Astrocyte Memories - Sleep Transitions - Death Folds - Postpartum Depression
Breedlove, S
https://www.nature.com/articles/d41586-025-03366-0
How emotional memories are engraved on the brain, with surprising helper cells
Katie Kavanagh
Why are we able to remember emotional events so well? According to a study published today in Nature1, a type of cell in the brain called an astrocyte is a key player in stabilizing memories for long-term recall.
Astrocytes were thought to simply support neurons in creating the physical traces of memories in the brain, but the study found that they have a much more active role — and can even be directly triggered by repeated emotional experiences. The researchers behind the finding suggest that the cells could be a fresh target for treating memory conditions such as those associated with post-traumatic stress disorder and Alzheimer’s disease.
“We provide an answer to the question of how a specific memory is stored for the long term,” says study co-author Jun Nagai, a neuroscientist at RIKEN Center for Brain Science in Wako, Japan. By studying astrocytes, Nagai said, the study identifies how the brain selectively filters important memories at the cellular level.
Stable memories
Nagai and his colleagues focused on the question of memory stabilization: how a short-term memory becomes more permanent in the brain. Previous research had found physical traces of memories in neuronal networks in brain regions such as the hippocampus and amygdala2. But it was unclear how these ‘engrams’ were stored in the brain as lasting memories after repeated exposure to the same stimulus.
To dig deeper, the researchers developed a method for measuring activation patterns in astrocytes across a whole brain of a mouse as it completes a memory task. They measured the upregulation of a gene called Fos — an early marker of cell activity that is associated with the physical traces of memories in the brain3.
© 2025 Springer Nature Limited
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How the Brain Moves From Waking Life to Sleep (and Back Again)
By Yasemin Saplakoglu
The pillow is cold against your cheek. Your upstairs neighbor creaks across the ceiling. You close your eyes; shadows and light dance across your vision. A cat sniffs at a piece of cheese. Dots fall into a lake. All this feels very normal and fine, even though you don’t own a cat and you’re nowhere near a lake.
You’ve started your journey into sleep, the cryptic state that you and most other animals need in some form to survive. Sleep refreshes the brain and body in ways we don’t fully understand: repairing tissues, clearing out toxins and solidifying memories. But as anyone who has experienced insomnia can attest, entering that state isn’t physiologically or psychologically simple.
To fall asleep, “everything has to change,” said Adam Horowitz (opens a new tab), a research affiliate in sleep science at the Massachusetts Institute of Technology. The flow of blood to the brain slows down, and the circulation of cerebrospinal fluid speeds up. Neurons release neurotransmitters that shift the brain’s chemistry, and they start to behave differently, firing more in sync with one another. Mental images float in and out. Thoughts begin to warp.
“Our brains can really rapidly transform us from being aware of our environments to being unconscious, or even experiencing things that aren’t there,” said Laura Lewis (opens a new tab), a sleep researcher at MIT. “This raises deeply fascinating questions about our human experience.”
It’s still largely mysterious how the brain manages to move between these states safely and efficiently. But studies targeting transitions both into and out of sleep are starting to unravel the neurobiological underpinnings of these in-between states, yielding an understanding that could explain how sleep disorders, such as insomnia or sleep paralysis, can result when things go awry.
Sleep has been traditionally thought of as an all-or-nothing phenomenon, Lewis said. You’re either awake or asleep. But the new findings are showing that it’s “much more of a spectrum than it is a category.”
© 2025 Simons Foundation
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'Death fold' proteins can make cells self-destruct. Scientists want to control them
Jon Hamilton
In Alzheimer's, brain cells die too soon. In cancer, dangerous cells don't die soon enough.
That's because both diseases alter the way cells decide when to end their lives, a process called programmed cell death.
"Cell death sounds morbid, but it's essential for our health," says Douglas Green, who has spent decades studying the process at St. Jude Children's Research Hospital in Memphis, Tennessee.
For example, coaxing nerve cells to live longer could help people with Alzheimer's disease, Parkinson's disease or ALS (Lou Gehrig's disease), he says, while getting tumor cells to die sooner could help people with cancer.
So researchers have been searching for disease treatments that "modify or modulate the tendency of a cell to die," Green says.
One of these researchers is Randal Halfmann at the Stowers Institute for Medical Research in Kansas City, Missouri.
He has been studying immune cells that self-destruct when they come into contact with molecules that present a threat to the body.
"They have to somehow recognize that [threat] in this vast array of other complex molecules," he says, "and then within minutes, kill themselves."
They do this much the way a soldier might dive on a grenade to save others' lives.
Halfmann's team has been focusing on special proteins inside cells that can trigger this process.
When these proteins recognize molecules associated with a virus or some other pathogen, he says, "they implode."
The proteins crumple and begin linking up with other crumpled proteins to form a structure called a "death fold" polymer. That starts a chain reaction of polymerization that ultimately kills the cell.
Halfmann's team knew this process takes a burst of energy. But they couldn't locate the source.
© 2025 npr
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https://knowablemagazine.org/content/article/mind/2025/postpartum-depression-predictive-blood-test
Postpartum depression: Better remedies, and now a predictive blood test
By Michele Cohen Marill
Like many first-time mothers, Lisette Lopez-Rose thought childbirth would usher in a time of joy. Instead, she had panic attacks as she imagined that something bad was going to happen to her baby, and she felt weighed down by a sadness that wouldn’t lift. The San Francisco Bay Area mother knew her extreme emotions weren’t normal, but she was afraid to tell her obstetrician. What if they took her baby away?
At about six months postpartum, she discovered an online network of women with similar experiences and ultimately opened up to her primary care doctor. “About two months after I started medication, I started to feel like I was coming out of a deep hole and seeing light again,” she says. Today, Lopez-Rose works at Postpartum Support International, coordinating volunteers to help new mothers form online connections.
About one in eight US women go through a period of postpartum depression, making it among the most common complications of childbirth. It typically occurs in the first few weeks after delivery, when there’s a sudden drop in the reproductive hormones estrogen and progesterone. As scientists unravel chemical and genetic changes caused by those shifting hormones, they are discovering new ways to diagnose and treat postpartum depression, and even ways to identify who is at risk for it.
Graph showing a steady rise in levels of estradiol and progesterone after conception and then a very steep drop-off right after birth.
The hormones estradiol (the main form of estrogen) and progesterone rise during pregnancy. In some women, their sudden drop after childbirth triggers the onset of postpartum depression.
The first-ever drug for postpartum depression, containing a derivative of progesterone, received US Food and Drug Administration approval in 2019. That marked a new approach to the disorder. This winter, in another major advance, a San Diego-based startup company will launch a blood test that predicts a pregnant woman’s risk of postpartum depression with more than 80 percent accuracy.
© 2025 Annual Reviews
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