Max Kozlov How does the brain know when it’s time to wake up? Researchers have identified1 a chemical signal that serves as a timer in the mouse brain, logging both the length of a single sleep session and the number of interruptions and predicting how likely an animal is to wake up at any given moment. This signal could offer a new way to measure ‘sleep debt’, or accumulated sleep loss. Such a biomarker could one day lead to methods for checking whether someone is sleep-deprived, says Ketema Paul, a neuroscientist at the University of California, Los Angeles, who was not involved in the research. “We really don’t have what a lot of people call the sobriety test for sleep,” Paul says, adding that such a test could be useful to ensure that people in high-stakes occupations, such as driving trucks or working in a hospital emergency department, are able to remain alert. “The negative effects of sleep loss can have serious negative consequences.” Previous sleep research has focused mostly on the brain circuitry that snaps people awake in seconds or on how sleep debt accrues after days of bad sleep. But the intermediate time scale — how the brain keeps track of the minutes or hours spent in a single continuous session of sleep — has remained a mystery. To investigate, Yao Chen, a neuroscientist at Washington University in St. Louis, Missouri, and her team searched for molecular signals that shift gradually during a sleep session. The researchers used a specialized fluorescent sensor in the brains of mice to watch, in real time, the effects of protein kinase A, or PKA — an enzyme also found in humans and previously linked to wakefulness2. This enzyme adds chemical ‘tags’ to proteins on the surface of brain cells. © 2026 Springer Nature Limited

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30346 - Posted: 07.29.2026

By Alissa de Chassey A hallmark of deep sleep—slow-wave brain activity that arises when cortical neurons cycle on and off synchronously between 0.5 and 4 Hertz—may drive some of sleep’s restorative functions, according to a new study published last month in Nature Neuroscience. “We provided direct evidence that these on and off patterns are what really matter,” says study investigator Chiara Cirelli, professor of psychiatry at the University of Wisconsin School of Medicine. As slow waves travel across the cortex during deep sleep, the excitatory synaptic strength that accrued during waking hours gradually returns to a baseline, a process that helps to consolidate memories, according to the synaptic homeostasis hypothesis of sleep that Cirelli and her husband, neuroscientist Giulio Tononi, proposed more than two decades ago. Computational models and studies of anesthetized animals support the idea, but the field has lacked evidence from non-anesthetized animals. “Anesthesia and sleep may share some features, but definitely overall they are not the same thing,” Cirelli says. She and her colleagues used optogenetics to induce sleep-like on/off firing patterns in select regions of the cortex in awake mice. “The idea was to induce these patterns in awake mice, and see whether this is enough to get sleep benefits,” Cirelli says. As expected, the animals showed a decreased need for sleep; reduced neuronal synchrony and synaptic strength during sleep; and improved memory consolidation afterward. © 2026 Simons Foundation

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30327 - Posted: 07.18.2026

By Sara Novak Whether tucked away in a colony of coral, hidden in the darkness of an aquatic cave or floating catatonic just above the ocean floor, fish take opportunities for rest and recovery, just as we do. Like humans, most fish are diurnal, meaning they sleep mostly at night; while they don’t have eyelids, and therefore can’t shut out the darkness, light does disrupt their sleep. And just like us, when they snooze they’re motionless and slow to respond to environmental stimuli. If you deprive them of sleep, they will make up for the loss by sleeping longer the next night. Now, a new study, released this month in Nature Communications, shows just how much fish sleep really does resemble our own. By tracking eye movements of zebrafish, the researchers were able to identify four different substates of sleep, akin to the “stages” of sleep that scientists have described in humans. “There’s complexity to their sleep structure,” said Jennifer Mengbo Li, a co-author of the study and a neuroscientist at the Max Planck Institute for Biological Cybernetics in Germany. Three of the four substates happen at night, lasting a total of 10 hours. The first — and deepest — is characterized by a stone-cold stare. As the waking hours near, a second, lighter substate sets in: The zebrafish’s eyes twitch, sideways in the same direction, before moving slowly back to center. In the third substate, entered as morning approaches, both eyes turn to the same side and stay there. During the fourth and final substate, which takes place in brief bursts during the day, the zebrafish’s eyes move back and forth, as if sweeping the surroundings for potential risks. But the eyes can be deceiving: These five-to-10-minute naps are deep enough that much of the brain activity is suppressed, and the zebrafish are hard to wake up. © 2026 The New York Times Company

