VIGILANCE STATES, EEG SPECTRA, AND CORTICAL TEMPERATURE IN THE GUINEA-PIG

Vigilance states, electroencephalogram (EEG) power spectra (0.25-25.0 Hz), and cortical temperature (T(CRT)) were obtained in nine guinea pi gs for 24 h in a 12:12-h light-dark (LD 12:12) schedule. Sleep was mar kedly polyphasic and fragmented and amounted to 32% of recording time, which is a low value compared with sleep in other rodents. There was 6.8% more sleep in the light period than in the dark period. EEG power density in non-rapid eye movement (NREM) sleep showed no significant temporal trend within the light or the dark period. The homeostatic as pects of sleep regulation, as proposed in the two-process model, can a ccount for the slow-wave activity (SWA) pattern also in the guinea pig : The small 24-h amplitude of the sleep-wakefulness pattern resulted i n a small, 12% decline of SWA within the light period. In contrast to more distinctly nocturnal rodents, SWA in the dark period was not high er than in the light period. T(CRT) showed no difference between the l ight and the dark period. T(CRT) in REM sleep and waking was higher th an T(CRT) in NREM sleep. T(CRT) increased after the transition from NR EM sleep to either REM sleep or waking, and decreased in the last minu te before the transition and after the transition from waking to NREM sleep. Motor activity measured in six animals for 11 days in constant darkness showed no apparent rhythm in three animals and a significant circadian rhythm in three others. Our data support the notion that gui nea pigs exhibit only a weak circadian rest-activity rhythm.