[Evolution over time of the electroencephalographic signal. Application in pharmacology]

The dynamics of transition from wakefulness to drowsiness can be modified by psycho-active compounds. These two states of vigilance have different electroencephalographic characteristics, which can be also modified by the administration of substances. This paper describes a method intended to discriminate between these two aspects of drug action, using a mini-computer. Investigation of sleep-wakefulness cycles with continuous EEG and EMG recording necessitates an efficient method of data reduction. On-line computation of Hjorth parameters with a micro-computer, and further processing witha mini-computer has been used. A pharmacological approach to the study of sleep-wakefulness cycles is proposed; this avoids a strict distinction of sleep phases, and concentrates on the coninuum of vigilance states. Differents ways of showing drug-induced modifications on that continuum are presented with examples.