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 wa king, light and deep slow-wave sleep, transition-type sleep, and rapid -eye-movement (REM) sleep were investigated for 8 h during the light p eriod 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 a s power densities in the rest of the spectrum (5-20 Hz) including a fr equencies also increased. This is in parallel with other rat studies b ut contrasts findings in humans, where EEG a activity is reported to d ecrease as sleep deepens. During the 8-h recording period, delta activ ity decreased whereas sigma activity increased. (C) 1998 Elsevier Scie nce Inc.