Why sleep has restorative—or damaging—effects on cognition and brain health has been an enduring mystery in biology. Researchers think cerebrospinal fluid (CSF) may flush toxic waste out, “cleaning” the brain and studies have shown that garbage clearance is hugely improved during sleep. They were not sure exactly how all this works, however, or why it should be so enhanced during sleep.
One aspect of sleep that is well understood is how the slow electrical oscillations (or “slow waves”) that characterize deep, non-REM sleep contribute to memory consolidation, the process whereby new memories are transferred into long-term storage. A new study, from a team led by neuroscientist Laura Lewis of Boston University, now gives insight into what drives CSF flow through the brain, suggesting that the same slow waves that coordinate memory consolidation drive oscillations in blood flow and CSF in the brain.
The work has implications for understanding the relations between sleep disturbance and psychiatric and neurodegenerative conditions, and may even point to new approaches to diagnosis and treatment. “We’ve discovered there are really large waves of CSF that appear in the brain only during sleep,” Lewis says. “This effect is really striking, and we’re also interested in what it means for maintaining brain health, especially in disorders such as Alzheimer’s disease.”
In the study, published on October 31 in Science, the team set out to investigate how the dynamics of CSF flow changes during sleep, and how this might relate to alterations in brain blood flow and electrical activity. “We know sleep is really important for brain health, and waste clearance is probably a key reason why; what was less clear is: Why is this changed during sleep?” Lewis says. “That led us to ask what was happening in the CSF.”
The researchers used electroencephalography (EEG) to monitor the brain waves of 13 sleeping healthy adults, while also using a cutting-edge, “accelerated” fMRI technique to capture faster changes than standard fMRI can manage. That allowed for the measurement of both blood-oxygenation changes (which indicate blood flowing to electrically active, oxygen-hungry regions) and CSF flows. The latter was only possible due to a flaw in this method that means any newly arriving fluid (not just oxygenated blood) lights up in the image. “We realized we could take advantage of this to measure CSF flow at the same time as blood oxygenation,” Lewis says. “That was critical, because it turns out these things are coupled to each other in a way we never would have seen if we didn’t measure blood, CSF and electrical activity simultaneously.”
What the team found was that the slow waves seen in non-REM sleep occur in lockstep with changes in both blood flow and CSF. Just because things occur together doesn’t necessarily mean one causes the other, but the team also built a computer model incorporating what we know about the physics linking these processes, which predicted that slow waves would have just these kinds of effects on blood and CSF. What seems to be happening is that as brain activity alters blood flow, this reduces the volume of blood in the brain, and because the brain is a closed vessel, CSF flows in to fill the space. “It’s very convincing,” says neurologist Maiken Nedergaard of the University of Rochester, who was not involved with the research. “It also really makes sense: electrical activity drives blood flow changes, that then drive CSF changes.”
The team measured this CSF inflow going into the fourth ventricle, one of four fluid-filled cavities involved in producing CSF (by filtering blood plasma) and circulating it around the brain. As CSF usually flows out of the fourth ventricle, this suggests a “pulsatile” flow, like a wave. This pushes CSF around the ventricles and into spaces between membranes surrounding the brain and spinal cord, called the meninges, where it mixes with “interstitial fluid” within the brain to carry away toxic waste products.
As slow waves are important for memory consolidation, this links two disparate functions of sleep. “What’s exciting about this is it’s combining features of brain function that people don’t normally think of as connected,” Nedergaard says. It isn’t obvious things had to be this way, Lewis says, but it may represent an example of nature being efficient. “It’s a matter of nature not dividing tasks between higher level and lower level, like how you run a company, where you have a boss making decisions and cleaning people coming in,” Nedergaard says. “In biology, it’s everybody contributing, as it makes more sense.”
