A quantitative description of variations in EEG amplitude during stationary sleep stages

The amplitude of the EEG signal, as well as of some of its frequency band activities, changes significantly during sleep. A well-known example of this phenomenon is given by the delta activity, whose amplitude presents a damped-oscillation pattern which reflects the cyclic changes in sleep stage during the night and presents maximum values during stage 4. In addition to variations connected with changes in sleep stage, variations of higher frequency, which may occur during a stationary sleep stage, have been observed. The aim of our research is to propose an automatic method for a general description of these variations.