Wake-sleep transitions

The flip-flop switch controlling wake-sleep transitions... 

Complicated processes govern wakefulness, sleep, and the transitions leading to sleep initiation and maintenance. Although the neurophysiology of sleep is complex, certain neurotransmitters promote sleep and wakefulness in different areas of the central nervous system (CNS). Serotonin is thought to control non-REM sleep, whereas cholinergic and adrenergic transmitters mediate REM sleep. Dopamine, norepinephrine, hypocretin, substance P, and histamine all play a role in wakefulness. Perturbations of various neurotransmitters are responsible for some sleep disorders and explain why various treatment modalities are beneficial. 

Severe narcolepsy-cataplexy comparable to the human disorder. Cataplectic episodes can be separated from wakefulness-REM sleep transitions... 

Technical term for properties of electrical or neural circuits (flip-flop switch) to rest in two distinct states while avoiding intermediate states (e.g., behavioral state sleep-wake transitions). 

Birkeland, A. J. (1982). Plasma melatonin levels and nocturnal transitions between sleep and wakefulness. Neuroendocrinology 34, 126-31. 

The importance of peptide transmitters in the modulation of sleep and wakefulness has become apparent in recent years. Previous work had focused on the role of monoamines in the circuitry that regulates the transitions between states of vigilance. Histaminergic neurons in the tuberomammillary nucleus are known to be key players in the activation of subcortical afferents during wakefulness (Wada et al, 1991). Activity of noradrenergic neurons in the locus coeruleus correlates with the state of vigilance (Jones, 1991). The role of serotonergic neurons in rapid eye movement (REM) sleep has also been established (Lydic et al., 1987 Monti Jantos, 1992 Fabre et al., 2000). 

Inability to maintain wakefulness bouts Severe decrease in REM sleep latency Frequent cataplexy and direct transitions to REM sleep... 

Mild decrease in REM sleep latency Absence of cataplexy or direct transitions to REM sleep Inability to maintain wakefulness bouts Mild decrease in REM sleep latency Occasional cataplexy and direct transitions to REM sleep Inability to maintain wakefulness bouts Severe decrease in REM sleep latency Frequent cataplexy and direct transitions to REM sleep Inability to maintain wakefulness bouts Severe decrease in REM sleep latency Frequent cataplexy and direct transitions to REM sleep Inability to maintain wakefulness bouts Severe decrease in REM latency Frequent cataplexy and separable direct transitions to REM sleep... 

Figure 15.5 Exemplar EEG/EMG recordings, from an orexin/ataxin-3 rat, to show the differences between two episodes of behavioral arrest (i.e. cataplexy) (A) associated with complete muscle atonia and accompanied by an EEG with the characteristics of REM sleep, and (B) also associated with complete muscle atonia, but with minimal change to the EEG. Both of these episodes are therefore cataplectic, as characterized in the mouse and human, but only in (B) is wakefulness, and therefore consciousness, likely to be maintained. The existence of both types of episode in the rat adds support to the conceptualization of cataplexy in the human as a transitional state between wakefulness and REM sleep, or a fragmentary occurrence of REM sleep (Hishikawa Shimizu, 1995). The visual differences evident between the EEG signals recorded in these two examples were subsequently confirmed by spectral analysis. Adapted from Beuckmann et at (2004).

Recurrent intrusions of elements of rapid eye movement (REM) sleep into the transition between sleep and wakefulness, as manifested by either hypnopompic or hypnagogic hallucinations or sleep paralysis at the beginning or end of sleep episodes... 

The distinction between conscious and subconscious mentation may however be more a matter of degree than absolute divide. This is most obvious in the transition from waking to normal sleep and dreaming. The neurochemistry of dreaming may ultimately provide one of the most important clues as to the chemistry of consciousness. In addition the basis of some mental disorders may be, as proposed for schizophrenia for example, the intrusion of dreaming mentation into the awake state. According to Allan Hobson s de-... 

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