To Sleep, Perchance to Forget

Summary: Researchers report our synapses grow larger and stronger during day time, but shrink by almost 20 percent as we sleep.

Source: University of Wisconsin Madison.

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.

woman sleeping
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. NeuroscienceNews.com image is in the public domain.

The study was big news, picked up by outlets including The New York Times and National Public Radio. 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.

About this neuroscience research article

Source: Chiara Cirelli – University of Wisconsin Madison
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: The study will be presented at 2018 AAAS Annual Meeting.

Cite This NeuroscienceNews.com Article

[cbtabs][cbtab title=”MLA”]University of Wisconsin Madison “To Sleep, Perchance to Forget.” NeuroscienceNews. NeuroscienceNews, 19 February 2018.
< https://neurosciencenews.com/sleep-shy-8519/>.[/cbtab][cbtab title=”APA”]University of Wisconsin Madison (2018, February 19). To Sleep, Perchance to Forget. NeuroscienceNews. Retrieved February 19, 2018 from https://neurosciencenews.com/sleep-shy-8519/[/cbtab][cbtab title=”Chicago”]University of Wisconsin Madison “To Sleep, Perchance to Forget.” https://neurosciencenews.com/sleep-shy-8519/ (accessed February 19, 2018).[/cbtab][/cbtabs]

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  1. The Law of Sync and Think
    Regarding basic mechanism of synchronization systems in nature and neural communication I have a thinking to share.
    In the case of metronome, mechanical force makes two or more metronomes synchronized. I am trying to figure out that if other natural synchronized system shares the same mechanism. In synchronized flashing firefly case, photon is the major player; and in both synchronized school of fish and bird cases, radiation of body electromagnetic field (fish, a body length apart; birds 3-4 body length apart) is main player, also photon reflected by all the bodies’ scales and feathers could be involved. (https://www.ted.com/talks/steven_strogatz_on_sync)
    Because photon moves in light speed and electromagnetic wave is also a kind of light, so both would have momentum (p) if Einstein’s theory of relativity is applied. Then, the “mechanical force” would be established: which just like a light speed “rigid network”, every individual is tightly linked to each other timely and periodically. Although at the biological terminals, like the optic nerve and fish latera line organ, may have a brief delay, the whole picture of these synchronization systems would be a light speed rigid momentum network. In this picture, a radiation from one individual is also the stimulation to all others and these two functions occur exactly at same time. This mechanism also works with synchronized metronomes if we go back to the original, simplest nonlife synchronization system.

    The law of synchronization is: In any synchronization system, all the individual is connected to each other rigidly (or light speed momentum network), energy radiated from one individual will be propagated to and conserved in all other individuals in light speed. Energy radiated from all individuals will be fed back to each one individual at exactly same time. Energy tends to be not wasted as the form of entropy; entropy increase tends to be zero; one’s energy output is another’s energy input. The system tends to be energy conservatively beneficial and stable. Compare the randomly oscillating schools, synchronization has the lowest energy state (or the lowest energy cost), that is why all the synchronization systems are spontaneous processes and have universal appeal. Without extra energy input from outside of the system, the synchronization will not be broken.

    As for how the “school” of neurons in human brain behave like a light speed rigid network and concentrate on a task or “focus” on a neuro disorder, I have the following concern:
    In the University of Tokyo, I made such an observation: the traveling electrical field mediated transmission of action potentials between excitable cells with the cell-cell distance more than 10 mm (an anatomically astronomical distance in cortex). When longitudinal cells are arranged in parallel separately, the action potential generated from one cell can “jump” to other cells and cause all the cells to fire action potentials in concert. If two cells fire action potentials spontaneously and have their own rhythm, they tend to “learn” from each other, adjust their own pace, eventually lock their phases, and “remember” this common rhythm for a long while.
    For traveling electric field mediated cell-to-cell communication, we need the following conditions: 1) cells must be very sensitive; 2) cells must have certain length and arranged in parallel; 3) medium between cells must be relatively insulated; 4) electric field must be travelling to produce potential difference on the longitudinal cell surface. (see the paper in attachment http://gallica.bnf.fr/ark:/12148/bpt6k56752048/f705.image)

    Unlike synaptic neuronal network, which is a physiological transmission with the velocity of 0.2-120 m/s (synaptic delay period is not included), traveling electrical field mediated transmission is a physical process with the velocity of light speed because electromagnetic wave is also a kind of light. (see the power point in attachment: traveling electrical field mediated “learning, remembering and forgetting” process: learning is epiphany; remembering is lasting; forgetting is ambiguousness). Here again, the process obeys the law of synchronization. Without extra energy input, remembering will not be easily lost. In other word, forgetting is difficult. We could tell this human nature even from Greek mythology: Lethe, also known as the Ameles potamos (river of unmindfulness). Lethe was also the name of the Greek spirit of forgetfulness and oblivion,
    In a cortical circuit, the synaptic elements provide delicate and precise connections; while the other elements, traveling electrical field, may provide transient, rapid, flexible rather than fixed connections to synchronize rhythmic action potentials fired from axons which arrange in parallel and are well insulated by dielectric media. Whether exploring this invisible “tele” bridge linked synchronization or harmony in discrete regions of the brain, would bring exotic fresh air in the fields of neurological disorder, perception, recognition, learning and memory? I believe it is time for us to address “how the brain thinks”—that would fill the gap between brain and mind,
    The law of thinking is: The neural action potentials in human brain circuits produce clusters of traveling electrical fields. The traveling electrical field clusters with similar frequency tend to be synchronized. Integration, imagination, remembering, creation, etc. need some efforts sometimes, however, if these processes are simply synchronizations between different regions of the brain, the energy conservatively beneficial property of sync really makes human beings to perform these mental activities with great easy, great appeal and great pleasure.
    If this thinking temporarily is not recognized by neuroscience field, we benefit ourselves first: we all love parallel and symmetric things because our brain feels more comfortable and feels easier to remember. I predict that all kinds of(Hz) synchronization also happens between hemispheres (as well as between cerebral sulcus and cerebral convolution) of our brain in the speed of light speed to stock various information and to generate creative, imaginative ideas. If we are right-handed (I would like to point out some of left handed characters: Leonardo di Ser Piero da Vinci, Raffaello Sanzio, Michelangelo di Lodovico Buonarroti Simoni, Sir Isaac Newton and Albert Einstein) try hard to use left hand more and to do exercise in front of a mirror. Then, our brain would have more balance and more efficient synchronization or coherence, we remember things better, more clever than normal people, and sure enough, we have better daily life than all others (I am not joking).

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