Vol 9, No 3 - Chronobiology in Psychiatry
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I n   t h i s   i s s u e ... Chronobiology is the domain of research on temporal variations in biological function, ie, endogenous biologi- cal rhythms. These rhythms are a recognized fact of biol- ogy, and have already been observed in some bacteria. In multicellular organisms, there exist cells and groups of cells known as biological clocks that show spontaneous cycles in their activity levels. The existence of these cycles is independent of regular or irregular changes in the envi- ronment, but these changes modulate them. An evolu- tionary  hypothesis  states  that  endogenous  rhythms evolved in order for living beings to anticipate demands from the environment. Like any system, biological clocks can show peculiarities in their functioning, and these can be the causes of syndromes or disorders. Also, endoge- nous biological rhythms can be secondarily influenced by pathological situations. Thus, the theme of chronobiolo- gy is both fascinating and relevant for several human syn- dromes or disorders. In this issue of Dialogues in Clinical Neuroscience, two general themes are presented by the authors. The first concerns physiology: the genetics, bio- chemistry and neuroanatomy of biological clocks. The second is about the implication of biological clocks in neuropsychiatric syndromes and disorders. The State of the art paper by Pierre Schulz (p 237) lists a series of definitions that are a framework for a descrip- tive understanding of biological rhythms, and summa- rizes several facts of the anatomical and physiological organization of biological clocks. The author goes on to describe  a  few  unusual  phenotypic  expressions  of rhythms in healthy humans, such as rest-activity cycles of duration different than 24 hours. The core of the paper consists of a description of chronobiological changes that occur in several neuropsychiatric disorders, and of how these changes might be explained. The last part of the paper deals with the implications of chronobiology and chronopharmacology for the management of various dis- orders. In the first Basic research  paper, Ueli Schibler (p 257) illustrates  the  impressive  advances  of  knowledge  in chronobiology; several of the discoveries come from the author’s own laboratory. The enigma of how isolated and grouped cells manage to measure the passing of time seems to have been solved at the biochemical level, and the other enigma of how a cell-free assemblage of pro- teins could do the same, another tour de force of nature, is under study. His extensive review indicates that the main themes of chronobiological research have evolved over a couple of decades, from macroscopic studies on rhythms in animals and humans, and from mathematical modeling addressing the number and relationships of main  clocks,  to  molecular  mechanisms  of  biological clocks. Readers who are not familiar with molecular biol- ogy might be impressed by the large number of genes (written as abbreviations in italics) and proteins and enzymes (abbreviated in roman letters), and they will conclude from the list of these endogenous molecules that the molecular machinery of biological clocks is high- ly complex. This complexity also illustrates the many solu- tions achieved through natural evolution and selection, as well as the many sites where modifications might lead to clinical syndromes or disorders. The second Basic research paper, by Mehdi Tafti (p 273), is a review of the genetics of normal and abnormal sleep, mainly, but not exclusively, on the basis of research done in animals. The author underlines that the molecular basis of sleep is less well-known than that of circadian rhythms. His description of recent work done in a few laboratories, including his own, nevertheless suggests that the genes that influence diverse aspects of sleep, as can be measured using the electroencephalogram, will soon be better understood. He also indicates the possi- bility that given genes that play a role in sleep may have other roles as well, and this is alluded to, among several examples,  with  the  relationship  between  sleep  and memory. The first two Basic research papers are within the realm of biological and medical knowledge, while a third paper in this section, by Christian Oestreicher (p 279), is a his- torical account of philosophers’ and mathematicians’ thoughts about the structure of the universe, over cen- turies of discoveries that led to modern physics and to the theory of chaos. This article will prove a challenging read to many persons who are not mathematicians. The challenge consists in the theme itself of the paper, as well as in the concept that links between causes and effects can be difficult to identify and define, a concept oppo- site to that of determinism. (The lack of easily identified links between causes and effects, as can occur in patho- physiology, represents a real complication for the practice of clinical medicine). The challenge also consists in the fact that the paper, being a historical account, provides a list of successive constructs of reality, rather than a sin-