Blue light triggers memory and emphatic fear in mice via a non-invasive approach

January 21, 2020

Science Daily/Institute for Basic Science

Researchers at the Center for Cognition and Sociality, within the Institute for Basic Science (IBS) in South Korea, have engineered an improved biological tool that controls calcium (Ca2+) levels in the brain via blue light. Published in Nature Communications, this optogenetic construct, called monster-OptoSTIM1 or monSTIM1 for short, causes a change in mice's fear learning behavior without the need of optic fiber implants in the brain.

The brain utilizes Ca2+ signaling to regulate a variety of functions, including memory, emotion, and movement. Several evidences show correlation between abnormally regulated Ca2+ levels in certain brain cells and neurodegenerative diseases, but the details still remain obscure. For understanding the precise role of Ca2+ signaling, the IBS team is studying Ca2+-specific modulators that can be triggered in different parts of the brain at a designated time.

Optogenetics uses light to control Ca2+ signaling in the mouse brain. Since the brain is surrounded by hair, skin and skull, which prevent light from reaching deep tissues, optic fiber insertion in the brain used to be the norm in optogenetics. However, these implants can cause inflammation, morphological changes of neurons and disconnection of neural circuits. In this study, the research team improved their optogenetic tool so that it works with an external source of blue light, shone from the ceiling of the mouse cage, and without the need of brain implants.

MonSTIM1 is made of a part (CRY2) that responds to blue light and another part (STIM1) that activates calcium channels. Compared to the previously developed optogenetic techniques, the researchers were able to enhance CRY2's light-sensitivity approximately 55-fold and also avoid the increase of basal Ca2+ levels. The monSTIM1 construct was injected into the mouse brain through a virus, and was shown to activate Ca2+ signals in the cortex as well as in the deeper hippocampus and thalamus regions.

The team observed behavioral changes in mice with monSTIM1 expressed in excitatory neurons in the anterior cingulate cortex, a brain region that has a central function in empathic emotions. Mice with activated monSTIM1 froze with fear by looking at other mice, which experienced a mild electric foot shock. Twenty-four hours later the same mice remembered about it and showed again an enhanced fear response, indicating that Ca2+ signaling contributed to both short- and long-term social fear responses.

"MonSTIM1 can be applied to a wide range of brain calcium research and brain cognitive science research, because it allows easy manipulation of intracellular calcium signals without damaging the brain," says Won Do Heo (KAIST professor), leading author of this research.

https://www.sciencedaily.com/releases/2020/01/200121123953.htm

Blue light may not be as disruptive to our sleep patterns as originally thought

December 16, 2019

Science Daily/University of Manchester

Contrary to common belief, blue light may not be as disruptive to our sleep patterns as originally thought -- according to scientists. According to the team, using dim, cooler, lights in the evening and bright warmer lights in the day may be more beneficial to our health.

According to the team, using dim, cooler, lights in the evening and bright warmer lights in the day may be more beneficial to our health.

Twilight is both dimmer and bluer than daylight, they say, and the body clock uses both of those features to determine the appropriate times to be asleep and awake.

Current technologies designed to limit our evening exposure to blue light, for example by changing the screen colour on mobile devices, may therefore send us mixed messages, they argue.

This is because the small changes in brightness they produce are accompanied by colours that more resemble day.

The research, which was carried out on mice, used specially designed lighting that allowed the team to adjust colour without changing brightness.

That showed blue colours produced weaker effects on the mouse body clock than equally bright yellow colours.

The findings, say the team, have important implications for the design of lighting and visual displays intended to ensure healthy patterns of sleep and alertness.

The study is published in Current Biology and funded by the Biotechnology and Biological Sciences Research Council.

The body clock uses a specialised light sensitive protein in the eye to measure brightness, called melanopsin, which is better at detecting shorter wavelength photons.

This is why, say the team, researchers originally suggested blue light might have a stronger effect.

However, our perception of colour comes from the retinal cone cells and the new research shows that the blue colour signals they supply reduce the impact on light on the clock.

Dr Tim Brown, from The University of Manchester, said: "We show the common view that blue light has the strongest effect on the clock is misguided; in fact, the blue colours that are associated with twilight have a weaker effect than white or yellow light of equivalent brightness.

