Another intermediate-mass black hole discovered at the center of our galaxy

While researching a cluster of stars in the immediate vicinity of the supermassive black hole SgrA* (Sagittarius A*) at the centre of our galaxy, an international team of researchers led by PD Dr Florian Peißker has found signs of another, intermediate-mass black hole. Despite enormous research efforts, only about ten of these intermediate-mass black holes have been found in our entire universe so far. Scientists believe that they formed shortly after the Big Bang. By merging, they act as 'seeds' for supermassive black holes. The study 'The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic structure' was published in The Astrophysical Journal.

The analysed star cluster IRS 13 is located 0.1 light years from the centre of our galaxy.

This is very close in astronomical terms, but would still require travelling from one end of our solar system to the other twenty times to cover the distance.

The researchers noticed that the stars in IRS 13 move in an unexpectedly orderly pattern.

They had actually expected the stars to be arranged randomly.

Two conclusions can be drawn from this regular pattern: On the one hand, IRS 13 appears to interact with SgrA*, which leads to the orderly motion of the stars.

On the other hand, there must be something inside the cluster for it to be able to maintain its observed compact shape.

Multi-wavelength observations with the Very Large Telescope as well as the ALMA and Chandra telescopes now suggest that the reason for the compact shape of IRS 13 could be an intermediate-mass black hole located at the centre of the star cluster.

This would be supported by the fact that the researchers were able to observe characteristic X-rays and ionized gas rotating at a speed of several 100 km/s in a ring around the suspected location of the intermediate-mass black hole.

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Waste Styrofoam can now be converted into polymers for electronics

University of Delaware and Argonne National Laboratory have come up with a chemical reaction that can convert Styrofoam into a high-value conducting polymer known as PEDOT:PSS. In a new paper published in JACS Au, the study demonstrates how upgraded plastic waste can be successfully incorporated into functional electronic devices, including silicon-based hybrid solar cells and organic electrochemical transistors.

The research group of corresponding author Laure Kayser, assistant professor in the Department of Materials Science and Engineering in UD's College of Engineering with a joint appointment in the Department of Chemistry and Biochemistry in the College of Arts and Sciences, regularly works with PEDOT:PSS, a polymer that has both electronic and ionic conductivity, and was interested in finding ways to synthesize this material from plastic waste.

After connecting with Argonne chemist David Kaphan during an event hosted by UD's research office, the research teams at UD and Argonne began evaluating the hypothesis that PEDOT:PSS could be made by sulfonating polystyrene, a synthetic plastic found in many types of disposable containers and packing materials.

Sulfonation is a common chemical reaction where a hydrogen atom is replaced by sulfonic acid; the process is used to create a variety of products such as dyes, drugs and ion exchange resins. These reactions can either be "hard" (with higher conversion efficiency but that require caustic reagents) or "soft" (a less efficient method but one that uses milder materials).

In this paper, the researchers wanted to find something in the middle: "A reagent that is efficient enough to get really high degrees of functionalization but that doesn't mess up your polymer chain," Kayser explained.

The researchers first turned to a method described in a previous study for sulfonating small molecules, one that showed promising results in terms of efficiency and yield, using 1,3-Disulfonic acid imidazolium chloride ([Dsim]Cl). But adding functional groups onto a polymer is more challenging than for a small molecule, the researchers explained, because not only are unwanted byproducts harder to separate, any small errors in the polymer chain can change its overall properties.

To address this challenge, the researchers embarked on many months of trial and error to find the optimal conditions that minimized side reactions, said Kelsey Koutsoukos, a materials science doctoral candidate and second author of this paper.

"We screened different organic solvents, different molar ratios of the sulfonating agent, and evaluated different temperatures and times to see which conditions were the best for achieving high degrees of sulfonation," he said.

The researchers were able to find reaction conditions that resulted in high polymer sulfonation, minimal defects and high efficiency, all while using a mild sulfonating agent. And because the researchers were able to use polystyrene, specifically waste Styrofoam, as a starting material, their method also represents an efficient way to convert plastic waste into PEDOT:PSS.

Once the researchers had PEDOT:PSS in hand, they were able to compare how their waste-derived polymer performed compared to commercially available PEDOT:PSS.