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30263 - Posted: 05.30.2026

Andrew Gregory in Chicago Poor sleep may be fuelling the global rise in under-50s being diagnosed with cancer, two large studies suggest. The number of younger people diagnosed with the disease has risen by almost 80% in three decades. Worldwide cases of early-onset cancer increased from 1.82m in 1990 to 3.26m in 2019, while cancer deaths among people in their 40s, 30s or younger rose by 27%. Experts are still trying to understand the reasons behind the increase. However, research presented at the world’s largest cancer conference, the American Society of Clinical Oncology’s annual meeting in Chicago, suggests irregular sleeping patterns in younger people may be a contributing factor. Two studies led by MD Anderson Cancer Center in Houston, Texas, one of the world’s leading cancer research organisations, analysed health data for more than 18 million adults in the US aged between 18 and 50. Researchers found that people with poor sleeping patterns were more likely to develop early-onset bowel, breast, uterine or ovarian cancer. In some cases, under-50s diagnosed with insomnia were three times more likely to develop cancer within five years. “These findings suggest that sleep disruption may represent a clinically relevant, potentially modifiable risk factor in early-onset cancer risk stratification and warrants further investigation,” the researchers said. © 2026 Guardian News & Media Limited

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30260 - Posted: 05.30.2026

Pien Huang Adults should be getting at least seven hours of sleep each night, according to the American Academy of Sleep Medicine. "Below that, there's clear evidence that you're going to feel lethargic during the day," says James Rowley, a pulmonologist and the program director of the Sleep Medicine Fellowship at Rush University Medical Center, as well as a past president of the AASM board of directors. Rowley also says not getting enough sleep is linked with cardiometabolic disorders like diabetes and obesity, as well as cardiovascular problems. But many in the U.S. are not sleeping enough. A new data brief, published this week by the Centers for Disease Control and Prevention (CDC), finds that 30.5% of U.S. adults surveyed in 2024 are getting less than the recommended amount. The results have not changed much since 2020, when CDC researchers found that just under 30% of U.S. women and men were sleeping less than seven hours a night. Some people are working multiple jobs or shifts that cut into their sleeping time. But others are just doomscrolling, says Rowley, who was not involved in the paper. "Many patients tell me they go to bed with their cellphone, laptop or tablet," he says. "Patients tell me they see one YouTube video and before they know, it's an hour later." Some people are gaming, and others are watching TV late into the night. For many, that time could be better spent sleeping — an activity in which the brain repairs and restores itself. "A lot of people could go to bed earlier if they chose to," Rowley says. © 2026 npr

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30232 - Posted: 05.06.2026

Sleeping for 11 minutes more each night, doing 4.5 additional minutes of brisk walking and eating an extra 50g or so of vegetables each day can significantly reduce a person’s risk of heart attack, a study has found. Academics found these small changes could help people avoid major cardiovascular events, including heart attacks and strokes, by about 10%. Small behaviour changes were more “achievable and sustainable”, the research team said. The study, published in the European Journal of Preventive Cardiology, was conducted by experts from Australia, Chile and Brazil who examined data on more than 53,000 middle-aged UK adults taking part in the Biobank study. Researchers looked at sleep habits and levels of exercise through data from wearable technology such as smartwatches. People also self-reported on their dietary habits. The researchers found that 2,034 major cardiovascular events occurred during an eight-year follow-up period. They were able to identify the “optimal” way people could avoid these incidents, including a good diet, eight to nine hours sleep each night and a minimum of 42 minutes of moderate-to-vigorous physical activity each day. Combining these measures leads to a 57% lower risk of heart attacks and strokes. They also found the “clinically relevant” combination of behaviours that could reduce people’s risk, including more sleep, better diet and more moderate-to-vigorous activity. According to the NHS website, moderate activity can include brisk walking, dancing, pushing a lawn mower, water aerobics and riding a bike. Vigorous activity includes running, swimming, skipping and aerobics. Dr Nicholas Koemel, the study’s lead author and a research fellow at the University of Sydney, said: “We show that combining small changes in a few areas of our lives can have a surprisingly large positive impact on our cardiovascular health. “This is very encouraging news because making a few small, combined changes is likely more achievable and sustainable for most people when compared with attempting major changes in a single behaviour. © 2026 Guardian News & Media Limited

