Circadian modulation of sleep-wake dynamics evaluated by transition probabilities

Abstract

Behavioral states in rodents and other mammalian species alternate between wakefulness (WK), rapid eye movement (REM) and non-REM (NREM) sleep at time scale of hours (i.e., circadian and ultradian periodicties) and from several tens of minutes to seconds (i.e., brief awakenings during sleep). Quantified and statistical analysis of bout durations and transition probability analysis of sleep-wake dynamics constitute a powerful method for evaluating endogenous sleep control mechanisms and sleep disturbances. Here we studied the circadian influence over sleep-wake activity in mouse model by analyzing as a function of lightdark (LD) cycle, the Kaplan-Meier (KM) survival curves and the transition probability (TP) of Markov chains. Survival curves of WK showed a bimodal statistical distribution. Circadian rhythm modulated specifically WK bouts increasing its duration during activedark period. In contrast, NREM and REM KM curves did not change significantly along LD cycle. Circadian modulation of TP was found only for state-maintenance-probability in WK and for pwk→nrem transitions which increased and decreased respectively during activedark period. In conclusion, Markov modelling of sleep stages adequately evaluate the circadian and ultradian modulation of sleep-wake dynamics during dark and light phases.