"In this paper, we looked at two devices -- an organic electronic transistor and a solar cell," said Chun-Yuan Lo, a chemistry doctoral candidate and the paper's first author. "The performance of both types of conductive polymers was comparable, and shows that our method is a very eco-friendly approach for converting polystyrene waste into high-value electronic materials."

Specific analyses conducted at UD included X-ray photoelectron spectroscopy (XPS) at the surface analysis facility, film thickness analysis at the UD Nanofabrication Facility, and solar cell evaluation at the Institute of Energy Conversion. Argonne's advanced spectroscopy equipment, such as carbon NMR, was used for detailed polymer characterization. Additional support was provided by materials science and engineering professor Robert Opila for solar cell analysis and by David C. Martin, the Karl W. and Renate Böer Chaired Professor of Materials Science and Engineering, for the electronic device performance analyses.

One unexpected finding related to the chemistry, the researchers added, is the ability to use stoichiometric ratios during the reaction.

"Typically, for sulfonation of polystyrene, you have to use an excess of really harsh reagents. Here, being able to use a stoichiometric ratio means that we can minimize the amount of waste being generated," Koutsoukos said.

This finding is something the Kayser group will be looking into further as a way to "fine-tune" the degree of sulfonation. So far, they've found that by varying the ratio of starting materials, they can change the degree of sulfonation on the polymer. Along with studying how this degree of sulfonation impacts the electrical properties of PEDOT:PSS, the team is interested in seeing how this fine-tuning capability can be used for other applications, such as fuel cells or water filtration devices, where the degree of sulfonation greatly impacts a material's properties.

"For the electronic devices community, the key takeaway is that you can make electronic materials from trash, and they perform just as well as what you would purchase commercially," Kayser said. "For the more traditional polymer scientists, the fact that you can very efficiently and precisely control the degree of sulfonation is going to be of interest to a lot of different communities and applications."

The researchers also see great potential for how this research can contribute to ongoing global sustainability efforts by providing a new way to convert waste products into value-added materials.

"Many scientists and researchers are working hard on upcycling and recycling efforts, either by chemical or mechanical means, and our study provides another example of how we can address this challenge," Lo said.

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Ancient microbes offer clues to how complex life evolved

A new study published in Science Advances reveals a surprising twist in the evolutionary history of complex life. Researchers at Queen Mary University of London have discovered that a single-celled organism, a close relative of animals, harbors the remnants of ancient giant viruses woven into its own genetic code. This finding sheds light on how complex organisms may have acquired some of their genes and highlights the dynamic interplay between viruses and their hosts.

The study focused on a microbe called Amoebidium, a unicellular parasite found in freshwater environments.

By analysing Amoebidium's genome, the researchers led by Dr Alex de Mendoza Soler, Senior Lecturer at Queen Mary's School of Biological and Behavioural Sciences, found a surprising abundance of genetic material originating from giant viruses -- some of the largest viruses known to science.

These viral sequences were heavily methylated, a chemical tag that often silences genes.

"It's like finding Trojan horses hiding inside the Amoebidium's DNA," explains Dr de Mendoza Soler.

"These viral insertions are potentially harmful, but Amoebidium seems to be keeping them in check by chemically silencing them."

The researchers then investigated how widespread this phenomenon might be. They compared the genomes of several Amoebidium isolates and found significant variation in the viral content.

This suggests that the process of viral integration and silencing is ongoing and dynamic.

"These findings challenge our understanding of the relationship between viruses and their hosts," says Dr. de Mendoza Soler.

"Traditionally, viruses are seen as invaders, but this study suggests a more complex story. Viral insertions may have played a role in the evolution of complex organisms by providing them with new genes. And this is allowed by the chemical taming of these intruders DNA."

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Sun-like stars found orbiting hidden companions

Most stars in our universe come in pairs. While our own Sun is a loner, many stars like our Sun orbit similar stars, while a host of other exotic pairings between stars and cosmic orbs pepper the universe. Black holes, for example, are often found orbiting each other. One pairing that has proved to be quite rare is that between a Sun-like star and a type of dead star called a neutron star.