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30172 - Posted: 03.25.2026

By Bethany Brookshire When solving a puzzle, the answer could lie in your dreams. In a study of lucid dreamers, playing soundtracks linked with unsolved puzzles helped the sleepers solve the problems the next day, researchers report February 5 in Neuroscience of Consciousness. Stories of brilliant insights after a nap or daydream abound, but scientists have struggled to successfully influence people’s dreams and rigorously test the idea. “This study provides one of the first experimentally grounded demonstrations of such a link,” says Giulio Bernardi, a cognitive neuroscientist at IMT School for Advanced Studies Lucca, in Italy, who was not involved with the work. Whether we remember our dreams or not, we have countless dreams in our sleep, according to Karen Konkoly, a cognitive neuroscientist who performed the study at Northwestern University in Evanston, Ill. “Your dreams are such a big part of your inner life,” she says. And in the right circumstances, manipulating those dreams could help people think of problems in new ways. While some scientists have shown that sleeping on a problem increases the odds of solving it the next day, others have shown no benefit. Of course, it might help only if you actually think about the problem in your sleep. Konkoly and her colleagues were especially interested in helping sleepers think about specific topics using targeted memory reactivation, or TMR. “It’s this research technique where you have a sensory stimuli that’s associated with a memory,” Konkoly says. “It could be a very soft sound or a smell that’s presented to a sleeper, and it functions to remind the sleeping brain of the full memory.” While people dream in every stage of sleep, the effects of TMR have been strongest in deep, slow-wave sleep, she says. Konkoly wanted to look at the effects of TMR at a different sleep stage — rapid eye movement sleep, which could be helpful for creative thinking. © Society for Science & the Public 2000–2026.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 13: Memory and Learning
Link ID: 30145 - Posted: 03.04.2026

By Marla Vacek Broadfoot Nearly 1 in 8 dementia cases — about half a million nationwide — may be linked to insomnia. The new findings, reported December 27 in the Journals of Gerontology: Series A, add weight to growing evidence that sleep is a modifiable risk factor for dementia, akin to hearing loss and hypertension. The study does not establish a direct cause-and-effect relationship between insomnia and dementia for individuals, says Yuqian Lin, a data analyst at Massachusetts General Hospital in Boston. Rather, she says, it looks at the overall extent to which insomnia may contribute to dementia across the population. Lin and her colleagues analyzed data from the National Health and Aging Trends Study, or NHATS, a long-running survey of 5,900 U.S. adults ages 65 and older. Participants reported whether they had difficulty falling asleep, staying asleep or both. Dementia was identified using standard research tools that rely on cognitive testing and reports from family members or caregivers. To estimate the impact of insomnia on the population, Lin and her team calculated the proportion of dementia cases that could theoretically be prevented if insomnia-related sleep disturbances were eliminated. The calculation combined the prevalence of insomnia and dementia in the NHATS population with relative risk estimates drawn from recent large meta-analyses linking insomnia to dementia later in life. © Society for Science & the Public 2000–2026.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 13: Memory and Learning
Link ID: 30105 - Posted: 02.04.2026

