Understanding the behavior of microscopic aerosols expelled during coughing or sneezing has never been more critical, especially in light of ongoing global respiratory disease challenges such as influenza, COVID-19, and tuberculosis. These tiny particles, often invisible to the naked eye, serve as carriers for pathogens, enabling virus and bacteria transmission through the air. Numerous factors influence how these infectious aerosols disperse, including the strength of the exhalation, the intricacies of human respiratory anatomy, and environmental conditions. Recent groundbreaking research from the Universitat Rovira i Virgili (URV) has uncovered another vital element governing aerosol behavior: temperature. This revelation could transform how we understand and mitigate airborne disease spread indoors.

The research team from URV has demonstrated through meticulously controlled experiments that the temperature difference between exhaled air and the surrounding environment plays a significant role in the dispersion pattern and concentration of aerosols. Specifically, when warm exhaled air—mimicking body temperature—is introduced into cooler ambient air, the aerosol cloud maintains higher particle concentrations and travels further distances compared to situations where the temperature disparity is minimal. This relationship becomes more pronounced with increasing temperature gradients, shedding new light on the physical dynamics operating during respiratory emissions.

Central to this innovative study is the use of a sophisticated, three-dimensional-printed human airway model developed by the URV’s ECoMMFiT research group. This device replicates the biomechanics of human exhalation with exceptional stability and precision, allowing the researchers to simulate coughing and sneezing under tightly controlled parameters. By modifying this simulator to heat the exhaled air to 37 degrees Celsius—representing a slight fever condition—the team was able to explore interactions between temperature, respiratory flow dynamics, and aerosol dispersal in unprecedented detail.

Experiments were conducted within a climate-controlled chamber at the Catalonia Institute for Energy Research (IREC), where environmental conditions could be precisely manipulated. The team investigated three distinct ambient temperatures: 27°C, 17°C, and 7°C. These temperatures were combined with varying exhalation intensities and two different modes of nasal airflow: open and closed nasal cavities. This combination resulted in eighteen unique trial configurations, each rigorously repeated ten times for statistical robustness, culminating in a comprehensive dataset derived from 180 individual experiments.

The results reveal that the aerosol clouds generated under these varying conditions behave differently in predictable yet complex ways. As Nicolás Catalán, co-author and URV mechanical engineering researcher, explains, the increased temperature difference augments buoyancy effects. Warm exhaled air, less dense than the surrounding cooler air, rises and carries aerosol particles further and more cohesively. This buoyant lift sustains particle concentrations for longer periods, significantly extending the spatial range of potential pathogen transmission, particularly in colder environments.

A particularly striking finding relates to the role of the nasal cavity in shaping aerosol spread. The study confirms that partial airflow through the nose reduces horizontal propagation but promotes increased vertical dispersion. Conversely, when the simulator mimics mouth-only exhalation, aerosols tend to move more horizontally, covering greater frontline distances. This mechanistic insight highlights how variations in individual respiratory behaviors and anatomical structures can dramatically impact transmission risks.

The technical prowess of the study owes much to the utilization of high-speed videography and laser illumination techniques. These tools unveil the fine-scale structure and temporal evolution of the aerosol clouds. The recorded visualizations underscore how the interplay between ambient temperature gradients and respiratory airflow generates intricate aerosol flow patterns. This mechanistic understanding is crucial for modeling pathogen transport pathways more accurately within indoor environments, where interventions are typically applied.

Notably, the research contributes valuable experimental data that historically has been scarce in aerosol studies. Previous investigations frequently relied on numerical simulations or human trials, each limited in their control over parameters such as flow rate and temperature. In contrast, the URV’s 3D-printed airway simulator enables reproducible and stable experimental conditions, providing crucial validation points for computational fluid dynamic (CFD) models that predict aerosol dissemination and, by extension, infection risk.

