Comment

Comment by Dr. Krishna Kumari Challa 18 hours ago

How Microorganisms looks under the microscope

Comment by Dr. Krishna Kumari Challa 20 hours ago

How perceptions are influenced by expectations: Songbird study draws parallels with human speech processing

Past neuroscience and psychology studies have shown that people's expectations of the world can influence their perceptions, either by directing their attention to expected stimuli or by reducing their sensitivity (i.e., perceptual acuity) to variations within the categories of stimuli we expect to be exposed to.

Researchers carried out a study involving songbirds aimed at better understanding how expectation-fueled biases in perception shape brain activity and behaviour.  

Their findings, published in Nature Neuroscience, suggest that the perceptions of songbirds, like those of humans, are influenced by expectations, with peripheral sensory systems utilizing expectations to enhance sensory perception and retain high-fidelity representations of the world.

Human speakers are known to have different voices, while also pronouncing many words differently. Past studies suggest that the human brain possesses robust underlying mechanisms designed to address these differences, by grouping speech sounds into stable perceptual categories, a process referred to as "categorical perception". 

One of these mechanisms is that we use context to cue and bias our perception.

The researchers examined the vocal behaviour and perceptions of songbirds. This is because songbirds are known to share many similarities with humans in terms of their vocal behaviour, thus studying them can help to better understand human speech and speech-related perceptions.

The team's initial experiments utilizing synthesized birdsongs showed that, similarly to humans who are listening to others speak, the perceptions of songbirds while listening to birdsongs are biased by their expectations.

Overall, this study confirmed the hypothesis that the song perceptions of songbirds closely resemble the speech perceptions of humans. Specifically, it gathered strong evidence suggesting that the vocal perceptions of songbirds are also biased and influenced by expectations.

The second important finding of this study emerged from the team's second experiment probing the neural basis of context-dependent categorical perception in songbirds. While their first experiment showed that the birds' expectations influenced how they classified songs, the second was aimed at determining whether the birds' sensory systems reflected this shift in perception.

The findings showed that  the sensory brain appears to use expectation in a more clever way, by rededicating neural responses to focusing on relevant, expected signals, improving perceptual acuity.

"It then leaves the bias to downstream processing like motor and decision-making regions of the brain. In this way, the brain can retain high-fidelity, unbiased, representations of the world, while still incorporating bias to make optimal decisions.

Tim Sainburg et al, Expectation-driven sensory adaptations support enhanced acuity during categorical perception, Nature Neuroscience (2025). DOI: 10.1038/s41593-025-01899-1.

**

Comment by Dr. Krishna Kumari Challa 20 hours ago

New study validates lower limits of human heat tolerance

A new study has confirmed that the limits for human thermoregulation—our ability to maintain a stable body temperature in extreme heat—are lower than previously thought.

The findings are published in the journal Proceedings of the National Academy of Sciences.

The study found that many regions may soon experience heat and humidity levels that exceed the safe limits for human survival

Utilizing a widely used technique known as thermal-step protocols, researchers  exposed 12 volunteers to various heat and humidity conditions to identify the point at which thermoregulation becomes impossible. What made this study different was that participants returned to the laboratory for a daylong exposure to conditions just above their estimated limit for thermoregulation. Participants were subjected to extreme conditions, 42°C with 57% humidity, representing a humidex of approximately 62°C.

The results were clear. The participants' core temperature streamed upwards unabated, and many participants were unable to finish the 9-hour exposure. This data provides the first direct validation of thermal step protocols, which have been used to estimate upper limits for thermoregulation for nearly 50 years.

The implications of this research extend beyond academia. As cities prepare for hotter summers, understanding these limits can help guide health policies and public safety measures.

Robert D. Meade et al, Validating new limits for human thermoregulation, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2421281122

Comment by Dr. Krishna Kumari Challa 20 hours ago

Short-term reactivation of brain between encoding of memories enhances recall, study finds

Past neuroscience and psychology studies have shown that after the human brain encodes specific events or information, it can periodically reactivate them to facilitate their retention, via a process known as memory consolidation. The reactivation of memories has been specifically studied in the context of sleep or rest, with findings suggesting that during periods of inactivity, the brain reactivates specific memories, allowing people to remember them in the long term.

Researchers  recently conducted a study exploring the possibility that the brain engages in a similar reactivation process during wakefulness to store important information for shorter periods of time. Their findings, published in Nature Neuroscience, suggest that the spontaneous reactivation of specific stimuli in the brain during the brief intervals between their encoding predicts the accuracy with which people remember them at the end of a memory task.

