Evelyn Stern

Sleep States in Premature Infants

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.

Maturation of EEG activity during sleep in premature infants

Abstract 1. 1. Repeated polygraphic recording of long duration were made of seventeen premature, ten full-term, and five suspected small-for-dates infants. Besides EEG, these recordings included observation of behavior and monitoring of multiple physiological parameters. 2. 2. A 3-digit code was devised for EEG patterns of infants between 28 and 40 weeks conceptional age. The first 2 digits represent the conceptional age at which a variation on the basic pattern, identified by the third digit, generally occurs. The age designations of the code system were substantiated by the distributions of EEG patterns found in records at different conceptional ages. In addition, use of the coding system differentiated small-for-dates infants from prematures. 3. 3. The observations and physiological data were used in defining 2 sleep states: quiet sleep and active sleep. Examination of the distributions of EEG patterns within each state indicated progressively distinct relationships between state and EEG pattern with maturation. Determination of conceptional age and neurological maturation was based on these relationships.

A periodic cerebral rhythm in newborn infants

Abstract In premature and full-term infants the EEG during quiet sleep is characterized by bursts of large amplitude slow waves with superimposed rapid rhythms, alternating with attenuated periods of mixed frequencies. To trace the ontogenetic development of this pattern, the duration of the large amplitude activity (bursts) and attenuated periods (flats) was measured in recordings done at 29, 33, and 40 weeks conceptional age in premature infants and at 40 weeks in full-term and trisomy-21 (Downs syndrome) infants. All age-related changes were statistically significant. Between 29 and 40 weeks the length of the burst increased from 3.3 to 5.9 sec, the flat decreased from 9.3 to 4.4 sec, and the complete burst-flat unit decreased from 12.6 to 10.3 sec. The only difference between the groups occurred in the duration of bursts, which were longer in the prematures recorded at 40 weeks. Full-term and trisomy-21 infants of the same age showed no differences. The age changes were primarily due to numerous very long burst-to-burst intervals in the small premature infants. The modal interval at all ages was 9 sec, which suggests the presence of a central pacemaker that is not altered by maturation during intrauterine development. Consideration of parallels between EEG of immature animals and human infants led to the hypothesis that continuity of EEG activity (increasing burst length) is a function of cortical maturation involving increases in the complexity of interneuronal interaction and feedback circuits.