Scientists find that small regions of the brain can take micro-naps while the rest of the brain is awake and vice versa

Sleep and wake: they're totally distinct states of being that define the boundaries of our daily lives. For years, scientists have measured the difference between these instinctual brain processes by observing brain waves, with sleep characteristically defined by slow, long-lasting waves measured in tenths of seconds that travel across the whole organ.

For the first time, scientists have found that sleep can be detected by patterns of neuronal activity just milliseconds long, 1000 times shorter than a second, revealing a new way to study and understand the basic brain wave patterns that govern consciousness. They also show that small regions of the brain can momentarily "flicker" awake while the rest of the brain remains asleep, and vice versa from wake to sleep.

These findings, described in a new study published in the journal Nature Neuroscience, are from a collaboration between the laboratories of Assistant Professor of Biology Keith Hengen at Washington University in St. Louis and Distinguished Professor of Biomolecular Engineering David Haussler at UC Santa Cruz. The research was carried out by Ph.D. students David Parks (UCSC) and Aidan Schneider (WashU).

Over four years of work, Parks and Schneider trained a neural network to study the patterns within massive amounts of brain wave data, uncovering patterns that occur at extremely high frequencies that have never been described before and challenge foundational, long-held conceptions of the neurological basis of sleep and wake.

"With powerful tools and new computational methods, there's so much to be gained by challenging our most basic assumptions and revisiting the question of 'what is a state?'" Hengen said. "Sleep or wake is the single greatest determinant of your behavior, and then everything else falls out from there. So if we don't understand what sleep and wake actually are, it seems like we've missed the boat."

"It was surprising to us as scientists to find that different parts of our brains actually take little naps when the rest of the brain is awake, although many people may have already suspected this in their spouse, so perhaps a lack of male-female bias is what is surprising," Haussler quipped.

Understanding sleep

Neuroscientists study the brain via recordings of the electrical signals of brain activity, known as electrophysiology data, observing voltage waves as they crest and fall at different paces. Mixed into these waves are the spike patterns of individual neurons.

The researchers worked with data from mice at the Hengen Lab in St. Louis. The freely-behaving animals were equipped with a very lightweight headset that recorded brain activity from 10 different brain regions for months at a time, tracking voltage from small groups of neurons with microsecond precision.

This much input created petabytes -- which are one million times larger than a gigabyte -- of data. David Parks led the effort to feed this raw data into an artificial neural network, which can find highly complex patterns, to differentiate sleep and wake data and find patterns that human observation may have missed. A collaboration with the shared academic compute infrastructure located at UC San Diego enabled the team to work with this much data, which was on the scale of what large companies like Google or Facebook might use.

Knowing that sleep is traditionally defined by slow-moving waves, Parks began to feed smaller and smaller chunks of data into the neural network and asked it to predict if the brain was asleep or awake.

They found that the model could differentiate between sleep and wake from just milliseconds of brain activity data. This was shocking to the research team -- it showed that the model couldn't have been relying on the slow-moving waves to learn the difference between sleep and wake.. Just as listening to a thousandth of a second of a song couldn't tell you if it had a slow rhythm, it would be impossible for the model to learn a rhythm that occurs over several seconds by just looking at random isolated milliseconds of information.

"We're seeing information at a level of detail that's unprecedented," Haussler said. "The previous feeling was that nothing would be found there, that all the relevant information was in the slower frequency waves. This paper says, if you ignore the conventional measurements, and you just look at the details of the high frequency measurement over just a thousandth of a second, there is enough there to tell if the tissue is asleep or not. This tells us that there is something going on a very fast scale -- that's a new hint to what might be going on in sleep."

Hengen, for his part, was convinced that Parks and Schneider had missed something, as their results were so contradictory to bedrock concepts drilled into him over many years of neuroscience education. He asked Parks to produce more and more evidence that this phenomena could be real.

"This challenged me to ask myself 'to what extent are my beliefs based on evidence, and what evidence would I need to see to overturn those beliefs?" Hengen said. "It really did feel like a game of cat and mouse, because I'd ask David [Parks] over and over to produce more evidence and prove things to me, and he'd come back and say 'check this out!' It was a really interesting process as a scientist to have my students tear down these towers brick by brick, and for me to have to be okay with that."

Local patterns

Because an artificial neural network is fundamentally a black box and does not report back on what it learns from, Parks began stripping away layers of temporal and spatial information to try to understand what patterns the model could be learning from.

Eventually, they got down to the point where they were looking at chunks of brain data just a millisecond long and at the highest frequencies of brain voltage fluctuations.

"We'd taken out all the information that neuroscience has used to understand, define, and analyze sleep for the last century, and we asked 'can the model still learn under these conditions?'" Parks said. "This allowed us to look into signals we haven't understood before."

By looking at these data, they were able to determine that the hyper-fast pattern of activity between just a few neurons was the fundamental element of sleep that the model was detecting. Crucially, such patterns cannot be explained by the traditional, slow and widespread waves. The researchers hypothesize that the slow moving waves may be acting to coordinate the fast, local patterns of activity, but ultimately reached the conclusion that the fast patterns are much closer to the true essence of sleep.

If the slow moving waves traditionally used to define sleep are compared to thousands of people in a baseball stadium doing the wave, then these fast-moving patterns are the conversations between just a few people deciding to participate in the wave. Those conversations occurring are essential for the overall larger wave to take place, and are more directly related to the mood of the stadium -- the wave is a secondary result of that.

Observing flickers

In further studying the hyperlocal patterns of activity, the researchers began to notice another surprising phenomenon.

As they observed the model predicting sleep or wake, they noticed what looked at first like errors, in which for a split second the model would detect wake in one region of the brain while the rest of the brain remained asleep. They saw the same thing in wake states: for a split second, one region would fall asleep while the rest of the regions were awake. They call these instances "flickers."

"We could look at the individual time points when these neurons fired, and it was pretty clear that [the neurons] were transitioning to a different state," Schneider said. "In some cases, these flickers might be constrained to the area of just an individual brain region, maybe even smaller than that."

This compelled the researchers to explore what flickers could mean about the function of sleep, and how they affect behavior during sleep and wake.

"There's a natural hypothesis there; let's say a small part of your brain slips into sleep while you're awake -- does that mean your behavior suddenly looks like you're asleep? We started to see that that was often the case," Schneider said.

In observing the behavior of mice, the researchers saw that when a brain region would flicker to sleep while the rest of the brain was awake, the mouse would pause for a second, almost like it had zoned out. A flicker during sleep (one brain region "wakes up") was reflected by an animal twitching in its sleep.

Flickers are particularly surprising because they don't follow established rules dictating the strict cycle of the brain moving sequentially between wake to non-REM sleep to REM sleep.

"We are seeing wake to REM flickers, REM to non-REM flickers -- we see all these possible combinations, and they break the rules that you would expect based on a hundred years of literature," Hengen said. "I think they reveal the separation between the macro-state -- sleep and wake at the level of the whole animal, and the fundamental unit of state in the brain -- the fast and local patterns."

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Sleep resets brain connections -- but only for first few hours

During sleep, the brain weakens the new connections between neurons that had been forged while awake -- but only during the first half of a night's sleep, according to a new study in fish by UCL scientists.

The researchers say their findings, published in Nature, provide insight into the role of sleep, but still leave an open question around what function the latter half of a night's sleep serves.

The researchers say the study supports the Synaptic Homeostasis Hypothesis, a key theory on the purpose of sleep which proposes that sleeping acts as a reset for the brain.

Lead author Professor Jason Rihel (UCL Cell & Developmental Biology) said: "When we are awake, the connections between brain cells get stronger and more complex. If this activity were to continue unabated, it would be energetically unsustainable. Too many active connections between brain cells could prevent new connections from being made the following day.

"While the function of sleep remains mysterious, it may be serving as an 'off-line' period when those connections can be weakened across the brain, in preparation for us to learn new things the following day."

For the study, the scientists used optically translucent zebrafish, with genes enabling synapses (structures that communicate between brain cells) to be easily imaged. The research team monitored the fish over several sleep-wake cycles.

The researchers found that brain cells gain more connections during waking hours, and then lose them during sleep. They found that this was dependent on how much sleep pressure (need for sleep) the animal had built up before being allowed to rest; if the scientists deprived the fish from sleeping for a few extra hours, the connections continued to increase until the animal was able to sleep.

Professor Rihel added: "If the patterns we observed hold true in humans, our findings suggest that this remodelling of synapses might be less effective during a mid-day nap, when sleep pressure is still low, rather than at night, when we really need the sleep."

The researchers also found that these rearrangements of connections between neurons mostly happened in the first half of the animal's nightly sleep. This mirrors the pattern of slow-wave activity, which is part of the sleep cycle that is strongest at the beginning of the night.

