FUNCTIONAL-PROPERTIES OF THE BRAIN DURING SLEEP UNDER SUBCHRONIC ZOPICLONE ADMINISTRATION IN MAN

Zopiclone, a non-benzodiazepine, has been shown to be efficient in the treatment of transient, short-term or chronic sleep disorders. Apart from its hypnotic effects zopiclone has anxiolytic, anticonvulsant and myorelaxant properties and is therefore hardly distinguishable from b enzodiazepines. Dependence liability and discontinuation effects have been reported to be less pronounced. Therefore zopiclone seems to be a hypnotic drug which may cause fewer side effects than conventional be nzodiazepines. From the electrophysiological point of view one require s from a hypnotic drug the induction of a physiological sleep pattern as well as no alterations of information processing by the brain. The aim of the present study was to investigate the subchronic effect of z opiclone medication on some functional properties of the sleep EEG in healthy subjects. In order to get better insight into the principles o f information processing by the brain during sleep and its alterations under the influence of zopiclone we applied some tools from linear sy stem theory to sleep EEG data. For this purpose we investigated late c omponents of auditory and visual evoked potentials during different sl eep stages and calculated from these the so-called amplitude-frequency characteristic of the brain. This function describes the relationship between an input and the output of the investigated system. The main advantage of this kind of analysis is that it enables one to detect fu nctional differences during sleep stages. This information can hardly be obtained from conventional spectral analysis. As a result we could demonstrate that under subchronic zopiclone medication no quantitative or qualitative alterations of the functional sleep EEG properties con cerning the transfer properties of the brain under auditory and visual stimulation were detectable.