Cortical Development, Electroencephalogram Rhythms, and the Sleep/Wake Cycle

Abstract

During adulthood electroencephalographic (EEG) recordings are used to distinguish wake, non rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. However, the close association between behavioral states and EEG rhythms is reached only late during development, after birth in humans and by the end of the second postnatal week in rats and mice. This critical time is also when cortical activity switches from a discontinuous to a continuous pattern, and we will review the major cellular and network changes that can account for this transition. After this close link is established, new evidence suggests that the slow waves of NREM sleep may function as markers to track cortical development. Before the EEG can be used to identify behavioral states, however, two distinct sleep phases – quiet sleep and active sleep – are identified based on behavioral criteria and muscle activity. During this early phase of development cortical activity is far from being disorganized, despite the presence of long periods of neuronal silence and the poor modulation by behavioral states. Specific EEG patterns such as spindle bursts and gamma oscillations have been identified very early on, and are believed to play a significant role in the refinement of brain circuits. Since most early EEG patterns do not map to a specific behavioral state, their contribution to the presumptive role of sleep in brain maturation remains to be established, and should be a major focus for future research.

The Development of Nociceptive Network Activity in the Somatosensory Cortex of Freely Moving Rat Pups

“…The second week of life represents a pivotal point in the transition from immature to mature cortex in terms of cell growth, synaptogenesis, mechanisms of cortical plasticity, NMDA activity and GABA hyperpolarization (Dehorter et al 2012), marking a time when cortical activity becomes strongly modulated by behavioral states (Cirelli and Tononi 2015). The emergence of a “pain state” in the somatosensory cortex, characterized by initial suppression in slow and enhancement of fast activities, which emerges and matures through the third and fourth postnatal weeks, has similarities with the transition from quiet awake to active explorative states, which also emerge at this age.…”

Large Scale Cortical Functional Networks Associated with Slow-Wave and Spindle-Burst-Related Spontaneous Activity

“…It is well established that, although the gross patterning of the somatosensory cortex may occur independently of activity, refinement relies on activity in the sensorimotor system (Pallas, 2001; Price et al, 2006; Inan and Crair, 2007; Hanganu-Opatz, 2010; Kolb et al, 2012; Blumberg, 2015; Cirelli and Tononi, 2015). In particular, injuring or deafferenting a limb during the first few days of life in the rat results in a failure of the development of the corresponding sensory cortex, as well as changes in sensory regions of the remaining limbs (Wall and Cusick, 1986; Dawson and Killackey, 1987; Waters et al, 1990; Pearson et al, 1999).…”

“…First, we discuss recent findings related to the slow-wave activity (SWA), a 0.5–4 Hz oscillation in the sleeping adult brain which synchronizes sensory, motor and association cortices in non-REM (NREM) sleep (Contreras and Steriade, 1997). Second, we discuss spindle bursts, a pattern of intermittent fast oscillations at 5–25 Hz in the developing brain which play an important role in maturation of sensory systems (Khazipov and Luhmann, 2006; Blankenship and Feller, 2009; Blumberg et al, 2013; Cirelli and Tononi, 2015). In discussing how both patterns are generated and shaped by neural circuits, we hope to reinforce the concept that sleep-related activity within sensory systems and other regions of the brain are neither noise nor idle “holding-patterns”, but rather are actively formed and deployed for specific purposes.…”

Can Better Management of Periodontal Disease Delay the Onset and Progression of Alzheimer’s Disease?

“…The first observable state is non-rapid eye movement sleep characterized by the presence of "theta waves" and "delta waves". Second is rapid eye movement sleep characterized by EEG patterns similar to people who are awake 9 but distinguished by the presence of phasic events (twitching limbs), and tonic phenomena (loss of muscle tone) [78].…”