From a practical standpoint, these insights hold significant implications for public health and safety. Environments like hospitals, schools, biological labs, and public transportation systems, where pathogen exposure risk is elevated, can benefit from refined ventilation designs and tailored control measures based on thermal considerations. For example, in colder seasons or cooler indoor environments, the increased persistence and reach of respiratory aerosols could warrant enhanced air circulation strategies or modifications to heating systems to mitigate transmission potential.

While the research sheds new light on temperature’s role in aerosol dynamics, the authors caution that respiratory aerosol behavior is inherently multifaceted. Factors such as humidity, indoor ventilation patterns, and the longevity of suspended particles must be further investigated to achieve comprehensive risk assessments. The study encourages continued interdisciplinary research integrating experimental, computational, and epidemiological approaches to fully unravel the variables influencing airborne disease propagation.

The research team’s approach, combining experimental rigor with innovative simulation, establishes a robust framework for future investigations. Their novel use of a temperature-controlled exhalation model advances the field beyond simplistic or static assumptions about aerosol dynamics. This detailed analysis forms a foundational step towards predictive models capable of informing adaptive infection control protocols sensitive to thermal variances across seasons and indoor spaces.

In conclusion, the URV-led study emphasizes that temperature differences between exhaled and ambient air significantly affect bioaerosol transport, influencing both the extent and persistence of pathogen-laden particle clouds. By integrating anatomical realism through a 3D-printed airway model and employing precise climate control, the research advances our scientific understanding of respiratory aerosol physics. These findings promise to inform smarter environmental and public health strategies, reducing airborne transmission risks in indoor settings worldwide.

Subject of Research: Respiratory aerosol dynamics and pathogen transmission influenced by temperature differences.

Article Title: Bioaerosol transport dynamics in cold and warm environments: An experimental study using a three-dimensional-printed human airway model.

News Publication Date: 20-Mar-2026

Web References: http://dx.doi.org/10.1063/5.0303143

References:
Catalán, N., Cito, S., Varela Ballesta, S., Fabregat, A., Vernet, A., Graus, D., & Pallarès, J. (2026). Bioaerosol transport dynamics in cold and warm environments: An experimental study using a three-dimensional-printed human airway model. Physics of Fluids.

Keywords

Respiratory aerosols, airborne pathogens, bioaerosol transport, temperature effects, human airway model, aerosol dispersion, exhalation dynamics, infectious disease transmission, ventilation, computational fluid dynamics, public health, indoor air quality

A groundbreaking new study from NYU Langone Health has illuminated the complex ways in which the brain manages to store multiple memories without blending or erasing vital pieces of past information. This discovery centers on an intriguing subset of neurons within the hippocampus, an area known for its role in memory formation. Researchers found that approximately 25% of these hippocampal CA1 neurons act as hubs that facilitate the seamless transmission of information from one region of the brain to another, effectively functioning like a biological switchboard managing countless memory signals.

For decades, neuroscientists have grappled with the paradox of how the brain maintains a delicate balance between adaptability and stability—retaining established memories while accommodating new information. This study provides fresh insights into this dilemma by exploring the neural interplay along pathways between the hippocampus and the neocortex. Specifically, the focus was on the CA3 and CA1 regions of the hippocampus and their communication with the retrosplenial cortex, a crucial site involved in navigation and spatial memory recall.

The CA3 region is known to send rapid and fluid streams of information, and, remarkably, the research demonstrated that most of these incoming signals converge on a small cohort of CA1 neurons. These same neurons then process and relay information to the retrosplenial cortex, but in a distinctly different firing pattern, which creates an independent outgoing communication channel. This dual functionality allows the neurons to multiplex incoming and outgoing signals without blending them, preserving the clarity of each memory trace.

This complex system can be likened to an advanced electronic switchboard that directs multiple phone calls without their lines crossing, ensuring that new experiences are integrated into the brain’s map without disrupting existing knowledge. The retrosplenial cortex benefits from this arrangement by maintaining a stable representation of the environment—essential for spatial navigation—while the hippocampal regions continue adapting and learning from the ongoing stream of experiences.

