A study of slow changes in the EEG activity during sleep

Variations in the amplitude of some EEG activities during sleep are well-known. For instance, the delta activity power changes according to the cyclic changes in sleep stage and presents maximum values during stage 4 [1]. Other variations of higher frequency have been described [2], [3], [4]. The aim of our work has been to provide an automatic method for the quantitative analysis of these variations.