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Any activity is better for your heart than sitting -- even sleeping

The study, supported by the British Heart Foundation (BHF) and published in the European Heart Journal, is the first to assess how different movement patterns throughout the 24-hour day are linked to heart health. It is the first evidence to emerge from the international Prospective Physical Activity, Sitting and Sleep (ProPASS) consortium.

Cardiovascular disease, which refers to all diseases of the heart and circulation, is the number one cause of mortality globally. In 2021, it was responsible for one in three deaths (20.5m), with coronary heart disease alone the single biggest killer. Since 1997, the number of people living with cardiovascular disease across the world has doubled and is projected to rise further.

In this study, researchers at UCL analysed data from six studies, encompassing 15,246 people from five countries, to see how movement behaviour across the day is associated with heart health, as measured by six common indicators*. Each participant used a wearable device on their thigh to measure their activity throughout the 24-hour day and had their heart health measured.

The researchers identified a hierarchy of behaviours that make up a typical 24-hour day, with time spent doing moderate-vigorous activity providing the most benefit to heart health, followed by light activity, standing and sleeping compared with the adverse impact of sedentary behaviour.

The team modelled what would happen if an individual changed various amounts of one behaviour for another each day for a week, in order to estimate the effect on heart health for each scenario. When replacing sedentary behaviour, as little as five minutes of moderate-vigorous activity had a noticeable effect on heart health.

For a 54-year-old woman with an average BMI of 26.5, for example, a 30-minute change translated into a 0.64 decrease in BMI, which is a difference of 2.4%. Replacing 30 minutes of daily sitting or lying time with moderate or vigorous exercise could also translate into a 2.5 cm (2.7%) decrease in waist circumference or a 1.33 mmol/mol (3.6%) decrease in glycated haemoglobin.

Dr Jo Blodgett, first author of the study from UCL Surgery & Interventional Science and the Institute of Sport, Exercise & Health, said: "The big takeaway from our research is that while small changes to how you move can have a positive effect on heart health, intensity of movement matters. The most beneficial change we observed was replacing sitting with moderate to vigorous activity -- which could be a run, a brisk walk, or stair climbing -- basically any activity that raises your heart rate and makes you breathe faster, even for a minute or two."

The researchers pointed out that although time spent doing vigorous activity was the quickest way to improve heart health, there are ways to benefit for people of all abilities -- it's just that the lower the intensity of the activity, the longer the time is required to start having a tangible benefit. Using a standing desk for a few hours a day instead of a sitting desk, for example, is a change over a relatively large amount of time but is also one that could be integrated into a working routine fairly easily as it does not require any time commitment.

Those who are least active were also found to gain the greatest benefit from changing from sedentary behaviours to more active ones.

Professor Emmanuel Stamatakis, joint senior author of the study from the Charles Perkins Centre and Faculty of Medicine and Health at the University of Sydney, said: "A key novelty of the ProPASS consortium is the use of wearable devices that better differentiate between types of physical activity and posture, allowing us to estimate the health effects of even subtle variations with greater precision."

Though the findings cannot infer causality between movement behaviours and cardiovascular outcomes, they contribute to a growing body of evidence linking moderate to vigorous physical activity over 24 hours with improved body fat metrics. Further long-term studies will be crucial to better understanding the associations between movement and cardiovascular outcomes.

Professor Mark Hamer, joint senior author of the study from UCL Surgery & Interventional Science and the Institute of Sport, Exercise & Health, said: "Though it may come as no surprise that becoming more active is beneficial for heart health, what's new in this study is considering a range of behaviours across the whole 24-hour day. This approach will allow us to ultimately provide personalised recommendations to get people more active in ways that are appropriate for them."

James Leiper, Associate Medical Director at the British Heart Foundation, said: "We already know that exercise can have real benefits for your cardiovascular health and this encouraging research shows that small adjustments to your daily routine could lower your chances of having a heart attack or stroke. This study shows that replacing even a few minutes of sitting with a few minutes of moderate activity can improve your BMI, cholesterol, waist size, and have many more physical benefits.

"Getting active isn't always easy, and it's important to make changes that you can stick to in the long-term and that you enjoy -- anything that gets your heart rate up can help. Incorporating 'activity snacks' such as walking while taking phone calls, or setting an alarm to get up and do some star jumps every hour is a great way to start building activity into your day, to get you in the habit of living a healthy, active lifestyle."

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Healthy lifestyle can help prevent depression -- and new research may explain why

A healthy lifestyle that involves moderate alcohol consumption, a healthy diet, regular physical activity, healthy sleep and frequent social connection, while avoiding smoking and too much sedentary behaviour, reduces the risk of depression, new research has found.

In research published today in Nature Mental Health, an international team of researchers, including from the University of Cambridge and Fudan University, looked at a combination of factors including lifestyle factors, genetics, brain structure and our immune and metabolic systems to identify the underlying mechanisms that might explain this link.

According to the World Health Organization, around one in 20 adults experiences depression, and the condition poses a significant burden on public health worldwide. The factors that influence the onset of depression are complicated and include a mixture of biological and lifestyle factors.

To better understand the relationship between these factors and depression, the researchers turned to the UK Biobank, a biomedical database and research resource containing anonymised genetic, lifestyle and health information about its participants.

By examining data from almost 290,000 people -- of whom 13,000 had depression -- followed over a nine-year period, the team was able to identify seven healthy lifestyle factors linked with a lower risk of depression. These were:
 

• moderate alcohol consumption
• healthy diet
• regular physical activity
• healthy sleep
• never smoking
• low-to-moderate sedentary behaviour
• frequent social connection

Of all of these factors, having a good night's sleep -- between seven and nine hours a night -- made the biggest difference, reducing the risk of depression, including single depressive episodes and treatment-resistant depression, by 22%.

Frequent social connection, which in general reduced the risk of depression by 18%, was the most protective against recurrent depressive disorder.

Moderate alcohol consumption decreased the risk of depression by 11%, healthy diet by 6%, regular physical activity by 14%, never smoking by 20%, and low-to-moderate sedentary behaviour by 13%.

Based on the number of healthy lifestyle factors an individual adhered to, they were assigned to one of three groups: unfavourable, intermediate, and favourable lifestyle. Individuals in the intermediate group were around 41% less likely to develop depression compared to those in the unfavourable lifestyle, while those in the favourable lifestyle group were 57% less likely.

The team then examined the DNA of the participants, assigning each a genetic risk score. This score was based on the number of genetic variants an individual carried that have a known link to risk of depression. Those with the lowest genetic risk score were 25% less likely to develop depression when compared to those with the highest score -- a much smaller impact than lifestyle.

In people at high, medium, and low genetic risk for depression, the team further found that a healthy lifestyle can cut the risk of depression. This research underlines the importance of living a healthy lifestyle for preventing depression, regardless of a person's genetic risk.

Professor Barbara Sahakian, from the Department of Psychiatry at the University of Cambridge, said: "Although our DNA -- the genetic hand we've been dealt -- can increase our risk of depression, we've shown that a healthy lifestyle is potentially more important.

"Some of these lifestyle factors are things we have a degree control over, so trying to find ways to improve them -- making sure we have a good night's sleep and getting out to see friends, for example -- could make a real difference to people's lives."

To understand why a healthy lifestyle might reduce the risk of depression, the team studied a number of other factors.

First off, they examined MRI brain scans from just under 33,000 participants and found a number of regions of the brain where a larger volume -- more neurons and connections -- was linked to a healthy lifestyle. These included the pallidum, thalamus, amygdala and hippocampus.

Next, the team looked for markers in the blood that indicated problems with the immune system or metabolism (how we process food and produce energy). Among those markers found to be linked to lifestyle were the C-reactive protein, a molecule produced in the body in response to stress, and triglycerides, one of the primary forms of fat that the body uses to store energy for later.

These links are supported by a number of previous studies. For example, exposure to stress in life can affect how well we are able to regulate blood sugar, which may lead to a deterioration of immune function and accelerate age-related damage to cells and molecules in the body. Poor physical activity and lack of sleep can damage the body's ability to respond to stress. Loneliness and lack of social support have been found to increase the risk of infection and increase markers of immune deficiency.

The team found that the pathway from lifestyle to immune and metabolic functions was the most significant. In other words, a poorer lifestyle impacts on our immune system and metabolism, which in turn increases our risk of depression.

Dr Christelle Langley, also from the Department of Psychiatry at the University of Cambridge, said: "We're used to thinking of a healthy lifestyle as being important to our physical health, but it's just as important for our mental health. It's good for our brain health and cognition, but also indirectly by promoting a healthier immune system and better metabolism."

Professor Jianfeng Feng, from Fudan University and Warwick University, added: "We know that depression can start as early as in adolescence or young adulthood, so educating young people on the importance of a healthy lifestyle and its impact on mental health should begin in schools."

