title: The functions of sleep: further analysis.
abstract: Most theories addressed to the functions of sleep are proposed primarily according to the results in one area of sleep research and may not be compatible with the results in other areas of sleep research. This paper provides a new theory regarding the functions of sleep by integratively analyzing different areas of sleep research. First, it concludes from the phylogenetic studies and other related sleep research that sleep in mammals has at least one obligatory function which cannot be accomplished during waking. It also shows that the synchronized sleep (SS) period plays a critical role in accomplishing the obligatory functions of sleep and that the obligatory functions of sleep are related to the brain. Then it points out that adjusting and reorganizing emotional behaviors is a very important function of SS. Finally, this theory suggests that the gradual accumulation of various randomly learned memories in the limbic structures would inevitably imbalance and disorganize emotional behaviors so that sleep should be developed in evolution to adjust and reorganize emotions and so that the functions of SS for memory and emotional regulation are the obligatory functions of sleep. Although phylogenetic studies suggest that (PS) may not play obligatory functions across all mammals, there is no doubt that, in tight correlation with SS, PS also plays very important roles in memory and emotion which, however, are different from the corresponding SS roles in those mammals possessing PS.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Cai
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004644:Emotions / Q000502:physiology*; D006801:Humans; D008032:Limbic System / Q000502:physiology; D011939:Mental Recall / Q000502:physiology*; D010802:Phylogeny; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D013045:Species Specificity