"There is lots of interest in altering the impact of light on the clock by adjusting the brightness signals detected by melanopsin but current approaches usually do this by changing the ratio of short and long wavelength light; this provides a small difference in brightness at the expense of perceptible changes in colour."

He added: "We argue that this is not the best approach, since the changes in colour may oppose any benefits obtained from reducing the brightness signals detected by melanopsin.

"Our findings suggest that using dim, cooler, lights in the evening and bright warmer lights in the day may be more beneficial.

"Research has already provided evidence that aligning our body clocks with our social and work schedules can be good for our health. Using colour appropriately could be a way to help us better achieve that."

https://www.sciencedaily.com/releases/2019/12/191216173654.htm

Daily exposure to blue light may accelerate aging, even if it doesn't reach your eyes

October 17, 2019

Science Daily/Oregon State University

Prolonged exposure to blue light, such as that which emanates from your phone, computer and household fixtures, could be affecting your longevity, even if it's not shining in your eyes.

New research at Oregon State University suggests that the blue wavelengths produced by light-emitting diodes damage cells in the brain as well as retinas.

The study, published today in Aging and Mechanisms of Disease, involved a widely used organism, Drosophila melanogaster, the common fruit fly, an important model organism because of the cellular and developmental mechanisms it shares with other animals and humans.

Jaga Giebultowicz, a researcher in the OSU College of Science who studies biological clocks, led a research collaboration that examined how flies responded to daily 12-hour exposures to blue LED light -- similar to the prevalent blue wavelength in devices like phones and tablets -- and found that the light accelerated aging.

Flies subjected to daily cycles of 12 hours in light and 12 hours in darkness had shorter lives compared to flies kept in total darkness or those kept in light with the blue wavelengths filtered out. The flies exposed to blue light showed damage to their retinal cells and brain neurons and had impaired locomotion -- the flies' ability to climb the walls of their enclosures, a common behavior, was diminished.

Some of the flies in the experiment were mutants that do not develop eyes, and even those eyeless flies displayed brain damage and locomotion impairments, suggesting flies didn't have to see the light to be harmed by it.

"The fact that the light was accelerating aging in the flies was very surprising to us at first," said Giebultowicz, a professor of integrative biology. "We'd measured expression of some genes in old flies, and found that stress-response, protective genes were expressed if flies were kept in light. We hypothesized that light was regulating those genes. Then we started asking, what is it in the light that is harmful to them, and we looked at the spectrum of light. It was very clear cut that although light without blue slightly shortened their lifespan, just blue light alone shortened their lifespan very dramatically."

Natural light, Giebultowicz notes, is crucial for the body's circadian rhythm -- the 24-hour cycle of physiological processes such as brain wave activity, hormone production and cell regeneration that are important factors in feeding and sleeping patterns.

"But there is evidence suggesting that increased exposure to artificial light is a risk factor for sleep and circadian disorders," she said. "And with the prevalent use of LED lighting and device displays, humans are subjected to increasing amounts of light in the blue spectrum since commonly used LEDs emit a high fraction of blue light. But this technology, LED lighting, even in most developed countries, has not been used long enough to know its effects across the human lifespan."

Giebultowicz says that the flies, if given a choice, avoid blue light.

"We're going to test if the same signaling that causes them to escape blue light is involved in longevity," she said.

Eileen Chow, faculty research assistant in Giebultowicz's lab and co-first author of the study, notes that advances in technology and medicine could work together to address the damaging effects of light if this research eventually proves applicable to humans.

"Human lifespan has increased dramatically over the past century as we've found ways to treat diseases, and at the same time we have been spending more and more time with artificial light," she said. "As science looks for ways to help people be healthier as they live longer, designing a healthier spectrum of light might be a possibility, not just in terms of sleeping better but in terms of overall health."

In the meantime, there are a few things people can do to help themselves that don't involve sitting for hours in darkness, the researchers say. Eyeglasses with amber lenses will filter out the blue light and protect your retinas. And phones, laptops and other devices can be set to block blue emissions.

"In the future, there may be phones that auto-adjust their display based on the length of usage the phone perceives," said lead author Trevor Nash, a 2019 OSU Honors College graduate who was a first-year undergraduate when the research began. "That kind of phone might be difficult to make, but it would probably have a big impact on health."

https://www.sciencedaily.com/releases/2019/10/191017101253.htm

Blue-enriched white light to wake you up in the morning

March 6, 2019

Science Daily/The Korea Advanced Institute of Science and Technology (KAIST)

Here is good news for those who have difficulty with morning alertness. A research team proposed that a blue-enriched LED light can effectively help people overcome morning drowsiness. This study will provide the basis for major changes in future lighting strategies and thereby help create better indoor environments.

