EEG power densities (0.5-20 Hz) in different sleep-wake stages in rats

Frontofrontal and frontoparietal EEG power densities (0.5-20 Hz) in waking, light and deep slow-wave sleep, transition-type sleep, and rapid-eye-movement (REM) sleep were investigated for 8 h during the light period in 16 male Wistar rats. The data indicate that as delta activity (0.5-4.5 Hz) increased from light to deep slow-wave sleep, the number of epochs per scoring epoch with high a activity (11-16 Hz) as well as power densities in the rest of the spectrum (5-20 Hz) including a frequencies also increased. This is in parallel with other rat studies but contrasts findings in humans, where EEG a activity is reported to decrease as sleep deepens. During the 8-h recording period, delta activity decreased whereas sigma activity increased. (C) 1998 Elsevier Science Inc.