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Napping neurons

Populations of neurons in the brains of sleep-deprived rats go to sleep though the animals remain awake

By | April 27, 2011

Sleeping neurons may be at the root of the most common symptoms of sleep deprivation, including attention lapses, poor judgment, and frequent mistakes in cognitive tasks. Specifically, populations of neurons in the brains of rats forced to stay awake briefly go "off-line," into a sleep-like state, according to a study published today (April 27) in linkurl:Nature.;http://www.nature.com/nature/current_issue.html
Sleep-deprived rat during sugar pellet test
Courtesy of Yuval Nir, University of Wisconsin-Madison
"We've all have this experience where we're forcing ourselves to stay awake later than we usually do," said linkurl:Christopher Colwell,;http://faculty.bri.ucla.edu/institution/personnel?personnel_id=45975 who studies sleep and circadian rhythms at the University of California, Los Angeles, and was not involved in the study. "We can still perform -- we're still obviously awake -- but...a person's performance is not as good," he said. "So, what's going on during that time?" Neuroscientist linkurl:Giulio Tononi,;http://tononi.psychiatry.wisc.edu/People/GiulioTononi.html along with Vlad Vyazovskiy and a team at the University of Wisconsin-Madison, set out to see what happens to neurons after they have been pushed beyond a normal waking period into a state of sleep deprivation. The researchers kept rats, a nocturnal species, awake for four extra hours in the morning, and attached microwires to neurons in the motor and parietal cortices to monitor neuronal activity. They found that though rats were active and had an overall "awake" electroencephalogram (EEG) -- low-voltage, high-frequency waves -- populations of neurons in one or the other cortex at times seemed to deviate briefly from this pattern, for about 50 milliseconds at a time, demonstrating a local slow wave EEG pattern indicative of non-REM sleep, the most common type of sleep. Even within the same cortical area, some neurons went offline while others stayed on. And the longer rats were kept awake, the more often populations of neurons went offline into the sleep-like pattern of activity. The team assessed the rats' behavioral performance while neurons were offline. Tasked with reaching a sugar pellet, rats' poor performance was correlated with the occurrence of offline periods of neurons in the motor cortex, a region typically engaged during the task. And performance worsened with prolonged sleep deprivation when such periods occurred more frequently. The finding stands in contrast with a long-standing belief that sleep is a global phenomenon, one that affects the whole brain. "Sleep and wake are still by and large global behaviors," said Tononi. "But there is more and more evidence now, and very strong evidence, that these things can happen locally." Colwell agrees, "It's been causing me, as I look at the literature, to change the way I'm thinking about [sleep]." The finding that neurons are locally online or offline is not entirely surprising, says Tononi. Human sleepwalking, for example, is evidence that some parts of the brain can be awake while other sleep. Marine mammals and birds also show a special ability to keep one hemisphere of the brain awake -- to keep the animal moving continuously through the water to breathe, for example -- while the other half sleeps. "The implications are somewhat obvious if [the new findings] were also to apply to humans," said Tononi. "Many of the symptoms and signs of sleep deprivation, including bad judgment, irritability, and various other things that are well known, might actually be due to neurons going offline randomly in your brain." But whether similar events are indeed happening in humans remains to be seen, said Colwell, author of an accompanying News & Views article in Nature. In addition, it would be valuable to prove not just a correlation between offline neurons and performance, but a direct cause and effect demonstration. "It's an important first step and an exciting study," said Colwell, "but the next thing is to show you can manipulate these same parameters and get the predicted effect." Vyazovskiy, V., et al., "Local sleep in awake rats," Nature, 472:443-7, 2011.
**__Related stories:__***linkurl:Cavefish lose sleep;http://www.the-scientist.com/news/display/58108/
[7th April 2011] *linkurl:Sleep adjusts fly synapses;http://www.the-scientist.com/blog/display/55573/
[2nd April 2009] *linkurl:Disappearing Before Dawn;http://www.the-scientist.com/2009/04/1/34/1/
[1st April 2009]
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Comments

Avatar of: Mike Waldrep

Mike Waldrep

Posts: 155

April 27, 2011

Interesting! I hope that everyone njoyed the recent holidays that we've had and I'm sorry for being late with my comments,but my computer has been down for a couple of days and I just got my computer to working again.
Avatar of: Mike Waldrep

Mike Waldrep

Posts: 155

April 27, 2011

I mesant "enjoyed." I'm sorry for the typo.
Avatar of: Mike Waldrep

Mike Waldrep

Posts: 155

April 27, 2011

I meant "enjoyed." Maybe this will work.
Avatar of: Mark Otto

Mark Otto

Posts: 2

April 27, 2011

Curious. It seems to fit to this article:\nthe-scientist.com/news/display/58108\nPossibly the cave fish have been selected for partial sleep of the brain.
Avatar of: David Allsebrook

David Allsebrook

Posts: 1

April 29, 2011

How finely can the activities of synapses be measured? By the synapse? By each function of a synapse?\nIs there a continuum of incidence of synapses going to sleep from one at a time upwards in number?\nAre there other reasons synapses close down and activate?\nWhat signals trigger these states?\nNo need to have this research done by tomorrow. End of next week will do.\nDavid\n\n
Avatar of: Russell Mills

Russell Mills

Posts: 9

April 29, 2011

This article helps explain a phenomenon I've noticed: When I briefly fall asleep while listening to music or to speech, my motor system seems to fall asleep before my auditory system does. If I sleep for just a few seconds and begin to snore but quickly awake, I usually experience no lapse of auditory awareness and can recall what was said while I was snoring.
Avatar of: sisi liu

sisi liu

Posts: 1

May 3, 2011

In the cone system motor neuron cell bodies lower brain movement in nuclear and spinal cord ventral Angle motion cells, their axon composed nerve and spinal respectively, the dominant systemic skeletal muscle voluntary movement. When next motor neuron damage due to lose nerve, muscle control, decreased muscle tone, show atony sexual paralysis; Muscle for nutrition obstacles and atrophy; Because all reflex arc is interrupted, shallow and deep reflection are disappear; No pathological reflex\nNext motor neuron
Avatar of: frank gorman

frank gorman

Posts: 1

May 17, 2011

1. I raise the question of how the neurons are signalled to go off line. My theory, which has been expressed in my book: 'The Scientific Basis of Spinal Manipulation Therapy for Constitutional Illnesses', is that such 'going off line' is a vascular phenomenon of the ischemic penumbra type.\n\n2. Second, in the book, I talk about the 'massing effect', in that dispersed neurons, which are offline, work together as a quotient, even though they are widely separated. Interesting stuff from a non scientist.\n\n3. My book can be obtained from Amazon.\n\nhttps://www.createspace.com/3567171\n\nDr. R. Frank Gorman

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