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Comment by Dr. Krishna Kumari Challa on October 17, 2025 at 8:29am

Men experience more brain atrophy with age despite women's higher Alzheimer's risk

Many women complained to me that their husbands "behaved strangely" as they got older and older. 

It seems they complained more, got irritated and angry more, understood situations less, grumbled a lot, ... and the descriptions take a strange turn as they go on describing them.

Now we have an explanation for such behaviours.

Women are far more likely than men to end up with Alzheimer's disease (AD). This may, at least partially, be due to women's longer average lifespans, but many scientists think there is probably more to the story. It would be easy to surmise that the increased risk is also related to differences in the way men's and women's brains change as they age. 

Now, a new study, published in Proceedings of the National Academy of Sciences, indicates that it's men who experience greater decline in more regions of the brian as they age. Researchers involved in the study analyzed 12,638 brain MRIs from 4,726 cognitively healthy participants (at least two scans per person) from the ages of 17–95 to find how age-related changes occurred and whether they differed between men and women.

The results showed that men experienced declines in cortical thickness and surface area in many regions of the brain and a decline in subcortical structures in older age. Meanwhile, women showed greater decline only in a few regions and more ventricular expansion in older adults. So, while differences in brain aging between the sexes are apparent, the cause of increased AD prevalence in women is still a bit mysterious.

These findings suggest that the higher prevalence of AD diagnoses in women likely stems from factors beyond differential rates of age-related brain atrophy," the study authors write.

One factor that might be to blame is genetics, particularly the APOE ε4 allele, which may affect protein accumulation in the brain and work differently in men and women. Other factors might include differences in hormonal changes, diagnosis patterns, and sociocultural influences.

Survival bias may also skew the results in AD studies, as more men may have been diagnosed with AD if their average lifespans matched women's more closely. In this particular study, participants were also more educated on average, which is a protective factor for AD—leading to a potential representativity bias.

When the researchers corrected for life expectancy, they say some of the differences did clear up for men and additional differences cropped up in women.

"The interpretation of these sex differences is complicated by our life expectancy analyses, which removed several cortical decline effects in men while revealing effects in women, including greater hippocampal decline. Whether this reflects the removal of proximity-to-death artifacts or elimination of biological aging differences cannot be determined, and these findings should be interpreted with caution, especially considering representativity bias in our sample with potentially healthier men," the authors explain.

Anne Ravndal et al, Sex differences in healthy brain aging are unlikely to explain higher Alzheimer's disease prevalence in women, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2510486122

Comment by Dr. Krishna Kumari Challa on October 17, 2025 at 8:17am

The way we talk to chatbots affects their accuracy, new research reveals

Whether we're seeking customer support, looking for recommendations, or simply asking a quick question, AI chatbots are designed to give us the answers we're looking for. But there's more going on beneath the surface. Every time we chat with them, they are learning from us to improve their understanding and responses. And the type of language we use, whether formal or informal, directly affects the quality of their answers, according to new research.

In general, people naturally adapt their conversation style to the person they are speaking with. 

The researchers compared thousands of messages people sent to human agents with those sent to AI chatbots, focusing on features like grammar, vocabulary and politeness. They found that people were 14.5% more polite and formal and 5.3% more grammatically fluent when chatting with humans than when talking with AI, based on analysis by the Claude 3.5 Sonnet model.

Next, they trained an AI model called Mistral 7B on about 13,000 real chats between people, then tested how well it understood more than 1,300 messages people had sent to chatbots. To broaden the AI's exposure, they also created blunt and polite rewrites of those messages to simulate different communication styles.

It turns out that chatbots trained on a diverse mix of message styles, including real and fake messages, were 2.9% better at understanding user intent than AI trained solely on original human conversations. The researchers also tried to improve Mistral AI's understanding by rewriting informal messages at the last minute to be more formal, but this led to a drop in understanding by almost 2%.

So the best way to make chatbots smarter is to train them on a range of communication styles, as the researchers state in their paper published on the arXiv preprint server. "Training-time exposure to diverse linguistic variation is more effective than inference-time normalization. Models must learn to interpret diverse communication styles during training, rather than rely on brittle post-hoc transformations that risk semantic distortion."

