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Whether to check the time or to waste time, people often watch their smartphone after waking up in the middle of the night.
Although this burst of acute light makes sleep more difficult, a new study from Northwestern University indicates that it will not interfere with the body's circadian rhythms.
For the first time, researchers have directly tested how the brain turns the body into light impulses to affect sleep. They discovered that separate areas of the brain are responsible for mild impulses compared to prolonged exposure to light. This discovery challenges the widely accepted belief that all light information is relayed by the suprachiasmatic nucleus of the brain (SCN), which synchronizes the sleep / wake cycles of the body.
"Before the widespread use of electricity, our exposure to light and darkness has occurred according to a highly predictable pattern," said Tiffany Schmidt, of Northwestern, who said directed the study. "But the light has become very cheap, we all have smartphones and their screens are very bright, we are all exposed to the light at the wrong times of the day, and it is increasingly important to understand how these different types of Information about the light is relayed to the brain. "
The newspaper will publish on July 23 in the journal eLife. Schmidt is an badistant professor of neurobiology at Weinberg College of Arts and Sciences in Northwestern. The study was conducted in collaboration with the laboratories of Fred Turek, neurobiology professor Charles and Emma Morrison in Weinberg, and Samer Hattar, section chief at the National Institute of Mental Health.
Once light enters the eye, specialized neurons called intrinsically photosensitive retinal ganglion cells (ipRGC) transmit light information to the brain. Prior to the Northwestern study, researchers were generally confident that all the light information went through the SCN, a densely populated area of the hypothalamus called "circadian pacemaker" of the body.
"The bright information arrives in the SCN, and that is what syncs all the body clocks with the light / dark cycle," Schmidt said. "This main stimulator ensures that everything is synchronized."
To conduct this study, Schmidt and his team used a genetically modified mouse model in which the ipRGCs were only projected on the RCS, but not in other regions of the brain. Since mice are nocturnal, they fall asleep when exposed to light. However, the mice participating in the experiment remained awake when they were exposed to brief pulses of light at night. The body temperature of the mice, which is also correlated with sleep, has also not reacted to light in the short term.
The mice maintained a normal sleep / wake cycle and normal body temperature rhythms, suggesting that their overall circadian rhythms remain intact. This helps to understand why a night of restless sleep and looking at a smartphone can tire a person the next day but not have a long-term effect on the body.
"If these two effects – acute and long-term exposure to light – went through the same path, any exposure to minor light could completely alter the circadian rhythms of our body," said Schmidt.
Now that researchers know that the light response system follows several paths, Schmidt said more work is needed to map these pathways. On the one hand, we still do not know which region of the brain is responsible for the treatment of acute light.
After learning more, researchers could understand how to optimize light exposure to increase the vigilance of those who need it, such as nurses, shiftworkers and emergency personnel, while mitigating the adverse effects of dementia. a radical change in circadian rhythms.
"The light at the wrong time of day is now recognized as a carcinogen," Schmidt said. "We want people to feel alert when they are exposed to light without incurring the health risks badociated with offbeat circadian rhythms, such as diabetes, depression and even cancer."
The study, titled "Separate subpopulations of ipRGC attenuate the acute and circadian effects of light on body temperature and sleep," was funded by the National Institutes of Health (reference numbers 1DP2EY027983 , GM076430 and EY024452), a Klingenstein-Simons Fellowship in Neuroscience Research and a Research Fellowship in Neuroscience.
Source of the story:
Material provided by Northwestern University. Original written by Amanda Morris. Note: Content can be changed for style and length.
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