October 1999, the movie Fight Club was released. The story was about a man that suffered from intense insomnia " 4 months of consecutive wakefulness. .
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Sleep.
Sleep is the biological process that a person spends almost a third of their life doing. After decades of research, we still cannot say we have a full understanding of this process. One thing that is safe to say is that it has a function; considering the large amount of time that organisms spend on it, if it was not adaptive, it would not survive through evolution. As for what kind of function it serves, there is still no definite answer (Pinel 1999 [Rechtschaffan 1998]). But there are two main theories that are trying to explain what we do know so far. .
The first theory is the Recuperation Theory, which is the way most people perceive and explain sleep. It sees sleep as a repairing process that reverses the imbalance of our system caused by daily activity. It assumes that activities during our wakefulness disturbs our body's homeostasis. The common concept of needing more sleep to catch up' previously lost sleep would belong to this theory. .
The second theory is the Circadian Theory. It explains that sleep is just a way for animals to conserve energy and to avoid unnecessary activities. It also focuses on circadian rhythms (Pinel 1999 [Hastings, 1997]), which are the cycles an animal follows for sleeping and waking, with each cycle lasting about 24 hours. According to Groos, 1983, "it is virtually impossible to find a physiological, biochemical or behavioral process in animals which does not display some measure of circadian rhythmicity-. And in order for our circadian cycles to be synchronized with the 24 hour day, we rely on zeitgebers, environmental cues, to adjust our cycles. .
Even though the recuperation theory is more widely acknowledged, it seems the circadian theory explains more of the picture. For example, the recuperation theory would predict sleep deprivation would cause serious physiological dysfunction, but research shows that is not the case (Pinel 1999 [Karadzic 1973, Horne 1983 and Martin 1986]).