The findings have implications for neurodegenerative diseases, which are thought to be caused by build-up of toxic proteins in the brain, such as amyloid-Beta in Alzheimer’s disease. Previous research has shown that amyloid-Beta is cleared more efficiently during sleep, which is often disrupted in patients. Disturbances in slow-wave sleep also often accompany aging, which may be linked to cognitive decline. “We know that people with Alzheimer’s have fewer slow waves, so we may find they also have fewer CSF waves,” Lewis says. “We have to do these studies now in older adults and patient populations, to understand what this might mean for those disorders.” Sleep disturbance is also a feature of many psychiatric disorders, from depression to schizophrenia. “Different electrical signatures of sleep are disrupted in different psychiatric conditions,” she says. “So this will be very interesting to follow up on in a multitude of disorders.”
The team next hope to nail down whether electrical oscillations truly do cause the changes they observed in CSF flow, by experimentally manipulating brain activity. “It would be great to find the right collaborator and do a study in mice where we manipulate neural activity, then watch the downstream consequences,” Lewis says. “We’re also thinking about ways to safely and noninvasively manipulate neural oscillations in humans.” It may ultimately be possible to use electromagnetic stimulation to influence brain waves as a treatment for brain disorders. Researchers have already seen encouraging results of this approach in mice, and these findings may help explain why. Another potential application may come from assessing whether changes in CSF flows can serve as a diagnostic marker for some of these conditions. “It gives us a ton of interesting new biology to explore and understand, since it seems like things the brain is doing during sleep are related to each other in surprising ways,” Lewis says.“Maybe the most important take-home message is that sleep is a serious thing,” Nedergaard says. “You really need to sleep to keep a healthy brain because it links electrical activity to a practical housekeeping function.”
Screen time above a two-hour threshold at five years of age is associated with an increased risk of clinically relevant externalizing problems such as inattention, according to a study published April 17 in the open-access journal PLOS ONE by Piush Mandhane of the University of Alberta, and colleagues.
Increased screen time in children has been associated with unhealthy dietary patterns, poor sleep quality, cardiovascular disease, and obesity. There has been a significant increase in screen options in recent years, from device choices to streaming content, with rising concern that screen time may have negative consequences for mental health. But there is relatively little research examining associations between screen-time exposure and behavioral development in the preschool years. Most studies have focused on school-aged children or have only considered traditional screen sources such as television viewing. To address this gap in knowledge, Mandhane and colleagues analyzed data from the population-based Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort study to determine associations between screen time and behavioral outcomes at age five years.
Parents reported their child's total screen time including gaming and mobile devices and completed the Child Behavior Checklist when the child was five years old. Mean screen time was 1.4 hours per day at five years and 1.5 hours per day at three years. Compared to children with less than 30 minutes per day of screen time, the 13.7% who watched more than two hours each day were five times more likely to report clinically significant externalizing problems, and were 5.9 times more likely to report clinically significant inattention problems. Moreover, children with more than two hours of screen time per day had a 7.7-fold increased risk of meeting criteria for attention-deficit/hyperactivity disorder. According to the authors, the findings indicate that preschool may be a critical period for educating parents and families about limiting screen time and encouraging physical activity.
The authors add: "How much is too much screen time for children? Using data from a large Canadian cohort, we found that children with more than 2 hours of screen time per day had significantly more behavior problems at five years of age. Interestingly, the more time children spent doing organized sports, the less likely they were to exhibit behavioral problems. Taken together, our results support an active beginning for children with screen time replaced by more organized sports."
Citation: Tamana SK, Ezeugwu V, Chikuma J, Lefebvre DL, Azad MB, Moraes TJ, et al. (2019) Screen-time is associated with inattention problems in preschoolers: Results from the CHILD birth cohort study. PLoS ONE 14(4): e0213995. https://doi.org/10.1371/journal.pone.0213995
Funding: This work was supported by: 1. The Allergy Genes and Environment Network of Centres of Excellence (AllerGen NCE). 2. Women's and Children's Health Research Institute. 3. The Canadian Institutes of Health Research (CIHR). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.
DALLAS, Aug. 6, 2018 -- Screen time from computers, phones, tablet computers, video games, TV and other screen-based devices is associated with an increased amount of sedentary behavior in children and teens, according to a new scientific statement released by the American Heart Association and published in its journal Circulation.
Sedentary behaviors include sitting, reclining or laying down while awake -- activities which exert little physical energy - and contribute to overweight and obesity in children and teens.