Read more at Science Daily

How sleep deprivation can harm the brain

Not only does a lack of sleep make you feel awful, research has shown it impairs the brain. What's more, sleep loss over long periods can even increase risk for Alzheimer's and other neurological diseases. Researchers want to understand how sleep deprivation causes this harm. In a new study in ACS' Journal of Proteome Research, a team working with mice has identified a protective protein whose level declines with sleep deprivation, leading to neuronal death.

Studies indicate that lack of sleep leads to neurological damage in the hippocampus, a part of the brain involved in learning and memory. To better understand the changes responsible for this effect, scientists have begun examining shifts in the abundance of proteins and RNA, which contains genetically encoded instructions derived from DNA. In this way, previous studies have identified some factors linking sleep loss to damage; however, researchers haven't generally confirmed they play a role in cognitive function within larger animal populations. So, Fuyi Xu, Jia Mi and their colleagues set out to further explore how sleep loss damages the brain and to corroborate their findings.

To start off, the researchers evaluated how well mice navigated a simple maze and learned to recognize new objects after having been sleep deprived for two days. They then extracted the proteins in the animals' hippocampi and identified those whose abundance changed. Then, to further narrow the possibilities, they looked at data linking these proteins to maze performance in related strains of mice that had not experienced sleep deprivation.

This approach led the researchers to pleiotrophin (PTN), which declined in the sleep-deprived mice. Through an analysis of RNA, the team identified the molecular pathway by which a loss of PTN causes cells in the hippocampus to die. When they looked at genetic studies in humans, they found that PTN is implicated in Alzheimer's and other neurodegenerative diseases. This research has uncovered a new mechanism by which sleep protects brain function, according to the researchers, who also note that PTN levels could serve as an indicator of cognitive impairment resulting from insomnia.

From Science Daily

Wind farm noise exposure doesn't wake people up from their slumber more than road traffic noise

Short exposure to wind farm and road traffic noise triggers a small increase in people waking from their slumber that can fragment their sleep patterns, according to new Flinders University research.

But importantly, the new study also shows that wind farm noise isn't more disruptive to sleep than road traffic, which was a little more disruptive at the loudest audio level but not at more common levels.

Sleep researchers at Flinders University have studied the impact of exposure to wind farm noise during sleep in three new scientific publications to better understand its impact on Australians.

The study played 20-second wind farm and road traffic noise samples repeatedly during participants sleep using 3 different sound pressure levels to compare their sleep disruption responses between the two different noise types.

On a separate night, the study tested if longer 3-minute noise samples, including very low-frequency wind farm infrasound alone, resulted in sleep disturbance.

The researchers also found that wind farm infrasound at realistic levels was not audible to the human ear during wake and produced no evidence of sleep disruption. These findings were presented at the International conference on Wind Farm Noise in Dublin on June 22, 2023 and are still to be journal peer reviewed.

The project took 5 years to complete and involved over 460 sleep study nights from 68 participants who each spent seven consecutive nights in the sleep laboratory.

The participants were recruited from four groups, including people living near a wind farm with and without noise related sleep difficulties, a group of residents living near a busy suburban road and people living in quiet rural areas.

"In order to capture the most representative wind farm noise features and levels, we used noise samples from long-term measurements of wind farm noise. These were then reproduced in the sleep laboratory to replicate real-life noises in a much more controlled environment than is possible in field studies, where wind and noise conditions are highly variable. The study included direct sleep measurements using electroencephalography (EEG) as well as hearing tests and a range of daytime listening tests," says Dr. Bastient Lechat, one of several acoustics experts on the research team.

Professor Peter Catcheside, a sleep expert from Flinders University and the chief investigator, says that the findings show that both wind farm noise and road traffic noise disrupt sleep, depending mainly on noise loudness and sleep depth at the time of noise exposure.

"However, at realistic levels, these effects were quite small. We also found no evidence to suggest that wind farm noise is any more disruptive to sleep than road traffic noise. At the highest exposure level, road traffic noise was a little more sleep disruptive than wind farm noise."

Professor Catcheside says one of the study's aims was to determine if realistic levels of wind farm infrasound could be heard by study participants during wake or show any sign of EEG recorded brain activity changes when played during sleep.

"Our results align with previous studies and showed that infrasound played at realistic levels was not audible during wakefulness and produced no detectable EEG changes during sleep. Infrasound is therefore unlikely to explain noise complaints from wind farms, suggesting that other low frequency audible rumbling and thumping components deserve more attention towards better understanding wind farm noise effects on sleep."

Professor Catcheside says that while this study provides strong evidence that wind farm noise is not more disruptive to established sleep than road traffic noise, this does not rule out that people who are particularly noise sensitive or annoyed may find it more difficult to get to sleep when noise levels are noticeable.

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Losing sleep over losing sleep: how watching the clock impacts insomnia, use of sleep aids

Watching the clock while trying to fall asleep exacerbates insomnia and the use of sleep aids, according to research from an Indiana University professor -- and a small change could help people sleep better.

The research, led by Spencer Dawson, clinical assistant professor and associate director of clinical training in the College of Arts and Sciences' Department of Psychological and Brain Sciences, focuses on a sample of nearly 5,000 patients presenting for care at a sleep clinic.

Insomnia affects between 4 and 22% of adults and is associated with long-term health problems including cardiovascular disease, diabetes and depression.

Participants completed questionnaires about the severity of their insomnia, their use of sleep medication and the time they spent monitoring their own behavior while trying to fall asleep. They were also asked to report any psychiatric diagnoses. Researchers conducted mediation analyses to determine how the factors influenced each other.

"We found time monitoring behavior mainly has an effect on sleep medication use because it exacerbates insomnia symptoms," Dawson said. "People are concerned that they're not getting enough sleep, then they start estimating how long it will take them to fall back asleep and when they have to be up. That is not the sort of activity that's helpful in facilitating the ability to fall asleep -- the more stressed out you are, the harder time you're going to have falling asleep."

As the frustration over sleeplessness grows, people are more likely to use sleep aids in an attempt to gain control over their sleep.

The results are published in The Primary Care Companion for CNS Disorders. Additional co-authors are Dr. Barry Krakow, professor of psychiatry and behavioral health in the Mercer University School of Medicine; Patricia Haynes, associate professor in the Mel and Enid Zuckerman School of Public Health at the University of Arizona and Darlynn Rojo-Wissar, a postdoctoral fellow at Alpert Medical School of Brown University.

Dawson said the research indicates a simple behavioral intervention could provide help for those struggling with insomnia. He gives the same advice to every new patient the first time they meet.

"One thing that people could do would be to turn around or cover up their clock, ditch the smart watch, get the phone away so they're simply not checking the time," Dawson said. "There's not any place where watching the clock is particularly helpful."

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Elephant seals drift off to sleep while diving far below the ocean surface

For the first time, scientists have recorded brain activity in a free-ranging, wild marine mammal, revealing the sleep habits of elephant seals during the months they spend at sea.

The new findings, published April 20 in Science, show that while elephant seals may spend 10 hours a day sleeping on the beach during the breeding season, they average just 2 hours of sleep per day when they are at sea on months-long foraging trips. They sleep for about 10 minutes at a time during deep, 30-minute dives, often spiraling downward while fast asleep, and sometimes lying motionless on the seafloor.

First author Jessica Kendall-Bar led the study as a UC Santa Cruz graduate student working with Daniel Costa and Terrie Williams, both professors of ecology and evolutionary biology at UCSC.

"For years, one of the central questions about elephant seals has been when do they sleep," said Costa, who directs UCSC's Institute of Marine Sciences. Costa's lab has led the UCSC elephant seal research program at Año Nuevo Reserve for over 25 years, using increasingly sophisticated tags to track the movements and diving behavior of the seals during their foraging migrations, when they head out into the North Pacific Ocean for as long as 8 months.

"The dive records show that they are constantly diving, so we thought they must be sleeping during what we call drift dives, when they stop swimming and slowly sink, but we really didn't know," Costa said. "Now we're finally able to say they're definitely sleeping during those dives, and we also found that they're not sleeping very much overall compared to other mammals."

In fact, during their months at sea, elephant seals rival the record for the least sleep among all mammals, currently held by African elephants, which appear to sleep just two hours per day based on their movement patterns.

"Elephant seals are unusual in that they switch between getting a lot of sleep when they're on land, over 10 hours a day, and two hours or less when they're at sea," said Kendall-Bar, who is currently a postdoctoral fellow at UC San Diego's Scripps Institution of Oceanography.

Elephant seals are most vulnerable to predators such as sharks and killer whales when they are at the surface in the open ocean, so they only spend a minute or two breathing at the surface in between dives.

"They're able to hold their breath for a long time, so they can go into a deep slumber on these dives deep below the surface where it's safe," Kendall-Bar said.

Kendall-Bar developed a system that can reliably record brain activity (as an electroencephalogram or EEG) in wild elephant seals during their normal diving behavior at sea. With a neoprene headcap to secure the EEG sensors and a small data logger to record the signals, the system can be recovered when the animals return to the beach at Año Nuevo.

