Development of sleep and wakefulness in the foetal lamb

Abstract

The evolution of cortical activity was studied from 0.6 of term in utero in eleven foetal lambs, and through most of parturition and the early post-partum period in two newborn lambs. At 0.8 of term the alternating periods of wakefulness and sleep were definite. During a period of electrocorticographic desynchronization paradoxical sleep could be recognized by the return to slow wave sleep that occurs at the sounding of a bell and also by rapid eye movements. No apparent major modification of electrocortical activity accompanied the transition from intra-uterine to extra-uterine life. At parturition there was a sudden increase in muscular tone and a 50% decrease in paradoxical sleep.