American Heart Association scientific statements are developed by a panel of experts who review existing scientific literature and evidence to provide an overview of a topic related to cardiovascular disease or stroke. In this review, the writing group found that the available scientific literature is based almost entirely on self-reported screen time, with very few breaking down the type of device or the context in which it is used, which means that the studies are not designed to prove cause and effect.
The writing group determined that over the last twenty years, TV viewing by children and adolescents has declined but the recreational use of other screen-based devices, such as smart phones, tablet computers and others has resulted in a net increase in screen time overall. Current estimates are that 8- to 18-year-olds spend more than 7 hours using screens daily.
"Still, the available evidence is not encouraging: overall screen time seems to be increasing -- if portable devices are allowing for more mobility, this has not reduced overall sedentary time nor risk of obesity," according to Tracie A. Barnett, Ph.D., a researcher at the INRS-Institut Armand Frappier and Sainte-Justine University Hospital Research Center, in Montreal, Canada, and the chair of the writing group.
"Although the mechanisms linking screen time to obesity are not entirely clear, there are real concerns that screens influence eating behaviors, possibly because children 'tune out' and don't notice when they are full when eating in front of a screen. There is also evidence that screens are disrupting sleep quality, which can also increase the risk of obesity," Barnett said.
The message to parents and children is to take steps to limit screen time. "We want to reinforce the American Heart Association's long-standing recommendation for children and teens to get no more than 1-2 hours of recreational screen time daily. Given that most youth already far exceed these limits, it is especially important for parents to be vigilant about their child's screen time, including phones." Barnett said.
Recommended interventions to minimize screen time emphasize the importance of involving parents. Parents can help their children reduce screen time by setting a good example with their own screen use and by establishing screen time regulations.
"Ideally, screen-based devices should not be in bedrooms, especially because some studies have found that having screen-based devices in the bedroom can affect sleep. Maximize face-to-face interactions and time outdoors," Barnett said. "In essence: Sit less; play more."
According to Barnett, more research is needed because the patterns of screen-based media use and their long-term effects on children and teens are not yet known. In addition, the authors report that not much is known about how to help youth be less sedentary and the appeal of screens is making this an even greater challenge. Future research should focus on how to achieve greater balance. Detailed information on the overall impact of today's sedentary pursuits - especially with respect to screen-based devices - is needed, Barnett said.
Co-authors are Aaron S. Kelly, Ph.D.; Deborah R. Young, Ph.D.; Cynthia K. Perry, Ph.D.; Charlotte A. Pratt, Ph.D., M.S., R.D.; Nicholas Edwards, M.D., M.P.H.; Goutham Rao, M.D.; and Miram Vos, M.D. M.S.P.H. Author disclosures are on the manuscript.
The American Heart Association/American Stroke Association receives funding mostly from individuals. Foundations and corporations donate as well, and fund specific programs and events. Strict policies are enforced to prevent these relationships from influencing the association's science content. Financial information for the American Heart Association, including a list of contributions from pharmaceutical and device manufacturers and health insurance providers are available at http://www.heart.org/corporatefunding.
About the American Heart Association
The American Heart Association is devoted to saving people from heart disease and stroke - the two leading causes of death in the world. We team with millions of volunteers to fund innovative research, fight for stronger public health policies, and provide lifesaving tools and information to prevent and treat these diseases. The Dallas-based association is the nation's oldest and largest voluntary organization dedicated to fighting heart disease and stroke. To learn more or to get involved, call 1-800-AHA-USA1, visit heart.org or call any of our offices around the country. Follow us on Facebook and Twitter.
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While training and feedback opportunities abound for K-12 educators, the same can't be said for instructors in higher education. Currently, the most effective mechanism for professional development is for an expert to observe a lecture and provide personalized feedback. But a new system developed by Carnegie Mellon University researchers offers a comprehensive real-time sensing system that is inexpensive and scalable to create a continuous feedback loop for the instructor.
