The development of sleep–wake rhythms and the search for elemental circuits in the infant brain.

Abstract

Despite the predominance of sleep in early infancy, developmental science has yet to play a major role in shaping concepts and theories about sleep and its associated ultradian and circadian rhythms. Here we argue that developmental analyses help us to elucidate the relative contributions of the brainstem and forebrain to sleep-wake control and to dissect the neural components of sleep-wake rhythms. Developmental analysis also makes it clear that sleep-wake processes in infants are the foundation for those of adults. For example, the infant brainstem alone contains a fundamental sleep-wake circuit that is sufficient to produce transitions among wakefulness, quiet sleep, and active sleep. Also, consistent with the requirements of a “flip-flop” model of sleep-wake processes, this brainstem circuit supports rapid transitions between states. Later in development, strengthening bidirectional interactions between the brainstem and forebrain contribute to the consolidation of sleep and wake bouts, the elaboration of sleep homeostatic processes, and the emergence of diurnal or nocturnal circadian rhythms. The developmental perspective promoted here critically constrains theories of sleep-wake control and provides a needed framework for the creation of fully realized computational models. Finally, with a better understanding of how this system is constructed developmentally, we will gain insight into the processes that govern its disintegration due to aging and disease.

Call it Worm Sleep

“…While the physiological differences between mechanisms generating REM and non-REM sleep are widely appreciated, the function and regulation of these states are incompletely understood [21]. Likewise, little is known about the physiological and functional differences between infection-induced sleep and circadian sleep, or between sleep at different developmental stages [22]. …”

“…In Drosophila , sleep in young animals plays a role in the development of neural circuitry required for courtship behavior [84]. Sleep in neonatal rats has been described as distinct from both REM and non-REM sleep in adult animals, suggesting that developmental sleep may serve different functions than sleep in adults [22]. Thus, C. elegans DTS may prove to be a useful model for understanding the importance of sleep in growth and development.…”

The Visual Scoring of Sleep in Infants 0 to 2 Months of Age

“…The ontogenetic development of sleep follows orderly reproducible patterns. [40][41][42][43][44] The behavioral correlates of REM sleep are seen as early as 28-30 w CA when the EEG was still undifferentiated; recognizable EEG patterns of REM and NREM sleep first appear at 32-34 w CA. 32,33,45,46 Piaget 47 and Piers and Piaget 48 thought play was the major "work" of children, but for infants it is sleep.…”

“…Myoclonic twitching during sleep in early development are thought to: (1) sculpt nascent neuronal circuits in the cerebral cortex; (2) guide the formation, rearrangement, and elimination of synapses; and (3) construct sensory maps for auditory, motor, touch, and noxious topographic regions of the brain and the infant connectome. 53 Blumberg et al (2014) argue that myoclonic twitches during REM sleep in infants represent a form of motor exploration which help human infants and other mammals explore limb biomechanics, build motor synergies, and lay a foundation for complex, automatic, and goal-directed movements when awake.…”

A new view of “dream enactment” in REM sleep behavior disorder

“…Sleep in early infancy is a process of change across several dimensions: New sleep components (e.g., cortical delta activity) emerge and coalesce with already-existing sleep components, initially fragmented bouts consolidate, homeostatic mechanisms are refined, and circadian rhythmicity develops (for reviews, see [22,23]). However, infant and adult sleep are also similar in many important ways, especially with regard to motor behavior and its neural control [24].…”