PDA

View Full Version : Sleep is for forgetfullness



Angela
04-02-17, 18:40
Well, at least partly.

See:
https://www.nytimes.com/2017/02/02/science/sleep-memory-brain-forgetting.html?ribbon-ad-idx=2&rref=science&module=Ribbon&version=context&region=Header&action=click&contentCollection=Science&pgtype=article

"Over the years, scientists have come up with a lot of ideas about why we sleep.Some have argued that it’s a way to save energy. Others have suggested that slumber provides an opportunity to clear away the brain’s cellular waste. Still others have proposed that sleep simply forces animals to lie still, letting them hide from predators.
A pair of papers published on Thursday in the journal Science offer evidence for another notion: We sleep to forget some of the things we learn each day.
In order to learn, we have to grow connections, or synapses, between the neurons in our brains. These connections enable neurons to send signals to one another quickly and efficiently. We store new memories in these networks.
In 2003, Giulio Tononi and Chiara Cirelli, biologists at the University of Wisconsin-Madison, proposed that synapses (http://science.sciencemag.org/cgi/doi/10.1126/science.aah5982)grew so exuberantly during the day that our brain circuits got “noisy.” When we sleep, the scientists argued, our brains pare back the connections to lift the signal over the noise."

In the years since they figured out a way to test it in the lab.

"The synapses in the brains of sleeping mice, they found, were 18 percent smaller than in awake ones. “That there’s such a big change over all is surprising,” Dr. Tononi said.
The second study (http://science.sciencemag.org/cgi/doi/10.1126/science.aai8355)was led by Graham H. Diering, a postdoctoral researcher at Johns Hopkins University."

"they found that the number of surface proteins dropped during sleep. That decline is what you would expect if the synapses were shrinking.
Dr. Diering and his colleagues then searched for the molecular trigger for this change. They found that hundreds of proteins increase or decrease inside of synapses during the night. But one protein in particular, called Homer1A, stood out."

"Dr. Diering’s research suggests that sleepiness triggers neurons to make Homer1A and ship it into their synapses. When sleep arrives, Homer1A turns on the pruning machinery."

"In their own experiment, Dr. Tononi and his colleagues found that the pruning didn’t strike every neuron. A fifth of the synapses were unchanged. It’s possible that these synapses encode well-established memories that shouldn’t be tampered with.
“You can forget in a smart way,” Dr. Tononi said.
Other researchers cautioned that the new findings weren’t definitive proof of the synaptic homeostasis hypothesis."

Wheal
28-09-17, 16:42
This makes me wonder if the clearing "of cellular waste" is what happens in alzheimer's patients who have Sundowner's Syndrome.

firetown
28-09-17, 21:10
So maybe when we have insomnia due to too much on our mind, it could it be that ee simply cannot sleep knowing we cannot allow ourselves to forget what we have yet to deal with.

Angela
28-09-17, 21:33
So maybe when we have insomnia due to too much on our mind, it could it be that ee simply cannot sleep knowing we cannot allow ourselves to forget what we have yet to deal with.

That's an interesting take on it. You are constantly running through scenarios, trying to prepare for all eventualities.

timetraveller
24-11-17, 15:28
Agree this is interesting. For me it's the opposite. I usually study before sleeping and in the next morning after a good sleep, I am able to remember and recall everything I studied. I think sleeping also help our brain to organize and filter important memory to keep.

LeBrok
24-11-17, 17:47
Agree this is interesting. For me it's the opposite. I usually study before sleeping and in the next morning after a good sleep, I am able to remember and recall everything I studied. I think sleeping also help our brain to organize and filter important memory to keep.What it meant was that not important things are forgotten, pruning system - not to waste valuable brain space, but important memories retained and solidified.

Jovialis
18-02-18, 02:42
The researchers have expanded on this study today:



The debate in sleep science has gone on for a generation. People and other animals sicken and die if they are deprived of sleep, but why is sleep so essential?

Psychiatrists Chiara Cirelli and Giulio Tononi of the Wisconsin Center for Sleep and Consciousness proposed the "synaptic homeostasis hypothesis" (SHY) in 2003. This hypothesis holds that sleep is the price we pay for brains that are plastic and able to keep learning new things.

A few years ago, they went all in on a four-year research effort that could show direct evidence for their theory.

The result, published in February 2017 in Science, offered direct visual proof of SHY. Cirelli, a professor in the University of Wisconsin's School of Medicine and Public Health, expanded on the research today (Feb. 17, 2018) at the annual meeting of the American Association for the Advancement of Science.

Striking electron-microscope pictures from inside the brains of mice suggest what happens in our own brain every day: Our synapses - the junctions between nerve cells - grow strong and large during the stimulation of daytime, then shrink by nearly 20 percent while we sleep, creating room for more growth and learning the next day.

A large team of researchers sectioned the brains of mice and then used a scanning electron microscope to photograph, reconstruct, and analyze two areas of cerebral cortex. They were able to reconstruct 6,920 synapses and measure their size.

The team deliberately did not know whether they were analyzing the brain cells of a well-rested mouse or one that had been awake. When they finally "broke the code" and correlated the measurements with the amount of sleep the mice had during the six to eight hours before the image was taken, they found that a few hours of sleep led on average to an 18 percent decrease in the size of the synapses. These changes occurred in both areas of the cerebral cortex and were proportional to the size of the synapses.

The study was big news. It was bolstered by a companion Johns Hopkins University study that analyzed brain proteins to also confirm SHY's prediction that the purpose of sleep is to scale back synapses.

For Cirelli, the study was a big gamble that paid off. But she's not resting on her laurels. Her lab is now looking at new brain areas, and at the brains of young mice to understand the role sleep plays in brain development.

https://medicalxpress.com/news/2018-02-perchance.html

https://aaas.confex.com/aaas/2018/meetingapp.cgi/Paper/21072