February 11, 2007
Lack Of Sleep Suppresses Neurogenesis And Memory Formation

Elizabeth Gould at Princeton University found that sleep deprivation in rats inhibits the replication of neural stem cells and therefore prevents creation of new neurons.

Prolonged sleep deprivation is stressful and has been associated with adverse consequences for health and cognitive performance. Here, we show that sleep deprivation inhibits adult neurogenesis at a time when circulating levels of corticosterone are elevated. Moreover, clamping levels of this hormone prevents the sleep deprivation-induced reduction of cell proliferation. The recovery of normal levels of adult neurogenesis after chronic sleep deprivation occurs over a 2-wk period and involves a temporary increase in new neuron formation. This compensatory increase is dissociated from glucocorticoid levels as well as from the restoration of normal sleep patterns. Collectively, these findings suggest that, although sleep deprivation inhibits adult neurogenesis by acting as a stressor, its compensatory aftereffects involve glucocorticoid-independent factors.

Professor Gould thinks that the lack of sleep produces the stress hormone glucocorticoid which suppresses neurogenesis.

In a recent study by psychology professor Elizabeth Gould, rats who were sleep-deprived for 72 hours exhibited increased levels of the stress hormone glucocorticoid. These high stress levels in turn reduced neurogenesis — the birth of new neurons — in the rats' hippocampuses, a part of the brain critical for learning and memory.

Harvard Medical School researcher Seung-Schik Yoo asked a human group to stay up all night and then showed them images. People who stayed up all night did not remember the images as well as those who were well rested when they saw the images.

They correctly identified 74% of the previously viewed images, on average. By comparison, another group who had a proper night’s rest before viewing the 150 images at the start of the experiment correctly identified 86% of these pictures in the pop quiz.

Adequate sleep is needed for proper brain functioning. Of course you already knew that. But maybe the scientific evidence will serve as a useful reminder that you ought to act on that knowledge.

Share |      Randall Parker, 2007 February 11 11:02 PM  Brain Memory


Comments
Kurt9 said at February 12, 2007 8:53 AM:

This was obvious to me 10 years ago. Ever since they discovered stem cells in the early 90's, it was clear that the body, including the brain (the so-called "non-dividing" tissue) slowly regenerates itself and that much of this regeneration process occurs during sleep. It was already known at the time that neurons grow and delete dendrites (long term memory formation) during sleep. So, it was only natural to assume that new neurons are created by the stem cells during sleep as well.

This is why I think these new drugs are are supposed to do away with the need for sleep are hokey.

Randall Parker said at February 12, 2007 7:17 PM:

Kurt,

I would like to know how quickly blood glucocorticoid goes up when people are on modafinil (brand name Provigil). Does glucocorticoid go up as rapidly if you are on modafinil as if you just force yourself to stay awake?

I'd also like to know how fast blood glucocorticoid goes up if one just gets 1 or 2 fewer hours than one needs and could one use blood glucocorticoid as a test of just how much sleep one really needs?

Kurt9 said at February 13, 2007 9:00 AM:

Yeah, that might be a useful test of the amount of sleep one needs. Modafinil is one drug I will definitely skip.

Cedric Morrison said at February 15, 2007 4:58 AM:

The big use I see for modafinil isn't as a way to skip sleep, but as a way to increase alertness during a normal day. I wish I could get it over the counter.

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