Now, astronomers led by Caltech's Kareem El-Badry have uncovered what appear to be 21 neutron stars in orbit around stars like our Sun. Neutron stars are dense burned-out cores of massive stars that exploded. On their own, they are extremely faint and usually cannot be detected directly. But as a neutron star orbits around a Sun-like star, it tugs on its companion, causing the star to shift back and forth in the sky. Using the European Space Agency's Gaia mission, the astronomers were able to catch these telltale wobbles to reveal a new population of dark neutron stars.

"Gaia is continuously scanning the sky and measuring the wobbles of more than a billion stars, so the odds are good for finding even very rare objects," says El-Badry, an assistant professor of astronomy at Caltech and an adjunct scientist at the Max Planck Institute for Astronomy in Germany.

The new study, which includes a team of co-authors from around the world, was published in The Open Journal for Astrophysics. Data from several ground-based telescopes, including the W. M. Keck Observatoryon Maunakea, Hawai'i; La Silla Observatory in Chile; and the Whipple Observatory in Arizona, were used to follow up the Gaia observations and learn more about the masses and orbits of the hidden neutron stars.

While neutron stars have previously been detected in orbit around stars like our Sun, those systems have all been more compact. With little distance separating the two bodies, a neutron star (which is heavier than a Sun-like star) can steal mass away from its partner. This mass transfer process makes the neutron star shine brightly at X-ray or radio wavelengths. In contrast, the neutron stars in the new study are much farther from their partners -- on the order of one to three times the distance between Earth and the Sun.

That means the newfound stellar corpses are too far from their partners to be stealing material from them. They are instead quiescent and dark. "These are the first neutron stars discovered purely due to their gravitational effects," El-Badry says.

The discovery comes as somewhat of a surprise because it is not clear how an exploded star winds up next to a star like our Sun.

"We still do not have a complete model for how these binaries form," explains El-Badry. "In principle, the progenitor to the neutron star should have become huge and interacted with the solar-type star during its late-stage evolution." The huge star would have knocked the little star around, likely temporarily engulfing it. Later, the neutron star progenitor would have exploded in a supernova, which, according to models, should have unbound the binary systems, sending the neutron stars and Sun-like stars careening in opposite directions.

"The discovery of these new systems shows that at least some binaries survive these cataclysmic processes even though models cannot yet fully explain how," he says.

Gaia was able to find the unlikely companions due to their wide orbits and long periods (the Sun-like stars orbit around the neutron stars with periods of six months to three years). "If the bodies are too close, the wobble will be too small to detect," El-Badry says. "With Gaia, we are more sensitive to the wider orbits." Gaia is also most sensitive to binaries that are relatively nearby. Most of the newly discovered systems are located within 3,000 light-years of Earth -- a relatively small distance compared, for example, to the 100,000 light-year-diameter of the Milky Way Galaxy.

The new observations also suggest just how rare the pairings are. "We estimate that about one in a million solar-type stars is orbiting a neutron star in a wide orbit," he said.

El-Badry also has an interest in finding unseen dormant black holes in orbit with Sun-like stars. Using Gaia data, he has found two of these quiet black holes hidden in our galaxy. One, called Gaia BH1, is the closest known black hole to Earth at 1,600 light-years away.

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Rural belts around cities can reduce urban summer temperatures by up to 0.5°C

The key to cooling 'urban heat islands' may lie in the countryside, according to a new study from scientists at the University of Surrey and Southeast University (China).

Using 20 years of data, researchers showed how nearby rural areas could bring a city's temperature down.

The biggest cooling effects happen where the rural ring around a city extends for at least half the city's diameter.

Professor Shi-Jie Cao, the lead author and visiting professor at the University of Surrey's Global Centre for Clean Air Research (GCARE), said:

"We often focus on how green spaces, wetlands or waterways can cool down cities. Yet, urban land is precious, and these measures can be hard to find space for. We have now shown how land use outside a city can make a big difference to temperatures downtown.

"Our findings allow us to make quite specific recommendations. We found that urban over-heating was mitigated more by joining up patches of rural land, planting more woodland scattered around a city, and by having fewer, bigger lakes rather than lots of little bodies of water.

As warm air rises in a city, it creates a layer of low pressure close to the ground.

This sucks cooler air in from surrounding rural areas. This process is greatly shaped by the size of a city, and the land cover of neighbouring rural areas.

To find out exactly how, scientists compared the areas around 30 Chinese cities between 2000-2020.

