Daytime sleep-wake cycle in the rat.

The daytime sleep-wake cycle of 20 male, albino rats was observed for a 8:00 a.m. to 8:00 p.m. period. EEG, EMG, gross body movement and eyelid position were continuously monitored throughout the 12 hr observation period. Based on percent of total time the results indicate that the rat's sleep-wake activities during the day are: awake, 24% (active, 17%; restings, 7%); SWS, 67% (light SWS, 13%; deep SWS, 54%); PS, 9%; and total sleep, 76%. The rats had a mean of 396 wake-ups from either SWS and PS per day. Visual observations revealed a sleep phenomenon not previously reported for the rat and termed “paradoxical awake”; an animal would generate typical light and deep SWS, EEG waves with either one or both eyes opened. The present results compared to previous findings revealed significant variability in estimates of the rat's sleep-wake activities which may be a function of illumination cycles, sleep observation times or duration of the adaptation periods.