Considerable research has been devoted to unmasking circadian rhythms. The 2017 Nobel Prize in Physiology or Medicine went to Jeffrey C. Hall, Michael Rosbash, and Michael W. Young for unveiling the molecular mechanisms that control circadian rhythms. In particular, the relationship between light and its physiological effects has been investigated since the discovery of a novel, third type of photoreceptor in the human retina in the early 2000s. Rods and cones regulate visual effects, while the third type, photosensitive retinal ganglion cells, regulate a large variety of biological and behavioral processes including melatonin and cortisol secretion, alertness, and functional magnetic resonance imaging (fMRI).

Initial studies on light sources have shown that blue monochromatic, fully saturated lights are effective for stimulating physiological responses, but the relative effectiveness of commercially available white light sources is less well understood. Moreover, the research was more focused on the negative effects of blue light; for instance, when people are exposed to blue light at night, they have trouble achieving deep sleep because the light restrains melatonin secretion.

However, Professor Hyeon-Jeong Suk and Professor Kyungah Choi from the Department of Industrial Design and their team argue that the effects of blue-enriched morning light on physiological responses are time dependent, and that it has positive effects on melatonin levels and the subjective perception of alertness, mood, and visual comfort compared with warm white light.

The team conducted an experiment with 15 university students. They investigated whether an hour of morning light exposure with different chromaticity would affect their physiological and subjective responses differently. The decline of melatonin levels was significantly greater after the exposure to blue-enriched white light in comparison with warm white light.

Professor Suk said, "Light takes a huge part of our lives since we spend most of our time indoors. Light is one of the most powerful tools to affect changes in how we perceive and experience the environment around us."

Professor Choi added, "When we investigate all of the psychological and physiological effects of light, we see there is much more to light than just efficient quantities. I believe that human-centric lighting strategies could be applied to a variety of environments, including residential areas, learning environments, and working spaces to improve our everyday lives."

This research was collaborated with Professor Hyun Jung Chung from the Graduate School of Nanoscience and Technology.

https://www.sciencedaily.com/releases/2019/03/190306100602.htm

Blue lighting is scientifically proven to help us relax faster than white lighting after an argument

November 10, 2017

Science Daily/University of Granada

Researchers say that blue light accelerates the relaxation process after acute psychosocial stress such as arguing with a friend or when someone pressures you to quickly finish some task.

Said stress is a kind of short-term stress (acute stress) that occurs during social or interpersonal relationships, for example while arguing with a friend or when someone pressures you to finish a certain task as soon as possible.

The researchers, which belong to the BCI Lab (Brain-Computer Interface Lab) at the University of Granada, note that psychosocial stress produces some physiological responses that can be measured by means of bio-signals. That stress is very common and negatively affects people's health and quality of life.

For their work, whose results have been published in the PlosOne journal, the researchers made twelve volunteers to be stressed and then perform a relaxation session within the multisensory stimulation room at the School for Special Education San Rafael.

In said room the participants lied down with no stimulus but a blue (group 1) or white (group 2) lighting. Diverse bio-signals, such as heart rate and brain activity, were measured throughout the whole session (by means of an electrocardiogram and an electroencephalogram, respectively).

The results showed that blue lighting accelerates the relaxation process, in comparison with conventional white lighting.

https://www.sciencedaily.com/releases/2017/11/171110113936.htm

Blue light emitted by screens damages our sleep

August 22, 2017

Science Daily/University of Haifa

The short-wavelength blue light, emitted by the screens we watch, damages the duration, and even more so, the quality of our sleep. The study also found that watching screens that emit red light does not cause damage, and sleep after exposure to it was similar to normal sleep.