Fulei Zhang et al, Mind the Gap: Linguistic Divergence and Adaptation Strategies in Human-LLM Assistant vs. Human-Human Interactions, arXiv (2025). DOI: 10.48550/arxiv.2510.02645

Comment by Dr. Krishna Kumari Challa on October 17, 2025 at 8:10am

Interestingly, when the team disrupted this pathway's activity, they found that mice no longer stopped drinking and developed hyponatremia. This is a condition characterized by overhydration and an abnormally low concentration of sodium in the blood.

This recent study gathered new valuable insight into how the mouse brain prevents overhydration, signaling that it is time to stop drinking.

Lingyu Xu et al, A bottom-up septal inhibitory circuit mediates anticipatory control of drinking, Nature Neuroscience (2025). DOI: 10.1038/s41593-025-02056-4.

Part 2

Comment by Dr. Krishna Kumari Challa on October 17, 2025 at 8:10am

Preventing overhydration: Study uncovers a neural circuit that prompts mice to stop drinking

Identifying the neural mechanisms that support the regulation of vital physiological processes, such as drinking, eating and sleeping, is a long-standing goal within the neuroscience research community. As the disruption of these processes can severely impact people's health and everyday functioning, uncovering their neural and biological underpinnings is of the utmost importance.

New insights gathered by neuroscientists could ultimately inform the development of more effective interventions designed to regulate vital physiological processes. Thirst and hunger are known to be regulated by homeostatic processes, biological processes that allow the body to maintain internal stability.

Yet drinking behaviour can also be anticipatory, which means that animals and humans often adjust their actions (i.e., stop drinking) before the concentration of substances in the blood changes in response to drinking water. The mechanisms through which the brain predicts when it is the right time to stop drinking remain poorly understood.

Researchers  recently carried out a study involving mice aimed at shedding new light on these mechanisms. Their findings, published in Nature Neuroscience, led to the identification of a neural pathway that reduces neural activity in specific regions of the mouse brain, signaling that the body has received enough water.

Drinking behaviour is not only homeostatically regulated but also rapidly adjusted before any changes in blood osmolality occur, known as anticipatory thirst satiation.

Homeostatic and anticipatory signals converge in the subfornical organ (SFO); however, the neural pathways conveying peripheral information to the SFO before changes in blood composition are incompletely understood till now.

Researchers now  reveal an inhibitory pathway from the medial septum (MS) to the SFO that is involved in the control of anticipatory drinking behaviour in mice.

As part of their experiments, researchers observed the drinking behavior of adult mice, while recording their neural activity. This led to the discovery of a neural pathway connecting the MS, a small region in the mouse brain that contributes to the synchronization of brain circuits, and the SFO, a region implicated in the monitoring of bodily fluids.

"MS γ-aminobutyric acid (GABA)ergic neurons encode water-satiation signals by integrating cues from the oral cavity and tracking gastrointestinal signals," wrote the authors in their research paper. "These neurons receive inputs from the parabrachial nucleus and relay to SFOCaMKII neurons, forming a bottom-up pathway with activity that prevents overhydration. Disruption of this circuit leads to excessive water intake and hyponatremia."

Essentially, the researchers found that after a mouse starts drinking, GABAergic neurons in the MS become active and receive signals from the parabrachial nucleus, a brain region that processes signals originating from the mouth and gut. These GABAergic neurons then send inhibitory signals to neurons in the SFO, which in turn modulate the feeling of thirst.

Part 1

Comment by Dr. Krishna Kumari Challa on October 16, 2025 at 10:54am

'Jump-scare' science: Study elucidates how the brain responds to fear

In haunted houses across the US this month, threatening figures will jump out of the shadows, prompting visitors—wide-eyed and heart racing—to instinctively freeze and flee.

Evolutionarily speaking, this "innate threat response" is key to survival, helping a wide variety of animal species escape predators. But when stuck in overdrive it can cause problems for humans.

A  research team has identified a novel brain circuit responsible for orchestrating this threat response. Known as the interpeduncular nucleus (IPN), this dense cluster of specialized neurons not only jump-starts that freeze-and-flee reaction, but dials it down when animals learn there's no real danger.

In people with anxiety or post-traumatic stress disorder (PTSD), this circuit may be broken, researchers say.

