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Nature sobre el sueño

Nature ha sacado un suplemento de acceso libre sobre la ciencia neurocognitiva del sueño.

Con tanto tutorial por ahí sobre cómo tunear los ciclos del sueño¹, siempre es bueno leer antes lo que dicen los expertos.

1. Introducción: sueño. The fundamental truths of sleep are not difficult to master: one sleeps when one is tired — mostly at night—and awakens the next day usually feeling rested and refreshed. So why put together an Insight on a topic that seems so straightforward? Although it is often true in biology that things are more complex than they seem at first glance, it is especially accurate for sleep.


2. El sueño es del cerebro, por el cerebro y para el cerebro. 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.


3. Regulación hipotalámica del sueño y los ritmos circadianos. 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.


4. Indicios de las funciones del sueño mamífero. 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.


5. Consolidación de la memoria dependiente del sueño. The concept of 'sleeping on a problem' is familiar to most of us. But with myriad stages of sleep, forms of memory and processes of memory encoding and consolidation, sorting out how sleep contributes to memory has been anything but straightforward. Nevertheless, converging evidence, from the molecular to the phenomenological, leaves little doubt that offline memory reprocessing during sleep is an important component of how our memories are formed and ultimately shaped.


6. Ideas a partir del estudio de los desórdenes humanos del sueño. 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.


7. ¿Cuáles son las fuentes de memoria del sueño?. 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.

¹ Ver, por ejemplo, Las alarmas son malas. Cómo levantarse y sentirse mejor., El plan de sueño de Uberman o Hackeando el sueño, tres enlaces populares en del.icio.us.