"We used the same sensors you'd use for a human sleep study at a sleep clinic and a removable, flexible adhesive to attach the headcap so that water couldn't get in and disrupt the signals," Kendall-Bar said.

In addition to the EEG system, the seals carried time-depth recorders, accelerometers, and other instruments that allowed the researchers to track the seals' movements along with the corresponding brain activity. The recordings show diving seals going into the deep sleep stage known as slow-wave sleep while maintaining a controlled glide downward, then transitioning into rapid-eye-movement (REM) sleep, when sleep paralysis causes them to turn upside down and drift downwards in a "sleep spiral."

"They go into slow-wave sleep and maintain their body posture for several minutes before they transition into REM sleep, when they lose postural control and turn upside down," Kendall-Bar said.

At the depths at which this happens, the seals are usually negatively buoyant and continue to fall passively in a corkscrew spiral "like a falling leaf," Williams said. In shallower waters over the continental shelf, elephant seals sometimes sleep while resting on the seafloor.

"It doesn't seem possible that they would truly go into paralytic REM sleep during a dive, but it tells us something about the decision-making processes of these seals to see where in the water column they feel safe enough to go to sleep," said Williams, who directs the Comparative Neurophysiology Lab at UCSC.

In developing the new EEG instrument, Kendall-Bar first deployed it on elephant seals housed temporarily in the marine mammal facilities at UCSC's Long Marine Laboratory. The next step was to deploy it on animals in the elephant seal colony at Año Nuevo Reserve north of Santa Cruz, where researchers could observe the animals on the beach.

"I spent a lot of time watching sleeping seals," Kendall-Bar said. "Our team monitored instrumented seals to make sure they were able to reintegrate with the colony and were behaving naturally."

Some of those seals took short excursions into the water, but to observe diving behavior the researchers used a translocation procedure developed by Costa's lab. Juvenile female elephant seals outfitted with the EEG sensors and trackers were transported from Año Nuevo to Monterey and released on a beach at the southern end of Monterey Bay. Over the next few days, the animals would swim back to Año Nuevo across the deep Monterey Canyon, where their dive behavior is very similar to that seen during much longer foraging trips in the open ocean.

With data on brain activity and dive behavior from 13 juvenile female elephant seals, including a total of 104 sleep dives, Kendall-Bar developed a highly accurate algorithm for identifying periods of sleep based on the dive data alone. This enabled her to estimate sleep quotas for 334 adult seals using dive data recorded over several months during their foraging trips.

"Because of the dataset that Dan Costa has curated over 25 years of working with elephant seals at Año Nuevo, I was able to extrapolate our results to over 300 animals and get a population-level look at sleep behavior," said Kendall-Bar, who now plans to use similar methods to study brain activity in other species of seals and sea lions and in human freedivers.

Williams called Kendall-Bar's work on the project a tour de force. "It's an amazing feat to pull this off," she said. "She developed an EEG system to work on an animal that's diving several hundred meters in the ocean. Then she uses the data to create data-driven animations so we can really visualize what the animal is doing as it dives through the water column."

The results may be helpful for conservation efforts by revealing a "sleepscape" of preferred resting areas, Williams said. "Normally, we're concerned about protecting the areas where animals go to feed, but perhaps the places where they sleep are as important as any other critical habitat," she said.

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Early morning university classes correlate with poor sleep and academic performance

Digital data from university students in Singapore suggest they could be getting better grades if their classes started later. The findings, from tens of thousands of students, were published by Duke-NUS Medical School researchers and colleagues in the journal Nature Human Behaviour.

Research in recent years has shown that postponing the start time of high schools improves the amount of sleep that students get and reduces their sleepiness during school hours. But findings are mixed about whether this has a positive impact on grades.

To determine the impact specifically on university students, Associate Professor Joshua Gooley, from Duke-NUS’ Neuroscience & Behavioural Disorders Programme and colleagues used student Wi-Fi connection data, log-ins to university digital learning platforms, and activity data from special sensing watches to conduct large-scale monitoring of class attendance and sleep behaviour of tens of thousands of university students.

“We implemented new methods that allow large-scale monitoring of class attendance and sleep behaviour by analysing students’ classroom Wi-Fi connection data and their interactions with digital learning platforms,” said Dr Yeo Sing Chen, first author of the study and a Duke-NUS PhD graduate.

From the data, the researchers found that early class start times were associated with lower attendance, with many students regularly sleeping past the start of such classes. When students did attend an early class, they lost about an hour of sleep. Morning classes on more days of the week were also associated with a lower grade point average.

“If the goal of formal education is to position our students to succeed in the classroom and workforce, why are we forcing many university students into the bad decision of either skipping morning class to sleep more or attending class while sleep-deprived?” asked Assoc Prof Gooley. “The take-home message from our study is that universities should reconsider mandatory early morning classes.”

The researchers drew insights using the Wi-Fi connection logs of 23,391 students to find out if early morning classes were associated with lower attendance. They then compared the data with six weeks of watch-derived activity data from a subset of 181 students to determine if the students were sleeping instead of attending early morning classes.

They also analysed activity data with the day and night patterns of digital learning platform logins of 39,458 students to determine if early morning classes were associated with waking up earlier and getting less sleep. Finally, they studied the grades of 33,818 students and the number of morning classes these students were taking to determine if it impacted their grade point average.

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Artificial neural networks learn better when they spend time not learning at all

Depending on age, humans need 7 to 13 hours of sleep per 24 hours. During this time, a lot happens: Heart rate, breathing and metabolism ebb and flow; hormone levels adjust; the body relaxes. Not so much in the brain.

"The brain is very busy when we sleep, repeating what we have learned during the day," said Maxim Bazhenov, PhD, professor of medicine and a sleep researcher at University of California San Diego School of Medicine. "Sleep helps reorganize memories and presents them in the most efficient way."

In previous published work, Bazhenov and colleagues have reported how sleep builds rational memory, the ability to remember arbitrary or indirect associations between objects, people or events, and protects against forgetting old memories.

Artificial neural networks leverage the architecture of the human brain to improve numerous technologies and systems, from basic science and medicine to finance and social media. In some ways, they have achieved superhuman performance, such as computational speed, but they fail in one key aspect: When artificial neural networks learn sequentially, new information overwrites previous information, a phenomenon called catastrophic forgetting.

"In contrast, the human brain learns continuously and incorporates new data into existing knowledge," said Bazhenov, "and it typically learns best when new training is interleaved with periods of sleep for memory consolidation."

Writing in the November 18, 2022 issue of PLOS Computational Biology, senior author Bazhenov and colleagues discuss how biological models may help mitigate the threat of catastrophic forgetting in artificial neural networks, boosting their utility across a spectrum of research interests.

The scientists used spiking neural networks that artificially mimic natural neural systems: Instead of information being communicated continuously, it is transmitted as discrete events (spikes) at certain time points.

They found that when the spiking networks were trained on a new task, but with occasional off-line periods that mimicked sleep, catastrophic forgetting was mitigated. Like the human brain, said the study authors, "sleep" for the networks allowed them to replay old memories without explicitly using old training data.

Memories are represented in the human brain by patterns of synaptic weight -- the strength or amplitude of a connection between two neurons.

"When we learn new information," said Bazhenov, "neurons fire in specific order and this increases synapses between them. During sleep, the spiking patterns learned during our awake state are repeated spontaneously. It's called reactivation or replay.

"Synaptic plasticity, the capacity to be altered or molded, is still in place during sleep and it can further enhance synaptic weight patterns that represent the memory, helping to prevent forgetting or to enable transfer of knowledge from old to new tasks."

When Bazhenov and colleagues applied this approach to artificial neural networks, they found that it helped the networks avoid catastrophic forgetting.

"It meant that these networks could learn continuously, like humans or animals. Understanding how human brain processes information during sleep can help to augment memory in human subjects. Augmenting sleep rhythms can lead to better memory.

"In other projects, we use computer models to develop optimal strategies to apply stimulation during sleep, such as auditory tones, that enhance sleep rhythms and improve learning. This may be particularly important when memory is non-optimal, such as when memory declines in aging or in some conditions like Alzheimer's disease."

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Five hours' sleep a night linked to higher risk of multiple diseases

Getting less than five hours of sleep in mid-to-late life could be linked to an increased risk of developing at least two chronic diseases, finds a new study led by UCL researchers.

The research, published in PLOS Medicine, analysed the impact of sleep duration on the health of more than 7,000 men and women at the ages of 50, 60 and 70, from the Whitehall II cohort study.

Researchers examined the relationship between how long each participant slept for, mortality and whether they had been diagnosed with two or more chronic diseases (multimorbidity) -- such as heart disease, cancer or diabetes -- over the course of 25 years.

People who reported getting five hours of sleep or less at age 50 were 20% more likely to have been diagnosed with a chronic disease and 40% more likely to be diagnosed with two or more chronic diseases over 25 years, compared to people who slept for up to seven hours.