Previous studies have already shown that watching screens before going to sleep damages our sleep. It has also been found that exposure to blue light with wave lengths of 450-500 nanometers suppresses the production of melatonin, a hormone secreted at night that is connected with normal body cycles and sleep. The new study, published in the journal Chronobiology International, was undertaken by researchers Prof. Abraham Haim, head of the Israeli center for interdisciplinary research in chronobiology at the University of Haifa; doctorate student Amit Shai Green of the Center for Interdisciplinary Chronobiological Research at the University of Haifa and the Sleep and Fatigue Center at Assuta Medical Center; Dr. Merav Cohen-Zion of the School of Behavioral Sciences at the Academic College of Tel Aviv-Yafo; and Prof. Yaron Dagan of the Research Institute for Applied Chronobiology at Tel Hai Academic College. The researchers sought to examine whether there is any difference in sleep patterns following exposure to blue screen light as compared to red light prior to sleep, and furthermore, to find which is more disruptive: wavelength or intensity?

The study participants were 19 healthy subjects aged 20-29 who were not aware of the purpose of the study. In the first part of the trial, the participants wore an actigraph for one week (an actigraph is a device that provides an objective measurement of the time when an individual falls asleep and wakes up). They also completed a sleep diary and a questionnaire about their sleeping habits and quality of sleep. In the second part of the trial, which took place at Assuta's Sleep Laboratory, the participants were exposed to computer screens from 9 p.m. to 11 p.m. -- the hours when the pineal gland begins to produce and excrete melatonin. The participants were exposed to four types of light: high-intensity blue light, low-intensity blue light, high-intensity red light, and low-intensity red light. Following exposure to light, they were connected to instruments that measure brain waves and can determine the stages of sleep a person undergoes during the course of the night, including awakenings not noticed by the participants themselves. In the morning, the participants completed various questionnaires relating to their feelings.

On average, exposure to blue light reduced the duration of sleep by approximately 16 minutes. In addition, exposure to blue light significantly reduced the production of melatonin, whereas exposure to red light showed a very similar level of melatonin production to the normal situation. The researchers explain that the impaired production of melatonin reflects substantial disruption of the natural mechanisms and the body's biological clock. Thus, for example, it was found that exposure to blue light prevents the body from activating the natural mechanism that reduces body temperature. "Naturally, when the body moves into sleep it begins to reduce its temperature, reaching the lowest point at around 4:00 a.m. When the body returns to its normal temperature, we wake up," Prof. Haim explains. "After exposure to red light, the body continued to behave naturally, but exposure to blue light led the body to maintain its normal temperature throughout the night -- further evidence of damage to our natural biological clock."

The most significant finding in terms of the disruption of sleep was that exposure to blue light drastically disrupts the continuity of sleep. Whereas after exposure to red light (at both intensities) people woke up an average of 4.5 times (unnoticed awakenings), following exposure to weak blue light 6.7 awakenings were recorded, rising to as many as 7.6 awakenings following exposure to strong blue light. Accordingly, it is hardly surprising that the participants reported in the questionnaires that the felt more tired and in a worse mood after exposure to blue light.

"Exposure to screens during the day in general, and at night in particular, is an integral part of our technologically advanced world and will only become more intense in the future. However, our study shows that it is not the screens themselves that damage our biological clock, and therefore our sleep, but the short-wave blue light that they emit. Fortunately various applications are available that filter the problematic blue light on the spectrum and replace it with weak red light, thereby reducing the damage to the suppression of melatonin," concludes Prof. Haim.

https://www.sciencedaily.com/releases/2017/08/170822103434.htm

Artificial light from digital devices lessens sleep quality

Melatonin skyrockets when blue light is blocked

July 28, 2017

Science Daily/University of Houston

Blue light emitted from digital devices could contribute to the high prevalence of reported sleep dysfunction, suggests new research.

There's no doubt we love our digital devices at all hours, including after the sun goes down. Who hasn't snuggled up with a smart phone, tablet or watched their flat screen TV from the comfort of bed? A new study by researchers at the University of Houston College of Optometry, published in Ophthalmic & Physiological Optics, found that blue light emitted from those devices could contribute to the high prevalence of reported sleep dysfunction.

Study participants, ages 17-42, wore short wavelength-blocking glasses three hours before bedtime for two weeks, while still performing their nightly digital routine. Results showed about a 58 percent increase in their nighttime melatonin levels, the chemical that signals your body that it's time to sleep. Those levels are even higher than increases from over-the-counter melatonin supplements, according to Dr. Lisa Ostrin, the UH College of Optometry assistant professor who lead the study.

"The most important takeaway is that blue light at night time really does decrease sleep quality. Sleep is very important for the regeneration of many functions in our body," Ostrin said.