David J. Halpern et al, Study-phase reinstatement predicts subsequent recall, Nature Neuroscience (2025). DOI: 10.1038/s41593-025-01884-8.

Comment by Dr. Krishna Kumari Challa on Saturday

Adverse outcomes increased with long-term inhaled corticosteroids in COPD

For patients with chronic obstructive pulmonary disorder (COPD), long-term inhaled corticosteroid (ICS) treatment is associated with increased rates of adverse composite and specific individual outcomes, according to a study published in the March/April issue of the Annals of Family Medicine.

examined electronic health record data for individuals older than 45 years with COPD to assess long-term ICS risks. The prevalent cohort had a COPD diagnosis any time during the observation period (318,385 individuals), and the inception cohort had a COPD diagnosis after entry into the database (209,062 individuals).

A composite outcome of any new diagnosis of type 2 diabetes, cataracts, pneumonia, osteoporosis, or nontraumatic fracture and recurrent event outcomes of repeated pneumonia or nontraumatic fracture were compared for long- versus short-term ICS exposure (>24 months versus <4 months).

The researchers found that the composite dichotomous outcome was significantly greater for long- versus short-term ICS use for both the prevalent and inception cohorts (hazard ratios, 2.65 and 2.60, respectively). The absolute risk difference of the composite outcome was 20.26% for the inception cohort, with a number needed to harm of five.

For recurrent pneumonia and recurrent fracture, the hazard ratios were significantly increased in the prevalent and inception cohorts (hazard ratios, 2.88 and 2.85 for pneumonia, respectively; 1.77 and 1.57 for fracture, respectively).

"The clinical use of and indications for ICS therapy in COPD should be carefully considered for each individual before initiation of long-term ICS therapy," the authors write.

Wilson D. Pace et al, Adverse Outcomes Associated With Inhaled Corticosteroid Use in Individuals With Chronic Obstructive Pulmonary Disease, The Annals of Family Medicine (2025). DOI: 10.1370/afm.240030

**

Comment by Dr. Krishna Kumari Challa on Saturday

Measles outbreak leads to dangerous vitamin A toxicity

As a measles outbreak spreads across the U.S., doctors are now seeing a new and unexpected danger: children getting sick from taking too much vitamin A.

At Covenant Children's Hospital in Lubbock, Texas, several unvaccinated children showed signs of liver problems after taking large amounts of vitamin A, according to Dr. Lara Johnson, the hospital's chief medical officer.

U.S. Department of Health and Human Services Secretary Robert F. Kennedy Jr. has promoted vitamin A during the outbreak, even suggesting it might help prevent measles. But doctors say this isn't true.

If people have the mistaken impression that you have an either-or choice of MMR vaccine or vitamin A, you're going to get a lot of kids unnecessarily infected with measles. That's a problem, especially during an epidemic.

And second, you have this unregulated medicine in terms of doses being given and potential toxicities, say the doctors.

The measles, mumps and rubella (MMR) vaccine is the only proven way to prevent measles. It is 97% effective after two doses. 

Vitamin A can be helpful as a supplement for people with measles when given the right dose by a doctor. But taking too much, especially without medical supervision, can be dangerous.

Vitamin A is fat-soluble and can build up in the body. This can lead to dry skin, blurry vision, bone problems and liver damage. In pregnant women, it can even cause birth defects.

If kids are well nourished,  they don't need extra vitamin A.

Recovery for patients with acute toxicity can be rapid when the vitamin is discontinued. Sadly, some of the more serious problems with vitamin A toxicity are not always reversible.

The Council for Responsible Nutrition (CRN), a group representing supplement makers, also warned parents not to give their children high doses of vitamin A.

"While vitamin A plays an important role in supporting overall immune function, research hasn't established its effectiveness in preventing measles infection. CRN is concerned about reports of high-dose vitamin A being used inappropriately, especially in children," it said in a statement.

Doctors say some parents may be following questionable advice from social media or health influencers.

Source: News agencies

**

Comment by Dr. Krishna Kumari Challa on Saturday

They found that population, environment, and language all significantly contribute to the variation in hearing across human groups, but it wasn't clear whether this was due to the whole body being affected by the environment or due to long-term adaptations to varying soundscapes, noise levels, or exposure to pollution.

The researchers suggest that people living in forests could have higher sensitivity because they've adapted to soundscapes with lots of non-human sounds, where vigilance is essential for survival. Or it could be due to being exposed to lower levels of pollution.

