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SUMMARY Suggestions that rapid eye movement (REM) sleep is ontogenetically primitive and observations of the behaviour of premature infants led to an attempt to trace the development of sleep in human infants from the premature period to three months after the expected date of delivery. Three sleep states were established, Quiet Sleep, Active Sleep (REM sleep), and Transitional Sleep, for the categorization of each 20 second interval of sleep during lengthy electroence‐phalographic and polygraphic recordings. Criteria regarding observed movements, eye movements, respiratory pattern, heart rate, chin electromyogram, and the EEG were used for a visual analysis of the tracings, with the specification that only four of the six criteria had to be met for classification of a 20 second interval as one sleep state or another. A second analysis, by means of computer sorting, was more rigid in that each 20 second interval had to meet all three criteria regarding observed movement, respiratory pattern, and eye movements. The other criteria were omitted. The second stricter analysis yielded a greater percentage of intervals that could not be called Active or Quiet Sleep and were, therefore, classified as Transitional Sleep, especially below 35 weeks gestational age. This finding/supports the concept that the sleep states of the more premature infants are less well defined and that the simultaneous occurrence of all the necessary criteria, particularly in Active 5jileep, is rarer than at later ages. Both analyses showed that the amount of Quiet Sleep increases as the infant matures, from 10 per cent at 31–32 weeks gestational age to roughly 50 per cent at 3 months past term. Conversely, Active Sleep decreases with maturation, the exact amount depending on the method of categorization. When the records were analysed visually, Active Sleep was found to constitute 68 per cent of the total sleep at 33–34 weeks gestational age and diminished to 36 per cent at 3 months; with computer sorting the comparable figures were 45 per cent and 25 per cent. Nevertheless, the figures for premature infants at term and 3 months were similar to those for full‐term infants at the same ages. The ill‐defined nature of the Active Sleep state in the early gestational ages and its subsequent delineation and diminution in amount amplify previous characterizations of this sleep state as a neurophysiologically primitive state and predecessor of the later stage during which dreaming occurs. RÉSUMÉ EAtats de sommeil chez les prématurés On a suggéré que le sommeil avec mouvements rapides des yeux (REM) est primitif ontogénétiquement; ceci, ajoutéà des observations du comportement des prématurés, nous a amenéà tenter de tracer le développement du sommeil chez les nouveaux‐nés humains depuis la période prématurée jusqu'à trois mois après la date prévue de l'accouchement. Trois états de sommeil ont étéétablis: Sommeil Tranquille, Sommeil Actif (Sommeil REM), et Sommeil Transitoire; pour la caractérisation de chacun d'entre eux on a étudié des intervalles de 20...

This study was done to compare time‐lapse video recordings of eye and body activity with polygraphically determined states of activity from human premature infants. Time‐lapse video recording in neonates is new, and was first reported by Anders and Sostek (1976) who have used time‐lapse video recordings of sleep‐wake activity in full‐term infants. We recorded 8 prematurely born human infants, 5 males and 3 females between 29 and 34 weeks gestational age at birth. Behavioral and physiological states were scored from the polygraphic records. The video‐tape observations were coded for three levels of body movement: no body movement, some body movement, and a lot of body movement, and eyes: closed no rapid eye movements (REMs), REMs, and open. The following relationships (concordance) were observed: 1) 60% of the non‐REM/no movement epochs were in the Quiet state on the polygraph; 2) 83% of the REM/some movement epochs were in the REM state on the polygraph; and 3) 82% of the REM/ a lot of movement epochs were in the REM state on the polygraph.

Within the sleep of adults and infants there are cyclic fluctuations between quiet and active sleep. These fluctuations may also persist during wakefulness as rest-activity cycles but are less readily detected. They constitute a fundamental biological rhythm on which other daily rhythms are superimposed. In adults the rest-activity cycle is 90 minutes in duration. The quiet-active sleep cycles of term, 3-, and 8-month-old infants were determined by polygraphic recording of eye and body movements, respirations, and electroencephalogram. The cycle length at term was 47 minutes and 49 and 50 minutes at 3 and 8 months. The increase in cycle length with maturation was not significant, but there was a significant change in the proportion of quiet to active sleep within a cycle. At term they were equal, while at 8 months quiet sleep was twice as long as active sleep. Quiet sleep is a highly controlled state requiring complex feedback mechanisms. The increasing proportion of quiet sleep may be a significant measure of normal brain development.