[Polygraphic study of sleep in young chickens at hatching, evolution at third and fourth days]

A polygraphic study of the states of vigilance in the young chicken was performed in the first week after hatching. At hatching, three stages of vigilance were present and their polygraphic characteristics were similar to those of the adult. Quantitative data showed a relative immaturity of the young chicken since percentages of paradoxical sleep and slow wave sleep were high in the first 8 h after hatching (PS/TS equals 16.5%). These values diminished rapidly and reached the adult values observed on the third day (PS/TS equals 6.4%). Our experimental conditions showed the presence of a nycthemeral rhythm of the states of vigilance by the third day.