Dr. Joaquín Gonzalez, a postdoctoral fellow and co-lead author of the study, emphasized the significance of this firing pattern adjustment: “Instead of recruiting new neurons for every novel experience, the brain modifies the firing patterns of a stable cellular core, thereby organiz-ing information effectively and safeguarding previously encoded memories.” This mechanism highlights the brain’s remarkable ability to adapt dynamically while retaining long-term memory integrity.

Interestingly, the study also uncovered that these pivotal CA1 neurons are not confined to processing information during active waking hours—they remain engaged during sleep, participating in sharp-wave ripple events that are critical for memory consolidation. This nocturnal activity is believed to involve the replay and reinforcement of memory traces, further stabilizing learning while the brain rests.

The persistence of activity in these core neurons during sleep suggests a continuous information relay between the hippocampus and cortex, facilitating the integration of memories into long-term storage. By employing the same neural architecture for both daytime encoding and nighttime replay, the brain ensures that its memory network remains both flexible and coherent.

Dr. Mihály Vöröslakos, another postdoctoral researcher on the team, highlighted the methodological breakthrough that made this discovery possible: “Our ability to simultaneously record hundreds of individual neurons across multiple connected brain regions in freely moving mice was instrumental. This approach revealed the nuanced patterns of communication that traditional recording methods could not detect.”

Moreover, the study’s findings carry potential implications beyond basic neuroscience. The analogy between neural switchboards and artificial intelligence systems underlines a key challenge in AI—catastrophic forgetting—where machines lose previously learned information upon training on new tasks. By understanding how the mammalian brain protects old memories while learning new ones, scientists hope to inspire the development of next-generation AI technologies that can continuously learn without forgetting.

Dr. György Buzsáki, co-senior author and a renowned neuroscience expert, suggested that this research might shed light on neurodegenerative conditions such as Alzheimer’s disease, where memory circuits deteriorate. “Our discovery of a ‘memory switchboard’ within the hippocampus could provide vital clues about the early mechanisms of memory failure in such diseases,” Dr. Buzsáki remarked.

The experiment involved training six mice to traverse a linear track rewarded at both ends with water. As the animals moved, high-density electrode arrays captured the simultaneous neural activity across hippocampal and cortical regions, while behavioral tracking allowed researchers to correlate precise brain signals with physical navigation and exploration.

Further analysis during sleep revealed that while the original patterns of activity were replayed, they mutat-ed dynamically within and between the hippocampus and neocortex, underscoring a sophisticated neural choreography that supports memory consolidation and flexibility concurrently.

Despite the advances, the authors caution that extrapolation to human brain function requires further research. The controlled environment of the study and differences between species mean that confirming the presence of similar switchboard mechanisms in humans remains an open question.

As they look to the future, the research team plans to explore whether comparable subspace communication channels exist in other areas of the brain responsible for diverse types of memory processing. Such investigations could lead to a more comprehensive neural map of memory architecture, with profound impact for both neuroscience and artificial intelligence.

This research was supported by several grants from the National Institutes of Health, highlighting the critical role of federal funding in fostering cutting-edge brain science. The collaborative effort included leading neuroscientists and scholars from NYU Langone Health and NYU Grossman School of Medicine.

By unlocking new dimensions of how individual neurons coordinate complex memory signals, this study offers unprecedented insights into one of biology’s most enduring mysteries—how the brain manages to be both ever-changing and enduring, preserving the richness of past experience while embracing the potential of new learning.

Subject of Research: Animals
Article Title: Subspace communication in the hippocampal–retrosplenial axis
News Publication Date: 13-May-2026
Web References: http://dx.doi.org/10.1038/s41586-026-10481-z
References: Nature, May 13, 2026; DOI: 10.1038/s41586-026-10481-z

Keywords

Memory, Long term memory, Memory formation, Memory processes, Spatial memory, Sleep, Hippocampal neurons, CA1 cells, CA3 cells, Hippocampus, Hippocampal circuits, Artificial intelligence

Transmission 4.1.2 traz correções importantes para bugs e problemas no cliente BitTorrent, otimizando a experiência do usuário.

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