Additionally, sleeping for five hours or less at the age of 50, 60, and 70 was linked to a 30% to 40% increased risk of multimorbidity when compared with those who slept for up to seven hours.

Researchers also found that sleep duration of five hours or less at age 50 was associated with 25% increased risk of mortality over the 25 years of follow-up -- which can mainly be explained by the fact that short sleep duration increases the risk of chronic disease(s) that in turn increase the risk of death.

Lead author, Dr Severine Sabia (UCL Institute of Epidemiology & Health, and Inserm, Université Paris Cité) said: "Multimorbidity is on the rise in high income countries and more than half of older adults now have at least two chronic diseases. This is proving to be a major challenge for public health, as multimorbidity is associated with high healthcare service use, hospitalisations and disability.

"As people get older, their sleep habits and sleep structure change. However, it is recommended to sleep for 7 to 8 hours a night -- as sleep durations above or below this have previously been associated with individual chronic diseases.

"Our findings show that short sleep duration is also associated with multimorbidity.

"To ensure a better night's sleep, it is important to promote good sleep hygiene, such as making sure the bedroom is quiet, dark and a comfortable temperature before sleeping. It's also advised to remove electronic devices and avoid large meals before bedtime. Physical activity and exposure to light during the day might also promote good sleep."

As part of the study, researchers also assessed whether sleeping for a long duration, of nine hours or more, affected health outcomes. There was no clear association between long sleep durations at age 50 and multimorbidity in healthy people.

However, if a participant had already been diagnosed with a chronic condition, then long sleep duration was associated with around a 35% increased risk of developing another illness. Researchers believe this could be due to underlying health conditions impacting sleep.

Jo Whitmore, senior cardiac nurse at the British Heart Foundation said: "Getting enough sleep allows your body to rest. There are a host of other ways that poor sleep could increase the risk of heart disease or stroke, including by increasing inflammation and increasing blood pressure.

"This research adds to a growing body of research that highlights the importance of getting a good night's sleep."

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Infants, young children finally get relief from eczema's terrible itch

The first study to treat moderate-to-severe eczema in infants and children 6 months to 5 years old with a biologic drug (monoclonal antibody) rather than immune-suppressing medications shows the drug was highly effective in reducing the signs and symptoms of moderate-to-severe eczema, report researchers involved in a new multi-site international phase III study led by Northwestern Medicine.

A 16-week course of dupilumab, a medication that targets a key immune pathway in allergies, resulted in more than half the children having at least a 75% reduction in signs of eczema and highly significant reductions in itch with improved sleep.

This is the first large-scale, randomized, placebo-controlled trial of a monoclonal antibody in any skin disease, including eczema, in children as young as 6 months. The study, which included 31 sites in Europe and North America, will be published Sept. 15 in The Lancet.

"Preschoolers who are constantly scratching, awake multiple times a night with their parents, irritable and markedly curtailed in their ability to do what other children their ages can do improved to the extent that they sleep through the night, change their personalities and have a normal life -- as babies and children should," said lead study author Dr. Amy Paller, chair of dermatology at Northwestern University Feinberg School of Medicine and an attending physician at Ann & Robert H. Lurie Children's Hospital of Chicago.

Eczema, also known as atopic dermatitis, is a chronic inflammatory skin disorder characterized by red, dry, often oozing skin and itch that can profoundly affect the lives of affected patients and their families.

An estimated 19% or more of all children under 6 years of age have eczema and 85 to 90% of individuals affected overall with eczema have the onset of disease during the first five years of life.

The children's debilitating itch leads to sleep disturbance, poor neurocognitive development and, on average, a full night of sleep lost per week.

"The ability to take this drug will significantly improve the quality of life for infants and young children who suffer tremendously with this disease," Paller said. "Atopic dermatitis or eczema is so much more than just itchy skin. It is a devastating disease. The quality of life of severe eczema -- not only for the child but also parents -- is equivalent to many life-threatening diseases."

As a result of this study, this medication is now available to infants and preschoolers as young as 6 months of age. It has "an outstanding safety profile" and does not even require any laboratory tests before starting the medication, Paller said.

Although one-half to two-thirds of young children with eczema have mild symptoms, which can be handled with steroid ointment and moisturizers, the other one-third or more have moderate-to-severe disease and require more aggressive management.

"Up to now, all we have had to treat more severe eczema is immune-suppressing medications, such as oral steroids, which we try to avoid in children, because they are associated with so many side effects and thus are not a preferred treatment for a chronic skin disease," Paller said. "The potential long-term impact on the development of the immune system in young children is also of concern with these immunosuppressants."

During the past few years, a new medication has become available called dupilumab, which is the first "biologic" drug to treat eczema in a targeted manner, meaning a narrow attack on just what scientists have found is causing the manifestations of the disease in skin. This medication was found to be effective and safe in studies with adults, then adolescents, then other school-aged children.

"But the group in whom we worry the most about safety -- those under 5 -- had not been tested and were unable to get this medication," Paller said.

The parent or a health care provider gives the child a monthly shot to administer the medication.

"The effect for most of these younger children is dramatic and at least as good as we've seen with the risky immunosuppressant medications," Paller said.

Potential added benefit by treating associated allergies

This medication has also been shown to be effective for treating asthma, gastrointestinal manifestations of allergy and other allergy-mediated problems but is not yet approved for these indications in infants and young children.

In fact, 66% of children in this trial had developed their eczema during the first six months of life and, by the time of initiating the dupilumab, more than 80% had already developed at least one allergic disorder, such as asthma or food allergy.

"By treating more aggressively to calm the immune system activation in these young children with early, severe eczema, we may also reduce the risk of their developing a range of allergic problems, changing their life beyond improving eczema," Paller said. "These associated allergic issues most often begin after the eczema starts."

Children were randomized to receive either a placebo injection or the dupilumab (weight-based dosing) every four weeks for 16 weeks. Only children who were not responding adequately to topical medications were allowed to enroll, and they had to be of a high severity, even with the topical medications.

As a result of the study, Paller said, scientists and physicians can start to better understand the relationships between eczema and a variety of allergic disorders and can consider the possibility of using this medication for other disorders that affect these very young children.

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Good sleepers have lower risk of heart disease and stroke

Nine in ten people do not get a good night's sleep, according to research presented at ESC Congress 2022.1 The study found that suboptimal sleep was associated with a higher likelihood of heart disease and stroke. The authors estimated that seven in ten of these cardiovascular conditions could be prevented if everyone was a good sleeper.

"The low prevalence of good sleepers was expected given our busy, 24/7 lives," said study author Dr. Aboubakari Nambiema of INSERM (the French National Institute of Health and Medical Research), Paris, France. "The importance of sleep quality and quantity for heart health should be taught early in life when healthy behaviours become established. Minimising night-time noise and stress at work can both help improve sleep."

Previous studies on sleep and heart disease have generally focused on one sleep habit, such as sleep duration or sleep apnoea, where breathing stops and starts while sleeping. In addition, prior studies have often assessed sleep at baseline only. The current study used a healthy sleep score combining five sleep habits. The researchers investigated the association between the baseline sleep score, and changes over time in the sleep score, and incident cardiovascular disease.

This study included 7,200 participants of the Paris Prospective Study III (PPP3), an observational community-based prospective cohort. Men and women aged 50 to 75 years and free of cardiovascular disease were recruited in a preventive medical centre between 2008 and 2011. The average age was 59.7 years and 62% were men. Participants underwent a physical examination and completed questionnaires on lifestyle, personal and family medical history, and medical conditions.

Questionnaires were used to collect information on five sleep habits at baseline and two follow up visits. Each factor was given 1 point if optimal and 0 if not. A healthy sleep score ranging from 0 to 5 was calculated, with 0 or 1 considered poor and 5 considered optimal. Those with an optimal score reported sleeping 7 to 8 hours per night, never or rarely having insomnia, no frequent excessive daytime sleepiness, no sleep apnoea, and an early chronotype (being a morning person). The researchers checked for incident coronary heart disease and stroke every two years for a total of 10 years.

At baseline, 10% of participants had an optimal sleep score and 8% had a poor score. During a median follow up of eight years, 274 participants developed coronary heart disease or stroke. The researchers analysed the association between sleep scores and cardiovascular events after adjusting for age, sex, alcohol consumption, occupation, smoking, body mass index, physical activity, cholesterol level, diabetes, and family history of heart attack, stroke or sudden cardiac death. They found that the risk of coronary heart disease and stroke decreased by 22% for every 1 point rise in the sleep score at baseline. More specifically, compared to those with a score of 0 or 1, participants with a score of 5 had a 75% lower risk of heart disease or stroke.

The researchers estimated the proportion of cardiovascular events that could be prevented with healthier sleep. They found that if all participants had an optimal sleep score, 72% of new cases of coronary heart disease and stroke might be avoided each year.