Wearing activity and sleep monitors 24 hours a day, the 22 study participants also reported sleeping better, falling asleep faster, and even increased their sleep duration by 24 minutes a night, according to Ostrin.

The largest source of blue light is sunlight, but it's also found in most LED-based devices. Blue light boosts alertness and regulates our internal body clock, or circadian rhythm, that tells our bodies when to sleep. This artificial light activates photoreceptors called intrinsically photosensitive retinal ganglion cells (ipRGCs), which suppresses melatonin.

Ostrin recommends limiting screen time, applying screen filters, wearing computer glasses that block blue light, or use anti-reflective lenses to offset the effects of artificial light at nighttime. Some devices even include night mode settings that limit blue light exposure.

"By using blue blocking glasses we are decreasing input to the photoreceptors, so we can improve sleep and still continue to use our devices. That's nice, because we can still be productive at night," Ostrin said.

According to the most recent findings from the National Sleep Foundation's Sleep Health Index®, while three quarters of Americans are satisfied with their sleep over the past week, more than four in ten Americans reported that their daily activities were significantly impacted by poor or insufficient sleep at least once during the past seven days.

https://www.sciencedaily.com/releases/2017/07/170728121414.htm

Blue Light Could Help Teenagers Combat Stress

October 22, 2012

Science Daily/Rensselaer Polytechnic Institute (RPI)

A new study shows that exposure to morning short-wavelength “blue” light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.

Adolescents can be chronically sleep deprived because of their inability to fall asleep early in combination with fixed wakeup times on school days. According to the CDC, almost 70 percent of school children get insufficient sleep -- less than 8 hours on school nights. This type of restricted sleep schedule has been linked with depression, behavior problems, poor performance at school, drug use, and automobile accidents.

A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute shows that exposure to morning short-wavelength "blue" light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.

Levels of cortisol, a hormone produced by the adrenal gland, follow a daily 24-hour rhythm. Cortisol concentrations are low throughout the day reaching a broad minimum in the evening before rising slowly again throughout the night. In addition to this gradual elevation of cortisol at night, cortisol levels rise sharply within the first 30 to 60 minutes after waking.

This is known as the cortisol awakening response (CAR). In nocturnal animals, the cortisol spike occurs at night, at the start of activity. It appears to be associated with the time of transition from rest to activity, upon waking. A high CAR has been associated with better preparedness for stressful and challenging activities.

"The present results are the first to show that low levels of short-wavelength light enhance CAR in adolescents who were restricted from sleep," said Figueiro. "Morning light exposure may help to wake up the body when it is time to be active, thus preparing individuals for any environmental stress they might experience."

Short-wavelength light has been shown to maximally suppress production of nocturnal melatonin and phase shift the timing of the biological clock. The effect of short-wavelength light on other biomarkers has not been widely studied.

The study included three overnight sessions, at least one week apart. All participants wore a Dimesimeter on a wrist band to measure light exposure and to verify the regularity of their activity/rest periods during the three-week study. The Dimesimeter is a small calibrated light meter device developed by the LRC that continuously records circadian light and activity levels.

During the study, adolescents aged 12 to 17 years went to sleep at 1:30 a.m. and woke up at 6:00 a.m., a 4.5-hour sleep opportunity. Each week, participants either experienced morning short-wavelength blue light (40 lux of 470-nanometer light) or remained in dim light.

http://www.sciencedaily.com/releases/2012/10/121022112847.htm

Blue-Blocking Glasses to Improve Sleep and ADHD Symptoms Developed

November 14, 2007

Science Daily/John Carroll University

Scientists at John Carroll University, working in its Lighting Innovations Institute, have developed an affordable accessory that appears to reduce the symptoms of ADHD. Their discovery also has also been shown to improve sleep patterns among people who have difficulty falling asleep. The John Carroll researchers have created glasses designed to block blue light, therefore altering a person's circadian rhythm, which leads to improvement in ADHD symptoms and sleep disorders.

The individual puts on the glasses a couple of hours ahead of bedtime, advancing the circadian rhythm. The special glasses block the blue rays that cause a delay in the start of the flow of melatonin, the sleep hormone. Normally, melatonin flow doesn't begin until after the individual goes into darkness. Studies indicate that promoting the earlier release of melatonin results in a marked decline of ADHD symptoms.

http://www.sciencedaily.com/releases/2007/11/071112143308.htm