Why Yawn? - Eating Neurotoxins - Memories & Depression - Alzheimer's Pill?

[Breedlove, S]

https://www.theguardian.com/lifeandstyle/2025/oct/26/why-do-we-yawn-almost-certainly-not-for-the-reason-you-think

Why do we yawn? It’s almost certainly not for the reason you think

Joel Snape

All vertebrates yawn, or indulge in a behaviour that’s at least recognisable as yawn-adjacent. Sociable baboons yawn, but so do semi-solitary orangutans. Parakeets, penguins and crocodiles yawn – and so, probably, did the first ever jawed fish. Until relatively recently, the purpose of yawning wasn’t clear, and it’s still contested by researchers and scientists. But this commonality provides a clue to what it’s really all about – and it’s probably not what you’re expecting.

“When I poll audiences and ask: ‘Why do you think we yawn?’, most people suggest that it has to do with breathing or respiration and might somehow increase oxygen in the blood,” says Andrew Gallup, a professor in behavioural biology at Johns Hopkins University. “And that’s intuitive because most yawns do have this clear respiratory component, this deep inhalation of air. However, what most people don’t realise is that that hypothesis has been explicitly tested and shown to be false.”

To test the idea that we yawn to bring in more oxygen or expel excess carbon dioxide, studies published in the 1980s manipulated the levels of both gases in air inhaled by volunteers – and they found that while changes did significantly affect other respiratory processes, they didn’t influence the regularity of yawns. There also doesn’t seem to be any systematically measurable difference in the yawning behaviour of people suffering from illnesses associated with breathing and lung function – which is what you would expect if yawns were respiration-related.

This, more or less, was where Gallup came to the subject. “When I was pursuing my honours thesis, my adviser at the time said, well, why not study yawning, because nobody knows why we do it?” he says. “That was intriguing – we knew it had to serve some underlying physiological function. So I started to examine the motor action pattern it involves – this extended gaping of the jaw that’s accompanied by this deep inhalation of air, followed by a rapid closure of the jaw and a quicker exhalation. And it occurred to me that this likely has important circulatory consequences that are localised to the skull.”

© 2025 Guardian News & Media Limited 
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https://knowablemagazine.org/content/article/living-world/2025/animals-deal-with-toxins

Animals that eat poisons and don’t die
 
By Katarina Zimmer 

The 10 snakes faced a tough predicament.

Collected from the Colombian Amazon, they had been without food for several days in captivity and then were presented with extremely unappetizing prey: three-striped poison dart frogs, Ameerega trivittata. The skin of those frogs contains deadly toxins — such as histrionicotoxins, pumiliotoxins and decahydroquinolines — that interfere with essential cell proteins.

Six of the royal ground snakes (Erythrolamprus reginae) preferred to go hungry. The other four intrepidly slithered in for the kill. But before swallowing their meals, they dragged the frogs across the ground — akin to the way some birds rub toxins off their prey, noted biologist Valeria Ramírez Castañeda of the University of California, Berkeley, and her colleagues, who conducted the experiment.

In a recent study, some royal ground snakes dragged poison frogs along the ground before eating them, probably in an effort to rub off some of the frogs’ deadly toxins.

Three of the four snakes survived the meal — suggesting that their bodies were capable of handling the toxins that remained.

Living beings have been wielding deadly molecules to kill each other for hundreds of millions of years. First came microbes that used the chemicals to weed out competitors or attack host cells they were invading; then animals, to kill prey or ward off predators, and plants, to defend against herbivores. In response, many animals have evolved ways to survive these toxins. They sometimes even store them to use against opponents.

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https://undark.org/2025/10/29/interview-steve-ramirez/

 How Memories Might Be Used to Help Heal the Brain

By Sara Talpos

As a new Ph.D. student in 2011, Steve Ramirez and his mentor performed a groundbreaking experiment in the field of memory manipulation. They placed a mouse in a small distinctive box and administered a mild electrical shock to its feet. When the rodent was placed in the box a second time, it froze up — anticipating another shock.