The findings could help explain why some people have a greater appetite for risk than others and lead to new therapies for psychiatric disorders.

The brain's threat system is like an alarm. It needs to sound when danger is real, but it needs to shut off when it's not. This new study shows how the brain learns to fine-tune those responses through experience, helping us adapt to the world.

 Elora W. Williams et al, Interpeduncular GABAergic neuron function controls threat processing and innate defensive adaptive learning, Molecular Psychiatry (2025). DOI: 10.1038/s41380-025-03131-9

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Comment by Dr. Krishna Kumari Challa on October 16, 2025 at 10:45am

Why women's brains face higher risk: Scientists pinpoint X-chromosome gene behind MS and Alzheimer's

New research has identified a sex-chromosome linked gene that drives inflammation in the female brain, offering insight into why women are disproportionately affected by conditions such as Alzheimer's disease and multiple sclerosis as well as offering a potential target for intervention.

The study, published in the journal Science Translational Medicine, used a mouse model of multiple sclerosis to identify a gene on the X chromosome that drives inflammation in brain immune cells, known as microglia. Because females have two X chromosomes, as opposed to only one in males, they get a "double dose" of inflammation, which plays a major role in aging, Alzheimer's disease and multiple sclerosis.

When the gene, known as Kdm6a, and its associated protein were deactivated, the multiple sclerosis-like disease and neuropathology were both ameliorated with high significance in female mice.

Multiple sclerosis and Alzheimer's disease each affect women more often than men, about two to three times as often. Also, two-thirds of healthy women have 'brain fog' during menopause. These new findings explain why and point to a new treatment to target this.

When researchers genetically "knocked out" the gene Kdm6a in brain immune cells, the inflammatory molecules shifted from being activated to a resting state. Additionally, they  performed a pharmacologic "knock down" of the protein made by this gene using metformin. Metformin is widely used as a treatment for diabetes but is currently being researched for potential anti-aging properties.

While these interventions were highly significant in female mice, their effect was almost undetectable in males.

This is consistent with there being 'more to block' in females due to having two copies of the X-linked gene.

It's also why females are more likely to get MS and AD than males. This has implications for the clinic. Women may respond differently to metformin treatment than men.

The findings may also have implications for explaining a connection to brain fog in healthy women during menopause.

Sex chromosomes and sex hormones achieve a balance through evolution. There is a selection bias to do so. Females have a balance between X chromosome-driven inflammation that can be good to fight infections at child-bearing ages. This is held in check by estrogen, which is anti-inflammatory and neuroprotective. As women age, menopause causes loss of estrogen, unleashing the proinflammatory and neurodegenerative effects of this X chromosome in brain immune cells.

Yuichiro Itoh et al, Microglia-specific deletion of the X-chromosomal gene Kdm6a reverses the disease-associated microglia translatome in female mice, Science Translational Medicine (2025). DOI: 10.1126/scitranslmed.adq3401. www.science.org/doi/10.1126/scitranslmed.adq3401

Comment by Dr. Krishna Kumari Challa on October 16, 2025 at 10:24am

Scientists turned off moths' sex signals—this could be the key to greener pest control

A single "sexy" gene could help us combat one of the world's most destructive fruit pests. By deleting the gene that lets female moths produce their mating scent, researchers  created an "unsexy" moth—and showed one way to turn insect attraction into a powerful pest control tool.

You've probably seen moths flittering around a bright lamppost on a balmy summer night. Those same insects, in their larval form, are the worms that burrow into your apples and peaches, making them serious pests in agriculture.
Moths are usually controlled with chemical pesticides, but pests evolve resistance and these sprays also harm bees and other pollinators. We need new and more sustainable methods to protect important crops targeted by moth larvae, like apples, maize, tomatoes and rice.

In a new study published in the Journal of Chemical Ecology, researchers have demonstrated a way to unravel sexual communication in insects and provide a more sustainable alternative to pesticides. Yes, now  we can stop moths by using their natural instincts against them.

