram changes, which have not been investigated by the use of the technique of magnetoencephalography (MEG).

Objective. The present study investigated whether the spontaneous magnetoencephalographic (MEG) activity in patients treated with clozapine differs from MEG-activity in patients treated with haloperidol and untreated control subjects.

Methods. A 2×37 channel biomagnetic system (Magnes II, Biomagnetic Technologies, San Diego, CA) was used to record spontaneous magnetic activity for the frequency ranges (2–6 Hz, 7.5–12 Hz, 12.5–30 Hz) in schizophrenic patients and controls in two trials within three weeks. After data acquisition the processed data were digitally filtered, the spatial distribution of dipoles was determined by a 3-D convolution with a Gaussian envelope. The dipole localisation was calculated by the dipole density plot and the principal component analysis (Kober et al. 1992). The target parameters were absolute dipole values and the dipole localizations. The relationship between absolute dipole values, dipole localizations and psychopathological findings (documented by the use of the PANSS, BPRS-scale) during a three-week period with constant doses of clozapine and haloperidol was investigated using correlation analysis.

Results. Our results lend strong support to the assumption of a significant elevation of absolute dipole values (dipole density maximum [D_max], dipole number [D_total], absolute and relative dipole density) in the fast frequency range (12.5–30 Hz) over the left hemisphere, especially in the temporoparietal region by clozapine. In this area we found a dipole concentration effect only in patients treated with the atypical neuroleptic, whereas the dipole distribution in patients treated with haloperidol and healthy controls was concentrated in the central region. With regard to the absolute dipole values in the frequency ranges 2–6 Hz (δ, θ) and 7.5–12 Hz (α) we found no statistically significant differences between the groups investigated. In the slow fre-quency range (2–6 Hz) no difference was found between the clozapine and haloperidol group for the dipole localization, which predominated in the temporoparietal region in contrast to the central dipole distribution in control subjects.

Conclusions. The results of an increase in beta activity under clozapine illustrate a smaller reduction in activity in terms of unspecific sensory and motor paradigms in comparison with typical neuroleptics.

The temporoparietal concentration of dipoles, in particular over the left half of the brain, might illustrate either their special role in the disease process, or the effects of the medication. The latter possibility was supported by the differing dipole distribution in the clozapine group with a left temporoparietal centre in both frequency ranges, and a deviating central dipole localisation in the fast activity range in the haloperidol group.