Paradoxical sleep augmentation after imprinting in the domestic chick.

The EEG and EMG of two groups of chicks (Gallus domesticus), (an experimental one who was imprinted, and a control one who was not), were recorded during 3 hours before and 3 hours after imprinting. The fertilized eggs were kept in an incubator under controlled temperature and humidity until ecclosion occurred. The recording session began 10 hours after ecclosion and after two hours of habituation to the recording conditions. During the imprinting session, E group met a natural stuffed white hen moved by a slow motor. The total amount of time spent in paradoxical sleep (PS), as well as the number of PS episodes increased significantly following imprinting in the E group. Opposite results were found in C group: total amount and number of PS episodes decreased significantly after the pseudo-imprinting session. Neither slow wave sleep, nor wakefulness were modified.