Over two follow ups, almost half of participants (48%) changed their sleep score: in 25% it decreased whereas in 23% it improved. When the researchers examined the association between the change in score and cardiovascular events, they found that a 1 point increment over time was associated with a 7% reduction in the risk of coronary heart disease or stroke.

Dr. Nambiema said: "Our study illustrates the potential for sleeping well to preserve heart health and suggests that improving sleep is linked with lower risks of coronary heart disease and stroke. We also found that the vast majority of people have sleep difficulties. Given that cardiovascular disease is the top cause of death worldwide, greater awareness is needed on the importance of good sleep for maintaining a healthy heart."

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Sleepless and selfish: Lack of sleep makes us less generous

Humans help each other -- it's one of the foundations of civilized society. But a new study by scientists at the University of California, Berkeley, reveals that a lack of sleep blunts this fundamental human attribute, with real-world consequences.

Lack of sleep is known to be associated with an increased risk of cardiovascular disease, depression, diabetes, hypertension and overall mortality. However, these new discoveries show that a lack of sleep also impairs our basic social conscience, making us withdraw our desire and willingness to help other people.

In one portion of the new study, the scientists showed that charitable giving in the week after the beginning of Daylight Saving Time, when residents of most states "spring forward" and lose one hour of their day, dropped by 10% -- a decrease not seen in states that do not change their clocks or when states return to standard time in the fall.

The study, led by UC Berkeley research scientist Eti Ben Simon and Matthew Walker, a UC Berkeley professor of psychology, adds to a growing body of evidence demonstrating that inadequate sleep not only harms the mental and physical well-being of an individual, but also compromises the bonds between individuals -- and even the altruistic sentiment of an entire nation.

"Over the past 20 years, we have discovered a very intimate link between our sleep health and our mental health. Indeed, we've not been able to discover a single major psychiatric condition in which sleep is normal," Walker said. "But this new work demonstrates that a lack of sleep not only damages the health of an individual, but degrades social interactions between individuals and, furthermore, degrades the very fabric of human society itself. How we operate as a social species -- and we are a social species -- seems profoundly dependent on how much sleep we are getting."

"We're starting to see more and more studies, including this one, where the effects of sleep loss don't just stop at the individual, but propagate to those around us," said Ben Simon. "If you're not getting enough sleep, it doesn't just hurt your own well-being, it hurts the well-being of your entire social circle, including strangers."

Ben Simon, Walker and colleagues Raphael Vallat and Aubrey Rossi will publish their results August 23 in the open access journal PLOS Biology. Walker is the director of the Center for Human Sleep Science. He and Ben Simon are members of the Helen Wills Neuroscience Institute at UC Berkeley.

Sleeplessness dampens theory of mind network

The new report describes three separate studies that assessed the impact of sleep loss on people's willingness to help others. In the first study, the scientists placed 24 healthy volunteers in a functional magnetic resonance imager (fMRI) to scan their brains after eight hours of sleep and after a night of no sleep. They found that areas of the brain that form the theory of mind network, which is engaged when people empathize with others or try to understand other people's wants and needs, were less active after a sleepless night.

"When we think about other people, this network engages and allows us to comprehend what other person's needs are: What are they thinking about? Are they in pain? Do they need help?" Ben Simon said. "However, this network was markedly impaired when individuals were sleep deprived. It's as though these parts of the brain fail to respond when we are trying to interact with other people after not getting enough sleep."

In a second study, they tracked more than 100 people online over three or four nights. During this time, the researchers measured the quality of their sleep -- how long they slept, how many times they woke up -- and then assessed their desire to help others, such as holding an elevator door open for someone else, volunteering or helping an injured stranger on the street.

"Here, we found that a decrease in the quality of someone's sleep from one night to the next predicted a significant decrease in the desire to help other people from one subsequent day to the next," Ben Simon said. "Those with poor sleep the night prior were the ones that reported being less willing and keen to help others the following day."

The third part of the study involved mining a database of 3 million charitable donations in the United States between 2001 and 2016. Did the number of donations change after the transition to Daylight Saving Time and the potential loss of an hour of sleep? They found a 10% drop in donations. This same dent in compassionate gift-giving was not seen in regions of the country that did not change their clocks.

"Even a very modest 'dose' of sleep deprivation -- here, just the loss of one single hour of sleep opportunity linked to daylight saving time -- has a very measurable and very real impact on people's generosity and, therefore, how we function as a connected society," Walker said. "When people lose one hour of sleep, there's a clear hit on our innate human kindness and our motivation to help other people in need."

An earlier study by Walker and Ben Simon showed that sleep deprivation forced people to socially withdraw and become more socially isolated. A lack of sleep also increased their feelings of loneliness. Worse still, when those sleep-deprived individuals interacted with other people, they spread their loneliness to those other individuals, almost like a virus, Walker said.

"Looking at the big picture, we're starting to see that a lack of sleep results in a quite asocial and, from a helping perspective, anti-social individual, which has manifold consequences to how we live together as a social species," he said. "A lack of sleep makes people less empathetic, less generous, more socially withdrawn, and it's infectious -- there is contagion of loneliness."

"The realization that the quantity and quality of sleep affects an entire society, caused by an impairment in prosocial behavior, may provide insights into our societal state of affairs in the present day," Walker added.

This finding also offers a novel approach to improving these specific aspects of our society.

"Promoting sleep, rather than shaming people for sleeping enough, could very palpably help shape the social bonds we all experience every day," Ben Simon said.

"Sleep, it turns out, is an incredible lubricant to prosocial, connected, empathic, kind and generous human behavior. In these divisive times, if there was ever a need for a strong, prosocial lubricant to enable the very best version of ourselves within society, now seems to be it," said Walker, author of the international bestseller, Why We Sleep. "Sleep may be a wonderful ingredient that enables the alacrity of helping between human beings."

"Sleep is essential for all aspects of our physical, mental and emotional lives," Ben Simon said. "When sleep is undervalued in society, not only do we get sleep-deprived doctors, nurses and students, but we also suffer from unkind and less empathic interactions on a daily basis."

Read more at Science Daily

Why heat makes us sleepy

On the hottest summer days, you may find yourself dozing off in the middle of the day. In some parts of the world, it's a cultural norm to schedule "siestas" and shutter businesses during the warmest hours of the day. As it turns out, biology, not just culture, may be behind this.

Temperature affects the span of human behavior, from eating and activity levels to sleep-wake cycles. We may have a harder time sleeping in the summer and be slow to get out of bed on colder mornings. But the link between sensory neurons and neurons that control this cycle are not understood completely.

Northwestern University neurobiologists have found a few clues about what's happening. In a new study, published today (Aug. 17) in the journal Current Biology, researchers found that fruit flies are pre-programmed to take a nap in the middle of the day. A follow-up to their 2020 Biology paper that identified a brain thermometer only active in cold weather, the new paper explores a similar "thermometer" circuit for hot temperatures.

"Changes in temperature have a strong effect on behavior in both humans and animals, and offer animals a cue that is time to adapt to the changing seasons," said Marco Gallio, associate professor of neurobiology in the Weinberg College of Arts and Sciences. "The effect of temperature on sleep can be quite extreme, with some animals deciding to sleep off an entire season -- think of a hibernating bear -- but the specific brain circuits that mediate the interaction between temperature and sleep centers remain largely unmapped."

Gallio led the study and said fruit flies are a particularly good model to study big questions like "why do we sleep," and "what does sleep do for the brain" because they don't attempt to disrupt instinct in the same way humans do when we pull all-nighters, for example. They also allow researchers to study the influence of external cues like light and temperature on cellular pathways.

Cells that stay on longer

The paper is the first to identify "absolute heat" receptors in fly head, which respond to temperatures above about 77 degrees Fahrenheit -- the fly's favorite temperature. As it turns out, the common laboratory fruit fly (Drosophila) has colonized nearly the entire planet by forming a close association with humans. Not surprisingly, its favorite temperature also matches that of many humans.

Just as they expected based on the results of their previous paper on cold temperature, researchers found that brain neurons receiving information about heat are part of the broader system that regulates sleep. When the hot circuit, which runs parallel to the cold circuit, is active, the target cells that promote midday sleep stay on longer. This results in an increase in midday sleep that keeps flies away from the hottest part of the day.

The study was enabled by a 10-year initiative that produced the first completed map of neural connections in an animal (a fly), called the connectome. With the connectome, researchers have access to a computer system that tells them all possible brain connections for each of the fly's ~100,000 brain cells. However, even with this extremely detailed road map, researchers still need to figure out how information in the brain goes from point A to B. This paper helps fill that gap.

The different circuits for hot versus cold temperatures make sense to Gallio because "hot and cold temperatures can have quite different effects on physiology and behavior," he said. This separation may also reflect evolutionary processes based on heat and cold cycles of the Earth. For example, the possibility that brain centers for sleep may be directly targeted in humans by a specific sensory circuit is now open to be investigated based on this work.