People living at higher altitudes may have reduced sensitivity due to a number of reasons, including the impact of lower atmospheric pressure on measurements, potential sound reduction in high altitude environments, or physiological adaptations to lower oxygen levels.

The team also found a difference between urban and rural populations, with those living in cities having a shift towards higher frequencies, possibly due to filtering out low-frequency traffic noise.

Patricia Balaresque et al, Sex and environment shape cochlear sensitivity in human populations worldwide, Scientific Reports (2025). DOI: 10.1038/s41598-025-92763-6

Part 2

Comment by Dr. Krishna Kumari Challa on Saturday

Women can hear better than men: Researchers find amplitude more influenced by sex than age

Scientists have found that sex is the leading factor explaining differences in hearing sensitivity, with women having significantly more sensitive hearing than men.

Hearing problems are on the rise worldwide, and while hearing sensitivity is well known to decrease with age, little research has been done on the other biological and environmental factors that influence them, such as sex, ear side, language, ethnicity, and local environment.

So researchers conducted hearing tests for 450 individuals across 13 global populations—Equador, England, Gabon, South Africa, and Uzbekistan. These populations were selected to capture a wide range of ecological and cultural contexts, including underrepresented rural and non-European groups.

They investigated the sensitivity of the cochlea in the ear, looking at how it transmitted brain signals in response to different amplitudes and frequencies of sound by measuring so-called Transient-Evoked Otoacoustic Emissions (TEOAE).

It's already well known that people generally have better hearing in their right ear, compared with their left, and that hearing usually declines with age. However, the researchers were surprised by their results on the effects of sex and the environment.

Their findings, published in the journal Scientific Reports, show that hearing amplitude is more influenced by sex than age, with women showing an average of two decibels more sensitive hearing than men across all the populations studied.

The second most significant influence was the environment, which not only affected the response to volume but also the range of frequencies of sound perceived. People living in forest areas had the highest hearing sensitivity and those living at high altitudes had the lowest.

Part 1

Comment by Dr. Krishna Kumari Challa on Saturday

The phenomenon that organisms survive in dormancy over very long periods of time and can therefore potentially recolonize habitats under suitable conditions is also known from other studies—for example for plant seeds or small crustaceans, some of which remain viable for several centuries, even millennia.

However, the successful resurrection of a dormant stage after such a long time, as in the case of S. marinoi, has rarely been documented. At around 7000 years old, the tiny cells of this diatom are among the oldest organisms to have been successfully revived from an intact dormant stage. From aquatic sediments, no older such cases are known to date.

Sarah Bolius et al, Resurrection of a diatom after 7000 years from anoxic Baltic Sea sediment, The ISME Journal (2025). DOI: 10.1093/ismejo/wrae252

Part 3

Comment by Dr. Krishna Kumari Challa on Saturday

The researchers examined sediment cores taken from 240 meters water depth in the Eastern Gotland Deep during an expedition with the research vessel Elisabeth Mann Borgese in 2021.

In favorable nutrient and light conditions, viable algae could be awakened from dormancy from nine sediment samples and individual strains were isolated. The samples were taken from different sediment layers that represent a time span of around 7,000 years and thus the main climate phases of the Baltic Sea.
The diatom species Skeletonema marinoi was the only phytoplankton species that was revived from all samples. It is very common in the Baltic Sea and typically occurs during the spring bloom. The oldest sample with viable cells of this species was dated to an age of 6,871 ± 140 years.

"It is remarkable that the resurrected algae have not only survived 'just so,' but apparently have not lost any of their 'fitness,' i. e. their biological performance ability. They grow, divide and photosynthesize like their modern descendants.
The measurement of photosynthetic performance also showed that even the oldest algae isolates can still actively produce oxygen—with average values of 184 micromoles of oxygen per milligram of chlorophyll per hour. These are also values that are comparable to those of current representatives of this species.
The researchers also analyzed the genetic profiles of the resurrected algae using microsatellite analysis—a method in which certain short DNA segments are compared. The result: The samples from sediment layers of different ages formed distinctive genetic groups.

Firstly, this ruled out the possibility that cross contamination could have occurred during the cultivation of the strains from sediment layers of different ages. Secondly, this proves that successive populations of S. marinoi in the Baltic Sea have changed genetically over the millennia.
Part 2

• ‹ Previous
• 1
• 2
• 3
• …
• 1042
• Next ›
• Page