Segmentation of REM sleep into three substages

The study of REM sleep has certainly important implications for the study of dreams, because of the connection between changes in significant features of mentation during sleep and periodic occurrence of REM epochs. A basic property of REM sleep is that it is not a uniform stage. A large amount of literature has demonstrated that "tonic" and "phasic" REM sleep should be distinguished, on the basis of differences in electrophysiological signals (EEG, EOG and EMG), in fMRI images, and in mental activity (about the last point, see in particular Molinari & Foulkes, 1969). Furthermore, recent research has shown that, in addition to Rapid Eye Movements (REMs), Slow Eye Movements (SEMs) are remarkably present as well during REM sleep, although their presence is mainly referred to Stage 1 in the manual of Rechtschaffen and Kales. In the light of this data, we set out a research project aiming to segment REM sleep into three substages, respectively characterized by: REM enhancement, selective SEM enhancement, eye movement reduction.