[Interest of a new method of graphic analysis for the study of the organization of stage II sleep in man (author's transl)]. / Apport d'une nouvelle méthode d'analyse graphique à l'étude de l'organisation du stade II du sommeil de l'homme.

The organization of stage II and its modifications according to its occurrence in the cycle are studied using an analogical method of graphic analysis. The latter offers a continuous display on a limited record length, of the EEG amplitude in the sigma, alpha, theta and delta bands, of the muscle tone and of eye movement. Thus, it is noted that stage II, preceding paradoxical sleep at the end of the cycle, differs from stage II at the beginning of the cycle by 3 essential elements: the different evolution of delta activity during this stage and its irregular or alternating characteristics at the end of the cycle; the existence of a high muscle tone and an abundant phasic muscle activity during stage II at the end of the cycle; the different relation of these two types of stage II with the depth of the cycle. These observations, compiled from 100 records in healthy, non-insomniac subjects, are compared to those from studies on the heterogeneity of stage II and from those which provide evidence for the existence of phasic phenomena during slow sleep prior to the paradoxical stage in man as well as in the animal.