Zopiclone versus diazepam effects on EEG power maps in healthy volunteers.

EEG effects of zopiclone (7.5 mg), a cyclopyrrolone derivative with hypnotic action, were compared with effects of diazepam (10 mg). Multichannel EEG recordings, double-blind crossover trials with placebo, and oral single doses were used in healthy volunteers. Vigilance-controlled EEG before and after zopiclone (and placebo), and before and after diazepam (and placebo) were analyzed into FFT power spectra. Effects were assessed as placebo-referred pre-post-medication power differences in four frequency bands. Overall statistics showed significant (P < 0.007) global differences between medication effects in the delta frequency band (0.5-3.5 Hz). After zopiclone, fronto-central delta increased bilaterally, whereas after diazepam delta decreased over centro-parietal to right temporo-occipital regions. These spatially different brain electric effects show that different neuronal populations must have become active in response to zopiclone and diazepam.