Phases and states of sleep in the rat

The sleep of 60 Wistar albino rats was studied with chronically implanted electrodes to record the electrocorticogram (ECoG), the cervical electromyogram, and eye movements. The ECoG changes in areas 10, 4, 6, 1, 2, 2a, 3 and 7 paralleled the patterns found in the human EEG during the various stages of sleep, whereas in areas 23, 24, 29b, and 29c the waves were in synchronism with the dorsal hippocampus, thus allowing to follow the limbic electrical activity during sleep. The desynchronization of arousal was found distinct from the pattern recorded during the paradoxical phase. It is suggested that what is termed slow-wave or synchronized sleep, and paradoxical phase or desynchronized sleep be considered, respectively, synchronized and desynchronized states of sleep, each one comprising more than one phase or stage.