Some drugs offer the promise of sleep to those who cannot, while others disrupt the sleep architecture of those who can. But despite its central role in all our lives, sleep remains the terra incognita of physiology and pharmacology. Research has recently begun to map this unknown land, unraveling the nature of sleep, offering insights into sleep-related conditions and suggesting new therapeutic targets. The latter could help develop a potentially lucrative market - especially as increasing numbers of people deliberately alter their biological rhythms, while insomnia remains a common, often inadequately treated condition. People have pondered the problem since Aristotle, and still nobody really knows.
Theories are legion, though most offer variations on three themes.
Firstly, that sleep restores chemical, physical, and mental reserves run down during the day - though exactly what it is that sleep might be restoring is not clear. And, finally, sleep may maintain circadian rhythms, keeping our physiology in a state in which it can respond to changing environmental and internal factors. More recently, in an extensive review of the evidence for their position, they argue that while diurnal activity in reptiles is bound to the circadian variations through the brain stem, control of awakening in mammals has moved to the cerebral cortex. Sleepwalking, for instance, is in our opinion a regression. Also, cot death might be understood as a regressive phenomenon because the undeveloped brain of a baby is in many aspects similar to the brain of a reptile.