Sleep and its disorders

By Dr. Stefano Casali

Introduction

The man spends an average of a third of his life sleeping. But sleeping does not mean cutting the bridges completely with reality: during sleep a complex series of phenomena is determined, first of all the dream (Mancia M., 1996). it is only in these last decades that we have tried to deepen and understand the mechanisms of this phenomenon, so complex and important, that for a long time, and in part still, remains similar to the dark side of the Moon.

In fact, despite the enormous amount of studies, the problems to be solved, the questions to be answered, are still many. If highlighting the two phases of Sleep (REM and non-REM) constituted a first fundamental step for an objective study of Sleep, it is also true that we know little not only about the cyclical mechanisms that trigger Sleep and its phases, but also on what happens in the human body during sleep (Drucker-Colin R., 1979). The importance of sleep can also be seen on the evolutionary plane: absent in fish and amphibians, it begins to appear in reptiles, while the REM and non-REM phases make a timid appearance in birds, to be definitively structured in mammals (Jouvet M., 2000). But apart from the importance of the neurophysiological study of Sleep, the problem of Sleep pathology is also open: namely insomnia, parasomnias, hypersomnias. It is estimated that currently around a quarter of the population over the age of 40 suffers from insomnia. If we take into account this high incidence and the fact that chronic insomnia is not only a sleep disorder but of the whole personality, we can understand the importance of the study of sleep, not only on a theoretical level, but also on that clinical (G. Coccagna., 2000).

»Considerations on the functional meaning of sleep
	second part (theory of recovery, conservation of energy, learning, evolutionary)
»Sleep disorders
	insomnia
	hypersomnia
	Sleep-wake disorders (introduction and transient disorders)
		second part (persistent disturbances)
	The parasomnias
	Obstructive sleep apnea
»	Sleep and thermoregulation
»	Sleep of the newborn
»	REM sleep, non-REM sleep and insomnia
»	Herbal tea for sleeping - Supplements for sleeping - Medications for sleeping

Considerations on the functional meaning of sleep

In spite of the great time we spend sleeping and the amount of research that has been done on sleep in physiology and experimental and clinical psychology, we are far from a satisfactory understanding of the meaning or functional meanings that this physiological state has. The effects of the sleep deprivation and the extreme organic depletion up to the death of the animal totally and almost deprived of Sleep, suggest that this physiological condition is indispensable for the biological and mental economy and for the same vital functions. In this perspective, Sleep presents analogies with the functions of other systems, aimed at ensuring that each animal can adapt to its ecological niche and can survive the attack of predators. The absence of REM sleep, for example, of some cetaceans (dolphins) despite their high encephalization quotient, could precisely respond to these adaptive and survival needs (Jouvet M., 2000). A discourse on the functional meaning of Sleep must be able to take into consideration the two great stages (NREM and REM) of which Sleep is composed. It is a common opinion that NREM sleep, especially its delta component, is related to the preservation and restoration of basic vegetative functions, while REM sleep seems to be connected above all to higher brain functions and mental functions that are organized in this phase. In particular, the delta NREM sleep seems to have a relationship, perhaps regulated by an instinctual situation, with the vigil that preceded it and with the metabolic, thermoregulatory and homeostatic needs related to it. In favor of this hypothesis are the secretion of growth hormone (GH), the homeostatic and thermoregulatory processes active in this phase of sleep and the increase in its percentage after prolonged physical exercise. Sleep related to NREM also appears to be in agreement with decreased neuronal activity that is observed at this stage. On the other hand, desynchronized sleep can perform the primary function of cerebral refreshment and cortical maturation. It is therefore a phase involved in psychological functions to constitute a "biological framework" suitable for the development of specific mental activities. In favor of this hypothesis there are some considerations that underline the coincidence between REM sleep and dream and the increase of protein synthesis that is observed in the REM phase. These data provide a satisfying biological basis for interpreting the information processing process and storing it that occurs with particular evidence during REM sleep (Block V. et Al., 1981; Gigli GL. Et al., 1985). The cortical maturation process also appears to be influenced by the REM-active sleep that in the fetus before and in the newborn then dominates the electropoligraphic and behavioral framework and is considered an indispensable endogenous stimulus for cortical synaptogenesis. REM sleep also seems to participate in the development and refinement of oculomotor control in ontogenesis. The intense rebound of REM sleep following the selective deprivation of this stage, together with the psychophysiological observations linking this phase to the dream experience, have suggested that REM sleep may be for brain and mental functions, more important than NREM sleep ( Jouvet M., 2000; Marks GA., Shaffety JP. Et al., 1995). The processes of synaptogenesis appear as the neurobiological basis of information organization and learning, REM sleep can be considered the stage in which information, which reached the brain in wake, undergoes a reorganization (which would allow a process adaptive) and a consolidation (which would allow memorization and remembrance). It is however relevant that the mental processes with more intense emotional participation that are connected to learning are parallel to a motor and sensory inhibition, to an increase in specific thalamocortical activity, to an intense EEG desynchronization and to a significant increase with bursts of activity of a high percentage of cortical neurons.

CONTINUE: second part »