An EEG computerized system for the evaluation of hypnotic drugs

Digital recording of sleep EEG allows computer analysis and quantitative evaluations of sleep disorders and pharmacological effects. A system for polygraphic signal acquisition and storage, which performs a Fourier transform to compute series of spectra representing the evolution of EEG frequency composition through different sleep stages is described. The time course of spectral descriptors like relative band power is used to study the cyclic patterns of sleep and to compute the DSRI (Delta Sleep Regularity Index), a synthetic measure of sleep quality. The method is compared with conventional sleep scoring and examples of applications to normal, pathological and pharmacological conditions are shown. The topographical distribution of spectral parameters is analyzed by means of mapping techniques, allowing the detection of regional variations of EEG in specific pharmacological conditions.