Sleep Regulation in the Djungarian Hamster: Comparison of the Dynamics Leading to the Slow-Wave Activity Increase After Sleep Deprivation and Daily Torpor

Emerging from daily torpor, Djungarian hamsters (Phodopus sungorus) show an initial increase in electroencephalographic slow-wave activity (power density between 0.75 and 4.0 Hz) during sleep that gradually declines. This feature is typical for sleep following prolonged waking and supports the hypothesis that sleep pressure increases during daily torpor. After hamsters were subjected to sleep deprivation or partial non-rapid eye movement sleep deprivation immediately following torpor, slow-wave activity remained high and decreased only when sleep was allowed. An analysis of the dynamics of the process underlying the build-up of sleep pressure during episodes of waking and torpor may provide insights into the regulation of normal sleep and wakefulness. We have analyzed in more detail the timecourse of the process that is common for waking and daily torpor and that could account for the subsequent increase in slow-wave activity.