Satellite data told them how warm the ground was, and how the land was used.

Professor Prashant Kumar, one of the authors of the study, founding director of GCARE and co-director of Surrey's Institute of Sustainability, said:

"We already suspected that belts of rural land around a city could help cool down the urban centre. Now, thanks to our detailed analysis, we can say which forms of land use lead to the biggest effects.

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Scientists define new type of memory loss in older adults

Researchers at Mayo Clinic have established new criteria for a memory-loss syndrome in older adults that specifically impacts the brain's limbic system. It can often be mistaken for Alzheimer's disease. The good news: Limbic-predominant Amnestic Neurodegenerative Syndrome, or LANS, progresses more slowly and has a better prognosis, and is now more clearly defined for doctors working to find answers for memory loss patients.

Prior to the researchers developing clinical criteria published in the journal Brain Communications, the hallmarks of the syndrome could be confirmed only by examining brain tissue after a person's death. The proposed criteria provide a framework for neurologists and other experts to classify the condition in patients living with symptoms, offering a more precise diagnosis and potential treatments. They consider factors such as age, severity of memory impairment, brain scans, and biomarkers indicating the deposits of specific proteins in the brain.

The criteria were developed and validated using data from more than 200 participants in databases for the Mayo Clinic Alzheimer's Disease Research Center, the Mayo Clinic Study of Aging and the Alzheimer's Disease Neuroimaging Initiative.

Understanding the condition will lead to better management of symptoms and more tailored therapies for patients suffering from this type of cognitive decline, distinct from Alzheimer's disease, says David T. Jones, M.D., a Mayo Clinic neurologist and senior author of the study.

"In our clinical work, we see patients whose memory symptoms appear to mimic Alzheimer's disease, but when you look at their brain imaging or biomarkers, it's clear they don't have Alzheimer's. Until now, there has not been a specific medical diagnosis to point to, but now we can offer them some answers," Jones says. "This research creates a precise framework that other medical professionals can use to care for their patients. It has major implications for treatment decisions, including amyloid-lowering drugs and new clinical trials, and counseling on their prognosis, genetics and other factors."

Decades of work to understand and classify different types of dementia is ongoing, says Nick Corriveau-Lecavalier, Ph.D., the paper's first author. These findings build upon scientists' continued efforts to untangle neurological conditions that often have similar symptoms or can occur simultaneously, but can have drastically different treatments and prognoses.

"Historically, you might see someone in their 80s with memory problems and think they may have Alzheimer's disease, and that is often how it's being thought of today," Corriveau-Lecavalier says. "With this paper, we are describing a different syndrome that happens much later in life. Often, the symptoms are restricted to memory and will not progress to impact other cognitive domains, so the prognosis is better than with Alzheimer's disease."

Without signs of Alzheimer's disease, the researchers looked at the involvement of one possible culprit -- a buildup of a protein called TDP-43 in the limbic system that scientists have found in the autopsied brain tissue of older adults. Researchers have classified the build-up of these protein deposits as limbic-predominant age-related TDP-43 encephalopathy, or LATE. These protein deposits could be associated with the newly defined memory loss syndrome, but there are also other likely causes and more research is needed, the authors say.

With clinical criteria established by Jones, Corriveau-Lecavalier and co-authors, practitioners could soon diagnose LANS in patients so those living with memory loss might better understand options for treatment and potential progression of the disease, opening doors for research to further illuminate the characteristics of the disease.

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Llama nanobodies: A breakthrough in building HIV immunity

A research team at Georgia State University has developed tiny, potent molecules that are capable of targeting hidden strains of HIV. The source? Antibody genes from llama DNA.

The research, led by Assistant Professor of Biology Jianliang Xu, uses llama-derived nanobodies to broadly neutralize numerous strains of HIV-1, the most common form of the virus. A new study from this team has been published in the journal Advanced Science.

"This virus has evolved a way to escape our immune system. Conventional antibodies are bulky, so it's difficult for them to find and attack the virus' surface," Xu explained. "These new antibodies can do this in an easier way."

Scientists in pursuit of effective HIV treatment and prevention have been working with animals in the camelid family -- like llamas -- for about 15 years. That's because the shape and features of their antibodies make them nimbler and more effective at identifying and neutralizing foreign objects, like the HIV virus.