From there, the young neuroscientists placed the mouse in a different box, one where nothing bad had happened. They then directed pulses of light to a very specific region in the mouse’s brain that had been genetically modified to respond to the light. This caused the mouse to immediately freeze. Ramirez and his mentor, it turned out, had found a way to artificially activate a fear-inducing memory.

“How to Change a Memory: One Neuroscientist’s Quest to Alter the Past,” by Steve Ramirez will be available on November 4, 2025 (Princeton University Press, 256 pages).

What was the point? A central goal of such science is to learn how memories form and function in the brain and to then apply this knowledge to treat brain disorders, writes Ramirez in his forthcoming book, “How to Change a Memory: One Neuroscientist’s Quest to Alter the Past.” Perhaps one day, he suggests, it will be possible to activate positive memories to curb depression or to retrieve memories that have seemingly been lost to Alzheimer’s disease.

In the book, Ramirez explores the fascinating science of memory while tracing his own journey to becoming a successful professor at Boston University. His path was not without challenges, including the sudden death of his mentor and a decade-long struggle with alcohol addiction. “This book,” he writes, “is my attempt to make sense of the enigma of memory — the snippets of remembrances, the brief moments in time, the decisions we make, the blackouts, the imagined, and the dreamt of — all the things the brain does to breathe life into the past so that we can heal and become whole again.”
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https://www.npr.org/sections/shots-health-news/2025/10/29/nx-s1-5575561/alzheimers-pill-apoe4-high-risk-lecanemab-donanemab

Alzheimer's pill appears to protect some in a high-risk population

Jon Hamilton

In April, the future was looking bleak for an experimental Alzheimer's drug called valiltramiprosate, or ALZ-801.

Researchers had just released topline results of a study of more than 300 people age 50 or older, who were genetically predisposed to Alzheimer's. Overall, those who got the drug did no better than those given a placebo.

But in September, a closer look at the results revealed benefits for a subgroup of 125 people who had only mild memory problems when they started taking the drug.

Those participants, initially diagnosed with mild cognitive impairment rather than mild dementia, "showed very meaningful responses," says Dr. Susan Abushakra, chief medical officer of Alzheon, the drug's maker.

By one measure, the drug slowed cognitive decline by 52% in people with mild cognitive impairment. That result appears comparable with benefits from the two Alzheimer's drugs now on the market: lecanemab and donabemab.

But the true effect of ALZ-801 is hard to quantify because of the relatively small number of participants in the group with mild cognitive impairment.
Three scientists learned they carry genes that significantly increase their risk for Alzheimer’s. Here's how they're grapping with the news, and working to keep their brains healthy.

More robust results came from measures of brain atrophy — the shrinkage that tends to come with Alzheimer's.

    © 2025 npr


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https://www.sciencenews.org/article/genetic-shifts-helped-humans-walk-two-legs

Two tiny genetic shifts helped early humans walk upright

By Roberta McLain

Two small genetic changes reshaped the human pelvis, setting our early ancestors on the path to upright walking, scientists say.

One genetic change flipped the ilium — the bone your hands rest on when you put them on your hips — 90 degrees. The rotation reoriented the muscles that attach to the pelvis, turning a system for climbing and running on all four legs into one for standing and walking on two legs. The other change delayed how long it takes for the ilium to harden from soft cartilage into bone, evolutionary biologist Gayani Senevirathne of Harvard University and colleagues report in the Sept. 25 Nature. The result: a distinctive bowl-shaped pelvis that supports an upright body.

While nonhuman primates can walk upright to some extent, they typically move on all fours. The newly identified changes to human pelvic development were “essential for creating and shifting muscles that are usually on the back of the animal, pushing the animal forward, to now being on the sides, helping us stay upright as we walk,” says coauthor Terence Capellini, a Harvard evolutionary biologist.

The researchers examined tiny slices of developing pelvic tissue from humans, chimpanzees and mice under a microscope, and paired those findings with CT imaging. Human ilium cartilage grows sideways, not vertically as it does in other primates, the team found. What’s more, the cartilage transitions to bone more slowly than in nonhuman primates and in other human body parts. Together, these shifts allow the pelvis to expand sideways and maintain its wide, bowl-like shape as it grows. 

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