Friday, August 14, 2009

The science of sleep

We tend to be more interested in the things that we don't have. In my case, I have found sleep increasingly intriguing and mysterious. (Of course it has to do with the several insomnia patients around me as well.) I just wanna share some of the things I found:

- We sleep every day. (Well, maybe not...) But scientist are still debating about the true purpose/function of sleep. Here are some arguments that support "sleep is essential." 1) There's no convincing case of a species of animal that does not sleep. 2) There's no indication that one can forgo sleep without a compensatory rebound. 3) There's no indication that one can forgo sleep without negative consequences.

- Although the entire body benefits from sleep, the brain suffers the most from lack of sleep. The most immediate, unavoidable effect of sleep deprivation is cognitive impairment.

- You think you will lose weight if you don't sleep much? Several studies, on the contrary, suggest that sleep deprivation is one of the causes of obesity. This may be happening because sleep deprivation could be disrupting hormones that regulate glucose metabolism and appetite.

- Sleep deprivation also makes you grumpy. Researchers at Harvard Medical School and UC Berkeley showed emotional-provocative images to volunteers after keeping them awake for 35 hours. They found out blood flow to the amygdala (an emotion-processing part of the brain) increased by over 60% in sleep-deprived brains. Some other studies linked this to the production of cortisol ("stress hormone").

- Feeling sleepy is different from being tired. Pure sleepiness can be conceptualized as the effect of central sleep-promoting mechanisms telling the brain it is time to sleep, whether or not brain cells need to do so. Examples are jet lag, food coma, or simply being in a boring environment. Pure tiredness can be conceptualized as the inability of brain cells to continue functioning in their normal waking mode, despite the central wake-promoting mechanisms telling the brain it should be fully alert. Do you really need examples for this?

- Multiple studies indicate that sleep may be a good time for consolidating and integrating newly acquired information in memory without interference from ongoing activities. The observation that neural circuits activated during learning are “reactivated” during sleep is consistent with this possibility.

- Researchers at UCSF found abnormal copies of DEC2 gene in those who need far less sleep than average. The gene is known to affect circadian rhythms and oxygen regulation in mammals. When the scientists bred mice to have the same mutation, the mice slept less and were more active than their regular rodent peers. I would be great to be a mutant!

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