January 30, 2008
Sleep Weakens Excess Brain Connections

We need to sleep to unburden ourselves of an excessive strengthening of neural connections.

MADISON – Most people know it from experience: After so many hours of being awake, your brain feels unable to absorb any more—and several hours of sleep will refresh it.

Now new research from the University of Wisconsin School of Medicine and Public Health clarifies this phenomenon, supporting the idea that sleep plays a critical role in the brain’s ability to change in response to its environment. This ability, called plasticity, is at the heart of learning.

Reporting in the Jan. 20, 2008, online version of Nature Neuroscience, the UW-Madison scientists showed by several measures that synapses — nerve cell connections central to brain plasticity — were very strong when rodents had been awake and weak when they had been asleep.

The new findings reinforce the UW-Madison researchers’ highly-debated hypothesis about the role of sleep. They believe that people sleep so that their synapses can downsize and prepare for a new day and the next round of learning and synaptic strengthening.

The human brain expends up to 80 percent of its energy on synaptic activity, constantly adding and strengthening connections in response to all kinds of stimulation, explains study author Chiara Cirelli, associate professor of psychiatry.

The idea is that we form lots of connections and not all of them matter. Probably if we form similar connections day after day those end up not getting weakened by sleep.

Share |      Randall Parker, 2008 January 30 10:23 PM  Brain Sleep

James Bowery said at January 31, 2008 2:43 PM:

Occam's Razor cuts while you sleep.

You may be interested in the effort, published this month, by Legg and Hutter to formalize their survey of definitions of natural intelligence:


Basically, they have found a way of directly expressing natural intelligence as data compression.

Peter Melia said at January 31, 2008 5:09 PM:

So all of these synapses are piled up at the end of the day?
I am blessed with deep dreamless sleep, and wake up each morning quite refreshed.
My wife on the other hand experiences the most incredible and detailed dreams, every night. She never seems to be, each morning, as fresh as I am.
Is this something to do with synapse activities? Could it be that because of my wife's dreams her synapses are not relaxing sufficiently?
Peter Melia

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