A developmental marker of central nervous system maturation: Part I.

Sleep is the predominant behavioral state of the neonate and the neurophysiologic expression of cerebral function during rapid brain growth and maturation that characterizes the neonatal period. The ontogeny of electroencephalographic (EEG) sleep in the neonate can be monitored by serial EEG/polygraphic recordings. A variety of physiologic markers accompany neonatal sleep, such as specific EEG patterns, rapid eye movements, arousals, autonomic signs, and body movements. These parameters vary in occurrence and abundance during different segments of the neonatal sleep cycle. Time-dependent interrelationships among these different physiologic components can be assessed by visual inspection of EEG recordings to monitor specific patterns that appear during one or more sleep cycles. Mathematical modeling and computer technologies permit the study of interactions among neurophysiologic signals which are not apparent by visual inspection. An understanding of biological rhythm relationships among different sleep events offers insights into the effects of extrauterine environment on the development of the central nervous system in the healthy preterm neonate and the disturbances in the sleep EEG rhythm in abnormal neonates. Sleep EEG analysis may be useful prognostically because "normalization" of abnormal EEG patterns often occurs following the initial acute illness. Suitable, normative data from very premature neonates are needed before pediatric neurologists can rely on neonatal EEG as an indicator of brain maturation in this low-birth weight group. An understanding of the biologic significance of the ontogeny of neonatal sleep, as well as the clinical significance of perturbations in this sleep cycle with disease, will lead to more reliable analyses of sleep physiology for research and clinical purposes.