Andee Tagle He couldn't stop fixating on it. "I started getting into the frame of mind most people get sucked into. I worried, 'What's going on? Is there something wrong with me?'" he says. That fear of not being able to sleep is a phenomenon called "sleep anxiety," says Orma, who went on to become a specialist in insomnia treatment. Left untreated, that anxiety can prevent people from actually falling asleep. "The more you focus on it, the less chance you'll sleep, which then makes you more anxious. That's the cycle that spins," he says. One of the most powerful ways to overcome sleep anxiety is cognitive behavioral therapy for insomnia (CBT-I). It's well studied, doesn't rely on sleep drugs and has been shown to be effective for clinical insomnia. Orma used this treatment to heal his sleep, and it's now the main focus of his therapy practice. Typically, a CBT-I program lasts about six to eight weeks, and each week, you and a provider work on a strategy to reset sleep behaviors and restructure your thinking around rest. But you don't have to be in an official program to benefit from CBT-I. Whether you're dealing with some sleep stress or just the occasional off-night, these CBT-I practices can help. Wake up at the same time every day Having a consistent wake-up time helps your body know when it's time to get sleepy, says Aric Prather, a sleep scientist and the author of The Sleep Prescription: 7 Days to Unlocking Your Best Rest. The sleepy cues are managed by your circadian rhythm, or your body's internal clock. A set wake-up time keeps your internal clock ticking on time. © 2026 npr

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30082 - Posted: 01.17.2026

By Jack Tamisiea You don’t need a brain to benefit from a good night of sleep. Despite lacking a central nervous system, jellyfish and sea anemones have sleep patterns remarkably similar to those of humans, researchers report today in Nature Communications. The work supports the idea that sleep arose early in animal evolution to help the first neurons repair themselves, says Cheryl Van Buskirk, a geneticist at California State University, Northridge who was not involved with the research. “This study is another nail in the coffin of the idea that sleep evolved to manage complex, powerful brains.” In nature, sleep is risky: Snoozing organisms are vulnerable to predators. Yet species across the animal kingdom spend multiple hours a day dozing off—even ancient groups including cnidarians, which include jellyfish, anemones, and corals—all among the earliest animals to develop neurons. Researchers have recorded sleeplike behavior in upside-down jellyfish in the genus Cassiopea and small freshwater relatives of jellyfish known as hydra. To learn more about why these simple animals sleep, researchers in Israel studied the starlet sea anemone (Nematostella vectensis) and an upside-down jellyfish (Cassiopea andromeda). Both species reside along the bottoms of shallow lagoons with their tentacles hovering in the water to snag prey. In the lab, the team housed several jellyfish in an aquarium and exposed them to 12 hours of light and 12 hours of darkness over multiple days. They used infrared cameras to monitor how often the critters pulsed their umbrellalike bells, a sign of wakefulness. © 2026 American Association for the Advancement of Science.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30070 - Posted: 01.07.2026

By Lauren Schenkman In pursuit of the brain’s secrets, neuroscientist Paul-Antoine Libourel has traveled to the ends of the earth. But during the COVID-19 lockdown in 2020, he worked closer to home—in his own darkened garage in Lyon, filming a sleeping chameleon. Libourel, a researcher at the Center for Functional and Evolutionary Ecology in Montpelier, had heard that chameleons lose their ability to camouflage during sleep. But as the hours passed in his garage, he observed something extraordinary: The chameleon’s skin fluctuated from bright to dark to bright again every few minutes. This strobing skin display, Libourel and his colleagues have since discovered, reflects an inner rhythm. The chameleon’s brain activity alternates between waves of higher and lower amplitude, synchronized with increased and decreased eye movements, plus changes in the animal’s heart rate and breathing rate. Six other species of lizard, including bearded dragons—along with rats, mice, pigeons and humans—show the same “infraslow fluctuations” in EEG activity during non-REM sleep, according to a study Libourel’s team published today in Nature Neuroscience. Because reptiles and mammals diverged about 320 million years ago, the findings mean these cycles “are a central thing, maybe a core building block of sleep,” says study investigator Antoine Bergel, research director at the Centre National de la Recherche Scientifique. They also raise the question of why these rhythms are so conserved, Bergel and Libourel say, and hint at how sleep has evolved. The sleep field, which tends to focus on mice and humans, needed this type of comparative study, says Philippe Mourrain, associate professor of psychiatry and behavioral sciences at Stanford University, who studies sleep in zebrafish but was not involved in the new work. “It’s a tour de force to do science on nonconventional species.” © 2025 Simons Foundation