Marie Inger Dam et al, Sex pheromone biosynthesis in the Oriental fruit moth Grapholita molesta involves Δ8 desaturation, Insect Biochemistry and Molecular Biology (2025). DOI: 10.1016/j.ibmb.2025.104307

Comment by Dr. Krishna Kumari Challa on October 16, 2025 at 10:21am

Human cells activate self-destruction when viruses disrupt RNA production, study shows

Viruses are masters at taking over our cells: They disable our defenses and hijack the cellular machinery in order to multiply successfully. For example, the herpes simplex virus 1, which causes blister-like skin rashes, and influenza viruses specifically block a crucial step in gene activity in which the production of RNA molecules is completed—known as transcription termination. The blockade results in unnaturally long RNA molecules that cannot be translated into proteins. This suppresses the antiviral defense in the cells and creates optimal conditions for the viruses to multiply.

A new study published in Nature now shows that human cells are not helpless against this viral sabotage. They recognize the disruption of transcription termination as an alarm signal, activate a "self-destruction program" and sacrifice themselves—even before the virus can multiply in them. This enables them to nip the spread of the infection in the bud.

Researchers discovered that the unnaturally long RNA molecules adopt a special structure: They twist into left-turning double strands, known as Z-RNAs. These unusual RNA forms are recognized by the cellular protein ZBP1. And then the controlled cell death begins.

It is particularly noteworthy that Z-RNAs form primarily in those sections of these unnaturally long RNA molecules that originate, among other things, from remnants of previous viral infections. These otherwise silent areas of our genome are only transcribed into RNA due to the virus-related disruption of transcription termination.

Our cells therefore use these genetic remnants of ancient viral infections to detect and ward off current viral attacks.

Evolution has thus turned the tables: what once began as a viral invasion now serves as an alarm signal for the antiviral immune defense. This discovery impressively demonstrates how closely virus and host have been intertwined over millions of years—and how our cells can transform viral sabotage into highly effective protective strategies.

 Chaoran Yin et al, Host cell Z-RNAs activate ZBP1 during virus infections, Nature (2025). DOI: 10.1038/s41586-025-09705-5

Comment by Dr. Krishna Kumari Challa on October 16, 2025 at 10:16am

Differences in coexistence create new species

A simple change in species composition can impact the course of evolution: A research team shows that the presence of just one other fish species is enough to drive the emergence of new species in sticklebacks.

It has long been assumed that adaptation to different habitats plays an important role in the evolution of new species. Yet how important this influence truly is—particularly during the initial stages of the speciation process—and which ecological differences are most critical remain major questions in evolutionary research.

For the current study, the research team studied populations of threespine stickleback—small fish about the size of a finger—from lakes in western Canada. These lakes formed after glaciers from the last ice age melted less than 12,000 years ago and were then colonized by sticklebacks from the sea. While many of these lakes are environmentally similar, they differ in one aspect: in some, another fish species, the prickly sculpin, lives alongside sticklebacks, while in other lakes sculpins are absent.

This seemingly simple ecological difference—living with or without sculpins—has repeatedly pushed sticklebacks down distinct evolutionary paths: in lakes with sculpins, sticklebacks have evolved into slimmer open-water forms, while in sculpin-free lakes they have become stockier bottom-feeding specialists.

 Marius Roesti et al, A species interaction kick-starts ecological speciation in allopatry, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2506625122

Comment by Dr. Krishna Kumari Challa on October 16, 2025 at 10:13am

Electric charge connects jumping worm to aerial prey

A tiny worm that leaps high into the air—up to 25 times its body length—to attach to flying insects uses static electricity to perform this astounding feat, scientists have found.

The journal PNAS published the work on the nematode Steinernema carpocapsae, a parasitic roundworm. 

Researchers identified the electrostatic mechanism this worm uses to hit its target, and we've shown the importance of this mechanism for the worm's survival. Higher voltage, combined with a tiny breath of wind, greatly boosts the odds of a jumping worm connecting to a flying insect.

They conducted the experiments, including the use of high-speed microscopy techniques to film the parasitic worm—whose length is about the diameter of a needle point—as it leaped onto electrically charged fruit flies.

The researchers showed how a charge of a few hundred volts, similar to that generated by an insect's wings beating the air, initiates an opposite charge in the worm, creating an attractive force. They identified electrostatic induction as the charging mechanism driving this process.

Using physics, scientists learned something new and interesting about an adaptive strategy in an organism.

Ranjiangshang Ran et al, Electrostatics facilitate midair host attachment in parasitic jumping nematodes, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2503555122

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