Next steps

Next, Gallio's team hopes to figure out the common targets of the cold and hot circuit, to discover how each can influence sleep.

"We identified one neuron that could be a site of integration for the effects of hot and cold temperatures on sleep and activity in Drosophila," said Michael Alpert, the paper's first author and a post-doctoral researcher in the Gallio lab. "This would be the start of interesting follow-up studies."

Gallio added that the team is interested in looking at the long-term effects of temperature on behavior and physiology to understand the impact of global warming, looking at how adaptable species are to change.

"People may choose to take an afternoon nap on a hot day, and in some parts of the world this is a cultural norm, but what do you choose and what is programmed into you?" Gallio said. "Of course, it's not culture in flies, so there actually might be a very strong underlying biological mechanism that is overlooked in humans."

Read more at Science Daily

A warming planet could mess with our sleep -- and make us more vulnerable to infectious disease

It's a scene that will be familiar for many after yet another scorching summer: You're lying awake during a warm night, bedsheets kicked aside, an overmatched ceiling fan providing little respite as you struggle to get a good night's sleep.

But a warming planet doesn't just mean more people may find it harder to get quality sleep. There is also evidence suggesting that sleep disturbance could make it harder for the body to fend off infection, according to a new research paper from Dr. Michael Irwin, a professor of psychiatry and biobehavorial sciences at UCLA.

Irwin, who has extensively studied how sleep regulates the immune system, said while there are few studies on how ambient, or surrounding air, temperature affects sleep, they indicate that warmer temperatures contribute to sleep disturbance. Studies have also shown that poor sleep is associated with heightened risk of infectious disease and could make some vaccination less effective, Irwin writes in a research review published in the peer-reviewed journal Temperature last week.

Given research showing a potential link between poor sleep and reduced immune response, Irwin said this raises timely questions about whether climate change results in heightened infectious disease risk amid the ongoing COVID-19 pandemic, a monkeypox outbreak and the reemergence of the poliovirus in New York and London.

"No one has previously put together this notion that the ongoing climate crisis is contributing to sleep disturbance and that it's possibly contributing to the altered risk of infectious disease we're seeing," said Irwin, the director of the Cousins Center for Psychoneuroimmunology at the Jane and Terry Semel Institute for Neuroscience and Human Behavior at UCLA.

Irwin said the issue also raises important implications about disparities, since low-income communities and communities of color face heightened risk from heat and have less access to air conditioning.

What the research shows

Irwin's paper reviews how poor sleep affects the immune system and could make people more vulnerable to infectious disease threats. Among the research he cites:

- There's a strong association between sleep and thermoregulation, or how humans maintain a steady core internal temperature. Experimental studies have shown that reducing air temperatures to a range in which humans can maintain a normal body temperature without expending excess energy improves sleep quality, while increases in air temperature result in increased wakefulness. Survey data of 765,000 people in the United States also found increases in nighttime temperatures amplified self-reported nights of insufficient sleep, with the largest effects during the summer and among lower-income and elderly people.

- It's thought that sleep helps prepare the body's response to possible injury or infection that could occur the following day. When sleep is disrupted, that contributes to increases in inflammation and dampens the body's ability to fight off infections. That means there may be heightened risk among older adults and patients with inflammatory disorders, like cardiovascular disease and some types of depression, who have higher prevalence of insomnia.

- Some small experimental studies in humans indicate that poor sleep could also result in poorer vaccine response. In one study, for instance, people who had four straight nights of partial sleep deprivation before receiving a trivalent influenza vaccine had a 50% reduction in antibody titers compared to those with normal sleep. Other studies that tested the effects of sleep disruption after influenza or hepatitis vaccination suggest that short sleep duration, at least in healthy adults, is likely associated with a reduced adaptive immunologic response and possibly clinical protection.

- Sleep duration is also associated with infectious disease risk outcomes. Basic research has shown that longer sleep leads to decreases in bacterial load and improved survival in a variety of infectious disease models. Self-reported surveys have also shown an association between shorter sleep and higher infection risk.

- While there's abundant evidence that sleep disturbance and depressive symptoms have greatly increased during the COVID-19 pandemic, there's little known about how poor sleep may be affecting risk of COVID-19 infection and outcomes. However, a recent study of over 46,000 patients indicated that a significant sleep disturbance was associated with an over 2-fold increase in the mortality risk for patients who had COVID-19, while no similar association was found in those who did not.

Irwin said that future research on this topic should evaluate how altering ambient temperatures affects sleep and, as a result, immune function. He said there should also be a focus on how rising ambient temperatures may be affecting diverse and disadvantaged communities.

Read more at Science Daily

Study shows link between frequent naps and high blood pressure

Napping on a regular basis is associated with higher risks for high blood pressure and stroke, according to new research published today in Hypertension, an American Heart Association journal.

Researchers in China examined whether frequent naps could be a potential causal risk factor for high blood pressure and/or stroke. This is the first study to use both observational analysis of participants over a long period of time and Mendelian randomization -- a genetic risk validation to investigate whether frequent napping was associated with high blood pressure and ischemic stroke.

"These results are especially interesting since millions of people might enjoy a regular, or even daily nap," says E Wang, Ph.D., M.D., a professor and chair of the Department of Anesthesiology at Xiangya Hospital Central South University, and the study's corresponding author.

Researchers used information from UK Biobank, a large biomedical database and research resource containing anonymized genetic, lifestyle and health information from half a million UK participants. UK Biobank recruited more than 500,000 participants between the ages of 40 and 69 who lived in the United Kingdom between 2006 and 2010. They regularly provided blood, urine and saliva samples, as well as detailed information about their lifestyle. The daytime napping frequency survey occurred 4 times from 2006 -- 2019 in a small proportion of UK Biobank participants.

Wang's group excluded records of people who had already had a stroke or had high blood pressure before the start of the study. This left about 360,000 participants to analyze the association between napping and first-time reports of stroke or high blood pressure, with an average follow-up of about 11 years. Participants were divided into groups based on self-reported napping frequency: "never/rarely," "sometimes," or "usually."

The study found:

• A higher percentage of usual-nappers were men, had lower education and income levels, and reported cigarette smoking, daily drinking, insomnia, snoring and being an evening person compared to never- or sometimes-nappers;
• When compared to people who reported never taking a nap, people who usually nap had a 12% higher likelihood of developing high blood pressure and 24% higher likelihood of having a stroke;
• Participants younger than age 60 who usually napped had a 20% higher risk of developing high blood pressure compared to people the same age who never napped. After age 60, usual napping was associated with 10% higher risk of high blood pressure compared to those who reported never napping;
• About three-fourths of participants remained in the same napping category throughout the study;
• The Mendelian randomization result showed that If napping frequency increased by one category (from never to sometimes or sometimes to usually) high blood pressure risk increased 40%. Higher napping frequency was related to the genetic propensity for high blood pressure risk.

"This may be because, although taking a nap itself is not harmful, many people who take naps may do so because of poor sleep at night. Poor sleep at night is associated with poorer health, and naps are not enough to make up for that," said Michael A. Grandner, Ph.D., MTR, a sleep expert and co-author of the American Heart Association's new Life's Essential 8 cardiovascular health score, which added sleep duration in June 2022 as the 8th metric for measuring optimal heart and brain health. "This study echoes other findings that generally show that taking more naps seems to reflect increased risk for problems with heart health and other issues." Grander is director of the Sleep Health Research Program and the Behavioral Sleep Medicine Clinic and associate professor of psychiatry at the University of Arizona in Tucson.

The authors recommend further examination of the associations between a healthy sleep pattern, including daytime napping, and heart health.

The study has several important limitations to consider. Researchers only collected daytime napping frequency, not duration, so there is no information how or whether the length of nap affects blood pressure or stroke risks. Additionally, nap frequency was self-reported without any objective measurements, making estimates nonquantifiable. The study's participants were mostly middle-aged and elderly with European ancestry, so the results may not be generalizable. Finally, researchers have not yet discovered the biological mechanism for the effect of daytime napping on blood pressure regulation or stroke.

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During sleep the brain's reaction to sound remains strong, but one critical feature of conscious attention disappears

A new discovery from Tel Aviv University may provide a key to a great scientific enigma: How does the awake brain transform sensory input into a conscious experience? The groundbreaking study relied on data collected from electrodes implanted, for medical purposes, deep in the human brain. The information was utilized to examine differences between the response of the cerebral cortex to sounds in sleep vs. wakefulness, at a resolution of single neurons.

The researchers were surprised to discover that the brain's response to sound remains powerful during sleep in all parameters but one: the level of alpha-beta waves associated with attention to the auditory input and related expectations. This means that during sleep, the brain analyzes the auditory input but is unable to focus on the sound or identify it, and therefore no conscious awareness ensues.

