The organization of sleep and wakefulness after maternal separation in young rats.

Two-week-old infant rats were studied before and after 24 hr of maternal absence. This experience produced an increase in time spent awake, a reduction in time spent in paradoxical sleep (PS), and an increased frequency of state transitions with more frequent and shorter periods of both slow-wave sleep (SWS) AND PS. Body movements were increased and nonnutritive sucking decreased during PS after separation. Other aspects of sleep organization were relativly stable: the pattern of probability of direction of state transitions, the integration of the physiological and behavioral determinants of state, the pattern and amount of nonnutritive sucking, and the underlying PS cycle period. These findings, and the results of 2 control experiments, suggest that some aspects of the prolonged absence of the mother produce a shift in the infant's central neutral state regulation through processes yet to be understood.