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30062 - Posted: 12.31.2025

By Emily Cataneo Imagine having a dream that you are trapped in a room with five rabid tigers. No matter how hard you try, you can’t escape. The tigers are screeching and thrashing and you’re terrified. Now imagine repurposing this dream. Imagine it from the perspective of one of the tigers. Now, you realize that the animals are panicking only because they want to escape. You open the door, inviting them to freedom, and they lie down, docile. Suddenly, the dream has become peaceful and calm, not terrifying and chaotic. BOOK REVIEW — “Nightmare Obscura: A Dream Engineer’s Guide Through the Sleeping Mind,” by Michelle Carr (Henry Holt and Co., 272 pages). Freud might have had a field day with this dream, but thanks in part to psychoanalysis’ fall from grace over the last century, medical professionals no longer put much stock in our minds’ nighttime wanderings as markers of either physical or mental health. That’s what dream scientist Michelle Carr aims to change. Carr, who serves as director of the Dream Engineering Laboratory in the Center for Advanced Research in Sleep Medicine in Montreal, has spent two decades gathering data on people like the tiger dreamer: She’s spent countless nights in labs watching people sleep, probing why we dream, why we have bad dreams, and how studying and even manipulating dreams can improve mental and physical health. In “Nightmare Obscura: A Dream Engineer’s Guide Through the Sleeping Mind,” Carr makes a passionate case for why the answers to these questions matter, deeply, especially for sufferers of trauma and suicidal ideation. What emerges is a passionate case for why dreams and nightmares are not just “random electrophysiological noise produced by the brain during sleep,” as scientists believed for many years, but rather a nightly exercise in “revising the shape of our autobiography.” In other words, Carr argues, our dreamscapes are essential pillars of who we are.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30040 - Posted: 12.06.2025

Sara Protasi I love napping. I love napping in the summer, when rhythms are more relaxed and the guilt of taking a break less intense (if only slightly). But I also love napping in the winter, when it’s cold outside, and burying myself under a warm blanket makes me feel like I’m hibernating. No matter the season, when lying in bed, I luxuriate in the feeling of my body relaxing, waiting for the moment when odd images start forming somewhere in that space between my closed lids and my corneas – or, most likely, somewhere in my mind. I love drifting into unconsciousness without worrying about the next item on my to-do list. I’m not a sound sleeper or someone who falls asleep easily at night, but napping comes easily and sweetly. I treasure the days in which I can nap. And I treasure even more the nights in which I sleep long and well. Yet our culture prizes efficiency and productivity, often seeing sleep as a waste of time. ‘Tech bros’ boast about regularly working more than 70 hours a week, and aim to reduce their sleep time as much as possible. Elon Musk suggested even more intense work schedules for government workers during his time at the US Department of Government Efficiency (DOGE). His approach resonated with many adherents of the Silicon Valley grind culture, which has sought to ‘hack’ sleep for a long time. As one CEO of a cost-cutting firm told the news site Business Insider this year: ‘While a 120-hour workweek isn’t a practical or sustainable solution for most, the principle behind it resonates. Companies that prioritise efficiency, automation and proactive cost management will always outperform those weighed down by bureaucracy.’ This approach is mirrored in a seemingly contradictory trend in the tech industry: a number of years ago, tech companies such as Apple and Google started introducing nap time for their workers. However, this approach was less a gesture of care than a response to exhaustion and sleep deprivation induced by their grind mentality, providing ‘recharging time’ to boost creativity and sustain the long hours required for work. Workers in less high-paying careers, who need to work multiple jobs, rarely have time to nap, and often have to resort to drugs such as modafinil, a stimulant prescribed for narcolepsy and used, often illegally, by students cramming for exams. This substance has gained the attention of the military. The US defence research agency DARPA has funded pharmaceutical companies and researchers to reduce sleep deprivation, with the long-term ambitious goal of operating without any need for sleep in the field. And the US isn’t alone: militaries worldwide are exploring how to keep their soldiers awake and functioning when sleep is in short supply. © Aeon Media Group Ltd. 2012-2025.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 30039 - Posted: 12.06.2025

