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jueves, 8 de noviembre de 2012

El misterioso reino de Morfeo en Nature

Insight: Sleep

Vol. 437, No. 7063 pp1207-1396

In this supplement

  Aquí he escogido algunos de los fascinantes artículos dedicados al sueño que publica el vol 437 de Nature. Noten las veces que los investigadores reconocen lo poco que se sabe, o todo lo que queda por averiguar, en torno a una función vital como es el sueño. La vida es, biológicamente sueño.

Sleep is of the brain, by the brain and for the brain

J. Allan Hobson1
Sleep is a widespread biological phenomenon, and its scientific study is proceeding at multiple levels at the same time. Marked progress is being made in answering three fundamental questions: what is sleep, what are its mechanisms and what are its functions? The most salient answers to these questions have resulted from applying new techniques from basic and applied neuroscience research. The study of sleep is also shedding light on our understanding of consciousness, which undergoes alteration in parallel with sleep-induced changes in the brain.

What are the memory sources of dreaming?

Tore A. Nielsen1,2 & Philippe Stenstrom1,3
Investigators since Freud have appreciated that memories of the people, places, activities and emotions of daily life are reflected in dreams but are typically so fragmented that their predictability is nil. The mechanisms that translate such memories into dream images remain largely unknown. New research targeting relationships between dreaming, memory and the hippocampus is producing a new theory to explain how, why and when we dream of waking life events.

Neuroscience: A memory boost while you sleep

Robert Stickgold1
It is generally agreed that sleep aids memory consolidation, but the reasons for this are a mystery. Part of the answer may lie in the patterns of synchronous brain activity unique to the state of slumber.
Only ten years ago, discussions about the purpose of sleep offered great hypotheses, but these were based on flimsy evidence. So scant were the data that some researchers argued that sleep might have no use at all.

Review Article Hypothalamic regulation of sleep and circadian rhythms

Clifford B. Saper1, Thomas E. Scammell1 & Jun Lu1
A series of findings over the past decade has begun to identify the brain circuitry and neurotransmitters that regulate our daily cycles of sleep and wakefulness. The latter depends on a network of cell groups that activate the thalamus and the cerebral cortex. A key switch in the hypothalamus shuts off this arousal system during sleep. Other hypothalamic neurons stabilize the switch, and their absence results in inappropriate switching of behavioural states, such as occurs in narcolepsy. These findings explain how various drugs affect sleep and wakefulness, and provide the basis for a wide range of environmental influences to shape wake–sleep cycles into the optimal pattern for survival.

Review Article Clues to the functions of mammalian sleep

Jerome M. Siegel1
The functions of mammalian sleep remain unclear. Most theories suggest a role for non-rapid eye movement (NREM) sleep in energy conservation and in nervous system recuperation. Theories of REM sleep have suggested a role for this state in periodic brain activation during sleep, in localized recuperative processes and in emotional regulation. Across mammals, the amount and nature of sleep are correlated with age, body size and ecological variables, such as whether the animals live in a terrestrial or an aquatic environment, their diet and the safety of their sleeping site. Sleep may be an efficient time for the completion of a number of functions, but variations in sleep expression indicate that these functions may differ across species.

Review Article Insights from studying human sleep disorders

Mark W. Mahowald1 & Carlos H. Schenck1
Problems with sleep are one of the commonest reasons for seeking medical attention. Knowledge gained from basic research into sleep in animals has led to marked advances in the understanding of human sleep, with important diagnostic and therapeutic implications. At the same time, research guided by human sleep disorders is leading to important basic sleep concepts. For example, sleep may not be a global, but rather a local, brain phenomenon. Furthermore, contrary to common assumptions, wakefulness, rapid eye movement (REM) and non-REM sleep are not mutually exclusive states. This striking realization explains a fascinating range of clinical phenomena.