Sleep patterns in the parakeet Melopsittacus undulatus.

Electrophysiological and behavioral studies of vigilance states were performed on adult specimens of the parakeet Melopsittacus undulatus. Four states of vigilance were identified: Wakefulness, drownsiness, slow wave sleep and paradoxical sleep. During wakefulness, a low voltage fast EEG pattern was observed. This pattern was progressively increasing in amplitude and decreasing in frequency when passing from drowsiness to slow wave sleep. Sleep spindles were not present. Slow wave sleep was frequently interrupted by paradoxical sleep episodes of short duration (6.4 +/- 3.2 sec), characterized by an EEG pattern similar to that of waking state. During wakefulness there were body and eye movements. This motor activity decreased when animals went into drowsiness and slow wave sleep. Paradoxical sleep was characterized by slight motor automatisms, including sometimes ocular movements.