This new research presents a widely applicable method to enhance the performance of nanobodies. Nanobodies are engineered antibody fragments that are about one-tenth the size of a conventional antibody. They are derived from flexible, Y-shaped heavy chain-only antibodies -- made up of two heavy chains -- which are more effective at fighting certain viruses than conventional antibodies with light chains.

The nanobodies are derived from flexible, Y-shaped antibodies made up of heavy-chain peptides which may be more effective at fighting certain viruses.

For the study, researchers immunized llamas with a specially designed protein which results in the production of neutralizing nanobodies. Xu and his team then identified nanobodies that can target vulnerable sites on the virus. When the team engineered the nanobodies into a triple tandem format -- by repeating short lengths of DNA -- the resulting nanobodies demonstrated remarkable effectiveness, neutralizing 96 percent of a diverse panel of HIV-1 strains.

Further analysis uncovered that these nanobodies mimic the recognition of the CD4 receptor -- a key player in HIV infection. To enhance their potency, the nanobodies were fused with a broadly neutralizing antibody (bNAb), resulting in a new antibody with unprecedented neutralizing abilities.

"Instead of developing a cocktail of antibodies, now we can make a single molecule that can neutralize HIV," Xu said. "We are working with a broadly neutralizing nanobody that can neutralize over 90 percent of the circulating HIV strains, and when we combine that with another bNAb which also neutralizes some 90 percent, together, they can neutralize close to 100 percent."

Xu began this research at the National Institutes of Health Vaccine Research Center in Bethesda, Md., where he collaborated with a team of more than 30 scientists. The team included Peter Kwong, professor of biochemistry and molecular biophysics at Columbia University and co-author of the study. Since coming to Georgia State in 2023, Xu has been mentoring Payton Chan, a Ph.D. candidate at Georgia State. Together, they are working to expand these potential remedies.

Chan said she is excited about the prospects of the innovative research.

"These nanobodies are the best and most potently neutralizing antibodies to date, which I think is very promising for the future of HIV therapeutics and antibody research," Chan said. "I hope one day there will be approval of these nanobodies for the treatment of HIV."

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Bizarre 'garden sprinkler-like' jet is spotted shooting out of neutron star

A strange 'garden sprinkler-like' jet coming from a neutron star has been pictured for the first time.

The S-shaped structure is created as the jet changes direction due to the wobbling of the disc of hot gas around the star -- a process called precession, which has been observed with black holes but, until now, never with neutron stars.

This particular object sits in the binary system Circinus X-1 more than 30,000 light-years from Earth and formed from the core of a massive supergiant star that collapsed around the same time Stonehenge was built.

It is so dense that a teaspoon of its material weighs as much as Mount Everest.

Binary systems have two stars that are bound together by gravity. In the case of Circinus X-1, one of these is a neutron star.

Both neutron stars and black holes are cosmological monsters which form when the biggest stars in the Universe die and collapse under their own gravity.

However, the latter are considerably more massive and can only be detected through their gravitational effects, while the former can be observed directly despite their denseness.

They are some of the most extreme objects in the Universe and have interiors almost entirely made of neutrons.

The jet emanating from the neutron star was spotted by a team of astronomers at the University of Oxford, who used MeerKAT -- a radio telescope in South Africa -- to create the most detailed, high-resolution images of Circinus X-1.

The pictures, which were presented at this week's National Astronomy Meeting at the University of Hull, include the first-ever image of an S-shaped jet coming from a confirmed neutron star -- a breakthrough that could help unravel the extreme physics behind the astronomical phenomenon.

Lead researcher Fraser Cowie said there was another system known for its S-shaped jets, called SS433, but recent results suggest that object is likely a black hole.

"This image is the first time we have seen strong evidence for a precessing jet from a confirmed neutron star," he said.

"This evidence comes from both the symmetric S shape of the radio-emitting plasma in the jets and from the fast, wide shockwave, which can only be produced by a jet changing direction.

"This will give valuable information about the extreme physics behind the launching of the jet, a phenomenon which is still not well understood."

The neutron star's huge density creates a strong force of gravity that strips gas from the companion star, forming a disc of hot gas around it that spirals down towards its surface.