By Caroline Hopkins Legaspi In a study published Monday in JAMA Neurology, researchers linked obstructive sleep apnea, a condition that causes temporary pauses in breathing during sleep, with Parkinson’s disease. Parkinson’s disease is a progressive nervous system disorder that causes tremors, stiffness, and difficulty speaking, moving and swallowing. It is the second-most common neurodegenerative disease in the United States, after Alzheimer’s disease, with 90,000 people diagnosed each year. There is no cure for Parkinson’s disease, said Dr. Lee Neilson, a neurologist at Oregon Health & Science University who led the study. But the researchers did find that treating sleep apnea with a continuous positive airway pressure (or CPAP) machine was associated with a reduced likelihood of developing Parkinson’s. So identifying those at highest risk for the neurological condition — and intervening early, Dr. Neilson said, “might make the biggest impact.” The researchers analyzed medical records from more than 11 million U.S. veterans treated through the Department of Veterans Affairs between 1999 and 2022. The group was predominantly male with an average age of 60, representing those at highest risk for sleep apnea, experts said. The researchers found that about 14 percent of the participants had been diagnosed with sleep apnea between 1999 and 2022, according to their medical records. When the researchers looked at their health six years after those diagnoses, they found that the veterans with sleep apnea were nearly twice as likely to have developed Parkinson’s disease compared with those who had not been diagnosed with sleep apnea. This held even after controlling for other factors that could influence the development of sleep apnea or Parkinson’s disease, including high body mass index and conditions like diabetes, high blood pressure, traumatic brain injuries and depression. © 2025 The New York Times Company

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 5: The Sensorimotor System
Link ID: 30029 - Posted: 11.26.2025

Ian Sample Science editor It’s never a great look. The morning meeting is in full swing but thanks to a late night out your brain switches off at the precise moment a question comes your way. Such momentary lapses in attention are a common problem for the sleep deprived, but what happens in the brain in these spells of mental shutdown has proved hard to pin down. Now scientists have shed light on the process and found there is more to zoning out than meets the eye. The brief loss of focus coincides with a wave of fluid flowing out of the brain, which returns once attention recovers. “The moment somebody’s attention fails is the moment this wave of fluid starts to pulse,” said Dr Laura Lewis, a senior author on the study at MIT in Boston. “It’s not just that your neurons aren’t paying attention to the world, there’s this big change in fluid in the brain at the same time.” Lewis and her colleague Dr Zinong Yang investigated the sleep-deprived brain to understand the kinds of attention failures that lead drowsy drivers to crash and tired animals to become a predator’s lunch. In the study, 26 volunteers took turns to wear an EEG cap while lying in an fMRI scanner. This enabled the scientists to monitor the brain’s electrical activity and physiological changes during tests in which people had to respond as quickly as possible to hearing a tone or seeing crosshairs on a screen turn into a square. Each volunteer was scanned after a restful night’s sleep at home and after a night of total sleep deprivation supervised by scientists at the laboratory. Unsurprisingly, people performed far worse when sleep deprived, responding more slowly or not at all. © 2025 Guardian News & Media Limited

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 14: Attention and Higher Cognition
Link ID: 29993 - Posted: 11.01.2025

Imma Perfetto Anyone who has ever struggled through the day following a poor night’s sleep has had to wrench their attention back to the task at hand after their mind drifted off unexpectedly. Now, researchers have pinpointed exactly what causes these momentary failures of attention. The new study in Nature Neuroscience found that the brains of sleep-deprived people initiate waves of cerebrospinal fluid (CSF), the liquid which cushions the brain, which dramatically impaired attention. This process usually happens during sleep. The rhythmic flow of CSF into and out of the brain carries away protein waste which has built up over the course of the day. When this is maintenance interrupted due to lack of sleep, it seems the brain attempts to play catch up during its waking hours. “If you don’t sleep, the CSF waves start to intrude into wakefulness where normally you wouldn’t see them,” says study senior author Laura Lewis of Massachusetts Institute of Technology’s (MIT) Institute for Medical Engineering and Science. “However, they come with an attentional trade off, where attention fails during the moments that you have this wave of fluid flow. “The results are suggesting that at the moment that attention fails, this fluid is actually being expelled outward away from the brain. And when attention recovers, it’s drawn back in.” © Copyright CSIRO