The study was led by Dr. Hanna Hayat and with major contribution from Dr. Amit Marmelshtein, at the lab of Prof. Yuval Nir from the School of Medicine, the Sagol School of Neuroscience, and the Department of Biomedical Engineering, and co-supervised by Prof. Itzhak Fried from the UCLA Medical Center. Other participants included: Dr. Aaron Krom and Dr. Yaniv Sela from Prof. Nir's group, and Dr. Ido Strauss and Dr. Firas Fahoum from the Tel Aviv Sourasky Medical Center (Ichilov). The paper was published in the journal Nature Neuroscience.

Prof. Nir: "This study is unique in that it builds upon rare data from electrodes implanted deep inside the human brain, enabling high-resolution monitoring, down to the level of individual neurons, of the brain's electrical activity. For understandable reasons, electrodes cannot be implanted in the brain of living humans just for the sake of scientific research. But in this study, we were able to utilize a special medical procedure in which electrodes were implanted in the brains of epilepsy patients, monitoring activity in different parts of their brain for purposes of diagnosis and treatment. The patients volunteered to help examine the brain's response to auditory stimulation in wakefulness vs. sleep."

The researchers placed speakers emitting various sounds at the patients' bedside and compared data from the implanted electrodes -- neural activity and electrical waves in different areas of the brain -- during wakefulness vs. various stages of sleep. Altogether, the team collected data from over 700 neurons, about 50 neurons in each patient, over the course of 8 years.

Dr. Hayat: "After sounds are received in the ear, the signals are relayed from one station to the next within the brain. Until recently it was believed that during sleep these signals decay rapidly once they reach the cerebral cortex. But looking at the data from the electrodes, we were surprised to discover that the brain's response during sleep was much stronger and richer than we had expected. Moreover, this powerful response spread to many regions of the cerebral cortex. The strength of brain response during sleep was similar to the response observed during wakefulness, in all but one specific feature, where a dramatic difference was recorded: the level of activity of alpha-beta waves."

The researchers explain that alpha-beta waves (10-30Hz) are linked to processes of attention and expectation that are controlled by feedback from higher regions in the brain. As signals travel 'bottom-up' from the sensory organs to higher regions, a 'top-down' motion also occurs: the higher regions, relying on prior information that had accumulated in the brain, act as a guide, sending down signals to instruct the sensory regions as to which input to focus on, which should be ignored, etc. Thus, for example, when a certain sound is received in the ear, the higher regions can tell whether it is new or familiar, and whether it deserves attention or not. This kind of brain activity is manifested in the suppression of alpha-beta waves, and indeed, previous studies have shown a high level of these waves in states of rest and anesthesia. According to the current study, the strength of alpha-beta waves is the main difference between the brain's response to auditory inputs in states of wakefulness vs. sleep.

Prof Nir summarizes: "Our findings have wide implications beyond this specific experiment. First, they provide an important key to an ancient, fascinating enigma: What is the secret of consciousness? What is the 'X-factor', the brain activity that is unique to consciousness, allowing us to be aware of things happening around us when we are awake, and disappearing when we sleep? In this study we discovered a new lead, and in future research we intend to further explore the mechanisms responsible for this difference.

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How sleep helps to process emotions

Researchers at the Department of Neurology of the University of Bern and University Hospital Bern identified how the brain triages emotions during dream sleep to consolidate the storage of positive emotions while dampening the consolidation of negative ones. The work expands the importance of sleep in mental health and opens new ways of therapeutic strategies.

Rapid eye movement (REM or paradoxical) sleep is a unique and mysterious sleep state during which most of the dreams occur together with intense emotional contents. How and why these emotions are reactivated is unclear. The prefrontal cortex integrates many of these emotions during wakefulness but appears paradoxically quiescent during REM sleep. "Our goal was to understand the underlying mechanism and the functions of such a surprising phenomenon," says Prof. Antoine Adamantidis from the Department of Biomedical Research (DBMR) at the University of Bern and the Department of Neurology at the Inselspital, University Hospital of Bern.

Processing emotions, particularly distinguishing between danger and safety, is critical for the survival of animals. In humans, excessively negative emotions, such as fear reactions and states of anxiety, lead to pathological states like Post-Traumatic Stress Disorders (PTSD). In Europe, roughly 15% of the population is affected by persistent anxiety and severe mental illness. The research group headed by Antoine Adamantidis is now providing insights into how the brain helps to reinforce positive emotions and weaken strongly negative or traumatic emotions during REM sleep. This study was published in the journal Science.

A Dual mechanism

The researchers first conditioned mice to recognize auditory stimuli associated with safety and others associated with danger (aversive stimuli). The activity of neurons in the brain of mice was then recorded during sleep-wake cycles. In this way, the researchers were able to map different areas of a cell and determine how emotional memories are transformed during REM sleep.

Neurons are composed of a cell body (soma) that integrates information coming from the dendrites (inputs) and send signals to other neurons via their axons (outputs). The results obtained showed that cell somas are kept silent while their dendrites are activated. "This means a decoupling of the two cellular compartments, in other words soma wide asleep and dendrites wide awake," explains Adamantidis. This decoupling is important because the strong activity of the dendrites allows the encoding of both danger and safety emotions, while the inhibitions of the soma completely block the output of the circuit during REM sleep. In other words, the brain favours the discrimination of safety versus danger in the dendrites, but block the over-reaction to emotion, in particular danger.

A survival advantage

According to the researchers, the coexistence of both mechanisms is beneficial to the stability and survival of the organisms: "This bi-directional mechanism is essential to optimize the discrimination between dangerous and safe signals," says Mattia Aime from the DBMR, first author of the study. If this discrimination is missing in humans and excessive fear reactions are generated, this can lead to anxiety disorders. The findings are particularly relevant to pathological conditions such as post-traumatic stress disorders, in which trauma is over-consolidated in the prefrontal cortex, day after day during sleep.

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Seven hours of sleep is optimal in middle and old age, say researchers

Seven hours is the ideal amount of sleep for people in their middle age and upwards, with too little or too much little sleep associated with poorer cognitive performance and mental health, say researchers from the University of Cambridge and Fudan University.

Sleep plays an important role in enabling cognitive function and maintaining good psychological health. It also helps keep the brain healthy by removing waste products. As we get older, we often see alterations in our sleep patterns, including difficulty falling asleep and staying asleep, and decreased quantity and quality of sleep. It is thought that these sleep disturbances may contribute to cognitive decline and psychiatric disorders in the aging population.

In research published today in Nature Aging, scientists from the UK and China examined data from nearly 500,000 adults aged 38-73 years from the UK Biobank. Participants were asked about their sleeping patterns, mental health and wellbeing, and took part in a series of cognitive tests. Brain imaging and genetic data were available for almost 40,000 of the study participants.

By analysing these data, the team found that both insufficient and excessive sleep duration were associated with impaired cognitive performance, such as processing speed, visual attention, memory and problem-solving skills. Seven hours of sleep per night was the optimal amount of sleep for cognitive performance, but also for good mental health, with people experiencing more symptoms of anxiety and depression and worse overall wellbeing if they reported sleeping for longer or shorter durations.

The researchers say one possible reason for the association between insufficient sleep and cognitive decline may be due to the disruption of slow-wave -- 'deep' -- sleep. Disruption to this type of sleep has been shown to have a close link with memory consolidation as well as the build-up of amyloid -- a key protein which, when it misfolds, can cause 'tangles' in the brain characteristic of some forms of dementia. Additionally, lack of sleep may hamper the brain's ability to rid itself of toxins.

The team also found a link between the amount of sleep and differences in the structure of brain regions involved in cognitive processing and memory, again with greater changes associated with greater than or less than seven hours of sleep.

Having a consistent seven hours' sleep each night, without too much fluctuation in duration, was also important to cognitive performance and good mental health and wellbeing. Previous studies have also shown that interrupted sleep patterns are associated with increased inflammation, indicating a susceptibility to age-related diseases in older people.

Professor Jianfeng Feng from Fudan University in China said: "While we can't say conclusively that too little or too much sleep causes cognitive problems, our analysis looking at individuals over a longer period of time appears to support this idea. But the reasons why older people have poorer sleep appear to be complex, influenced by a combination of our genetic makeup and the structure of our brains."

The researchers say the findings suggest that insufficient or excessive sleep duration may be a risk factor for cognitive decline in ageing. This is supported by previous studies that have reported a link between sleep duration and the risk of developing Alzheimer's disease and dementia, in which cognitive decline is a hallmark symptom.

Professor Barbara Sahakian from the Department of Psychiatry at the University of Cambridge, one of the study's authors, said: "Getting a good night's sleep is important at all stages of life, but particularly as we age. Finding ways to improve sleep for older people could be crucial to helping them maintain good mental health and wellbeing and avoiding cognitive decline, particularly for patients with psychiatric disorders and dementias."

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