HIPPOCAMPAL EEG THETA-POWER-DENSITY IS SIMILAR DURING SLOW-WAVE SLEEPAND PARADOXICAL SLEEP - A LONG-TERM STUDY IN RATS

Rat hippocampal EEG and motor activity were studied during 15 days in relation to the vigilance state and to the light-dark cycle with a com puterized system. During slow-wave sleep (SS) the hippocampal EEG has an outstanding mean power density in the theta band, similar to the la rge values present during paradoxical sleep. A circadian modulation wa s found for motor activity in SS and wakefulness (i.e. day-sleep is mo re restless, day-wakefulness is more quiet than night), and for EEG me an theta power in SS (i.e. less during day-sleep than night-sleep). Th ese data underline the importance of analyzing the dark period when st udying nocturnal animals.