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 14: Attention and Higher Cognition
Link ID: 29992 - Posted: 11.01.2025

Rachel Fieldhouse Slow, sleep-like brain waves persist in part of the brain that has been surgically disconnected from the rest of the organ even though the person is awake. The findings1, published in PLoS Biology, add to researchers’ understanding of what conscious and unconscious brain states look like. Children with severe epilepsy who do not respond to medication can undergo a surgical procedure called a hemispherotomy. During surgery, clinicians disconnect the part of the brain in which seizures originate from the rest of the brain, stopping them from spreading. The disconnected tissue is left in the skull and has an intact blood supply. The team wanted to find out whether the disconnected part has some form of awareness — or was capable of exhibiting consciousness, says co-author Marcello Massimini, a neurophysiology researcher at the University of Milan in Italy. “The question arises because we have no access” to the disconnected region, he says, adding that it was unclear what happens once part of the brain is isolated. Studies investigating consciousness are difficult because there is no consensus on what conscious and unconscious states in the brain look like, says Ariel Zeleznikow-Johnston, a neuroscientist at Monash University in Melbourne, Australia. “There’s no generally accepted definitive signatures of consciousness in terms of electrical readings or brain activity,” he adds. Even defining unconsciousness is challenging, because activities associated with consciousness, such as remembering dreams, can occur during states associated with unconsciousness, such as sleep or anaesthesia, Massimini says. © 2025 Springer Nature Limited

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 29980 - Posted: 10.22.2025

By Yasemin Saplakoglu The pillow is cold against your cheek. Your upstairs neighbor creaks across the ceiling. You close your eyes; shadows and light dance across your vision. A cat sniffs at a piece of cheese. Dots fall into a lake. All this feels very normal and fine, even though you don’t own a cat and you’re nowhere near a lake. You’ve started your journey into sleep, the cryptic state that you and most other animals need in some form to survive. Sleep refreshes the brain and body in ways we don’t fully understand: repairing tissues, clearing out toxins and solidifying memories. But as anyone who has experienced insomnia can attest, entering that state isn’t physiologically or psychologically simple. To fall asleep, “everything has to change,” said Adam Horowitz (opens a new tab), a research affiliate in sleep science at the Massachusetts Institute of Technology. The flow of blood to the brain slows down, and the circulation of cerebrospinal fluid speeds up. Neurons release neurotransmitters that shift the brain’s chemistry, and they start to behave differently, firing more in sync with one another. Mental images float in and out. Thoughts begin to warp. “Our brains can really rapidly transform us from being aware of our environments to being unconscious, or even experiencing things that aren’t there,” said Laura Lewis (opens a new tab), a sleep researcher at MIT. “This raises deeply fascinating questions about our human experience.” It’s still largely mysterious how the brain manages to move between these states safely and efficiently. But studies targeting transitions both into and out of sleep are starting to unravel the neurobiological underpinnings of these in-between states, yielding an understanding that could explain how sleep disorders, such as insomnia or sleep paralysis, can result when things go awry. Sleep has been traditionally thought of as an all-or-nothing phenomenon, Lewis said. You’re either awake or asleep. But the new findings are showing that it’s “much more of a spectrum than it is a category.” © 2025 Simons Foundation