This process, called accretion, releases huge amounts of energy per second with more power than a million Suns. Some of this energy powers jets -- narrow beams of outflowing material from the binary system travelling close to the speed of light.

Recent upgrades to the MeerKAT telescope have resulted in excellent sensitivity and higher-resolution images. With these the team saw clear evidence of an S-shaped structure, similar in shape to water spraying from a garden sprinkler, in Circinus X-1's jet.

Not only that, but researchers also discovered moving termination shocks -- the first recorded from an X-ray binary. These are regions where the jet violently rams into the surrounding material, causing a shockwave.

Cowie's team measured the waves moving at roughly 10 per cent of the speed of light, confirming that they were caused by the fast-moving jet and not something slower such as a wind of material from the stars.

"The fact that these shockwaves span a wide angle agrees with our model," Cowie said. "So we have two strong pieces of evidence telling us the neutron star jet is precessing."

Measuring the velocity of the shockwaves will also help astronomers understand what the jet causing them is made from.

The shockwaves effectively act as particle accelerators in space -- producing high-energy cosmic rays -- and the maximum energy of particles that can be accelerated depends on their velocity.

"Circinus X-1 is one of the brightest objects in the X-ray sky and has been studied for over half a century," Cowie said. "But despite this, it remains one of the most enigmatic systems we know of.

"Several aspects of its behaviour are not well explained so it's very rewarding to help shed new light on this system, building on 50 years of work from others."

He added: "The next steps will be to continue to monitor the jets and see if they change over time in the way we expect.

"This will allow us to more precisely measure their properties and continue to learn more about this puzzling object."

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Nature-based solutions to disaster risk from climate change are cost effective

A new global assessment of scientific literature led by researchers at the University of Massachusetts Amherst finds that nature-based solutions (NbS) are an economically effective method to mitigate risks from a range of disasters -- from floods and hurricanes to heatwaves and landslides -- which are only expected to intensify as Earth continues to warm.

NbS are interventions where an ecosystem is either preserved, sustainably managed or restored to provide benefits to society and to nature. For instance, they can mitigate risk from a natural disaster, or facilitate climate mitigation and adaptation. NbS have emerged in combination with or as an alternative to engineering-based solutions. A classic example is restoring wetlands to address coastal flooding rather than constructing a seawall.

"Nature-based solutions are now recognized by major national policies and international global framework agreements to combat climate change, including those drafted by the U.N. and the White House. However, there has been limited scientific knowledge about the cost-effectiveness and equity outcomes of NbS," says Marta Vicarelli, assistant professor of economics and public policy at UMass Amherst and the study's lead author. "Our results indicate that not only are NbS economically effective in mitigating hazards, but that their benefits are still underestimated."

NbS were proven to be a consistently cost-effective approach to mitigating hazards in 71% of the more than 20,000 English-language peer-reviewed studies that researchers examined for the article, which is published in Science of the Total Environment. Another 24% of the studies found NbS to be cost effective under certain conditions. The ecosystem-based interventions most frequently found effective in mitigating hazards are associated with mangroves (80%), forests (77%) and coastal ecosystems (73%).

Of the studies that compared NbS with engineering-based solutions, 65% found the former always to be more effective at mitigating hazards and 24% partially more effective. No study found NbS consistently less effective than engineering solutions.

While every study reviewed for the article examined the hazard-mitigation benefits of NbS, many did not consider added environmental and socioeconomic benefits, such as maintaining biodiversity, climate mitigation and supporting underserved communities.

"The other benefits of NbS are vastly underestimated because they are difficult to quantify," Vicarelli explains. "How should we value improvements in air quality or in soil quality? How should we value the protection of an endangered species or the overall increase in biodiversity after the implementation of an NbS? And how about estimating the cultural or even spiritual value of an environmental asset? These assessments require complex and potentially expensive valuation techniques. For this reason, the additional benefits of NbS are often understudied and underestimated."

Another key finding of the research is that NbS have been financed mainly by the public sector, even when the interventions involve private property. For these solutions to have a truly global impact, additional funding is required, and a significant share must come from the private sector, Vicarelli says.

"A transformative upscaling of Nature-based Solutions requires both public and private financing," she adds. "The next step is developing innovative nature-based insurance and investment solutions."

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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."

Read more at Science Daily