Sleep cycles process memories

Memory replay during sleep probably facilitates the transfer of memories from intermediate storage in the hippocampus to long-term storage in the cortex. In a paper published in Neuron, Bollmann, Baracskay et al. reveal that memories are not static during this process, but are instead transformed into their long-term state during the sleep period. The authors tracked spatial memory ensembles in the hippocampus of rats across acquisition, a prolonged (17–20 h) sleep/rest period and recall the following day. 

Acquisition and recall induced distinct neuronal ensembles, and ensemble activity gradually evolved from an acquisition-like to a recall-like state during sleep. Interestingly, non-REM sleep pushed memory drift towards recall, whereas REM sleep counteracted this drift. These findings echo prior work that indicated a crucial role for non-REM sleep in consolidation and also offer intriguing clues regarding the potentially distinct roles of non-REM and REM sleep in this process.

Reference: Neuron https://doi.org/10.1016/j.neuron.2025.02.025 

The probiotic home: Where microbes are welcome guests!

Most of the world’s population lives in cities, and many people spend most of their days inside. A 2001 survey1 found that respondents in the United States spent 87% of their time inside sealed buildings, and a further 6% in vehicles.

The design of human structures, such as homes and offices, has been driven by a desire to keep humans isolated from animals, dirt and microbes. But scientists exploring probiotic indoor environments point to studies that suggest there are health benefits to mingling with microbes, particularly for young children.

Exposure to dust, farm animals and their associated microbes can have a positive effect on children’s immune systems. “People who grow up on a farm have a 50% reduction in the likelihood of developing atopy,” says Jack Gilbert, a pediatrician and microbiome researcher at the University of California, San Diego. Atopy, which causes people to overproduce certain kinds of antibody, can manifest as conditions such as asthma, dermatitis and food allergy.

If children’s developing immune systems need exposure to environmental microbes — and if such exposures turn out to have benefits for adults, too — then urban dwellers will often miss out.We can compare modern architecture to antibiotics. Just as the widespread use of these drugs has driven antibiotic resistance, architecture has “created its own monsters. There is evidence that autoimmune diseases, allergies and metabolic diseases, such as obesity, are influenced by the microbes that people are exposed to, and that the diversity of these microbes is decreasing.

Microbiome health and circadian health are interconnected!!!

 https://www.nature.com/immersive/d41586-025-03291-2/index.html?utm_source=Live+Audience&utm_campaign=a49d41753b-nature-briefing-daily-20251014&utm_medium=email&utm_term=0_-33f35e09ea-49956820

Why Do We Need Sleep? Scientists Trace the Answer to Mitochondria

Sleep may serve as more than rest for the mind; it may also function as essential upkeep for the body’s energy systems. A new study from University of Oxford researchers, published in Nature, shows that the drive to sleep is caused by electrical stress building up in the tiny energy-producing structures of brain cells.

In certain sleep-regulating neurons studied in fruit flies, mitochondria that become overloaded begin leaking electrons. This leakage produces harmful byproducts called reactive oxygen species. The leak functions as a signal that forces the brain into sleep, allowing balance to be restored before cellular damage spreads further.

Despite decades of research, no one had identified a clear physical trigger. The findings show that the answer may lie in the very process that fuels our bodies: aerobic metabolism. In certain sleep-regulating neurons, mitochondria – the cell’s energy producers – leak electrons when there is an oversupply. When the leak becomes too large, these cells act like circuit breakers, tripping the system into sleep to prevent overload.”

The findings help explain well-known links between metabolism, sleep, and lifespan. Smaller animals, which consume more oxygen per gram of body weight, tend to sleep more and live shorter lives. Humans with mitochondrial diseases often experience debilitating fatigue even without exertion, now potentially explained by the same mechanism.

“This research answers one of biology’s big mysteries,”  “Why do we need sleep? The answer appears to be written into the very way our cells convert oxygen into energy.”

Reference

Mitochondrial origins of the pressure to sleep” by Raffaele Sarnataro, Cecilia D. Velasco, Nicholas Monaco, Anissa Kempf and Gero Miesenböck, 16 July 2025, Nature.

DOI: 10.1038/s41586-025-09261-y

Irregular sleep patterns, not just how long we sleep, may significantly raise the risk of numerous diseases

A major international study published in Health Data Science has revealed strong links between sleep patterns and the development of 172 different diseases. By examining objective sleep data from 88,461 adults in the UK Biobank, researchers uncovered compelling evidence that consistent sleep routines, including stable bedtimes and circadian rhythms, play a much larger role in long-term health than previously thought.

The research, led by scientists from Peking University and Army Medical University, tracked participants using actigraphy over an average of 6.8 years. The findings showed that poor sleep habits contributed to more than 20 percent of the risk for 92 diseases.

Reference: “Phenome-wide Analysis of Diseases in Relation to Objectively Measured Sleep Traits and Comparison with Subjective Sleep Traits in 88,461 Adults” by Yimeng Wang, Qiaorui Wen, Siwen Luo, Lijuan Tang, Siyan Zhan, Jia Cao, Shengfeng Wang and Qing Chen, 3 June 2025, Health Data Science.

DOI: 10.34133/hds.0161

Connect to Sleep Yoga for healthy Sleep

 

Daily Sleep Yoga session by Chronoprakriti Wellness launched on International Yoga day 2025

 

Caffeine induces age-dependent increases in brain complexity and criticality during sleep

Caffeine isn’t just in your morning coffee. It’s also in tea, chocolate, energy drinks, and many popular soft drinks, making it one of the most widely consumed psychoactive substances around the globe. Now, new research from the University of Montreal reveals how caffeine might be doing more than just keeping you awake. In a study published in Communications Biology, scientists discovered that caffeine can actually change how the brain recovers overnight, affecting both physical restoration and cognitive function.

They showed for the first time that caffeine increases the complexity of brain signals and enhances brain “criticality” during sleep. Interestingly, this was more pronounced in younger adults.

“Criticality describes a state of the brain that is balanced between order and chaos,” said Jerbi. “It’s like an orchestra: too quiet and nothing happens, too chaotic and there’s cacophony. Criticality is the happy medium where brain activity is both organized and flexible. In this state, the brain functions optimally: it can process information efficiently, adapt quickly, learn, and make decisions with agility.”

The researchers also discovered striking changes in the brain’s electrical rhythms during sleep: caffeine attenuated slower oscillations such as theta and alpha waves, generally associated with deep, restorative sleep, and stimulated beta wave activity, which is more common during wakefulness and mental engagement.

“These changes suggest that even during sleep, the brain remains in a more activated, less restorative state under the influence of caffeine, Young adults showed a greater response to caffeine, likely due to a higher density of adenosine receptors in their brains. Adenosine is a molecule that gradually accumulates in the brain throughout the day, causing a feeling of fatigue.

“Adenosine receptors naturally decrease with age, reducing caffeine’s ability to block them and improve brain complexity, which may partly explain the reduced effect of caffeine observed in middle-aged participants,” Carrier said.

And these age-related differences suggest that younger brains may be more susceptible to the stimulant effects of caffeine. Given caffeine’s widespread use around the world, especially as a daily remedy for fatigue, the researchers stress the importance of understanding its complex effects on brain activity across different age groups and health conditions.

Ref:

Thölke, P., Arcand-Lavigne, M., Lajnef, T. et al. Caffeine induces age-dependent increases in brain complexity and criticality during sleep. Commun Biol 8, 685 (2025). https://doi.org/10.1038/s42003-025-08090-z