Sleep and EEG slow-wave activity in the domestic cat: effect of sleep deprivation

The 24-h sleep-wake distribution, the vigilance states and the time course of EEG slow-wave activity was investigated in 8 adult domestic cats individually maintained in isolation under 14-h light (06.00-20.00 h)/10-h dim conditions. The frontal EEG and motor activity were continuously recorded for 22 h (during the daily cleaning and food-replenishing period between 07.00 and 09.00 h the cats were only observed). Sleep was prevented for 14 h (07.00-21.00 h) by playing with the animals. Recovery from sleep deprivation was recorded for the remaining 10 h of the dim period. Non-rapid eye movement (non-REM) sleep, REM sleep and waking were uniformly distributed over the light and dim period, with the exception of the 2-h feeding period where the cats were always awake. EEG power density in the delta band (0.75-4.5 Hz; slow-wave activity) was computed in non-REM sleep. The values in the light period were higher than in the dim period. In neither of the lighting periods was a trend observed. After sleep deprivation a small increase of non-REM sleep and REM sleep was present. EEG slow-wave activity was initially enhanced and then declined progressively. We conclude that despite the small circadian difference in the sleep-wake pattern observed in our cats, sleep homeostasis is similar to that observed in other mammalian species.