The system, called EduSense, analyzes a variety of visual and audio features that correlate with effective instruction. "Today, the teacher acts as the sensor in the classroom, but that's not scalable," said Chris Harrison, assistant professor in CMU's Human-Computer Interaction Institute (HCII). Harrison said classroom sizes have ballooned in recent decades, and it's difficult to lecture and be effective in large or auditorium-style classes.
EduSense is minimally obtrusive. It uses two wall-mounted cameras -- one facing students and one facing the instructor. It senses things such as students' posture to determine their engagement, and how much time instructors pause before calling on a student. "These are codified things that educational practitioners have known as best practices for decades," Harrison said.
A single off-the-shelf camera can view everyone in the classroom and automatically identify information such as where students are looking, how often they're raising their hands and if the instructor moves through the space instead of staying behind a podium. The system uses OpenPose, another CMU project, to extract body position. "With advances in computer vision and machine learning, we can now provide insights that would take days if not months to get with manual observation," said Karan Ahuja, a member of the research team who is pursuing his Ph.D. in the HCII.
Harrison said learning scientists are interested in the instructional data. "Because we can track the body, it's like wearing a suit of accelerometers. We know how much you're turning your head and moving your hands. It's like you're wearing a virtual motion-capture system while you're teaching."
Using high-resolution cameras steaming 4K video for many classes at once is a "computational nightmare," Harrison said. To keep up, resources are elastically assigned to provide the best possible frame rate for real-time data.
The project also has a strong focus on privacy protection, guided by Yuvraj Agarwal, an associate professor in the university's Institute for Software Research. The team didn't want to identify individual students, and EduSense can't. No names or identifying information is used, and since camera data is processed in real time, it is discarded quickly.
Now that the team has demonstrated that they can capture the data, HCII faculty member Amy Ogan said their current challenge is wrapping it up and presenting it in a way that's educationally effective. The team will continue working on instructor-facing apps to see if professors can integrate the feedback into practice. "We have been focused on understanding how, when and where to best present feedback based on this data so that it is meaningful and useful to instructors to help them improve their practice," she said.
This research has been presented at Ubicomp, the International Conference of the Learning Sciences, and will be presented this coming April at the American Educational Research Association annual meeting.
A new Canadian public health campaign is beginning to promote the importance of a good night's sleep.
Lack of sleep costs Canada more than $ 21 billion in lost productivity. To address this situation, a bilingual Canadian awareness campaign is being launched today to promote the importance of a good night's sleep to stay alert and healthy.
Its goal? Demystify sleep, offer solutions to people living with sleep disorders and make restful sleep a public health priority. The campaign was announced at the World Sleep Congress in Vancouver, and a website was also launched to support this campaign.
"Our goal is to get people to consider sleep as a priority in their lives," said Julie Carrier, a professor of psychology at the Université de Montréal, a researcher at the University Integrated Center for Health and Social Services in the North. de-l'Île-de-Montréal and Scientific Director of the CSCN.
The national campaign aims to broadcast two key messages:
Sleep is essential to physical, emotional and cognitive health. To stay healthy, it is just as important to sleep well as to eat well and to engage in physical activity.
Solutions for many sleep disorders include insomnia, sleep apnea, sleepwalking, narcolepsy, restless legs syndrome, and shift-related sleep disorders.
This national campaign will also support and promote the creation of knowledge dissemination platforms that will help raise awareness of sleep management.
Did you know?
Lack of sleep can reduce your reaction rate as much as a blood alcohol level of 0.08 g, the legal limit for driving. Narcoleptics become sleepy and fall asleep at work, school or on the street.
In as little as six years, people who sleep only six hours a night gain more weight than those who sleep seven or eight hours.
Lack of sleep is also extremely expensive. According to the Organization for Economic Co-operation and Development, Canada is losing $ 21.4 billion annually in productivity due to absenteeism, accidents and injuries caused by lack of sleep.
"Canada is a leader in sleep research and now, with Sleep On It !, it's the first country in the world to make publicizing this work a public health priority." Julie Carrier said. We want to encourage other countries to do the same. That's why we're launching our campaign at the World Sleep Congress. Sleep research has made tremendous progress over the last 15 years, and the public, including people living with a sleep disorder, is entitled to the best, scientifically valid information presented with simplicity and originality."