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 29974 - Posted: 10.18.2025

Vladyslav Vyazovskiy After decades of research, there is still no clearly articulated scientific consensus on what sleep is or why it exists. Yet whenever sleep comes up as a topic of discussion, it is quickly reduced to its necessity and importance. Popular media remind us of what can, and will, go wrong if we do not sleep enough, and serve up some handy tips on how to overcome insomnia. Discussed exclusively in utilitarian terms, we are force-fed the idea that sleep exists solely for our immediate benefit. Is this really all we ever want to know about a third of our existence? Sleep is perhaps the biggest blind spot, or the longest blind stretch, if you will, of our life. Naturally, the health and societal implications of sleep are huge: from technogenic disasters caused by tiredness, to sleep deprivation as a form of torture or weapon of war, and to sleep disorders, some of which inflict so much suffering that they compete with chronic pain. However, in my opinion, to say sleep is important is to miss the point entirely. Sleep is the single most bizarre experience that happens to all of us, against our will, every day. The disconnect between old questions about sleep that have remained open for centuries and new, increasingly sophisticated technologies applied to solve them is ever growing. The predominant view is that sleep provides some sort of restoration for the brain or the body: what goes awry – out of balance – in waking is almost magically recalibrated by sleep. At the centre of this narrative is the individual-who-sleeps, a lone castaway, locked in a permanent, inexorable cycle of sleeping and waking, without hope of breaking free (except in death). From the moment of opening one’s eyes, the clock starts ticking, and there is a price to pay for every minute of wakeful time, measured precisely in proportion to the transgression of staying awake. Like a snake eating its own tail, waking and sleep consume each other in an endless cycle, without beginning or end. There is no mercy, and lack of sleep can be paid back only by sleep. The image of burning a candle at both ends endures. Despite vast technological advances in recent years, exponential growth in our understanding of nature and the cosmos, and major breakthroughs in biology and medicine, there is still no unified theory of sleep. I find myself pondering whether it is time to step back and seek a different angle. Medieval manuscript illustration depicting people sleeping in three beds, with two standing figures in dialogue beside them, and an ornate floral border. © Aeon Media Group Ltd. 2012-2025.

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 29971 - Posted: 10.15.2025

By Katarina Zimmer Few mammals sleep as deeply as the ampurta. When the blonde, rat-like marsupial returns to its burrow after a night of hunting in the Australian desert, it drifts into a slumber known as torpor. While many other mammals quickly burn through their energy reserves in order to maintain stable body temperatures as they fall asleep, ampurtas allow their bodies to cool down to as low as 50 degrees Fahrenheit, saving energy critical to survival in this harsh desert environment. “I’ve held some when they’re in torpor, and they feel like they’ve been in a freezer,” says wildlife ecologist Dympna Cullen of the University of New South Wales in Sydney. Instead of using their own energy to warm up again, upon waking, the animals drag themselves to the mouths of their burrows to soak up the morning sun. Some scientists say this energy-saving trick helped the ampurta—once thought doomed to extinction—to make a comeback during a severe drought. In what they call a “rare and hopeful conservation signal,” the authors document in a new study in Biological Conservation how, during a two-year drought that lasted from 2017 to 2019—one of the region’s harshest droughts on record—the vulnerable marsupials actually significantly extended their range, reclaiming a large chunk of lost habitat. “Everything crashes during a drought,” Cullen says, “so it was quite unexpected that not only were [ampurtas] increasing in abundance but also increasing their area of occupancy by quite a significant amount during a drought.” Like many other Australian mammals, the ampurta—the Aboriginal name for Dasycercus hillieri or the crest-tailed mulgara—once seemed like it might vanish from the Earth. Rabbits brought to Australia by European colonists in the 19th century wreaked ecological havoc on the continent. They ravaged Australia’s vegetation, robbing small native herbivores of cover and food, including some of the ampurta’s prey, such as smaller mammals. The rabbit boom also fed the spread of non-native foxes and cats, which picked off ampurtas and other native wildlife. But in 1996, the Australian government released a rabbit-killing virus to quash rabbit populations, which allowed some native species populations to recover. Ampurtas were downgraded from endangered in the mid-1990s to “vulnerable” in 2013, and eventually to a species of “least concern.” © 2025 NautilusNext Inc.,

Related chapters from BN: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 29949 - Posted: 10.01.2025